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
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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
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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