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183 lines
6.3 KiB
183 lines
6.3 KiB
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 |
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From: Vladimir Serbinenko <phcoder@gmail.com> |
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Date: Thu, 31 Dec 2015 15:29:28 +0100 |
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Subject: [PATCH] module-verifier: Check range-limited relative relocations. |
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Check that they point to the same module, so will end up in the same |
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chunk of memory. |
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--- |
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util/grub-module-verifier.c | 19 ++++++++++--- |
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util/grub-module-verifierXX.c | 62 ++++++++++++++++++++++++++++++++++-------- |
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include/grub/module_verifier.h | 1 + |
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3 files changed, 67 insertions(+), 15 deletions(-) |
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diff --git a/util/grub-module-verifier.c b/util/grub-module-verifier.c |
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index d2d6984033c..c027f0a0fb1 100644 |
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--- a/util/grub-module-verifier.c |
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+++ b/util/grub-module-verifier.c |
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@@ -15,9 +15,13 @@ struct grub_module_verifier_arch archs[] = { |
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{ "x86_64", 8, 0, EM_X86_64, GRUB_MODULE_VERIFY_SUPPORTS_RELA, (int[]){ |
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R_X86_64_64, |
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R_X86_64_PC64, |
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- /* R_X86_64_32, R_X86_64_32S, R_X86_64_PC32 are supported but shouldn't be used because of their limited range. */ |
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+ /* R_X86_64_32, R_X86_64_32S are supported but shouldn't be used because of their limited range. */ |
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-1 |
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- } }, |
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+ }, (int[]){ |
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+ R_X86_64_PC32, |
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+ -1 |
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+ } |
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+ }, |
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{ "powerpc", 4, 1, EM_PPC, GRUB_MODULE_VERIFY_SUPPORTS_RELA, (int[]){ |
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GRUB_ELF_R_PPC_ADDR16_LO, |
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GRUB_ELF_R_PPC_REL24, /* It has limited range but GRUB adds trampolines when necessarry. */ |
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@@ -39,17 +43,24 @@ struct grub_module_verifier_arch archs[] = { |
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} }, |
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{ "ia64", 8, 0, EM_IA_64, GRUB_MODULE_VERIFY_SUPPORTS_RELA, (int[]){ |
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R_IA64_PCREL21B, /* We should verify that it's pointing either |
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- to a function or to a section in the same module. */ |
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+ to a function or to a section in the same module. |
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+ Checking that external symbol is a function is |
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+ non-trivial and I have never seen this relocation used |
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+ for anything else, so assume that it always points to a |
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+ function. |
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+ */ |
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R_IA64_SEGREL64LSB, |
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R_IA64_FPTR64LSB, |
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R_IA64_DIR64LSB, |
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R_IA64_PCREL64LSB, |
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- R_IA64_GPREL22, /* We should verify that it's pointing to a section in the same module. */ |
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R_IA64_LTOFF22X, |
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R_IA64_LTOFF22, |
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R_IA64_LTOFF_FPTR22, |
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R_IA64_LDXMOV, |
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-1 |
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+ }, (int[]){ |
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+ R_IA64_GPREL22, |
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+ -1 |
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} }, |
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{ "mipsel", 4, 0, EM_MIPS, GRUB_MODULE_VERIFY_SUPPORTS_REL | GRUB_MODULE_VERIFY_SUPPORTS_RELA, (int[]){ |
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R_MIPS_HI16, |
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diff --git a/util/grub-module-verifierXX.c b/util/grub-module-verifierXX.c |
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index 904be27d39b..25988ebc21d 100644 |
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--- a/util/grub-module-verifierXX.c |
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+++ b/util/grub-module-verifierXX.c |
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@@ -161,14 +161,12 @@ check_license (const struct grub_module_verifier_arch *arch, Elf_Ehdr *e) |
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grub_util_error ("incompatible license"); |
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} |
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-static void |
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-check_symbols (const struct grub_module_verifier_arch *arch, Elf_Ehdr *e) |
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+static Elf_Sym * |
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+get_symtab (const struct grub_module_verifier_arch *arch, Elf_Ehdr *e, Elf_Word *size, Elf_Word *entsize) |
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{ |
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unsigned i; |
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Elf_Shdr *s, *sections; |
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Elf_Sym *sym; |
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- const char *str; |
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- Elf_Word size, entsize; |
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sections = (Elf_Shdr *) ((char *) e + grub_target_to_host (e->e_shoff)); |
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for (i = 0, s = sections; |
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@@ -181,11 +179,19 @@ check_symbols (const struct grub_module_verifier_arch *arch, Elf_Ehdr *e) |
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grub_util_error ("no symbol table"); |
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sym = (Elf_Sym *) ((char *) e + grub_target_to_host (s->sh_offset)); |
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- size = grub_target_to_host (s->sh_size); |
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- entsize = grub_target_to_host (s->sh_entsize); |
