----- Original Message ----- > On RHEL6(x86_64), debuginfo does not pick user_regs_struct on x86_64. > > # gdb /usr/lib/debug/lib/modules/2.6.32-71.el6.x86_64/vmlinux > GNU gdb (GDB) Red Hat Enterprise Linux (7.1-29.el6) > Copyright (C) 2010 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later > <http://gnu.org/licenses/gpl.html> > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. Type "show > copying" > and "show warranty" for details. > This GDB was configured as "x86_64-redhat-linux-gnu". > For bug reporting instructions, please see: > <http://www.gnu.org/software/gdb/bugs/>... > Reading symbols from > /usr/lib/debug/lib/modules/2.6.32-71.el6.x86_64/vmlinux...done. > (gdb) ptype struct user_regs_struct > No struct type named user_regs_struct. > > --- > x86_64.c | 25 +++++++++++++++++++++++++ > 1 files changed, 25 insertions(+), 0 deletions(-) > > diff --git a/x86_64.c b/x86_64.c > index a782334..853a1aa 100644 > --- a/x86_64.c > +++ b/x86_64.c > @@ -332,6 +332,31 @@ x86_64_init(int when) > MEMBER_OFFSET_INIT(user_regs_struct_ss, > "user_regs_struct", "ss"); > STRUCT_SIZE_INIT(user_regs_struct, "user_regs_struct"); > + if (!VALID_STRUCT(user_regs_struct)) { > + /* Use this hardwired version -- sometimes the > + * debuginfo doesn't pick this up even though > + * it exists in the kernel; it shouldn't change. > + */ > + struct x86_64_user_regs_struct { > + unsigned long long r15, r14, r13, r12, bp, bx; > + unsigned long long r11, r10, r9, r8, ax, cx, dx; > + unsigned long long si, di, orig_ax, ip, cs; > + unsigned long long flags, sp, ss, fs_base; > + unsigned long long gs_base, ds, es, fs, gs; > + }; > + ASSIGN_SIZE(user_regs_struct) = > + sizeof(struct x86_64_user_regs_struct); > + ASSIGN_OFFSET(user_regs_struct_rip) = > + offsetof(struct x86_64_user_regs_struct, ip); > + ASSIGN_OFFSET(user_regs_struct_rsp) = > + offsetof(struct x86_64_user_regs_struct, sp); > + ASSIGN_OFFSET(user_regs_struct_eflags) = > + offsetof(struct x86_64_user_regs_struct, flags); > + ASSIGN_OFFSET(user_regs_struct_cs) = > + offsetof(struct x86_64_user_regs_struct, cs); > + ASSIGN_OFFSET(user_regs_struct_ss) = > + offsetof(struct x86_64_user_regs_struct, ss); > + } > machdep->vmalloc_start = x86_64_vmalloc_start; > vt->vmalloc_start = machdep->vmalloc_start(); > machdep->init_kernel_pgd(); > -- > 1.7.1 Right -- over the years it has been "found" in some kernel version's debuginfo data, but certainly not in all kernel versions. (mostly not) But anyway, its potential non-existence has been worked around such that the offset_table entries are not required. I did test it out on ~150 sample dumpfiles, and while it doesn't break anything, it doesn't help either -- the "bt -a" output is identical with or without the patch.

Did you actually have a situation where a backtrace failed without it -- but then worked OK with your patch? And was there a reason you used "unsigned long long" declarations? I understand they are the same, but the kernel uses "unsigned long". Why the difference?

Dave