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init: add a segv debugging aid, disabled by default

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2012-01-30 12:15:22 +01:00
parent 1c7724bf2a
commit da2b2da6a7
1 changed files with 51 additions and 0 deletions
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51
init/init.c
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@ -108,6 +108,8 @@
//config: Note that on Linux, init attempts to detect serial terminal and //config: Note that on Linux, init attempts to detect serial terminal and
//config: sets TERM to "vt102" if one is found. //config: sets TERM to "vt102" if one is found.
#define DEBUG_SEGV_HANDLER 0
#include "libbb.h" #include "libbb.h"
#include <syslog.h> #include <syslog.h>
#include <paths.h> #include <paths.h>
@ -118,6 +120,15 @@
#endif #endif
#include "reboot.h" /* reboot() constants */ #include "reboot.h" /* reboot() constants */
#if DEBUG_SEGV_HANDLER
# undef _GNU_SOURCE
# define _GNU_SOURCE 1
# undef __USE_GNU
# define __USE_GNU 1
# include <execinfo.h>
# include <sys/ucontext.h>
#endif
/* Used only for sanitizing purposes in set_sane_term() below. On systems where /* Used only for sanitizing purposes in set_sane_term() below. On systems where
* the baud rate is stored in a separate field, we can safely disable them. */ * the baud rate is stored in a separate field, we can safely disable them. */
#ifndef CBAUD #ifndef CBAUD
@ -957,6 +968,33 @@ static int check_delayed_sigs(void)
} }
} }
#if DEBUG_SEGV_HANDLER
static
void handle_sigsegv(int sig, siginfo_t *info, void *ucontext)
{
long ip;
ucontext_t *uc;
uc = ucontext;
ip = uc->uc_mcontext.gregs[REG_EIP];
fdprintf(2, "signal:%d address:0x%lx ip:0x%lx\n",
sig,
/* this is void*, but using %p would print "(null)"
* even for ptrs which are not exactly 0, but, say, 0x123:
*/
(long)info->si_addr,
ip);
{
/* glibc extension */
void *array[50];
int size;
size = backtrace(array, 50);
backtrace_symbols_fd(array, size, 2);
}
for (;;) sleep(9999);
}
#endif
int init_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int init_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int init_main(int argc UNUSED_PARAM, char **argv) int init_main(int argc UNUSED_PARAM, char **argv)
{ {
@ -964,6 +1002,19 @@ int init_main(int argc UNUSED_PARAM, char **argv)
return kill(1, SIGHUP); return kill(1, SIGHUP);
} }
#if DEBUG_SEGV_HANDLER
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_sigaction = handle_sigsegv;
sa.sa_flags = SA_SIGINFO;
sigaction(SIGSEGV, &sa, NULL);
sigaction(SIGILL, &sa, NULL);
sigaction(SIGFPE, &sa, NULL);
sigaction(SIGBUS, &sa, NULL);
}
#endif
if (!DEBUG_INIT) { if (!DEBUG_INIT) {
/* Expect to be invoked as init with PID=1 or be invoked as linuxrc */ /* Expect to be invoked as init with PID=1 or be invoked as linuxrc */
if (getpid() != 1 if (getpid() != 1