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authorDenys Vlasenko <vda.linux@googlemail.com>2012-01-30 11:15:22 (GMT)
committer Denys Vlasenko <vda.linux@googlemail.com>2012-01-30 11:15:22 (GMT)
commitda2b2da6a708edffcc3b405ab5fd7f3f11af5d33 (patch)
treeaad306641009c4faccf419327d3b9ed724d52df5
parent1c7724bf2acb6ebe28b24bd6da3b740e716b46cf (diff)
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init: add a segv debugging aid, disabled by default
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--init/init.c51
1 files changed, 51 insertions, 0 deletions
diff --git a/init/init.c b/init/init.c
index c540faa..7248946 100644
--- a/init/init.c
+++ b/init/init.c
@@ -108,6 +108,8 @@
//config: Note that on Linux, init attempts to detect serial terminal and
//config: sets TERM to "vt102" if one is found.
+#define DEBUG_SEGV_HANDLER 0
+
#include "libbb.h"
#include <syslog.h>
#include <paths.h>
@@ -118,6 +120,15 @@
#endif
#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
* the baud rate is stored in a separate field, we can safely disable them. */
#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 UNUSED_PARAM, char **argv)
{
@@ -964,6 +1002,19 @@ int init_main(int argc UNUSED_PARAM, char **argv)
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) {
/* Expect to be invoked as init with PID=1 or be invoked as linuxrc */
if (getpid() != 1