From 378f84dbb099ae3b6afbf7ac5dc45564313e3830 Mon Sep 17 00:00:00 2001 From: Pawel Wieczorkiewicz Date: Wed, 21 Aug 2019 08:20:48 +0000 Subject: [PATCH] create-diff-object: Extend patchability verification: STN_UNDEF During verification check if all sections do not contain any entries with undefined symbols (STN_UNDEF). This situation can happen when a section is copied over from its original object to a patched object, but various symbols related to the section are not copied along. This scenario happens typically during stacked hotpatches creation (between 2 different hotpatch modules). Signed-off-by: Pawel Wieczorkiewicz Reviewed-by: Martin Pohlack Reviewed-by: Bjoern Doebel Reviewed-by: Norbert Manthey Reviewed-by: Andra-Irina Paraschiv Reviewed-by: Ross Lagerwall Signed-off-by: Ross Lagerwall --- create-diff-object.c | 66 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 66 insertions(+) diff --git a/create-diff-object.c b/create-diff-object.c index 4e0f3be..1c84f81 100644 --- a/create-diff-object.c +++ b/create-diff-object.c @@ -1536,6 +1536,61 @@ static void kpatch_print_changes(struct kpatch_elf *kelf) } } +static inline int get_section_entry_size(const struct section *sec, + struct kpatch_elf *kelf) +{ + int entry_size; + + /* + * Base sections typically do not define fixed size elements. + * Detect section's element size in case it's a special section. + * Otherwise, skip it due to an unknown sh_entsize. + */ + entry_size = sec->sh.sh_entsize; + if (entry_size == 0) { + struct special_section *special; + + /* Find special section group_size. */ + for (special = special_sections; special->name; special++) { + if (!strcmp(sec->name, special->name)) + return special->group_size(kelf, 0); + } + } + + return entry_size; +} + +static int kpatch_section_has_undef_symbols(struct kpatch_elf *kelf, + const struct section *sec) +{ + int offset, entry_size; + struct rela *rela; + size_t d_size; + + entry_size = get_section_entry_size(sec, kelf); + if (entry_size == 0) + return false; + + d_size = sec->base->data->d_size; + for (offset = 0; offset < d_size; offset += entry_size) { + list_for_each_entry(rela, &sec->relas, list) { + if (rela->offset < offset || + rela->offset >= offset + entry_size) { + continue; + } + + if ((GELF_R_SYM(rela->rela.r_info) == STN_UNDEF) || + (!rela->sym->include && rela->sym->status == SAME)) { + log_normal("section %s has an entry with an undefined symbol: %s\n", + sec->name, rela->sym->name ?: "none"); + return true; + } + } + } + + return false; +} + static void kpatch_verify_patchability(struct kpatch_elf *kelf) { struct section *sec; @@ -1568,6 +1623,17 @@ static void kpatch_verify_patchability(struct kpatch_elf *kelf) errs++; } } + + /* Check if a RELA section does not contain any entries with + * undefined symbols (STN_UNDEF). This situation can happen + * when a section is copied over from its original object to + * a patched object, but various symbols related to the section + * are not copied along. + */ + if (is_rela_section(sec)) { + if (kpatch_section_has_undef_symbols(kelf, sec)) + errs++; + } } /* -- 2.39.5