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>
Rename the dwarf dl_iterate_phdr callback routine and the callback_data
structure to dwarf_callback and dwarf_callback_data. Make it available
within libunwind by declaring the two at the dwarf.h header file.
Signed-off-by: Ken Werner <ken.werner@linaro.org>
Adds new function to perform a pure stack walk without unwinding,
functionally similar to backtrace() but accelerated by an address
attribute cache the caller maintains across calls.
Current implementation fails to find separate debug symbols when
.gnu_debuglink is set to the same name of the target ELF basename
(e.g. "libc.so.6" for /lib/libc.so.6). This patch fixes this by ignoring
separate debug files that contain a .gnu_debuglink section.
It also fixes a small typo in a related Debug() line.
Signed-off-by: Andris Zeila <andris.zeila@accenture.com>
the instruction after the call for a normal frame. libunwind uses
IP-1 to lookup unwind information. However, this is not necessary for
interrupted frames such as signal frames (or interrupt frames) in
the kernel context.
This patch handles both cases correctly.
Based on work by Mark Wielaard <mwielaard@redhat.com>
Original code was accessing rs_cache memory without holding a lock
in some cases. If there was sufficient cache pressure, entry being
accessed may be overwritten by another thread, resulting in a data
race.
We now make a thread local copy of the data, before releasing the
lock. If we end up supporting UNW_CACHE_PER_THREAD properly
in the future, this memcpy should be unnecessary.
Greetings,
Attached patch gets rid of additional unnecessary branch (rs_get_cache
can not return NULL unless caching_policy is UNW_CACHE_NONE), gets rid of
goto's, and makes apply_reg_state (major CPU consumer) execute with cache
lock not held (before the patch, apply_reg_state was called with lock held
for newly-inserted entries, but not for found-in-cache entries).
Tested on Linux/x86_64 with no regressions.
Thanks,
--
Paul Pluzhnikov
Greetings,
Attached patch is rather on the obvious side:
- rs1 can't be NULL since it's assigned on previous line
- rs_new never returns NULL, and if it ever did, we'd crash on memcpy that
preceeds the NULL check.
Tested on Linux/x86_64 with no regressions.
Thanks,
--
Paul Pluzhnikov
Currently, libunwind allocates several PATH_MAX entries on stack, while
trying to find a binary via /proc/.../maps.
However stack space may be at premium (especially when sigaltstack is used),
and PATH_MAX on Linux is 4096, while SIGSTKSZ is only 8192 on x86.
Attached patch eliminates multiple PATH_MAX stack allocations, and simplifies
code in maps_next, at the cost of being unable to do anything if we can't
mmap one page. It appears to me that under such low-memory conditions,
libunwind will fail shortly elsewhere anyway.
This patch also disables more of debug_frame-handling code when
CONFIG_DEBUG_FRAME is undefined.
Tested on Linux/x86_64 with and without CONFIG_DEBUG_FRAME, no regressions.
The behavior on wait vs abort unwind depends on the locking primitive
chosen by the user. This makes the API consistent and independent of
the locking primitive.
Greetings,
We use libunwind just for stack traces (I suspect many others do as well).
The use pattern is:
GetStackTrace(void** result, int max_depth)
{
...
unw_getcontext(&uc);
unw_init_local(&cursor, &uc);
while (n < max_depth) {
if (unw_get_reg(&cursor, UNW_REG_IP, (unw_word_t *) &ip) < 0) {
break;
}
result[n++] = ip;
if (unw_step(&cursor) <= 0) {
break;
}
}
Given this usage, it is quite convenient for us to block signals (or
prevent signal handlers from re-entering libunwind by other means) at the
"top level", which makes most of the sigprocmask calls performed by
libunwind itself unneccessary.
The second patch in this series adds a configure option which removes most
of the sigprocmask calls.
Attached patch is a preliminary for it -- consolidating all of the
"sigprocmask; mutex_lock;" sequences into lock_acquire and "mutex_unlock;
sigprocmask;" sequences into lock_release.
Thanks,
--
Paul Pluzhnikov
commit 402d15b123d54a7669db7cf17a76dd315094e472
Author: Paul Pluzhnikov <ppluzhnikov@google.com>
Date: Mon Sep 21 10:18:28 2009 -0700
Replace "sigprocmask + mutext_lock" with a single lock_acquire.
Likewise, replace "mutext_unlock + sigprocmask" with lock_release.
