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os: Fix instruction pointer written in xorg_backtrace 

The address retrieved in "pip.start_ip" is not necessarily the same
address as unw_get_proc_name finds as nearest symbol and returns in "off".
Therefore using "pip.start_ip + off" is not reliable, at least
visible in the binaries from the Debian repository.

Bug-Debian: https://bugs.debian.org/971088

Signed-off-by: Bernhard Übelacker <bernhardu@mailbox.org>
This commit is contained in:
Bernhard Übelacker 2020-09-27 18:03:48 +02:00
parent acc581c96f
commit c15dd0ba48
1 changed files with 5 additions and 2 deletions
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7
os/backtrace.c
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@ -45,6 +45,7 @@ xorg_backtrace(void)
{
unw_cursor_t cursor;
unw_context_t context;
unw_word_t ip;
unw_word_t off;
unw_proc_info_t pip;
int ret, i = 0;
@ -88,7 +89,9 @@ xorg_backtrace(void)
procname[1] = 0;
}
if (dladdr((void *)(uintptr_t)(pip.start_ip + off), &dlinfo) && dlinfo.dli_fname &&
if (unw_get_reg (&cursor, UNW_REG_IP, &ip) < 0)
ip = pip.start_ip + off;
if (dladdr((void *)(uintptr_t)(ip), &dlinfo) && dlinfo.dli_fname &&
*dlinfo.dli_fname)
filename = dlinfo.dli_fname;
else
@ -96,7 +99,7 @@ xorg_backtrace(void)
ErrorFSigSafe("%u: %s (%s%s+0x%x) [%p]\n", i++, filename, procname,
ret == -UNW_ENOMEM ? "..." : "", (int)off,
(void *)(uintptr_t)(pip.start_ip + off));
(void *)(uintptr_t)(ip));
ret = unw_step(&cursor);
if (ret < 0)