From 1e48901166efd65c574de9f6a2b7139721b72623 Mon Sep 17 00:00:00 2001 From: Yauheni Kaliuta Date: Wed, 19 Jul 2017 17:56:49 +0300 Subject: [PATCH] libkmod-elf: resolve CRC if module is built with MODULE_REL_CRCS Normally exported symbol's crc is stored as absolute (SHN_ABS) value of special named symbol __crc_. When the kernel and modules are built with the config option CONFIG_MODULE_REL_CRCS, all the CRCs are put in a special section and the __crc_ symbols values are offsets in the section. See patch description of the commit: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=56067812d5b0e737ac2063e94a50f76b810d6ca3 Add kmod support of this configuration. Signed-off-by: Yauheni Kaliuta --- libkmod/libkmod-elf.c | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/libkmod/libkmod-elf.c b/libkmod/libkmod-elf.c index 90da89aebbaf..ef4a8a3142a1 100644 --- a/libkmod/libkmod-elf.c +++ b/libkmod/libkmod-elf.c @@ -747,6 +747,31 @@ static inline uint8_t kmod_symbol_bind_from_elf(uint8_t elf_value) } } +static uint64_t kmod_elf_resolve_crc(const struct kmod_elf *elf, uint64_t crc, uint16_t shndx) +{ + int err; + uint64_t off, size; + uint32_t nameoff; + + if (shndx == SHN_ABS || shndx == SHN_UNDEF) + return crc; + + err = elf_get_section_info(elf, shndx, &off, &size, &nameoff); + if (err < 0) { + ELFDBG("Cound not find section index %"PRIu16" for crc", shndx); + return (uint64_t)-1; + } + + if (crc > (size - sizeof(uint32_t))) { + ELFDBG("CRC offset %"PRIu64" is too big, section %"PRIu16" size is %"PRIu64"\n", + crc, shndx, size); + return (uint64_t)-1; + } + + crc = elf_get_uint(elf, off + crc, sizeof(uint32_t)); + return crc; +} + /* array will be allocated with strings in a single malloc, just free *array */ int kmod_elf_get_symbols(const struct kmod_elf *elf, struct kmod_modversion **array) { @@ -830,6 +855,7 @@ int kmod_elf_get_symbols(const struct kmod_elf *elf, struct kmod_modversion **ar uint32_t name_off; uint64_t crc; uint8_t info, bind; + uint16_t shndx; #define READV(field) \ elf_get_uint(elf, sym_off + offsetof(typeof(*s), field),\ @@ -839,11 +865,13 @@ int kmod_elf_get_symbols(const struct kmod_elf *elf, struct kmod_modversion **ar name_off = READV(st_name); crc = READV(st_value); info = READV(st_info); + shndx = READV(st_shndx); } else { Elf64_Sym *s; name_off = READV(st_name); crc = READV(st_value); info = READV(st_info); + shndx = READV(st_shndx); } #undef READV name = elf_get_mem(elf, str_off + name_off); @@ -856,7 +884,7 @@ int kmod_elf_get_symbols(const struct kmod_elf *elf, struct kmod_modversion **ar else bind = ELF64_ST_BIND(info); - a[count].crc = crc; + a[count].crc = kmod_elf_resolve_crc(elf, crc, shndx); a[count].bind = kmod_symbol_bind_from_elf(bind); a[count].symbol = itr; slen = strlen(name); -- 2.14.0.rc0