From: Michael Ellerman Date: Fri, 6 Jul 2007 09:39:49 +0000 (-0700) Subject: Fix elf_core_dump() when writing arch specific notes (spu coredumps) X-Git-Tag: v2.6.22~21 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ef7320edb1dd2cf6c969d1dcef4a9499a42f24da;p=linux-2.6 Fix elf_core_dump() when writing arch specific notes (spu coredumps) elf_core_dump() supports dumping arch specific ELF notes, via the #define ELF_CORE_WRITE_EXTRA_NOTES. Currently the only user of this is the powerpc spu coredump code. There is a bug in the handling of foffset WRT the arch notes, which causes us to erroneously increment foffset by the size of the arch notes, leaving a block of zeroes in the file, and causing all subsequent data in the file to be at + . eg: LOAD 0x050000 0x00100000 0x00000000 0x20000 0x20000 R E 0x10000 Tells us we should have a chunk of data at 0x50000. The truth is the data is at 0x90dbc = 0x50000 + 0x40dbc (the size of the arch notes). This bug prevents gdb from reading the core file correctly. The simplest fix is to simply remember the size of the arch notes, and add it to foffset after we've written the arch notes. The only drawback is that if the arch code doesn't write as many bytes as it said it would, we end up with a broken core dump again. For now I think that's a reasonable requirement. Tested on a Cell blade, gdb no longer complains about the core file being bogus. While I'm here I should point out that the spu coredump code does not work if we're dumping to a pipe - we'll have to wait for 23 to fix that. Signed-off-by: Michael Ellerman Acked-by: Arnd Bergmann Acked-by: Benjamin Herrenschmidt Acked-by: Paul Mackerras Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index fa8ea33ab0..08e4414b83 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1499,6 +1499,9 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file) #endif int thread_status_size = 0; elf_addr_t *auxv; +#ifdef ELF_CORE_WRITE_EXTRA_NOTES + int extra_notes_size; +#endif /* * We no longer stop all VM operations. @@ -1628,7 +1631,8 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file) sz += thread_status_size; #ifdef ELF_CORE_WRITE_EXTRA_NOTES - sz += ELF_CORE_EXTRA_NOTES_SIZE; + extra_notes_size = ELF_CORE_EXTRA_NOTES_SIZE; + sz += extra_notes_size; #endif fill_elf_note_phdr(&phdr, sz, offset); @@ -1674,6 +1678,7 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file) #ifdef ELF_CORE_WRITE_EXTRA_NOTES ELF_CORE_WRITE_EXTRA_NOTES; + foffset += extra_notes_size; #endif /* write out the thread status notes section */