diff options
Diffstat (limited to 'tools/objtool/klp-diff.c')
| -rw-r--r-- | tools/objtool/klp-diff.c | 2213 |
1 files changed, 2213 insertions, 0 deletions
diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c new file mode 100644 index 000000000000..f8787d7d1454 --- /dev/null +++ b/tools/objtool/klp-diff.c @@ -0,0 +1,2213 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +#define _GNU_SOURCE /* memmem() */ +#include <subcmd/parse-options.h> +#include <stdlib.h> +#include <string.h> +#include <libgen.h> +#include <stdio.h> +#include <ctype.h> + +#include <objtool/objtool.h> +#include <objtool/warn.h> +#include <objtool/arch.h> +#include <objtool/klp.h> +#include <objtool/util.h> +#include <arch/special.h> + +#include <linux/align.h> +#include <linux/objtool_types.h> +#include <linux/livepatch_external.h> +#include <linux/stringify.h> +#include <linux/string.h> +#include <linux/jhash.h> + +#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER)) + +struct elfs { + struct elf *orig, *patched, *out; + const char *modname; +}; + +struct export { + struct hlist_node hash; + char *mod, *sym; +}; + +bool debug, debug_correlate, debug_clone; +int indent; + +static const char * const klp_diff_usage[] = { + "objtool klp diff [<options>] <in1.o> <in2.o> <out.o>", + NULL, +}; + +static const struct option klp_diff_options[] = { + OPT_GROUP("Options:"), + OPT_BOOLEAN('d', "debug", &debug, "enable all debug output"), + OPT_BOOLEAN(0, "debug-correlate", &debug_correlate, "enable correlation debug output"), + OPT_BOOLEAN(0, "debug-clone", &debug_clone, "enable cloning debug output"), + OPT_END(), +}; + +static DEFINE_HASHTABLE(exports, 15); + +static char *escape_str(const char *orig) +{ + size_t len = 0; + const char *a; + char *b, *new; + + for (a = orig; *a; a++) { + switch (*a) { + case '\001': len += 5; break; + case '\n': + case '\t': len += 2; break; + default: len++; + } + } + + new = malloc(len + 1); + if (!new) + return NULL; + + for (a = orig, b = new; *a; a++) { + switch (*a) { + case '\001': memcpy(b, "<SOH>", 5); b += 5; break; + case '\n': *b++ = '\\'; *b++ = 'n'; break; + case '\t': *b++ = '\\'; *b++ = 't'; break; + default: *b++ = *a; + } + } + + *b = '\0'; + return new; +} + +static int read_exports(void) +{ + const char *symvers = "Module.symvers"; + char line[1024], *path = NULL; + unsigned int line_num = 1; + FILE *file; + + file = fopen(symvers, "r"); + if (!file) { + path = top_level_dir(symvers); + if (!path) { + ERROR("can't open '%s', \"objtool diff\" should be run from the kernel tree", symvers); + return -1; + } + + file = fopen(path, "r"); + if (!file) { + ERROR_GLIBC("fopen"); + return -1; + } + } + + while (fgets(line, 1024, file)) { + char *sym, *mod, *type; + struct export *export; + + sym = strchr(line, '\t'); + if (!sym) { + ERROR("malformed Module.symvers (sym) at line %d", line_num); + return -1; + } + + *sym++ = '\0'; + + mod = strchr(sym, '\t'); + if (!mod) { + ERROR("malformed Module.symvers (mod) at line %d", line_num); + return -1; + } + + *mod++ = '\0'; + + type = strchr(mod, '\t'); + if (!type) { + ERROR("malformed Module.symvers (type) at line %d", line_num); + return -1; + } + + *type++ = '\0'; + + if (*sym == '\0' || *mod == '\0') { + ERROR("malformed Module.symvers at line %d", line_num); + return -1; + } + + export = calloc(1, sizeof(*export)); + if (!export) { + ERROR_GLIBC("calloc"); + return -1; + } + + export->mod = strdup(mod); + if (!export->mod) { + ERROR_GLIBC("strdup"); + return -1; + } + + export->sym = strdup(sym); + if (!export->sym) { + ERROR_GLIBC("strdup"); + return -1; + } + + hash_add(exports, &export->hash, str_hash(sym)); + } + + free(path); + fclose(file); + + return 0; +} + +static int read_sym_checksums(struct elf *elf) +{ + struct section *sec; + + sec = find_section_by_name(elf, ".discard.sym_checksum"); + if (!sec) { + ERROR("'%s' missing .discard.sym_checksum section, file not processed by 'objtool klp checksum'?", + elf->name); + return -1; + } + + if (!sec->rsec) { + ERROR("missing reloc section for .discard.sym_checksum"); + return -1; + } + + if (sec_size(sec) % sizeof(struct sym_checksum)) { + ERROR("struct sym_checksum size mismatch"); + return -1; + } + + for (int i = 0; i < sec_size(sec) / sizeof(struct sym_checksum); i++) { + struct sym_checksum *sym_checksum; + struct reloc *reloc; + struct symbol *sym; + + sym_checksum = (struct sym_checksum *)sec->data->d_buf + i; + + reloc = find_reloc_by_dest(elf, sec, i * sizeof(*sym_checksum)); + if (!reloc) { + ERROR("can't find reloc for sym_checksum[%d]", i); + return -1; + } + + sym = reloc->sym; + + if (is_sec_sym(sym)) { + ERROR("not sure how to handle section %s", sym->name); + return -1; + } + + if (is_func_sym(sym) || is_object_sym(sym)) + sym->csum.checksum = sym_checksum->checksum; + } + + return 0; +} + +static struct symbol *first_file_symbol(struct elf *elf) +{ + struct symbol *sym; + + for_each_sym(elf, sym) { + if (is_file_sym(sym)) + return sym; + } + + return NULL; +} + +static struct symbol *next_file_symbol(struct elf *elf, struct symbol *sym) +{ + for_each_sym_continue(elf, sym) { + if (is_file_sym(sym)) + return sym; + } + + return NULL; +} + +/* + * Certain static local variables should never be correlated. They will be + * used in place rather than referencing the originals. + */ +static bool is_uncorrelated_static_local(struct symbol *sym) +{ + static const char * const vars[] = { + "__already_done", + "__func__", + "__key", + "__warned", + "_entry", + "_entry_ptr", + "_rs", + "descriptor", + "CSWTCH", + }; + const char *dot; + + if (!is_object_sym(sym) || !is_local_sym(sym)) + return false; + + /* WARN_ONCE, etc */ + if (!strcmp(sym->sec->name, ".data..once")) + return true; + + dot = strchr(sym->name, '.'); + if (!dot) + return false; + + for (int i = 0; i < ARRAY_SIZE(vars); i++) { + size_t len = strlen(vars[i]); + + /* GCC: <var>.<id> */ + if (strstarts(sym->name, vars[i]) && (sym->name[len] == '.')) + return true; + + /* Clang: <func>.<var>[.<id>] */ + if (strstarts(dot + 1, vars[i]) && + (dot[1 + len] == '.' || dot[1 + len] == '\0')) + return true; + } + + return false; +} + +/* + * .L symbols are assembler-local labels not present in kallsyms. They must + * never become KLP relocations; instead their data is cloned into the patch + * module. This covers .Ltmp* (Clang temp labels), .L__const.