If dwarf_get returns 0 (indicating the end of call chain), we should
not override the return value to 1. This may result in the caller
continuing to unwind and getting spurious errors.
In the commit d04dc94cc2, the check for
dwarf.ip == 0 was removed from non-dwarf walker in x86_64 version of
unw_step(). Apparently this broke the detection of the end of frame
chain when NULL %rbp is specified, because the case just marked
dwarf.ip as 0. Explicitly set ret to 0 to indicate the end of
iteration.
Older kernels interpret the pid argument of the process information
sysctls as pid only. If libunwind UPT consumer passed tid to _UPT_create,
tdep_get_elf_image() returns error due to sysctls failure. Provide a
slow workaround by searching for a process owning the supplied tid if
sysctl returned ESRCH.
Currently the expression evaluation always succeeds,
and possible error is not propagated to the caller.
The ',' operator makes the condition always return 0.
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Paul Pluzhnikov <ppluzhnikov@google.com>
ALIGN lets you align pointers and STRUCT_MEMBER lets you get
structure members at a specific offset.
These are useful in general, and will be needed for the coredump notes
cleanup work.
These let you get the pid and the current signal from the coredump.
This isn't strictly unwind related, but these are trivial to implement
as we have the info, and you almost always want these when you're
printing a backtrace from a core file.
Move ptrace-independent code from src/ptrace/_UPT_find_proc_info.c
to src/dwarf/{G,L}find_unwind_table.c. Name this moved function
dwarf_find_unwind_table().
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
This is a common part of struct UPT_info
and struct UCD_info (to be introduced later).
Make _UPTi_find_unwind_table function operate only on this part
of struct UPT_info.
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Commit 7d43108f9c ("No
libunwind-generic.so if configured with --disable-shared") introduced a
check to avoid creating a broken libunwind-generic.so link, but the
result of the commit is that libunwind-generic.so is never created (at
least when installing to a clean directory).
We need to check for the installed libunwind-$(arch).so file,
libunwind-generic.so will be the symbolic link name.
There is a window of time between the munmap and the tls_cache being
marked as destroyed, where there could be a bad access to memory that
has been unmapped/freed. Reorder the code a bit to close the window.
Signed-off-by: Paul Pluzhnikov <ppluzhnikov@google.com>
Commit 297d9cd07d (Fix for failing test-setjmp)
breaks non glibc systems, since __GLIBC_PREREQ is not defined there.
As a consequence, preprocessor aborts with an error.
Trying to hide __GLIBC_PREREQ under #ifdef __GLIBC would require
either code duplication, or moving the longjmp implementation into
the separate file, which is included twice. In fact, I am not sure
in any use of the __GLIBC_PREREQ at the compile time, because the
compiled code can be run on the later version of glibc.
Below is the patch, tested on FreeBSD x86/x86_64 and Scientific Linux 6.1
x86_64. I compile the code always, but keep it in under unused static
symbol. In principle, the code could be optimized out by linker.
[ Minor formatting edits: asharma@fb.com ]
The crashes were tracked down to f->rpb_cfa_offset being incorrect.
The problem is that {rsp,rbp}_cfa_offset only have 15 bits, but for
SIGRETURN frame they are filled with:
// src/x86_64/Gstash_frame.c
f->cfa_reg_offset = d->cfa - c->sigcontext_addr;
f->rbp_cfa_offset = DWARF_GET_LOC(d->loc[RBP]) - d->cfa;
f->rsp_cfa_offset = DWARF_GET_LOC(d->loc[RSP]) - d->cfa;
The problem is that the delta here can be arbitrarily large when
sigaltstack is used, and can easily overflow the 15 and 30-bit fields.
When signal handler starts running, the stack layout is:
... higher addresses ...
ucontext
CFA->
__restore_rt (== pretcode in rt_sigframe from
linux-2.6/arch/x86/include/asm/sigframe.h)
SP ->
... sighandler runs on this stack.
... lower addresses ...
This makes it very convenient to find ucontext from the CFA.
Attached patch re-tested on Linux/x86_64, no new failures.
Signed-off-by: Paul Pluzhnikov <ppluzhnikov@google.com>
Reviwed-by: Lassi Tuura <lat@cern.ch>
On Mon, Nov 14, 2011 at 5:02 PM, Paul Pluzhnikov <ppluzhnikov@google.com> wrote:
> P.S. test-setjmp is failing for me (before or after the patch).
> When I enable assertions (to confirm my new assertions are correct), I see:
>
> lt-test-setjmp: ../../src/dwarf/Gparser.c:754: apply_reg_state: \
> Assertion `rs->reg[17].where == DWARF_WHERE_EXPR' failed.
>
> which likely explains that failure.
The problem is actually two-fold:
First, the loops in {sig,}longjmp.c are "do { ... } while (unw_step() >= 0);"
But unw_step() returns 0 on reaching the end of the chain (_start),
and the loop should stop there.
The second problem is that with this commit:
c67da0b50e
glibc obfuscates value of SP in jmp_buf, so we might as well just give up.
Patch attached.
Thanks,
--
Paul Pluzhnikov
The ARM EABI does not use the .eh_frame and .eh_frame_hdr sections for unwinding. Therefore it doesn't make sense to call dwarf_step if CONFIG_DEBUG_FRAME is not defined.