Yes, it casts to signed, but then converts right back to
unsigned via the return type. Fixed thus.
Signed-off-by: Richard Henderson <rth@redhat.com>
Signed-off-by: Arun Sharma <arun.sharma@google.com>
Now that dwarf_find_save_locs() not just finds the save-locations but
also updates the cursor-state, document this fact (the function really
is misnamed now).
2004/11/17 02:43:39-08:00 mostang.com!davidm
(struct callback_data): New structure.
(linear_search): New function.
(callback): Convert to getting auxiliary info passed via a pointer to
a callback_data structure, rather than an unw_dyn_info_t
structure.
Keep track of the maximum load address in max_load_addr.
If an object doesn't have a binary search-table, fall back
on a linear search.
(dwarf_find_proc_info): Fill in callback-data structure before calling
dl_iterate_phdr(). Upon returning, check whether
cb_data.single_fde is set and, if so, return directly, without
searching the DWARF unwind-table.
(dwarf_search_unwind_table): Adjust for renaming of
dwarf_parse_fde() to dwarf_extract_proc_info_from_fde().
If IP doesn't fall into the IP-range of the FDE-entry found
by the search, return UNW_ENOINFO.
(Logical change 1.290)
(parse_cie): Adjust for moving DWARF2 extra-info from
unw_dyn_dwarf_fde_info_t to dwarf_cie_info.
Add support for `S' augmentation ("special frames").
(dwarf_extract_proc_info_from_fde): Rename frm dwarf_parse_fde().
Convert to returning data via dwarf_cie_info rather than
unw_dyn-dwarf_fde_info_t. Allow 0-length FDE since those
can be used to indicate the end of the FDE-table. Return
the end of the FDE via *ADDRP. Ignore CIEs (we may pick them
up during linear searches through the FDE-table).
Fill in the unwind-info only if really needed. When needed,
return the info via a dynamically allocated dwarf_cie_info
structure. Add support for `S' augmentation (ABI/tag pairs).
(Logical change 1.290)
unwind-info, since DWARF expects us to do so (unlikey for ia64,
where we are guaranteed that the (return) IP points to the
correct unwind-info).
2004/11/17 02:43:39-08:00 mostang.com!davidm
(run_cfi_program): Switch over to using dwarf_cie_info instead of
unw_dyn_dwarf_fde_info_t.
(fetch_proc_info): Clear c->pi before filling it in.
(put_unwind_info): If we got non-dynamic unwind-info, free it
via a call to mempool_free().
(parse_fde): Switch over to using dwarf_cie_info instead of
unw_dyn_dwarf_fde_info_t.
(apply_reg_state): Drop accessees to c->cfa_is_sp.
2004/10/25 17:38:51+02:00 homeip.net!davidm
Fix typo: DW_CFA_CFA_expression -> DW_CFA_expression.
2004/10/21 11:15:44+02:00 homeip.net!davidm
Auto merged
2004/10/21 11:15:12+02:00 homeip.net!davidm
(run_cfi_program): Add missing newline in Debug statement.
(apply_reg_state): It was wrong to do a dwarf_get() on the CFA-location
returned by eval_location_expr(). Instead, we must make sure
we're dealing with a memory-location and, if so, just extract
the memory address as the CFA.
Also, update c->cfa only _after_ the other frame-state has
been updated. This seems to be necessary for correct parsing
of the sigtramp unwind info. Not sure yet this is 100% correct,
but it gets us through Gtest-resume-sig.
2004/10/19 23:24:56-07:00 mostang.com!davidm
(run_cfi_program): Fix typos in Debug statements.
(Logical change 1.290)
2004/10/19 23:15:02-07:00 mostang.com!davidm
(update_frame_state): Take additional argument "prev_cfa".
When we detect a NULL-frame, debug-print the IP and the CFA
so we know where things went wrong.
(dwarf_step): Get "prev_cfa" before we call dwarf_find_save_locs(),
since update_frame_state() doesn't actually update
the CFA.
(Logical change 1.290)
(pick): Likewise.
(dwarf_eval_expr): Fix "while" conditional so we see all operators.
Fix DW_OP_litN typo: "opcode = DW_OP_lit0" to
"opcode - DW_OP_lit0".
Add lots of Debug() statements so we can see what's going
on. Debug level 15 will show just entry/return values.
Debug level 16 shows all operators.
(Logical change 1.290)
