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