diff options
Diffstat (limited to 'arch/i386')
| -rw-r--r-- | arch/i386/Kconfig.debug | 10 | ||||
| -rw-r--r-- | arch/i386/kernel/alternative.c | 63 | ||||
| -rw-r--r-- | arch/i386/kernel/entry.S | 39 | ||||
| -rw-r--r-- | arch/i386/kernel/module.c | 11 | ||||
| -rw-r--r-- | arch/i386/kernel/paravirt.c | 44 | ||||
| -rw-r--r-- | arch/i386/kernel/vmlinux.lds.S | 6 |
6 files changed, 148 insertions, 25 deletions
diff --git a/arch/i386/Kconfig.debug b/arch/i386/Kconfig.debug index b31c0802e1cc..f68cc6f215f8 100644 --- a/arch/i386/Kconfig.debug +++ b/arch/i386/Kconfig.debug @@ -85,4 +85,14 @@ config DOUBLEFAULT option saves about 4k and might cause you much additional grey hair. +config DEBUG_PARAVIRT + bool "Enable some paravirtualization debugging" + default y + depends on PARAVIRT && DEBUG_KERNEL + help + Currently deliberately clobbers regs which are allowed to be + clobbered in inlined paravirt hooks, even in native mode. + If turning this off solves a problem, then DISABLE_INTERRUPTS() or + ENABLE_INTERRUPTS() is lying about what registers can be clobbered. + endmenu diff --git a/arch/i386/kernel/alternative.c b/arch/i386/kernel/alternative.c index 535f9794fba1..9eca21b49f6b 100644 --- a/arch/i386/kernel/alternative.c +++ b/arch/i386/kernel/alternative.c @@ -124,6 +124,20 @@ static unsigned char** find_nop_table(void) #endif /* CONFIG_X86_64 */ +static void nop_out(void *insns, unsigned int len) +{ + unsigned char **noptable = find_nop_table(); + + while (len > 0) { + unsigned int noplen = len; + if (noplen > ASM_NOP_MAX) + noplen = ASM_NOP_MAX; + memcpy(insns, noptable[noplen], noplen); + insns += noplen; + len -= noplen; + } +} + extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; extern struct alt_instr __smp_alt_instructions[], __smp_alt_instructions_end[]; extern u8 *__smp_locks[], *__smp_locks_end[]; @@ -138,10 +152,9 @@ extern u8 __smp_alt_begin[], __smp_alt_end[]; void apply_alternatives(struct alt_instr *start, struct alt_instr *end) { - unsigned char **noptable = find_nop_table(); struct alt_instr *a; u8 *instr; - int diff, i, k; + int diff; DPRINTK("%s: alt table %p -> %p\n", __FUNCTION__, start, end); for (a = start; a < end; a++) { @@ -159,13 +172,7 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end) #endif memcpy(instr, a->replacement, a->replacementlen); diff = a->instrlen - a->replacementlen; - /* Pad the rest with nops */ - for (i = a->replacementlen; diff > 0; diff -= k, i += k) { - k = diff; - if (k > ASM_NOP_MAX) - k = ASM_NOP_MAX; - memcpy(a->instr + i, noptable[k], k); - } + nop_out(instr + a->replacementlen, diff); } } @@ -209,7 +216,6 @@ static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end) static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end) { - unsigned char **noptable = find_nop_table(); u8 **ptr; for (ptr = start; ptr < end; ptr++) { @@ -217,7 +223,7 @@ static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end continue; if (*ptr > text_end) continue; - **ptr = noptable[1][0]; + nop_out(*ptr, 1); }; } @@ -343,6 +349,40 @@ void alternatives_smp_switch(int smp) #endif +#ifdef CONFIG_PARAVIRT +void apply_paravirt(struct paravirt_patch *start, struct paravirt_patch *end) +{ + struct paravirt_patch *p; + + for (p = start; p < end; p++) { + unsigned int used; + + used = paravirt_ops.patch(p->instrtype, p->clobbers, p->instr, + p->len); +#ifdef CONFIG_DEBUG_PARAVIRT + { + int i; + /* Deliberately clobber regs using "not %reg" to find bugs. */ + for (i = 0; i < 3; i++) { + if (p->len - used >= 2 && (p->clobbers & (1 << i))) { + memcpy(p->instr + used, "\xf7\xd0", 2); + p->instr[used+1] |= i; + used += 2; + } + } + } +#endif + /* Pad the rest with nops */ + nop_out(p->instr + used, p->len - used); + } + + /* Sync to be conservative, in case we patched following instructions */ + sync_core(); +} +extern struct paravirt_patch __start_parainstructions[], + __stop_parainstructions[]; +#endif /* CONFIG_PARAVIRT */ + void __init