From 1cd9502ee9275c6176a7312863f939cca9506114 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sun, 29 Dec 2024 00:45:28 +0900 Subject: module: get symbol CRC back to unsigned Commit 71810db27c1c ("modversions: treat symbol CRCs as 32 bit quantities") changed the CRC fields to s32 because the __kcrctab and __kcrctab_gpl sections contained relative references to the actual CRC values stored in the .rodata section when CONFIG_MODULE_REL_CRCS=y. Commit 7b4537199a4a ("kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS") removed this complexity. Now, the __kcrctab and __kcrctab_gpl sections directly contain the CRC values in all cases. The genksyms tool outputs unsigned 32-bit CRC values, so u32 is preferred over s32. No functional changes are intended. Regardless of this change, the CRC value is assigned to the u32 variable 'crcval' before the comparison, as seen in kernel/module/version.c: crcval = *crc; It was previously mandatory (but now optional) in order to avoid sign extension because the following line previously compared 'unsigned long' and 's32': if (versions[i].crc == crcval) return 1; versions[i].crc is still 'unsigned long' for backward compatibility. Signed-off-by: Masahiro Yamada Reviewed-by: Petr Pavlu --- include/linux/module.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/module.h b/include/linux/module.h index 94acbacdcdf1..903ef8fe4c04 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -430,7 +430,7 @@ struct module { /* Exported symbols */ const struct kernel_symbol *syms; - const s32 *crcs; + const u32 *crcs; unsigned int num_syms; #ifdef CONFIG_ARCH_USES_CFI_TRAPS @@ -448,7 +448,7 @@ struct module { /* GPL-only exported symbols. */ unsigned int num_gpl_syms; const struct kernel_symbol *gpl_syms; - const s32 *gpl_crcs; + const u32 *gpl_crcs; bool using_gplonly_symbols; #ifdef CONFIG_MODULE_SIG -- cgit v1.2.3 From d7476f24c9aa93d02ef3fd8d587a6114387b7667 Mon Sep 17 00:00:00 2001 From: Sami Tolvanen Date: Fri, 3 Jan 2025 20:45:38 +0000 Subject: export: Add __gendwarfksyms_ptr_ references to exported symbols With gendwarfksyms, we need each TU where the EXPORT_SYMBOL() macro is used to also contain DWARF type information for the symbols it exports. However, as a TU can also export external symbols and compilers may choose not to emit debugging information for symbols not defined in the current TU, the missing types will result in missing symbol versions. Stand-alone assembly code also doesn't contain type information for exported symbols, so we need to compile a temporary object file with asm-prototypes.h instead, and similarly need to ensure the DWARF in the temporary object file contains the necessary types. To always emit type information for external exports, add explicit __gendwarfksyms_ptr_ references to them in EXPORT_SYMBOL(). gendwarfksyms will use the type information for __gendwarfksyms_ptr_* if needed. Discard the pointers from the final binary to avoid further bloat. Signed-off-by: Sami Tolvanen Signed-off-by: Masahiro Yamada --- include/linux/export.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'include') diff --git a/include/linux/export.h b/include/linux/export.h index 2633df4d31e6..a8c23d945634 100644 --- a/include/linux/export.h +++ b/include/linux/export.h @@ -52,9 +52,24 @@ #else +#ifdef CONFIG_GENDWARFKSYMS +/* + * With CONFIG_GENDWARFKSYMS, ensure the compiler emits debugging + * information for all exported symbols, including those defined in + * different TUs, by adding a __gendwarfksyms_ptr_ pointer + * that's discarded during the final link. + */ +#define __GENDWARFKSYMS_EXPORT(sym) \ + static typeof(sym) *__gendwarfksyms_ptr_##sym __used \ + __section(".discard.gendwarfksyms") = &sym; +#else +#define __GENDWARFKSYMS_EXPORT(sym) +#endif + #define __EXPORT_SYMBOL(sym, license, ns) \ extern typeof(sym) sym; \ __ADDRESSABLE(sym) \ + __GENDWARFKSYMS_EXPORT(sym) \ asm(__stringify(___EXPORT_SYMBOL(sym, license, ns))) #endif -- cgit v1.2.3