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.
The testcase tests/Gtest-dyn1.c uses the signal() function and should
therefore include the corresponding header file.
Signed-off-by: Ken Werner <ken.werner@linaro.org>
Define GNU and processor specific values for the Phdr p_type field in case
they aren't defined by <elf.h> already.
Signed-off-by: Ken Werner <ken.werner@linaro.org>
Define unw_tdep_context rather than using ucontext_t in order to support
systems that lack ucontext.h. Note that POSIX.1-2008 removed getcontext,
makecontext and swapcontext from its specification.
Signed-off-by: Ken Werner <ken.werner@linaro.org>
Since the dl_iterate_phdr is required for local unwinding only the use of
struct dl_phdr_info can be eliminated in case libunwind gets compiled for
remote unwinding. This enhances libunwinds portability to targets that
don't provide any dl_iterate_phdr functionality.
Signed-off-by: Ken Werner <ken.werner@linaro.org>
Exclude <link.h> because it is only required for local unwinding when
iterating over the program headers.
Have the following DWARF related functions available in case of
UNW_REMOTE_ONLY because they are used by libunwind-ptrace:
dwarf_find_debug_frame
locate_debug_info
find_binary_for_address
load_debug_frame
debug_frame_tab_new
debug_frame_tab_append
debug_frame_tab_shrink
debug_frame_tab_compare
Signed-off-by: Ken Werner <ken.werner@linaro.org>
This change prevents libunwind_i.h from using a self-defined MAP_ANONYMOUS and
therefore avoids collisions in case the system header gets pulled in later.
Signed-off-by: Ken Werner <ken.werner@linaro.org>
Glibc calls thread-specific dtors in the order in which the keys were added,
so the first dtor is the trace_cache_free() one. Then thread-specific
data for some other key is free()d, which calls into unw_backtrace(),
which uses dangling cache and munmapped cache->frames.
[ Minor rename + compiler warning fix: asharma@fb.com ]
Signed-off-by: Paul Pluzhnikov <ppluzhnikov@google.com>
On FreeBSD, as well as on the Solaris < 10, weak pthread_once stub is
always exported from libc. But it does nothing, which means that if
threaded library is not loaded, then pthread_once() call do not actually
call the initializer finction. The construct
if (likely (pthread_once != 0))
{
pthread_once(&trace_cache_once, &trace_cache_init_once);
then fails to initialize the trace cache on x86_64.
Work around by checking that the initializer was indeed called.
Note that this can break if libthr is loaded dynamically, but my belief
is that there is no platforms which allow dynamic loading of the threading
library.
This keeps the definition on IA64 and all the other architectures in sync with
the declaration of _UPTi_find_unwind_table. This also mimics the behaviour of
what's done for local unwinding and allows the function to provide more than
one way to undwind.
Signed-off-by: Ken Werner <ken.werner@linaro.org>
In case the user doesn't specify whether to unwind using the ARM specific
unwind tabler or DWARF info libunwind should prefer the latter. Since DWARF
expressions are more powerful than the ARM specific unwind tables
arm_find_proc_info is changed to check for DWARF first.
Signed-off-by: Ken Werner <ken.werner@linaro.org>
Prevents unw_step from trying to unwind the stack using the ARM specific
unwind tables in case the DWARF based unwinding was successful.
Signed-off-by: Ken Werner <ken.werner@linaro.org>