* (Clang local + * constants), and any other assembler-local pattern. + */ +static bool is_local_label(struct symbol *sym) +{ + return strstarts(sym->name, ".L"); +} + +static bool is_special_section(struct section *sec) +{ + static const char * const specials[] = { + ".altinstructions", + ".kcfi_traps", + ".smp_locks", + "__bug_table", + "__ex_table", + "__jump_table", + "__mcount_loc", + + /* + * Extract .static_call_sites here to inherit non-module + * preferential treatment. The later static call processing + * during klp module build will be skipped when it sees this + * section already exists. + */ + ".static_call_sites", + }; + + static const char * const non_special_discards[] = { + ".discard.addressable", + ".discard.sym_checksum", + }; + + if (is_text_sec(sec)) + return false; + + for (int i = 0; i < ARRAY_SIZE(specials); i++) { + if (!strcmp(sec->name, specials[i])) + return true; + } + + /* Most .discard data sections are special */ + for (int i = 0; i < ARRAY_SIZE(non_special_discards); i++) { + if (!strcmp(sec->name, non_special_discards[i])) + return false; + } + + return strstarts(sec->name, ".discard."); +} + +/* + * These sections are referenced by special sections but aren't considered + * special sections themselves. + */ +static bool is_special_section_aux(struct section *sec) +{ + static const char * const specials_aux[] = { + ".altinstr_replacement", + ".altinstr_aux", + }; + + for (int i = 0; i < ARRAY_SIZE(specials_aux); i++) { + if (!strcmp(sec->name, specials_aux[i])) + return true; + } + + return false; +} + +/* + * Symbols created by ___ADDRESSABLE() are only used to convince the toolchain + * not to optimize out the referenced symbol. + */ +static bool is_addressable_sym(struct symbol *sym) +{ + return !strcmp(sym->sec->name, ".discard.addressable"); +} + +/* + * ABS symbols are typically assembly .set/.equ constants which are never + * referenced by relocations. (Exclude FILE symbols which are also SHN_ABS.) + */ +static bool is_abs_sym(struct symbol *sym) +{ + return sym->sym.st_shndx == SHN_ABS && !is_file_sym(sym); +} + +static bool is_initcall_sym(struct symbol *sym) +{ + return strstarts(sym->name, "__initcall__") || + strstarts(sym->name, "__initstub__"); +} + +/* + * Some .rodata is anonymous and can't be correlated due to there being no + * symbol names. + * + * The .rodata.cst* sections aren't technically anonymous, they're SHF_MERGE + * constant pool sections containing small fixed-size data (lookup tables, + * bitmasks) which are only read by value, so pointer equivalence isn't needed. + * They are typically referenced by UBSAN data sections. + */ +static bool is_anonymous_rodata(struct symbol *sym) +{ + return is_rodata_sec(sym->sec) && + (!is_object_sym(sym) || strstarts(sym->sec->name, ".rodata.cst")); +} + +/* + * These symbols should never be correlated, so their local patched versions + * are used instead of linking to the originals. + */ +static bool dont_correlate(struct symbol *sym) +{ + return is_file_sym(sym) || + is_null_sym(sym) || + is_sec_sym(sym) || + is_abs_sym(sym) || + is_prefix_func(sym) || + is_uncorrelated_static_local(sym) || + is_local_label(sym) || + is_string_sec(sym->sec) || + is_anonymous_rodata(sym) || + is_initcall_sym(sym) || + is_addressable_sym(sym) || + is_special_section(sym->sec) || + is_special_section_aux(sym->sec); +} + +static const char *llvm_suffix(const char *name) +{ + return strstr(name, ".llvm."); +} + +static bool is_llvm_sym(struct symbol *sym) +{ + return llvm_suffix(sym->name); +} + +/* + * Determine if two symbols have compatible source file origins: + * + * - If both symbols are local, only return true if they belong to the same + * ELF file symbol. + * + * - If both symbols are global, always return true, as globals don't have + * file associations. + * + * - If they have different scopes, also return true, as the patch might have + * changed the symbol's scope. + * + * Works for both same-ELF (direct pointer compare) and cross-ELF + * (compare via file->twin) cases. + */ +static bool maybe_same_file(struct symbol *sym1, struct symbol *sym2) +{ + if (!sym1->file || !sym2->file) + return true; + if (sym1->file == sym2->file) + return true; + return sym1->file->twin == sym2->file; +} + +/* + * Similar to maybe_same_file(), but strict: no scope changes allowed. + * + * Works for both same-ELF (direct pointer compare) and cross-ELF + * (compare via file->twin) cases. + */ +static bool same_file(struct symbol *sym1, struct symbol *sym2) +{ + if (llvm_suffix(sym1->name) && llvm_suffix(sym2->name)) + return true; + if (!sym1->file && !sym2->file) + return true; + if (!sym1->file || !sym2->file) + return false; + if (sym1->file == sym2->file) + return true; + return sym1->file->twin == sym2->file; +} + +/* + * Is it a local symbol, or at least was it local in the translation unit + * before LLVM promoted it? + */ +static bool is_tu_local_sym(struct symbol *sym) +{ + return is_local_sym(sym) || is_llvm_sym(sym); +} + +/* + * Try to find sym1's twin in patched using deterministic matching. + * + * Multiple symbols can share a demangled name (e.g., static functions in + * different TUs). This function counts same-named candidates through a + * funnel of progressively tighter filters. Each level is a strict subset + * of the previous one. + * + * The widest level that yields a 1:1 match wins. Narrower levels are only + * needed when the wider level is ambiguous (count > 1). + * + * Candidates are pre-filtered by maybe_same_file(), which narrows most + * local symbols to their own TU. For example, 19 different static + * type_show() functions across vmlinux.o each see only one candidate after + * pre-filtering, so they match immediately at Level 1. + * + * Level 1 (name): Works when the demangled name is unique after + * pre-filtering. Handles most symbols: unique globals like copy_signal(), + * or per-TU locals like pcspkr_probe(). + * + * Level 2 (scope): Filters by local-vs-global (TU-local-vs-not). Example: + * parse_header() exists as both a static and a global function. Level 1 + * sees both (same demangled name), but Level 2 separates them by scope. + * + * Level 3 (file): Strict file matching via same_file(), which rejects scope + * changes. Example: LLVM-promoted foo.llvm.12345 (global, no FILE symbol) + * vs genuine local foo (has FILE symbol). Both are TU-local so Level 2 + * can't distinguish them, but same_file() rejects the pair because one has + * a file association and the other doesn't. + * + * Level 4 (checksum): Distinguishes by function checksum. Example: + * usb_devnode.llvm.AAA and usb_devnode.llvm.BBB are two LLVM-promoted + * functions from different TUs with the same demangled name. After a TU + * change, the .llvm. hashes change but the functions themselves may be + * unchanged. Level 4 matches each to the patched candidate with the + * same checksum. + */ +static struct symbol *find_twin(struct elfs *e, struct symbol *sym1) +{ + struct symbol *name_last = NULL, *scope_last = NULL, + *file_last = NULL, *csum_last = NULL; + unsigned int name_orig = 0, name_patched = 0; + unsigned int scope_orig = 0, scope_patched = 0; + unsigned int file_orig = 0, file_patched = 0; + unsigned int csum_orig = 0, csum_patched = 0; + struct symbol *sym2, *match = NULL; + + /* Count orig candidates */ + for_each_sym_by_demangled_name(e->orig, sym1->demangled_name, sym2) { + if (sym2->twin || sym1->type != sym2->type || sym2->dont_correlate || + (!maybe_same_file(sym1, sym2))) + continue; + + /* Level 1: name match (widest filter) */ + name_orig++; + + /* Level 2: scope (scope changes allowed) */ + if (is_tu_local_sym(sym1) != is_tu_local_sym(sym2)) + continue; + scope_orig++; + + /* Level 3: file (scope changes disallowed) */ + if (!same_file(sym1, sym2)) + continue; + file_orig++; + + /* Level 4: checksum (unchanged symbols) */ + if (sym1->len != sym2->len || !sym1->csum.checksum || + sym1->csum.checksum != sym2->csum.checksum) + continue; + csum_orig++; + } + + /* Count patched candidates */ + for_each_sym_by_demangled_name(e->patched, sym1->demangled_name, sym2) { + if (sym2->twin || sym1->type != sym2->type || sym2->dont_correlate || + !maybe_same_file(sym1, sym2)) + continue; + + /* Level 1 */ + name_patched++; + name_last = sym2; + + /* Level 2 */ + if (is_tu_local_sym(sym1) != is_tu_local_sym(sym2)) + continue; + scope_patched++; + scope_last = sym2; + + /* Level 3 */ + if (!same_file(sym1, sym2)) + continue; + file_patched++; + file_last = sym2; + + /* Level 4 */ + if (sym1->len != sym2->len || !sym1->csum.checksum || + sym1->csum.checksum != sym2->csum.checksum) + continue; + csum_patched++; + csum_last = sym2; + } + + /* Return the widest level that yields a unique (1:1) match */ + if (name_orig == 1 && name_patched == 1) + match = name_last; + else if (scope_orig == 1 && scope_patched == 1) + match = scope_last; + else if (file_orig == 1 && file_patched == 1) + match = file_last; + else if (csum_orig == 1 && csum_patched == 1) + match = csum_last; + + if (!match) + return NULL; + + if (name_orig != 1 || name_patched != 1) + dbg_correlate("find_twin(): %s%s -> %s%s", + sym1->name, is_func_sym(sym1) ? "()" : "", + match->name, is_func_sym(match) ? "()" : ""); + + return match; +} + +struct llvm_suffix_pair { + struct hlist_node hash; + const char *orig; + const char *patched; +}; + +static DECLARE_HASHTABLE(suffix_map, 7); + +/* + * Build a mapping of known orig-to-patched LLVM suffixes based on + * already-correlated symbol pairs. All promoted symbols from the same TU + * share the same .llvm.<hash> suffix, so one correlated pair seeds the map + * for the entire TU. + */ +static int update_suffix_map(struct elf *elf) +{ + struct llvm_suffix_pair *entry; + struct symbol *sym; + + for_each_sym(elf, sym) { + const char *s1, *s2; + bool found; + + if (!sym->twin) + continue; + + s1 = llvm_suffix(sym->name); + s2 = llvm_suffix(sym->twin->name); + + if (!s1 || !s2) + continue; + + found = false; + hash_for_each_possible(suffix_map, entry, hash, str_hash(s1)) { + if (!strcmp(entry->orig, s1)) { + found = true; + break; + } + } + if (found) + continue; + + entry = calloc(1, sizeof(*entry)); + if (!entry) { + ERROR_GLIBC("calloc"); + return -1; + } + + entry->orig = s1; + entry->patched = s2; + hash_add(suffix_map, &entry->hash, str_hash(s1)); + } + + return 0; +} + +/* + * Match by translating the symbol's .llvm.<hash> suffix through the suffix + * map to find the corresponding hash suffix for the patched object. + * + * Example: In the original kernel, TU drivers/base/core.c contains + * foo.llvm.12345 and bar.llvm.12345 (same TU, same hash). After patching, + * they become foo.llvm.67890 and bar.llvm.67890. If foo was already + * correlated by find_twin() (e.g., unique by name), the suffix map records + * .llvm.12345 -> .llvm.67890. When processing bar.llvm.12345, this + * function looks up .llvm.12345, gets .llvm.67890, constructs the name + * bar.llvm.67890, and finds the match. + */ +static struct symbol *find_twin_suffixed(struct elf *elf, struct symbol *sym1) +{ + const char *suffix, *patched_suffix = NULL; + struct symbol *sym2, *match = NULL; + char name[SYM_NAME_LEN]; + struct llvm_suffix_pair *entry; + int count = 0; + + suffix = llvm_suffix(sym1->name); + if (!suffix) + return NULL; + + hash_for_each_possible(suffix_map, entry, hash, str_hash(suffix)) { + if (!strcmp(entry->orig, suffix)) { + patched_suffix = entry->patched; + break; + } + } + if (!patched_suffix) + return NULL; + + if (snprintf_check(name, SYM_NAME_LEN, "%s%s", + sym1->demangled_name, patched_suffix)) + return NULL; + + for_each_sym_by_name(elf, name, sym2) { + if (sym2->twin || sym1->type != sym2->type || sym2->dont_correlate) + continue; + count++; + match = sym2; + } + + if (count != 1) + return NULL; + + dbg_correlate("find_suffixed_twin(): %s%s -> %s%s", + sym1->name, is_func_sym(sym1) ? "()" : "", + match->name, is_func_sym(match) ? "()" : ""); + + return match; +} + +/* + * Last-resort positional matching. + * + * Finds a symbol with the same position in the symbol table among + * same-demangled-name candidates, similar to livepatch sympos. Note that + * LLVM-promoted symbols are globals, which come after locals in the symbol + * table, so we have to be careful not to compare different scopes. + * + * Example: arch/x86/events/intel/core.c defines many __quirk variables via + * X86_MATCH_*() macros. In the symbol table they appear as __quirk.90, + * __quirk.97, __quirk.101, etc., all with demangled name __quirk, same + * scope, and same FILE symbol. No deterministic filter can distinguish + * them, so they're matched by position: the 1st __quirk in orig matches the + * 1st in patched, the 2nd matches the 2nd, etc. + * + * This is less deterministic than the other strategies, so it's done last. + */ +static struct symbol *find_twin_positional(struct elfs *e, struct symbol *sym1) +{ + unsigned int idx_orig = 0, idx_patched = 0; + unsigned int sym1_pos = 0; + struct symbol *sym2, *match = NULL; + + for_each_sym_by_demangled_name(e->orig, sym1->demangled_name, sym2) { + if (sym2->twin || sym1->type != sym2->type || sym2->dont_correlate || + !maybe_same_file(sym1, sym2)) + continue; + if (is_tu_local_sym(sym1) != is_tu_local_sym(sym2) || + is_llvm_sym(sym1) != is_llvm_sym(sym2)) + continue; + if (sym1 == sym2) + sym1_pos = idx_orig; + idx_orig++; + } + + for_each_sym_by_demangled_name(e->patched, sym1->demangled_name, sym2) { + if (sym2->twin || sym1->type != sym2->type || sym2->dont_correlate || + !maybe_same_file(sym1, sym2)) + continue; + if (is_tu_local_sym(sym1) != is_tu_local_sym(sym2) || + is_llvm_sym(sym1) != is_llvm_sym(sym2)) + continue; + if (idx_patched == sym1_pos) + match = sym2; + idx_patched++; + } + + if (idx_orig != idx_patched) + return NULL; + + dbg_correlate("find_twin_positional(): %s%s -> %s%s", + sym1->name, is_func_sym(sym1) ? "()" : "", + match->name, is_func_sym(match) ? "()" : ""); + + return match; +} + +/* + * Correlate symbols between the orig and patched objects. This is a + * prerequisite for detecting changed functions, as well as for properly + * translating relocations so they point to the correct symbol. + */ +static int correlate_symbols(struct elfs *e) +{ + struct symbol *file1_sym, *file2_sym; + struct symbol *sym1, *sym2; + bool progress; + + for_each_sym(e->orig, sym1) + sym1->dont_correlate = dont_correlate(sym1); + for_each_sym(e->patched, sym2) + sym2->dont_correlate = dont_correlate(sym2); + + /* Correlate FILE symbols */ + file1_sym = first_file_symbol(e->orig); + file2_sym = first_file_symbol(e->patched); + + for (; ; file1_sym = next_file_symbol(e->orig, file1_sym), + file2_sym = next_file_symbol(e->patched, file2_sym)) { + + if (!file1_sym && file2_sym) { + ERROR("FILE symbol mismatch: NULL != %s", file2_sym->name); + return -1; + } + + if (file1_sym && !file2_sym) { + ERROR("FILE symbol mismatch: %s != NULL", file1_sym->name); + return -1; + } + + if (!file1_sym) + break; + + if (strcmp(file1_sym->name, file2_sym->name)) { + ERROR("FILE symbol mismatch: %s != %s", file1_sym->name, file2_sym->name); + return -1; + } + + file1_sym->twin = file2_sym; + file2_sym->twin = file1_sym; + } + + + /* + * Correlate in two phases: loop deterministic levels until no more + * progress, then use positional fallback for the rest. This prevents + * the nondeterministic positional matching from stealing symbols that + * have deterministic matches. + */ + hash_init(suffix_map); + do { + progress = false; + for_each_sym(e->orig, sym1) { + if (sym1->twin || sym1->dont_correlate) + continue; + sym2 = find_twin(e, sym1); + if (!sym2) + continue; + sym1->twin = sym2; + sym2->twin = sym1; + progress = true; + } + + if (update_suffix_map(e->orig)) + return -1; + + for_each_sym(e->orig, sym1) { + if (sym1->twin || sym1->dont_correlate) + continue; + sym2 = find_twin_suffixed(e->patched, sym1); + if (!sym2) + continue; + sym1->twin = sym2; + sym2->twin = sym1; + progress = true; + } + } while (progress); + + for_each_sym(e->orig, sym1) { + if (sym1->twin || sym1->dont_correlate) + continue; + sym2 = find_twin_positional(e, sym1); + if (!sym2) + continue; + sym1->twin = sym2; + sym2->twin = sym1; + } + + for_each_sym(e->orig, sym1) { + if (sym1->twin || sym1->dont_correlate) + continue; + WARN("no correlation: %s", sym1->name); + } + + return 0; +} + +/* "sympos" is used by livepatch to disambiguate duplicate symbol names */ +static unsigned long find_sympos(struct elf *elf, struct symbol *sym) +{ + bool vmlinux = str_ends_with(objname, "vmlinux.o"); + unsigned long sympos = 0, nr_matches = 0; + bool has_dup = false; + struct symbol *s; + + if (sym->bind != STB_LOCAL) + return 0; + + if (vmlinux && is_func_sym(sym)) { + /* + * HACK: Unfortunately, symbol ordering can differ between + * vmlinux.o and vmlinux due to the linker script emitting + * .text.unlikely* before .text*. Count .text.unlikely* first. + * + * TODO: Disambiguate symbols more reliably (checksums?) + */ + for_each_sym(elf, s) { + if (strstarts(s->sec->name, ".text.unlikely") && + !strcmp(s->name, sym->name)) { + nr_matches++; + if (s == sym) + sympos = nr_matches; + else + has_dup = true; + } + } + for_each_sym(elf, s) { + if (!strstarts(s->sec->name, ".text.unlikely") && + !strcmp(s->name, sym->name)) { + nr_matches++; + if (s == sym) + sympos = nr_matches; + else + has_dup = true; + } + } + } else { + for_each_sym(elf, s) { + if (!strcmp(s->name, sym->name)) { + nr_matches++; + if (s == sym) + sympos = nr_matches; + else + has_dup = true; + } + } + } + + if (!sympos) { + ERROR("can't find sympos for %s", sym->name); + return ULONG_MAX; + } + + return has_dup ? sympos : 0; +} + +static int clone_sym_relocs(struct elfs *e, struct symbol *patched_sym); + +static struct symbol *__clone_symbol(struct elf *elf, struct symbol *patched_sym, + bool data_too) +{ + struct section *out_sec = NULL; + unsigned long offset = 0; + struct symbol *out_sym; + + if (data_too && !is_undef_sym(patched_sym)) { + struct section *patched_sec = patched_sym->sec; + + out_sec = find_section_by_name(elf, patched_sec->name); + if (!out_sec) { + out_sec = elf_create_section(elf, patched_sec->name, 0, + patched_sec->sh.sh_entsize, + patched_sec->sh.sh_type, + patched_sec->sh.sh_addralign, + patched_sec->sh.sh_flags); + if (!out_sec) + return NULL; + } + + if (is_string_sec(patched_sym->sec)) { + out_sym = elf_create_section_symbol(elf, out_sec); + if (!out_sym) + return NULL; + + goto sym_created; + } + + if (!is_sec_sym(patched_sym)) + offset = ALIGN(sec_size(out_sec), out_sec->sh.sh_addralign); + + if (patched_sym->len || is_sec_sym(patched_sym)) { + void *data = NULL; + size_t size; + + /* bss doesn't have data */ + if (patched_sym->sec->data && patched_sym->sec->data->d_buf) + data = patched_sym->sec->data->d_buf + patched_sym->offset; + + if (is_sec_sym(patched_sym)) + size = sec_size(patched_sym->sec); + else + size = patched_sym->len; + + if (!elf_add_data(elf, out_sec, data, size)) + return NULL; + } + } + + out_sym = elf_create_symbol(elf, patched_sym->name, out_sec, + patched_sym->bind, patched_sym->type, + offset, patched_sym->len); + if (!out_sym) + return NULL; + +sym_created: + patched_sym->clone = out_sym; + out_sym->clone = patched_sym; + + return out_sym; +} + +static const char *sym_type(struct symbol *sym) +{ + switch (sym->type) { + case STT_NOTYPE: return "NOTYPE"; + case STT_OBJECT: return "OBJECT"; + case STT_FUNC: return "FUNC"; + case STT_SECTION: return "SECTION"; + case STT_FILE: return "FILE"; + default: return "UNKNOWN"; + } +} + +static const char *sym_bind(struct symbol *sym) +{ + switch (sym->bind) { + case STB_LOCAL: return "LOCAL"; + case STB_GLOBAL: return "GLOBAL"; + case STB_WEAK: return "WEAK"; + default: return "UNKNOWN"; + } +} + +/* + * Copy a symbol to the output object, optionally including its data and + * relocations. + */ +static struct symbol *clone_symbol(struct elfs *e, struct symbol *patched_sym, + bool data_too) +{ + struct symbol *pfx; + + if (patched_sym->clone) + return patched_sym->clone; + + dbg_clone("%s%s", patched_sym->name, data_too ? " [+DATA]" : ""); + + /* Make sure the prefix gets cloned first */ + if (is_func_sym(patched_sym) && data_too) { + pfx = get_func_prefix(patched_sym); + if (pfx) + clone_symbol(e, pfx, true); + } + + if (!__clone_symbol(e->out, patched_sym, data_too)) + return NULL; + + if (data_too && clone_sym_relocs(e, patched_sym)) + return NULL; + + return patched_sym->clone; +} + +static void mark_included_function(struct symbol *func) +{ + struct symbol *pfx; + + func->included = 1; + + /* Include prefix function */ + pfx = get_func_prefix(func); + if (pfx) + pfx->included = 1; + + /* Make sure .cold parent+child always stay together */ + if (func->cfunc && func->cfunc != func) + func->cfunc->included = 1; + if (func->pfunc && func->pfunc != func) + func->pfunc->included = 1; +} + +/* + * Copy all changed functions (and their dependencies) from the patched object + * to the output object. + */ +static int mark_changed_functions(struct elfs *e) +{ + struct symbol *orig_sym, *patched_sym; + bool changed = false; + + /* Find changed functions */ + for_each_sym(e->orig, orig_sym) { + if (orig_sym->dont_correlate) + continue; + + patched_sym = orig_sym->twin; + if (!patched_sym) + continue; + + if (orig_sym->csum.checksum != patched_sym->csum.checksum) { + if (!is_func_sym(orig_sym)) { + ERROR("changed data: %s", orig_sym->name); + return -1; + } + + patched_sym->changed = 1; + mark_included_function(patched_sym); + changed = true; + } + } + + /* Find added functions and print them */ + for_each_sym(e->patched, patched_sym) { + if (!is_func_sym(patched_sym) || patched_sym->dont_correlate) + continue; + + if (!patched_sym->twin) { + printf("%s: new function: %s\n", objname, patched_sym->name); + mark_included_function(patched_sym); + changed = true; + } + } + + /* Print changed functions */ + for_each_sym(e->patched, patched_sym) { + if (patched_sym->changed) + printf("%s: changed function: %s\n", objname, patched_sym->name); + } + + return !changed ? 