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Message-ID: <176478772690.498.8199558037824404381.tip-bot2@tip-bot2>
Date: Wed, 03 Dec 2025 18:48:46 -0000
From: "tip-bot2 for Josh Poimboeuf" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Ingo Molnar <mingo@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
Alexandre Chartre <alexandre.chartre@...cle.com>,
David Laight <david.laight.linux@...il.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Nathan Chancellor <nathan@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: objtool/urgent] objtool: Add more robust signal error handling,
detect and warn about stack overflows
The following commit has been merged into the objtool/urgent branch of tip:
Commit-ID: 799647ddb4c0ce1d7084fcf5b524e9a0c7728325
Gitweb: https://git.kernel.org/tip/799647ddb4c0ce1d7084fcf5b524e9a0c7728325
Author: Josh Poimboeuf <jpoimboe@...nel.org>
AuthorDate: Tue, 02 Dec 2025 15:01:17 -08:00
Committer: Ingo Molnar <mingo@...nel.org>
CommitterDate: Wed, 03 Dec 2025 19:42:37 +01:00
objtool: Add more robust signal error handling, detect and warn about stack overflows
When the kernel build fails due to an objtool segfault, the error
message is a bit obtuse and confusing:
make[5]: *** [scripts/Makefile.build:503: drivers/scsi/qla2xxx/qla2xxx.o] Error 139
^^^^^^^^^
make[5]: *** Deleting file 'drivers/scsi/qla2xxx/qla2xxx.o'
make[4]: *** [scripts/Makefile.build:556: drivers/scsi/qla2xxx] Error 2
make[3]: *** [scripts/Makefile.build:556: drivers/scsi] Error 2
make[2]: *** [scripts/Makefile.build:556: drivers] Error 2
make[1]: *** [/home/jpoimboe/git/linux/Makefile:2013: .] Error 2
make: *** [Makefile:248: __sub-make] Error 2
Add a signal handler to objtool which prints an error message like if
the local stack has overflown (for which there's a chance as objtool
makes heavy use of recursion):
drivers/scsi/qla2xxx/qla2xxx.o: error: SIGSEGV: objtool stack overflow!
or:
drivers/scsi/qla2xxx/qla2xxx.o: error: SIGSEGV: objtool crash!
Also, re-raise the signal so the core dump still gets triggered.
[ mingo: Applied a build fix, added more comments and prettified the code. ]
Suggested-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Alexandre Chartre <alexandre.chartre@...cle.com>
Cc: David Laight <david.laight.linux@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: https://patch.msgid.link/mi4tihk4dbncn7belrhp6ooudhpw4vdggerktu5333w3gqf3uf@vqlhc3y667mg
---
tools/objtool/Build | 1 +-
tools/objtool/include/objtool/objtool.h | 2 +-
tools/objtool/objtool.c | 4 +-
tools/objtool/signal.c | 135 +++++++++++++++++++++++-
4 files changed, 141 insertions(+), 1 deletion(-)
create mode 100644 tools/objtool/signal.c
diff --git a/tools/objtool/Build b/tools/objtool/Build
index 9982e66..600da05 100644
--- a/tools/objtool/Build
+++ b/tools/objtool/Build
@@ -18,6 +18,7 @@ objtool-y += libstring.o
objtool-y += libctype.o
objtool-y += str_error_r.o
objtool-y += librbtree.o
+objtool-y += signal.o
$(OUTPUT)libstring.o: ../lib/string.c FORCE
$(call rule_mkdir)
diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h
index f7051bb..6dc12a5 100644
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -41,6 +41,8 @@ struct objtool_file {
char *top_level_dir(const char *file);
+int init_signal_handler(void);
+
struct objtool_file *objtool_open_read(const char *_objname);
int objtool_pv_add(struct objtool_file *file, int idx, struct symbol *func);
diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
