path: root/usr/gen_init_cpio.c
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authorOlof Johansson <olof@lixom.net>2010-12-10 02:09:23 -0600
committerMichal Marek <mmarek@suse.cz>2010-12-28 00:22:58 +0100
commit731ece41fb1047816303295a0cdfed90a528137e (patch)
tree432d7a12f14d6ca02fe139ed305c128885847de3 /usr/gen_init_cpio.c
parentMake fixdep error handling more explicit (diff)
modpost: Fix address calculation in reloc_location()
This patch fixes a segfault in modpost that is observed when the gold linker is used to link the input objects. The problem is that reloc_location (modpost.c) is computing the address of the relocation target incorrectly. Here, elf->hdr points to the beginning of the ELF file in memory, sechdr points to the relocation section header, section is the index of the section being relocated, and sechdrs[section].sh_offset would be the offset of that section, relative to the beginning of the ELF file. Adding elf->hdr + sechdrs[section].sh_offset gives you the address of the beginning of the section, and adding r->r_offset to that gives you the address of the location to be relocated. You do not need to subtract sechdrs[section].sh_addr from that -- the result of this is an address outside the file, and causes the segfault when addend_386_rel tries to dereference it. This bug is not observed when GNU ld is used to link the inputs. The object file ubuntu/omnibook/omnibook.o is the result of an ld -r of several other files. When GNU ld does an ld -r, it sets the vaddr field for each section to 0, but gold lays out the section addresses sequentially instead: Section Headers: [Nr] Name Type Addr Off Size ES Flg Lk Inf Al [ 0] NULL 00000000 000000 000000 00 0 0 0 [ 1] .text PROGBITS 00000000 000034 004794 00 AX 0 0 4 [ 2] .data PROGBITS 0000b9d0 0047c8 0009c0 00 WA 0 0 4 [ 3] .bss NOBITS 000162f8 005188 00013c 00 WA 0 0 4 [ 4] .rodata.str1.1 PROGBITS 00004f2d 0052c4 001b1a 01 AMS 0 0 1 [ 5] .init.text PROGBITS 00004794 006dde 0005fa 00 AX 0 0 1 [ 6] .exit.text PROGBITS 00004d8e 0073d8 00018a 00 AX 0 0 1 ... So the bug in the tool remained undiscovered because the section's vaddr always happened to be 0. Signed-off-by: Raymes Khoury <raymes@google.com> Signed-off-by: Olof Johansson <olof@lixom.net> Signed-off-by: Michal Marek <mmarek@suse.cz>
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