1 : 0; +} + +static int clone_included_functions(struct elfs *e) +{ + struct symbol *patched_sym; + + for_each_sym(e->patched, patched_sym) { + if (patched_sym->included) { + if (!clone_symbol(e, patched_sym, true)) + return -1; + } + } + + return 0; +} + +static struct export *find_export(struct symbol *sym) +{ + struct export *export; + + hash_for_each_possible(exports, export, hash, str_hash(sym->name)) { + if (!strcmp(export->sym, sym->name)) + return export; + } + + return NULL; +} + +static const char *__find_modname(struct elfs *e) +{ + struct section *sec; + char *name; + + sec = find_section_by_name(e->orig, ".modinfo"); + if (!sec) { + ERROR("missing .modinfo section"); + return NULL; + } + + name = memmem(sec->data->d_buf, sec_size(sec), "\0name=", 6); + if (name) + return name + 6; + + name = strdup(e->orig->name); + if (!name) { + ERROR_GLIBC("strdup"); + return NULL; + } + + for (char *c = name; *c; c++) { + if (*c == '/') + name = c + 1; + else if (*c == '-') + *c = '_'; + else if (*c == '.') { + *c = '\0'; + break; + } + } + + return name; +} + +/* Get the object's module name as defined by the kernel (and klp_object) */ +static const char *find_modname(struct elfs *e) +{ + const char *modname; + + if (e->modname) + return e->modname; + + modname = __find_modname(e); + e->modname = modname; + return modname; +} + +/* + * Copying a function from its native compiled environment to a kernel module + * removes its natural access to local functions/variables and unexported + * globals. References to such symbols need to be converted to KLP relocs so + * the kernel arch relocation code knows to apply them and where to find the + * symbols. Particularly, duplicate static symbols need to be disambiguated. + */ +static bool klp_reloc_needed(struct reloc *patched_reloc) +{ + struct symbol *patched_sym = patched_reloc->sym; + struct export *export; + + /* no external symbol to reference */ + if (patched_sym->dont_correlate) + return false; + + /* For included functions, a regular reloc will do. */ + if (patched_sym->included) + return false; + + /* + * If exported by a module, it has to be a klp reloc. Thanks to the + * clusterfunk that is late module patching, the patch module is + * allowed to be loaded before any modules it depends on. + * + * If exported by vmlinux, a normal reloc will do. + */ + export = find_export(patched_sym); + if (export) + return strcmp(export->mod, "vmlinux"); + + if (!patched_sym->twin) { + /* + * Presumably the symbol and its reference were added by the + * patch. The symbol could be defined in this .o or in another + * .o in the patch module. + * + * This check needs to be *after* the export check due to the + * possibility of the patch adding a new UNDEF reference to an + * exported symbol. + */ + return false; + } + + /* Unexported symbol which lives in the original vmlinux or module. */ + return true; +} + +/* Return -1 error, 0 success, 1 skip */ +static int convert_reloc_sym_to_secsym(struct elf *elf, struct reloc *reloc) +{ + struct symbol *sym = reloc->sym; + struct section *sec = sym->sec; + + if (is_sec_sym(sym)) + return 0; + + if (!sec->sym && !elf_create_section_symbol(elf, sec)) + return -1; + + reloc->sym = sec->sym; + set_reloc_sym(elf, reloc, sec->sym->idx); + set_reloc_addend(elf, reloc, sym->offset + reloc_addend(reloc)); + return 0; +} + +/* Return -1 error, 0 success, 1 skip */ +static int convert_reloc_secsym_to_sym(struct elf *elf, struct reloc *reloc) +{ + struct symbol *sym = reloc->sym; + struct section *sec = sym->sec; + + if (!is_sec_sym(sym)) + return 0; + + /* If the symbol has a dedicated section, it's easy to find */ + sym = find_symbol_by_offset(sec, 0); + if (sym && sym->len == sec_size(sec)) + goto found_sym; + + /* No dedicated section; find the symbol manually */ + sym = find_symbol_containing_inclusive(sec, arch_adjusted_addend(reloc)); + if (!sym) { + /* + * This is presumably an .altinstr_replacement section which is + * empty due to it only having zero-length replacement(s). + */ + if (!sec_size(sec)) + return 1; + + /* + * .rodata is a mixed bag of named objects and anonymous data. + * + * Convert section symbol references to named object symbols + * when possible, to preserve pointer identity for const + * structs like file_operations. Otherwise a section symbol is + * fine. + */ + if (is_rodata_sec(sec)) + return 0; + + /* + * This can happen for special section references to weak code + * whose symbol has been stripped by the linker. + */ + return -1; + } + +found_sym: + reloc->sym = sym; + set_reloc_sym(elf, reloc, sym->idx); + set_reloc_addend(elf, reloc, reloc_addend(reloc) - sym->offset); + return 0; +} + +/* + * Sections with anonymous or uncorrelated data (strings, UBSAN data, Clang + * anonymous constants) need section symbol references. + */ +static bool is_uncorrelated_section(struct section *sec) +{ + return is_string_sec(sec) || + strstarts(sec->name, ".data..Lubsan") || /* GCC */ + strstarts(sec->name, ".data..L__unnamed_") || /* Clang */ + strstarts(sec->name, ".data..Lanon."); /* Clang */ +} + +/* + * Convert a relocation symbol reference to the needed format: either a section + * symbol or the underlying symbol itself. Return -1 error, 0 success, 1 skip. + */ +static int convert_reloc_sym(struct elf *elf, struct reloc *reloc) +{ + struct section *sec = reloc->sym->sec; + + if (reloc_type(reloc) == R_NONE) + return 1; + + if (is_uncorrelated_section(sec)) + return convert_reloc_sym_to_secsym(elf, reloc); + + /* Everything else: references should use named symbols. */ + return convert_reloc_secsym_to_sym(elf, reloc); +} + +/* + * Convert a regular relocation to a klp relocation (sort of). + */ +static int clone_reloc_klp(struct elfs *e, struct reloc *patched_reloc, + struct section *sec, unsigned long offset, + struct export *export) +{ + struct symbol *patched_sym = patched_reloc->sym; + s64 addend = reloc_addend(patched_reloc); + const char *sym_modname, *sym_orig_name; + static struct section *klp_relocs; + struct symbol *sym, *klp_sym; + unsigned long klp_reloc_off; + char sym_name[SYM_NAME_LEN]; + struct klp_reloc klp_reloc; + unsigned long sympos; + + if (!patched_sym->twin) { + ERROR("unexpected klp reloc for new symbol %s", patched_sym->name); + return -1; + } + + /* + * Keep the original reloc intact for now to avoid breaking objtool run + * which relies on proper relocations for many of its features. This + * will be disabled later by "objtool klp post-link". + * + * Convert it to UNDEF (and WEAK to avoid modpost warnings). + */ + + sym = patched_sym->clone; + if (!sym) { + /* STB_WEAK: avoid modpost undefined symbol warnings */ + sym = elf_create_symbol(e->out, patched_sym->name, NULL, + STB_WEAK, patched_sym->type, 0, 0); + if (!sym) + return -1; + + patched_sym->clone = sym; + sym->clone = patched_sym; + } + + if (!elf_create_reloc(e->out, sec, offset, sym, addend, reloc_type(patched_reloc))) + return -1; + + /* + * Create the KLP symbol. + */ + + if (export) { + sym_modname = export->mod; + sym_orig_name = export->sym; + sympos = 0; + } else { + sym_modname = find_modname(e); + if (!sym_modname) + return -1; + + sym_orig_name = patched_sym->twin->name; + sympos = find_sympos(e->orig, patched_sym->twin); + if (sympos == ULONG_MAX) + return -1; + } + + /* symbol format: .klp.sym.modname.sym_name,sympos */ + if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_SYM_PREFIX "%s.