index 3c26ed5..1c36221 100644
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -104,11 +104,13 @@ char *top_level_dir(const char *file)
return str;
}
-
int main(int argc, const char **argv)
{
static const char *UNUSED = "OBJTOOL_NOT_IMPLEMENTED";
+ if (init_signal_handler())
+ return -1;
+
/* libsubcmd init */
exec_cmd_init("objtool", UNUSED, UNUSED, UNUSED);
pager_init(UNUSED);
diff --git a/tools/objtool/signal.c b/tools/objtool/signal.c
new file mode 100644
index 0000000..af5c65c
--- /dev/null
+++ b/tools/objtool/signal.c
@@ -0,0 +1,135 @@
+/*
+ * signal.c: Register a sigaltstack for objtool, to be able to
+ * run a signal handler on a separate stack even if
+ * the main process stack has overflown. Print out
+ * stack overflow errors when this happens.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sys/resource.h>
+#include <string.h>
+
+#include <objtool/objtool.h>
+#include <objtool/warn.h>
+
+static unsigned long stack_limit;
+
+static bool is_stack_overflow(void *fault_addr)
+{
+ unsigned long fault = (unsigned long)fault_addr;
+
+ /* Check if fault is in the guard page just below the limit. */
+ return fault < stack_limit && fault >= stack_limit - 4096;
+}
+
+static void signal_handler(int sig_num, siginfo_t *info, void *context)
+{
+ struct sigaction sa_dfl = {0};
+ const char *sig_name;
+ char msg[256];
+ int msg_len;
+
+ switch (sig_num) {
+ case SIGSEGV: sig_name = "SIGSEGV"; break;
+ case SIGBUS: sig_name = "SIGBUS"; break;
+ case SIGILL: sig_name = "SIGILL"; break;
+ case SIGABRT: sig_name = "SIGABRT"; break;
+ default: sig_name = "Unknown signal"; break;
+ }
+
+ if (is_stack_overflow(info->si_addr)) {
+ msg_len = snprintf(msg, sizeof(msg),
+ "%s: error: %s: objtool stack overflow!\n",
+ objname, sig_name);
+ } else {
+ msg_len = snprintf(msg, sizeof(msg),
+ "%s: error: %s: objtool crash!\n",
+ objname, sig_name);
+ }
+
+ msg_len = write(STDERR_FILENO, msg, msg_len);
+
+ /* Re-raise the signal to trigger the core dump */
+ sa_dfl.sa_handler = SIG_DFL;
+ sigaction(sig_num, &sa_dfl, NULL);
+ raise(sig_num);
+}
+
+static int read_stack_limit(void)
+{
+ unsigned long stack_start, stack_end;
+ struct rlimit rlim;
+ char line[256];
+ int ret = 0;
+ FILE *fp;
+
+ if (getrlimit(RLIMIT_STACK, &rlim)) {
+ ERROR_GLIBC("getrlimit");
+ return -1;
+ }
+
+ fp = fopen("/proc/self/maps", "r");
+ if (!fp) {
+ ERROR_GLIBC("fopen");
+ return -1;
+ }
+
+ while (fgets(line, sizeof(line), fp)) {
+ if (strstr(line, "[stack]")) {
+ if (sscanf(line, "%lx-%lx", &stack_start, &stack_end) != 2) {
+ ERROR_GLIBC("sscanf");
+ ret = -1;
+ goto done;
+ }
+ stack_limit = stack_end - rlim.rlim_cur;
+ goto done;
+ }
+ }
+
+ ret = -1;
+ ERROR("/proc/self/maps: can't find [stack]");
+
+done:
+ fclose(fp);
+
+ return ret;
+}
+
+int init_signal_handler(void)
+{
+ int signals[] = {SIGSEGV, SIGBUS, SIGILL, SIGABRT};
+ struct sigaction sa;
+ stack_t ss;
+
+ if (read_stack_limit())
+ return -1;
+
+ ss.ss_sp = malloc(SIGSTKSZ);
+ if (!ss.ss_sp) {
+ ERROR_GLIBC("malloc");
+ return -1;
+ }
+ ss.ss_size = SIGSTKSZ;
+ ss.ss_flags = 0;
+
+ if (sigaltstack(&ss, NULL) == -1) {
+ ERROR_GLIBC("sigaltstack");
+ return -1;
+ }
+
+ sa.sa_sigaction = signal_handler;
+ sigemptyset(&sa.sa_mask);
+
+ sa.sa_flags = SA_ONSTACK | SA_SIGINFO;
+
+ for (int i = 0; i < ARRAY_SIZE(signals); i++) {
+ if (sigaction(signals[i], &sa, NULL) == -1) {
+ ERROR_GLIBC("sigaction");
+ return -1;
+ }
+ }
+
+ return 0;
+}
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