--- Begin Message ---
To backtrace crashed thread from Linux core_pattern handler a special operation
similar to PTRACE_ATTACH needs to be done. This is implemented as a demo in
eu-stack's core_pattern function invoked by eu-stack's --core-pattern option.
The code of core_pattern function has been suggested by Oleg Nesterov.
src/
2014-11-26 Jan Kratochvil <jan.kratoch...@redhat.com>
* stack.c: Include sys/ptrace.h and sys/wait.h.
(OPT_CORE_PATTERN, opt_core_pattern, core_pattern): New.
(parse_opt): Handle OPT_CORE_PATTERN. Check opt_core_pattern option
validity. Call core_pattern. Pass it as assume_ptrace_stopped.
(main): Add "core-pattern" to options.
---
src/ChangeLog | 8 ++++++++
src/stack.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 60 insertions(+), 3 deletions(-)
diff --git a/src/ChangeLog b/src/ChangeLog
index 0082e65..d2c3800 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,11 @@
+2014-11-26 Jan Kratochvil <jan.kratoch...@redhat.com>
+
+ * stack.c: Include sys/ptrace.h and sys/wait.h.
+ (OPT_CORE_PATTERN, opt_core_pattern, core_pattern): New.
+ (parse_opt): Handle OPT_CORE_PATTERN. Check opt_core_pattern option
+ validity. Call core_pattern. Pass it as assume_ptrace_stopped.
+ (main): Add "core-pattern" to options.
+
2014-11-24 Mark Wielaard <m...@redhat.com>
* readelf.c (print_debug_line_section): Check line_range is not zero
diff --git a/src/stack.c b/src/stack.c
index c277dfd..b446a76 100644
--- a/src/stack.c
+++ b/src/stack.c
@@ -26,6 +26,8 @@
#include <string.h>
#include <locale.h>
#include <fcntl.h>
+#include <sys/ptrace.h>
+#include <sys/wait.h>
#include ELFUTILS_HEADER(dwfl)
#include <dwarf.h>
@@ -39,8 +41,9 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = print_version;
ARGP_PROGRAM_BUG_ADDRESS_DEF = PACKAGE_BUGREPORT;
/* non-printable argp options. */
-#define OPT_DEBUGINFO 0x100
-#define OPT_COREFILE 0x101
+#define OPT_DEBUGINFO 0x100
+#define OPT_COREFILE 0x101
+#define OPT_CORE_PATTERN 0x102
static bool show_activation = false;
static bool show_module = false;
@@ -52,6 +55,7 @@ static bool show_raw = false;
static bool show_modules = false;
static bool show_debugname = false;
static bool show_inlines = false;
+static bool opt_core_pattern = false;
static int maxframes = 256;
@@ -476,6 +480,35 @@ print_version (FILE *stream, struct argp_state *state
__attribute__ ((unused)))
fprintf (stream, "stack (%s) %s\n", PACKAGE_NAME, PACKAGE_VERSION);
}
+/* Provide PTRACE_ATTACH like operation compatible with Linux core_pattern
+ handler. */
+
+static void
+core_pattern (void)
+{
+ if (ptrace (PTRACE_SEIZE, pid, NULL, (void *) (uintptr_t) PTRACE_O_TRACEEXIT)
+ != 0)
+ error (EXIT_BAD, errno, "ptrace (PTRACE_SEIZE, PTRACE_O_TRACEEXIT)");
+ if (close (0) != 0)
+ error (EXIT_BAD, errno, "close (0; core file fd)");
+ int status;
+ pid_t got = waitpid (pid, &status, 0);
+ if (got == -1)
+ error (EXIT_BAD, errno, "waitpid ()");
+ if (got != pid)
+ error (EXIT_BAD, 0, "waitpid () returned %d but %d was expected",
+ got, pid);
+ if (! WIFSTOPPED (status))
+ error (EXIT_BAD, 0,
+ "waitpid () returned status 0x%x but WIFSTOPPED was expected",
+ status);
+ if ((status >> 8) != (SIGTRAP | (PTRACE_EVENT_EXIT << 8)))
+ error (EXIT_BAD, 0,
+ "waitpid () returned status 0x%x but (status >> 8)"
+ " == (SIGTRAP | (PTRACE_EVENT_EXIT << 8)) was expected",
+ status);
+}
+
static error_t
parse_opt (int key, char *arg __attribute__ ((unused)),
struct argp_state *state)
@@ -560,6 +593,10 @@ parse_opt (int key, char *arg __attribute__ ((unused)),
show_modules = true;
break;
+ case OPT_CORE_PATTERN:
+ opt_core_pattern = true;
+ break;
+
case ARGP_KEY_END:
if (core == NULL && exec != NULL)
argp_error (state,
@@ -573,6 +610,12 @@ parse_opt (int key, char *arg __attribute__ ((unused)),
argp_error (state,
N_("One of -p PID or --core COREFILE should be given."));
+ /* Other threads are already dead (WIFSIGNALED) and they cannot be
+ ptraced anymore. */
+ if (opt_core_pattern == true && show_one_tid == false)
+ argp_error (state,
+ N_("--core-pattern requires -1"));
+
if (pid != 0)
{
dwfl = dwfl_begin (&proc_callbacks);
@@ -601,7 +644,9 @@ parse_opt (int key, char *arg __attribute__ ((unused)),
if (pid != 0)
{
- int err = dwfl_linux_proc_attach (dwfl, pid, false);
+ if (opt_core_pattern)
+ core_pattern ();
+ int err = dwfl_linux_proc_attach (dwfl, pid, opt_core_pattern);
if (err < 0)
error (EXIT_BAD, 0, "dwfl_linux_proc_attach pid %d: %s", pid,
dwfl_errmsg (-1));
@@ -674,6 +719,10 @@ main (int argc, char **argv)
N_("Show at most MAXFRAMES per thread (default 256, use 0 for
unlimited)"), 0 },
{ "list-modules", 'l', NULL, 0,
N_("Show module memory map with build-id, elf and debug files
detected"), 0 },
+ { "core-pattern", OPT_CORE_PATTERN, NULL, 0,
+ N_("Attach process as Linux core_pattern handler; use --pid=%i; "
+ "core file fd 0 must be owned only by this process (e.g. use shell
exec); "
+ "see man 5 core"), 0 },
{ NULL, 0, NULL, 0, NULL, 0 }
};
--
1.9.3
--- End Message ---