%s,%ld", + sym_modname, sym_orig_name, sympos)) + return -1; + + klp_sym = find_symbol_by_name(e->out, sym_name); + if (!klp_sym) { + __dbg_clone("%s", sym_name); + + /* STB_WEAK: avoid modpost undefined symbol warnings */ + klp_sym = elf_create_symbol(e->out, sym_name, NULL, + STB_WEAK, patched_sym->type, 0, 0); + if (!klp_sym) + return -1; + } + + /* + * Create the __klp_relocs entry. This will be converted to an actual + * KLP rela by "objtool klp post-link". + * + * This intermediate step is necessary to prevent corruption by the + * linker, which doesn't know how to properly handle two rela sections + * applying to the same base section. + */ + + if (!klp_relocs) { + klp_relocs = elf_create_section(e->out, KLP_RELOCS_SEC, 0, + 0, SHT_PROGBITS, 8, SHF_ALLOC); + if (!klp_relocs) + return -1; + } + + klp_reloc_off = sec_size(klp_relocs); + memset(&klp_reloc, 0, sizeof(klp_reloc)); + + klp_reloc.type = reloc_type(patched_reloc); + if (!elf_add_data(e->out, klp_relocs, &klp_reloc, sizeof(klp_reloc))) + return -1; + + /* klp_reloc.offset */ + if (!sec->sym && !elf_create_section_symbol(e->out, sec)) + return -1; + + if (!elf_create_reloc(e->out, klp_relocs, + klp_reloc_off + offsetof(struct klp_reloc, offset), + sec->sym, offset, R_ABS64)) + return -1; + + /* klp_reloc.sym */ + if (!elf_create_reloc(e->out, klp_relocs, + klp_reloc_off + offsetof(struct klp_reloc, sym), + klp_sym, addend, R_ABS64)) + return -1; + + return 0; +} + +#define dbg_clone_reloc(sec, offset, patched_sym, addend, export, klp) \ + dbg_clone("%s+0x%lx: %s%s0x%lx [%s%s%s%s%s%s]", \ + sec->name, offset, patched_sym->name, \ + addend >= 0 ? "+" : "-", labs(addend), \ + sym_type(patched_sym), \ + is_sec_sym(patched_sym) ? "" : " ", \ + is_sec_sym(patched_sym) ? "" : sym_bind(patched_sym), \ + is_undef_sym(patched_sym) ? " UNDEF" : "", \ + export ? " EXPORTED" : "", \ + klp ? " KLP" : "") + +/* Copy a reloc and its symbol to the output object */ +static int clone_reloc(struct elfs *e, struct reloc *patched_reloc, + struct section *sec, unsigned long offset) +{ + struct symbol *patched_sym = patched_reloc->sym; + struct export *export = find_export(patched_sym); + long addend = reloc_addend(patched_reloc); + struct symbol *out_sym; + bool klp; + + klp = klp_reloc_needed(patched_reloc); + + dbg_clone_reloc(sec, offset, patched_sym, addend, export, klp); + + if (klp) { + if (clone_reloc_klp(e, patched_reloc, sec, offset, export)) + return -1; + + return 0; + } + + /* + * Why !export sets 'data_too': + * + * Unexported non-klp symbols need to live in the patch module, + * otherwise there will be unresolved symbols. Notably, this includes: + * + * - New functions/data + * - String sections + * - Special section entries + * - Uncorrelated static local variables + * - UBSAN sections + */ + out_sym = clone_symbol(e, patched_sym, patched_sym->included || !export); + if (!out_sym) + return -1; + + /* + * For strings, all references use section symbols, thanks to + * convert_reloc_sym(). clone_symbol() has cloned an empty + * version of the string section. Now copy the string itself. + */ + if (is_string_sec(patched_sym->sec)) { + const char *str = patched_sym->sec->data->d_buf + addend; + + __dbg_clone("\"%s\"", escape_str(str)); + + addend = elf_add_string(e->out, out_sym->sec, str); + if (addend == -1) + return -1; + } + + if (!elf_create_reloc(e->out, sec, offset, out_sym, addend, + reloc_type(patched_reloc))) + return -1; + + return 0; +} + +/* Copy all relocs needed for a symbol's contents */ +static int clone_sym_relocs(struct elfs *e, struct symbol *patched_sym) +{ + struct section *patched_rsec = patched_sym->sec->rsec; + struct reloc *patched_reloc; + unsigned long start, end; + struct symbol *out_sym; + + out_sym = patched_sym->clone; + if (!out_sym) { + ERROR("no clone for %s", patched_sym->name); + return -1; + } + + if (!patched_rsec) + return 0; + + if (!is_sec_sym(patched_sym) && !patched_sym->len) + return 0; + + if (is_string_sec(patched_sym->sec)) + return 0; + + if (is_sec_sym(patched_sym)) { + start = 0; + end = sec_size(patched_sym->sec); + } else { + start = patched_sym->offset; + end = start + patched_sym->len; + } + + for_each_reloc(patched_rsec, patched_reloc) { + unsigned long offset; + int ret; + + if (reloc_offset(patched_reloc) < start || + reloc_offset(patched_reloc) >= end) + continue; + + /* + * Skip any reloc referencing .altinstr_aux. Its code is + * always patched by alternatives. See ALTERNATIVE_TERNARY(). + */ + if (patched_reloc->sym->sec && + !strcmp(patched_reloc->sym->sec->name, ".altinstr_aux")) + continue; + + ret = convert_reloc_sym(e->patched, patched_reloc); + if (ret < 0) { + ERROR_FUNC(patched_rsec->base, reloc_offset(patched_reloc), + "failed to convert reloc sym '%s' to its proper format", + patched_reloc->sym->name); + return -1; + } + if (ret > 0) + continue; + + offset = out_sym->offset + (reloc_offset(patched_reloc) - patched_sym->offset); + + if (clone_reloc(e, patched_reloc, out_sym->sec, offset)) + return -1; + } + return 0; + +} + +static int create_fake_symbol(struct elf *elf, struct section *sec, + unsigned long offset, size_t size) +{ + char name[SYM_NAME_LEN]; + unsigned int type; + static int ctr; + char *c; + + if (snprintf_check(name, SYM_NAME_LEN, "%s_%d", sec->name, ctr++)) + return -1; + + for (c = name; *c; c++) + if (*c == '.') + *c = '_'; + + /* + * STT_NOTYPE: Prevent objtool from validating .altinstr_replacement + * while still allowing objdump to disassemble it. + */ + type = is_text_sec(sec) ? STT_NOTYPE : STT_OBJECT; + return elf_create_symbol(elf, name, sec, STB_LOCAL, type, offset, size) ? 0 : -1; +} + +/* + * Special sections (alternatives, etc) are basically arrays of structs. + * For all the special sections, create a symbol for each struct entry. This + * is a bit cumbersome, but it makes the extracting of the individual entries + * much more straightforward. + * + * There are three ways to identify the entry sizes for a special section: + * + * 1) ELF section header sh_entsize: Ideally this would be used almost + * everywhere. But unfortunately the toolchains make it difficult. The + * assembler .