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3.0 KiB

From 1e48901166efd65c574de9f6a2b7139721b72623 Mon Sep 17 00:00:00 2001
From: Yauheni Kaliuta <yauheni.kaliuta@redhat.com>
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_<symbol name>.
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_<symbol name> 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 <yauheni.kaliuta@redhat.com>
---
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