[Crash-utility] Re: Fix for source line numbers for x86_64 modules

This patch allows the dis -l command to show real source line numbers for module code, instead of this sort of thing: crash-4.0.9> dis -l bnx2_poll_msix include/linux/cpumask.h: 612 0xffffffffa008acc3 <bnx2_poll_msix>: push %rbp 0xffffffffa008acc4 <bnx2_poll_msix+1>: mov %rsp,%rbp 0xffffffffa008acc7 <bnx2_poll_msix+4>: push %r15 0xffffffffa008acc9 <bnx2_poll_msix+6>: push %r14 0xffffffffa008accb <bnx2_poll_msix+8>: push %r13 0xffffffffa008accd <bnx2_poll_msix+10>: mov %esi,%r13d 0xffffffffa008acd0 <bnx2_poll_msix+13>: push %r12 0xffffffffa008acd2 <bnx2_poll_msix+15>: xor %r12d,%r12d 0xffffffffa008acd5 <bnx2_poll_msix+18>: push %rbx 0xffffffffa008acd6 <bnx2_poll_msix+19>: mov %rdi,%rbx 0xffffffffa008acd9 <bnx2_poll_msix+22>: sub $0x8,%rsp The problem has to do with a symbol table in the kernel containing an abnormally huge text range because of a goofy vsyscall reference in the file "arch/x86/kernel/hpet.c". (gdb) p *(struct block *)0x8d664b0 $41 = {startaddr = 0xffffffff80225130, endaddr = 0xffffffffff6001b3, This range pretty much covers the entire module address space and since the kernel file is first in the object_files list, the search stops there and returns the closest symbol from the kernel, instead of looking on through the object list to the module of actual interest. This patch causes the code to keep looking through all modules and return the real best symbol thingy (you can tell how much I really know about gdb's symtab stuff, ahem). Thanks (and blame) to John Wright for suggesting the fix once I found the problem. The patch applies to the gdb patch file in the crash directory. John and I think that this code in gdb searches things too many times, particularly with this patch, but it's a start since it seems to fix the problem. Mayhaps some gdb experts can now help do it right. With the patch, the above example becomes: crash-4.0.9> dis -l bnx2_poll_msix /build/buildd/linux-2.6-clim-2.6.29-clim/debian/build/build_amd64_none_amd64/drivers/net/bnx2.c: 3215 0xffffffffa008acc3 <bnx2_poll_msix>: push %rbp 0xffffffffa008acc4 <bnx2_poll_msix+1>: mov %rsp,%rbp 0xffffffffa008acc7 <bnx2_poll_msix+4>: push %r15 0xffffffffa008acc9 <bnx2_poll_msix+6>: push %r14 0xffffffffa008accb <bnx2_poll_msix+8>: push %r13 0xffffffffa008accd <bnx2_poll_msix+10>: mov %esi,%r13d 0xffffffffa008acd0 <bnx2_poll_msix+13>: push %r12 /build/buildd/linux-2.6-clim-2.6.29-clim/debian/build/build_amd64_none_amd64/drivers/net/bnx2.c: 3219 0xffffffffa008acd2 <bnx2_poll_msix+15>: xor %r12d,%r12d /build/buildd/linux-2.6-clim-2.6.29-clim/debian/build/build_amd64_none_amd64/drivers/net/bnx2.c: 3215 0xffffffffa008acd5 <bnx2_poll_msix+18>: push %rbx 0xffffffffa008acd6 <bnx2_poll_msix+19>: mov %rdi,%rbx 0xffffffffa008acd9 <bnx2_poll_msix+22>: sub $0x8,%rsp