[push]section directive syntax only takes entsize when + * combined with SHF_MERGE. But Clang disallows combining SHF_MERGE with + * SHF_WRITE. And some special sections do need to be writable. + * + * Another place this wouldn't work is .altinstr_replacement, whose entries + * don't have a fixed size. + * + * 2) ANNOTATE_DATA_SPECIAL: This is a lightweight objtool annotation which + * points to the beginning of each entry. The size of the entry is then + * inferred by the location of the subsequent annotation (or end of + * section). + * + * 3) Simple array of pointers: If the special section is just a basic array of + * pointers, the entry size can be inferred by the number of relocations. + * No annotations needed. + * + * Note I also tried to create per-entry symbols at the time of creation, in + * the original [inline] asm. Unfortunately, creating uniquely named symbols + * is trickier than one might think, especially with Clang inline asm. I + * eventually just gave up trying to make that work, in favor of using + * ANNOTATE_DATA_SPECIAL and creating the symbols here after the fact. + */ +static int create_fake_symbols(struct elf *elf) +{ + struct section *sec; + struct reloc *reloc; + + /* + * 1) Make symbols for all the ANNOTATE_DATA_SPECIAL entries: + */ + + sec = find_section_by_name(elf, ".discard.annotate_data"); + if (!sec || !sec->rsec) + goto entsize; + + for_each_reloc(sec->rsec, reloc) { + unsigned long offset, size; + struct reloc *next_reloc; + + if (annotype(elf, sec, reloc) != ANNOTYPE_DATA_SPECIAL) + continue; + + offset = reloc_addend(reloc); + + size = 0; + next_reloc = reloc; + for_each_reloc_continue(sec->rsec, next_reloc) { + if (annotype(elf, sec, next_reloc) != ANNOTYPE_DATA_SPECIAL || + next_reloc->sym->sec != reloc->sym->sec) + continue; + + size = reloc_addend(next_reloc) - offset; + break; + } + + if (!size) + size = sec_size(reloc->sym->sec) - offset; + + if (create_fake_symbol(elf, reloc->sym->sec, offset, size)) + return -1; + } + + /* + * 2) Make symbols for sh_entsize, and simple arrays of pointers: + */ +entsize: + for_each_sec(elf, sec) { + unsigned int entry_size; + unsigned long offset; + + if (!is_special_section(sec) || find_symbol_by_offset(sec, 0)) + continue; + + if (!sec->rsec) { + ERROR("%s: missing special section relocations", sec->name); + return -1; + } + + entry_size = sec->sh.sh_entsize; + if (!entry_size) { + entry_size = arch_reloc_size(sec->rsec->relocs); + if (sec_size(sec) != entry_size * sec_num_entries(sec->rsec)) { + ERROR("%s: missing special section entsize or annotations", sec->name); + return -1; + } + } + + for (offset = 0; offset < sec_size(sec); offset += entry_size) { + if (create_fake_symbol(elf, sec, offset, entry_size)) + return -1; + } + } + + return 0; +} + +/* Keep a special section entry if it references an included function */ +static bool should_keep_special_sym(struct elf *elf, struct symbol *sym) +{ + bool annotate_insn = !strcmp(sym->sec->name, ".discard.annotate_insn"); + struct reloc *reloc; + + if (is_sec_sym(sym) || !sym->sec->rsec) + return false; + + sym_for_each_reloc(elf, sym, reloc) { + if (convert_reloc_sym(elf, reloc)) + continue; + + if (!reloc->sym->clone || is_undef_sym(reloc->sym->clone)) + continue; + + /* + * Keep special section references to cloned functions. + * In some cases annotate_insn can also reference cloned alt + * replacement fake symbols; keep those references as well. + */ + if (is_func_sym(reloc->sym) || + (annotate_insn && is_notype_sym(reloc->sym))) + return true; + } + + return false; +} + +/* + * Klp relocations aren't allowed for __jump_table and .static_call_sites if + * the referenced symbol lives in a kernel module, because such klp relocs may + * be applied after static branch/call init, resulting in code corruption. + * + * Validate a special section entry to avoid that. Note that an inert + * tracepoint or pr_debug() is harmless enough, in that case just skip the + * entry and print a warning. Otherwise, return an error. + * + * TODO: This is only a temporary limitation which will be fixed when livepatch + * adds support for submodules: fully self-contained modules which are embedded + * in the top-level livepatch module's data and which can be loaded on demand + * when their corresponding to-be-patched module gets loaded. Then klp relocs + * can be retired. + * + * Return: + * -1: error: validation failed + * 1: warning: disabled tracepoint or pr_debug() + * 0: success + */ +static int validate_special_section_klp_reloc(struct elfs *e, struct symbol *sym) +{ + bool static_branch = !strcmp(sym->sec->name, "__jump_table"); + bool static_call = !strcmp(sym->sec->name, ".static_call_sites"); + const char *code_sym = NULL; + unsigned long code_offset = 0; + struct reloc *reloc; + int ret = 0; + + if (!static_branch && !static_call) + return 0; + + sym_for_each_reloc(e->patched, sym, reloc) { + const char *sym_modname; + struct export *export; + + if (convert_reloc_sym(e->patched, reloc)) + continue; + + /* Static branch/call keys are always STT_OBJECT */ + if (reloc->sym->type != STT_OBJECT) { + + /* Save code location which can be printed below */ + if (reloc->sym->type == STT_FUNC && !code_sym) { + code_sym = reloc->sym->name; + code_offset = reloc_addend(reloc); + } + + continue; + } + + if (!klp_reloc_needed(reloc)) + continue; + + export = find_export(reloc->sym); + if (export) { + sym_modname = export->mod; + } else { + sym_modname = find_modname(e); + if (!sym_modname) + return -1; + } + + /* vmlinux keys are ok */ + if (!strcmp(sym_modname, "vmlinux")) + continue; + + if (!code_sym) + code_sym = "<unknown>"; + + if (static_branch) { + if (strstarts(reloc->sym->name, "__tracepoint_")) { + WARN("%s: disabling unsupported tracepoint %s", + code_sym, reloc->sym->name + 13); + ret = 1; + continue; + } + + if (strstr(reloc->sym->name, "__UNIQUE_ID_ddebug_")) { + WARN("%s: disabling unsupported pr_debug()", + code_sym); + ret = 1; + continue; + } + + ERROR("%s+0x%lx: unsupported static branch key %s. Use static_key_enabled() instead", + code_sym, code_offset, reloc->sym->name); + return -1; + } + + /* static call */ + if (strstarts(reloc->sym->name, "__SCK__tp_func_")) { + ret = 1; + continue; + } + + ERROR("%s()+0x%lx: unsupported static call key %s. Use KLP_STATIC_CALL() instead", + code_sym, code_offset, reloc->sym->name); + return -1; + } + + return ret; +} + +static int clone_special_section(struct elfs *e, struct section *patched_sec) +{ + struct symbol *patched_sym; + + /* + * Extract all special section symbols (and their dependencies) which + * reference included functions. + */ + sec_for_each_sym(patched_sec, patched_sym) { + int ret; + + if (!is_object_sym(patched_sym)) + continue; + + if (!should_keep_special_sym(e->patched, patched_sym)) + continue; + + ret = validate_special_section_klp_reloc(e, patched_sym); + if (ret < 0) + return -1; + if (ret > 0) + continue; + + if (!clone_symbol(e, patched_sym, true)) + return -1; + } + + return 0; +} + +/* Extract only the needed bits from special sections */ +static int clone_special_sections(struct elfs *e) +{ + struct section *sec, *annotate_insn = NULL; + + for_each_sec(e->patched, sec) { + if (is_special_section(sec)) { + if (!strcmp(sec->name, ".discard.annotate_insn")) { + annotate_insn = sec; + continue; + } + if (clone_special_section(e, sec)) + return -1; + } + } + + /* + * Do .discard.annotate_insn last, it can reference other special + * sections (alt replacements) so they need to be cloned first. + */ + if (annotate_insn) { + if (clone_special_section(e, annotate_insn)) + return -1; + } + + return 0; +} + +/* + * Create .init.klp_objects and .init.klp_funcs sections which are intermediate + * sections provided as input to the patch module's init code for building the + * klp_patch, klp_object and klp_func structs for the livepatch API. + */ +static int create_klp_sections(struct elfs *e) +{ + size_t obj_size = sizeof(struct klp_object_ext); + size_t func_size = sizeof(struct klp_func_ext); + struct section *obj_sec, *funcs_sec, *str_sec; + struct symbol *funcs_sym, *str_sym, *sym; + char sym_name[SYM_NAME_LEN]; + unsigned