alternative_instructions(void) { unsigned long flags; @@ -390,5 +430,6 @@ void __init alternative_instructions(void) alternatives_smp_switch(0); } #endif + apply_paravirt(__start_parainstructions, __stop_parainstructions); local_irq_restore(flags); } diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S index d274612e05cd..de34b7fed3c1 100644 --- a/arch/i386/kernel/entry.S +++ b/arch/i386/kernel/entry.S @@ -53,6 +53,19 @@ #include <asm/dwarf2.h> #include "irq_vectors.h" +/* + * We use macros for low-level operations which need to be overridden + * for paravirtualization. The following will never clobber any registers: + * INTERRUPT_RETURN (aka. "iret") + * GET_CR0_INTO_EAX (aka. "movl %cr0, %eax") + * ENABLE_INTERRUPTS_SYSEXIT (aka "sti; sysexit"). + * + * For DISABLE_INTERRUPTS/ENABLE_INTERRUPTS (aka "cli"/"sti"), you must + * specify what registers can be overwritten (CLBR_NONE, CLBR_EAX/EDX/ECX/ANY). + * Allowing a register to be clobbered can shrink the paravirt replacement + * enough to patch inline, increasing performance. + */ + #define nr_syscalls ((syscall_table_size)/4) CF_MASK = 0x00000001 @@ -63,9 +76,9 @@ NT_MASK = 0x00004000 VM_MASK = 0x00020000 #ifdef CONFIG_PREEMPT -#define preempt_stop DISABLE_INTERRUPTS; TRACE_IRQS_OFF +#define preempt_stop(clobbers) DISABLE_INTERRUPTS(clobbers); TRACE_IRQS_OFF #else -#define preempt_stop +#define preempt_stop(clobbers) #define resume_kernel restore_nocheck #endif @@ -226,7 +239,7 @@ ENTRY(ret_from_fork) ALIGN RING0_PTREGS_FRAME ret_from_exception: - preempt_stop + preempt_stop(CLBR_ANY) ret_from_intr: GET_THREAD_INFO(%ebp) check_userspace: @@ -237,7 +250,7 @@ check_userspace: jb resume_kernel # not returning to v8086 or userspace ENTRY(resume_userspace) - DISABLE_INTERRUPTS # make sure we don't miss an interrupt + DISABLE_INTERRUPTS(CLBR_ANY) # make sure we don't miss an interrupt # setting need_resched or sigpending # between sampling and the iret movl TI_flags(%ebp), %ecx @@ -248,7 +261,7 @@ ENTRY(resume_userspace) #ifdef CONFIG_PREEMPT ENTRY(resume_kernel) - DISABLE_INTERRUPTS + DISABLE_INTERRUPTS(CLBR_ANY) cmpl $0,TI_preempt_count(%ebp) # non-zero preempt_count ? jnz restore_nocheck need_resched: @@ -277,7 +290,7 @@ sysenter_past_esp: * No need to follow this irqs on/off section: the syscall * disabled irqs and here we enable it straight after entry: */ - ENABLE_INTERRUPTS + ENABLE_INTERRUPTS(CLBR_NONE) pushl $(__USER_DS) CFI_ADJUST_CFA_OFFSET 4 /*CFI_REL_OFFSET ss, 0*/ @@ -322,7 +335,7 @@ sysenter_past_esp: jae syscall_badsys call *sys_call_table(,%eax,4) movl %eax,PT_EAX(%esp) - DISABLE_INTERRUPTS + DISABLE_INTERRUPTS(CLBR_ECX|CLBR_EDX) TRACE_IRQS_OFF movl TI_flags(%ebp), %ecx testw $_TIF_ALLWORK_MASK, %cx @@ -364,7 +377,7 @@ syscall_call: call *sys_call_table(,%eax,4) movl %eax,PT_EAX(%esp) # store the return value syscall_exit: - DISABLE_INTERRUPTS # make sure we don't miss an interrupt + DISABLE_INTERRUPTS(CLBR_ANY) # make sure we don't miss an interrupt # setting need_resched or sigpending # between sampling and the iret TRACE_IRQS_OFF @@ -393,7 +406,7 @@ restore_nocheck_notrace: .section .fixup,"ax" iret_exc: TRACE_IRQS_ON - ENABLE_INTERRUPTS + ENABLE_INTERRUPTS(CLBR_NONE) pushl $0 # no error code pushl $do_iret_error jmp error_code @@ -436,7 +449,7 @@ ldt_ss: CFI_ADJUST_CFA_OFFSET 4 pushl %eax CFI_ADJUST_CFA_OFFSET 4 - DISABLE_INTERRUPTS + DISABLE_INTERRUPTS(CLBR_EAX) TRACE_IRQS_OFF lss (%esp), %esp CFI_ADJUST_CFA_OFFSET -8 @@ -451,7 +464,7 @@ work_pending: jz work_notifysig work_resched: call schedule - DISABLE_INTERRUPTS # make sure we don't miss an interrupt + DISABLE_INTERRUPTS(CLBR_ANY) # make sure we don't miss an interrupt # setting need_resched or sigpending # between sampling and the iret TRACE_IRQS_OFF @@ -509,7 +522,7 @@ syscall_exit_work: testb $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP), %cl jz work_pending TRACE_IRQS_ON - ENABLE_INTERRUPTS # could let do_syscall_trace() call + ENABLE_INTERRUPTS(CLBR_ANY) # could let do_syscall_trace() call # schedule() instead movl %esp, %eax movl $1, %edx @@ -693,7 +706,7 @@ ENTRY(device_not_available) GET_CR0_INTO_EAX testl $0x4, %eax # EM (math emulation bit) jne device_not_available_emulate - preempt_stop + preempt_stop(CLBR_ANY) call math_state_restore jmp ret_from_exception device_not_available_emulate: diff --git a/arch/i386/kernel/module.c b/arch/i386/kernel/module.c index 470cf97e7cd3..d7d9c8b23f72 100644 --- a/arch/i386/kernel/module.c +++ b/arch/i386/kernel/module.c @@ -108,7 +108,8 @@ int module_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, struct module *me) { - const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL; + const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL, + *para = NULL; char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) { @@ -118,6 +119,8 @@ int module_finalize(const Elf_Ehdr *hdr, alt = s; if (!strcmp(".smp_locks", secstrings + s->sh_name)) locks= s; + if (!strcmp(".parainstructions", secstrings + s->sh_name)) + para = s; } if (alt) { @@ -132,6 +135,12 @@ int module_finalize(const Elf_Ehdr *hdr, lseg, lseg + locks->sh_size, tseg, tseg + text->sh_size); } + + if (para) { + void *pseg = (void *)para->sh_addr; + apply_paravirt(pseg, pseg + para->sh_size); + } + return 0; } diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c index 478192cd4b90..d46460426446 100644 --- a/arch/i386/kernel/paravirt.c +++ b/arch/i386/kernel/paravirt.c @@ -45,6 +45,49 @@ char *memory_setup(void) return paravirt_ops.memory_setup(); } +/* Simple instruction patching code. */ +#define DEF_NATIVE(name, code) \ + extern const char start_##name[], end_##name[]; \ + asm("start_" #name ": " code "; end_" #name ":") +DEF_NATIVE(cli, "cli"); +DEF_NATIVE(sti, "sti"); +DEF_NATIVE(popf, "push %eax; popf"); +DEF_NATIVE(pushf, "pushf; pop %eax"); +DEF_NATIVE(pushf_cli, "pushf; pop %eax; cli"); +DEF_NATIVE(iret, "iret"); +DEF_NATIVE(sti_sysexit, "sti; sysexit"); + +static const struct native_insns +{ + const char *start, *end; +} native_insns[] = { + [PARAVIRT_IRQ_DISABLE] = { start_cli, end_cli }, + [PARAVIRT_IRQ_ENABLE] = { start_sti, end_sti }, + [PARAVIRT_RESTORE_FLAGS] = { start_popf, end_popf }, + [PARAVIRT_SAVE_FLAGS] = { start_pushf, end_pushf }, + [PARAVIRT_SAVE_FLAGS_IRQ_DISABLE] = { start_pushf_cli, end_pushf_cli }, + [PARAVIRT_INTERRUPT_RETURN] = { start_iret, end_iret }, + [PARAVIRT_STI_SYSEXIT] = { start_sti_sysexit, end_sti_sysexit }, +}; + +static unsigned native_patch(u8 type, u16 clobbers, void *insns, unsigned len) +{ + unsigned int insn_len; + + /* Don't touch it if we don't have a replacement */ + if (type >= ARRAY_SIZE(native_insns) || !native_insns[type].start) + return len; + + insn_len = native_insns[type].end - native_insns[type].start; + + /* Similarly if we can't fit replacement. */ + if (len < insn_len) + return len; + + memcpy(insns, native_insns[type].start, insn_len); + return insn_len; +} + static fastcall unsigned long native_get_debugreg(int regno) { unsigned long val = 0; /* Damn you, gcc! */ @@ -349,6 +392,7 @@ struct paravirt_ops paravirt_ops = { .paravirt_enabled = 0, .kernel_rpl = 0, + .patch = native_patch, .banner = default_banner, .arch_setup = native_nop, .memory_setup = machine_specific_memory_setup, diff --git a/arch/i386/kernel/vmlinux.lds.S b/arch/i386/kernel/vmlinux.lds.S index 6860f20aa579..5c69cf0e5944 100644 --- a/arch/i386/kernel/vmlinux.lds.S +++ b/arch/i386/kernel/vmlinux.lds.S @@ -165,6 +165,12 @@ SECTIONS .altinstr_replacement : AT(ADDR(.altinstr_replacement) - LOAD_OFFSET) { *(.altinstr_replacement) } + . = ALIGN(4); + __start_parainstructions = .; + .parainstructions : AT(ADDR(.parainstructions) - LOAD_OFFSET) { + *(.parainstructions) + } + __stop_parainstructions = .; /* .exit.text is discard at runtime, not link time, to deal with references from .altinstructions and .eh_frame */ .exit.text : AT(ADDR(.exit.text) - LOAD_OFFSET) { *(.exit.text) } |