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+ *size = grub_target_to_host (s->sh_size); |
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+ *entsize = grub_target_to_host (s->sh_entsize); |
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+ return sym; |
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+} |
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- s = (Elf_Shdr *) ((char *) sections + grub_target_to_host16 (e->e_shentsize) * grub_target_to_host32 (s->sh_link)); |
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- str = (char *) e + grub_target_to_host (s->sh_offset); |
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+static void |
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+check_symbols (const struct grub_module_verifier_arch *arch, Elf_Ehdr *e) |
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+{ |
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+ Elf_Sym *sym; |
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+ Elf_Word size, entsize; |
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+ unsigned i; |
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+ |
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+ sym = get_symtab (arch, e, &size, &entsize); |
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for (i = 0; |
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i < size / entsize; |
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@@ -208,19 +214,41 @@ check_symbols (const struct grub_module_verifier_arch *arch, Elf_Ehdr *e) |
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} |
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} |
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-/* Relocate symbols. */ |
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+static int |
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+is_symbol_local(Elf_Sym *sym) |
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+{ |
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+ switch (ELF_ST_TYPE (sym->st_info)) |
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+ { |
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+ case STT_NOTYPE: |
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+ case STT_OBJECT: |
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+ if (sym->st_name != 0 && sym->st_shndx == 0) |
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+ return 0; |
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+ return 1; |
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+ |
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+ case STT_FUNC: |
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+ case STT_SECTION: |
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+ return 1; |
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+ |
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+ default: |
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+ return 0; |
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+ } |
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+} |
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+ |
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static void |
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section_check_relocations (const struct grub_module_verifier_arch *arch, void *ehdr, |
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Elf_Shdr *s, size_t target_seg_size) |
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{ |
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Elf_Rel *rel, *max; |
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+ Elf_Sym *symtab; |
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+ Elf_Word symtabsize, symtabentsize; |
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+ |
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+ symtab = get_symtab (arch, ehdr, &symtabsize, &symtabentsize); |
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for (rel = (Elf_Rel *) ((char *) ehdr + grub_target_to_host (s->sh_offset)), |
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max = (Elf_Rel *) ((char *) rel + grub_target_to_host (s->sh_size)); |
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rel < max; |
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rel = (Elf_Rel *) ((char *) rel + grub_target_to_host (s->sh_entsize))) |
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{ |
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- Elf_Word *addr; |
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Elf_Sym *sym; |
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unsigned i; |
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@@ -235,8 +263,20 @@ section_check_relocations (const struct grub_module_verifier_arch *arch, void *e |
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for (i = 0; arch->supported_relocations[i] != -1; i++) |
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if (type == arch->supported_relocations[i]) |
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break; |
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- if (arch->supported_relocations[i] == -1) |
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+ if (arch->supported_relocations[i] != -1) |
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+ continue; |
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+ if (!arch->short_relocations) |
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grub_util_error ("unsupported relocation 0x%x", type); |
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+ for (i = 0; arch->short_relocations[i] != -1; i++) |
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+ if (type == arch->short_relocations[i]) |
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+ break; |
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+ if (arch->short_relocations[i] == -1) |
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+ grub_util_error ("unsupported relocation 0x%x", type); |
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+ sym = (Elf_Sym *) ((char *) symtab + symtabentsize * ELF_R_SYM (grub_target_to_host (rel->r_info))); |
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+ |
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+ if (is_symbol_local (sym)) |
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+ continue; |
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+ grub_util_error ("relocation 0x%x is not module-local", type); |
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} |
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} |
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diff --git a/include/grub/module_verifier.h b/include/grub/module_verifier.h |
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index 9e3a2ba720f..6cddff30f2e 100644 |
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--- a/include/grub/module_verifier.h |
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+++ b/include/grub/module_verifier.h |
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@@ -13,6 +13,7 @@ struct grub_module_verifier_arch { |
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int machine; |
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int flags; |
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const int *supported_relocations; |
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+ const int *short_relocations; |
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}; |
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void grub_module_verify64(void *module_img, size_t module_size, const struct grub_module_verifier_arch *arch);
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