int nr_funcs = 0; + const char *modname; + void *obj_data; + s64 addend; + + obj_sec = elf_create_section_pair(e->out, KLP_OBJECTS_SEC, obj_size, 0, 0); + if (!obj_sec) + return -1; + + funcs_sec = elf_create_section_pair(e->out, KLP_FUNCS_SEC, func_size, 0, 0); + if (!funcs_sec) + return -1; + + funcs_sym = elf_create_section_symbol(e->out, funcs_sec); + if (!funcs_sym) + return -1; + + str_sec = elf_create_section(e->out, KLP_STRINGS_SEC, 0, 0, + SHT_PROGBITS, 1, + SHF_ALLOC | SHF_STRINGS | SHF_MERGE); + if (!str_sec) + return -1; + + if (elf_add_string(e->out, str_sec, "") == -1) + return -1; + + str_sym = elf_create_section_symbol(e->out, str_sec); + if (!str_sym) + return -1; + + /* allocate klp_object_ext */ + obj_data = elf_add_data(e->out, obj_sec, NULL, obj_size); + if (!obj_data) + return -1; + + modname = find_modname(e); + if (!modname) + return -1; + + /* klp_object_ext.name */ + if (strcmp(modname, "vmlinux")) { + addend = elf_add_string(e->out, str_sec, modname); + if (addend == -1) + return -1; + + if (!elf_create_reloc(e->out, obj_sec, + offsetof(struct klp_object_ext, name), + str_sym, addend, R_ABS64)) + return -1; + } + + /* klp_object_ext.funcs */ + if (!elf_create_reloc(e->out, obj_sec, offsetof(struct klp_object_ext, funcs), + funcs_sym, 0, R_ABS64)) + return -1; + + for_each_sym(e->out, sym) { + unsigned long offset = nr_funcs * func_size; + unsigned long sympos; + void *func_data; + + if (!is_func_sym(sym) || is_cold_func(sym) || + !sym->clone || !sym->clone->changed) + continue; + + /* allocate klp_func_ext */ + func_data = elf_add_data(e->out, funcs_sec, NULL, func_size); + if (!func_data) + return -1; + + /* klp_func_ext.old_name */ + addend = elf_add_string(e->out, str_sec, sym->clone->twin->name); + if (addend == -1) + return -1; + + if (!elf_create_reloc(e->out, funcs_sec, + offset + offsetof(struct klp_func_ext, old_name), + str_sym, addend, R_ABS64)) + return -1; + + /* klp_func_ext.new_func */ + if (!elf_create_reloc(e->out, funcs_sec, + offset + offsetof(struct klp_func_ext, new_func), + sym, 0, R_ABS64)) + return -1; + + /* klp_func_ext.sympos */ + BUILD_BUG_ON(sizeof(sympos) != sizeof_field(struct klp_func_ext, sympos)); + sympos = find_sympos(e->orig, sym->clone->twin); + if (sympos == ULONG_MAX) + return -1; + memcpy(func_data + offsetof(struct klp_func_ext, sympos), &sympos, + sizeof_field(struct klp_func_ext, sympos)); + + nr_funcs++; + } + + /* klp_object_ext.nr_funcs */ + BUILD_BUG_ON(sizeof(nr_funcs) != sizeof_field(struct klp_object_ext, nr_funcs)); + memcpy(obj_data + offsetof(struct klp_object_ext, nr_funcs), &nr_funcs, + sizeof_field(struct klp_object_ext, nr_funcs)); + + /* + * Find callback pointers created by KLP_PRE_PATCH_CALLBACK() and + * friends, and add them to the klp object. + */ + + if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_PRE_PATCH_PREFIX "%s", modname)) + return -1; + + sym = find_symbol_by_name(e->out, sym_name); + if (sym) { + struct reloc *reloc; + + reloc = find_reloc_by_dest(e->out, sym->sec, sym->offset); + + if (!elf_create_reloc(e->out, obj_sec, + offsetof(struct klp_object_ext, callbacks) + + offsetof(struct klp_callbacks, pre_patch), + reloc->sym, reloc_addend(reloc), R_ABS64)) + return -1; + } + + if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_POST_PATCH_PREFIX "%s", modname)) + return -1; + + sym = find_symbol_by_name(e->out, sym_name); + if (sym) { + struct reloc *reloc; + + reloc = find_reloc_by_dest(e->out, sym->sec, sym->offset); + + if (!elf_create_reloc(e->out, obj_sec, + offsetof(struct klp_object_ext, callbacks) + + offsetof(struct klp_callbacks, post_patch), + reloc->sym, reloc_addend(reloc), R_ABS64)) + return -1; + } + + if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_PRE_UNPATCH_PREFIX "%s", modname)) + return -1; + + sym = find_symbol_by_name(e->out, sym_name); + if (sym) { + struct reloc *reloc; + + reloc = find_reloc_by_dest(e->out, sym->sec, sym->offset); + + if (!elf_create_reloc(e->out, obj_sec, + offsetof(struct klp_object_ext, callbacks) + + offsetof(struct klp_callbacks, pre_unpatch), + reloc->sym, reloc_addend(reloc), R_ABS64)) + return -1; + } + + if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_POST_UNPATCH_PREFIX "%s", modname)) + return -1; + + sym = find_symbol_by_name(e->out, sym_name); + if (sym) { + struct reloc *reloc; + + reloc = find_reloc_by_dest(e->out, sym->sec, sym->offset); + + if (!elf_create_reloc(e->out, obj_sec, + offsetof(struct klp_object_ext, callbacks) + + offsetof(struct klp_callbacks, post_unpatch), + reloc->sym, reloc_addend(reloc), R_ABS64)) + return -1; + } + + return 0; +} + +/* + * Copy all .modinfo import_ns= tags to ensure all namespaced exported symbols + * can be accessed via normal relocs. + */ +static int copy_import_ns(struct elfs *e) +{ + struct section *patched_sec, *out_sec = NULL; + char *import_ns, *data_end; + + patched_sec = find_section_by_name(e->patched, ".modinfo"); + if (!patched_sec) + return 0; + + import_ns = patched_sec->data->d_buf; + if (!import_ns) + return 0; + + for (data_end = import_ns + sec_size(patched_sec); + import_ns < data_end; + import_ns += strlen(import_ns) + 1) { + + import_ns = memmem(import_ns, data_end - import_ns, "import_ns=", 10); + if (!import_ns) + return 0; + + if (!out_sec) { + out_sec = find_section_by_name(e->out, ".modinfo"); + if (!out_sec) { + out_sec = elf_create_section(e->out, ".modinfo", 0, + patched_sec->sh.sh_entsize, + patched_sec->sh.sh_type, + patched_sec->sh.sh_addralign, + patched_sec->sh.sh_flags); + if (!out_sec) + return -1; + } + } + + if (!elf_add_data(e->out, out_sec, import_ns, strlen(import_ns) + 1)) + return -1; + } + + return 0; +} + +int cmd_klp_diff(int argc, const char **argv) +{ + struct elfs e = {0}; + int ret; + + argc = parse_options(argc, argv, klp_diff_options, klp_diff_usage, 0); + if (argc != 3) + usage_with_options(klp_diff_usage, klp_diff_options); + + if (debug) { + debug_correlate = true; + debug_clone = true; + } + + objname = argv[0]; + + e.orig = elf_open_read(argv[0], O_RDONLY); + e.patched = elf_open_read(argv[1], O_RDONLY); + e.out = NULL; + + if (!e.orig || !e.patched) + return -1; + + if (read_exports()) + return -1; + + if (read_sym_checksums(e.orig)) + return -1; + + if (read_sym_checksums(e.patched)) + return -1; + + if (correlate_symbols(&e)) + return -1; + + ret = mark_changed_functions(&e); + if (ret < 0) + return -1; + if (ret > 0) + return 0; + + e.out = elf_create_file(&e.orig->ehdr, argv[2]); + if (!e.out) + return -1; + + /* + * Special section fake symbols are needed so that individual special + * section entries can be extracted by clone_special_sections(). + * + * Note the fake symbols are also needed by clone_included_functions() + * because __WARN_printf() call sites add references to bug table + * entries in the calling functions. + */ + if (create_fake_symbols(e.patched)) + return -1; + + if (clone_included_functions(&e)) + return -1; + + if (clone_special_sections(&e)) + return -1; + + if (create_klp_sections(&e)) + return -1; + + if (copy_import_ns(&e)) + return -1; + + if (elf_write(e.out)) + return -1; + + return elf_close(e.out); +} |