From 8c30fba366c6814c7bb1795fdda16265eb48efb0 Mon Sep 17 00:00:00 2001 From: Alan Modra Date: Sun, 8 Nov 2015 09:29:00 -0800 Subject: [PATCH 06/11] ELF unexec: _OBJC_ symbols in bss sections This code assumed that there was only one bss section. Rather than checking for a particular index, check the section type. Also, handle the possibility that the section was SHT_NOBITS originally and is unchanged, in which case no clearing is needed (and sh_offset isn't necessarily valid, which can lead to a wild memset). * unexelf.c (unexec): Properly handle _OBJC_ symbols in bss sections. --- src/unexelf.c | 31 ++++++++++++++++++------------- 1 file changed, 18 insertions(+), 13 deletions(-) diff --git a/src/unexelf.c b/src/unexelf.c index 286ba2e..df99f92 100644 --- a/src/unexelf.c +++ b/src/unexelf.c @@ -1176,20 +1176,25 @@ temacs: "_OBJC_", sizeof ("_OBJC_") - 1) == 0) { ElfW (Shdr) *new_shdr = &NEW_SECTION_H (symp->st_shndx); - ptrdiff_t reladdr = symp->st_value - new_shdr->sh_addr; - ptrdiff_t newoff = reladdr + new_shdr->sh_offset; - - /* "Unpatch" index. */ - nn = symp->st_shndx; - if (nn > old_bss_index) - nn--; - if (nn == old_bss_index) - memset (new_base + newoff, 0, symp->st_size); - else + if (new_shdr->sh_type != SHT_NOBITS) { - ElfW (Shdr) *old_shdr = &OLD_SECTION_H (nn); - ptrdiff_t oldoff = reladdr + old_shdr->sh_offset; - memcpy (new_base + newoff, old_base + oldoff, symp->st_size); + ElfW (Shdr) *old_shdr; + ptrdiff_t reladdr = symp->st_value - new_shdr->sh_addr; + ptrdiff_t newoff = reladdr + new_shdr->sh_offset; + + /* "Unpatch" index. */ + nn = symp->st_shndx; + if (nn > old_bss_index) + nn--; + old_shdr = &OLD_SECTION_H (nn); + if (old_shdr->sh_type == SHT_NOBITS) + memset (new_base + newoff, 0, symp->st_size); + else + { + ptrdiff_t oldoff = reladdr + old_shdr->sh_offset; + memcpy (new_base + newoff, old_base + oldoff, + symp->st_size); + } } } #endif -- 2.7.4