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charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the objtool/urgent branch of tip: Commit-ID: 799647ddb4c0ce1d7084fcf5b524e9a0c7728325 Gitweb: https://git.kernel.org/tip/799647ddb4c0ce1d7084fcf5b524e9a0c= 7728325 Author: Josh Poimboeuf AuthorDate: Tue, 02 Dec 2025 15:01:17 -08:00 Committer: Ingo Molnar 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 Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Alexandre Chartre Cc: David Laight Cc: Linus Torvalds Cc: Nathan Chancellor Cc: Peter Zijlstra Link: https://patch.msgid.link/mi4tihk4dbncn7belrhp6ooudhpw4vdggerktu5333w3= gqf3uf@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 +=3D libstring.o objtool-y +=3D libctype.o objtool-y +=3D str_error_r.o objtool-y +=3D librbtree.o +objtool-y +=3D signal.o =20 $(OUTPUT)libstring.o: ../lib/string.c FORCE $(call rule_mkdir) diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/includ= e/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 { =20 char *top_level_dir(const char *file); =20 +int init_signal_handler(void); + struct objtool_file *objtool_open_read(const char *_objname); =20 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; } =20 - int main(int argc, const char **argv) { static const char *UNUSED =3D "OBJTOOL_NOT_IMPLEMENTED"; =20 + 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 +#include +#include +#include +#include +#include + +#include +#include + +static unsigned long stack_limit; + +static bool is_stack_overflow(void *fault_addr) +{ + unsigned long fault =3D (unsigned long)fault_addr; + + /* Check if fault is in the guard page just below the limit. */ + return fault < stack_limit && fault >=3D stack_limit - 4096; +} + +static void signal_handler(int sig_num, siginfo_t *info, void *context) +{ + struct sigaction sa_dfl =3D {0}; + const char *sig_name; + char msg[256]; + int msg_len; + + switch (sig_num) { + case SIGSEGV: sig_name =3D "SIGSEGV"; break; + case SIGBUS: sig_name =3D "SIGBUS"; break; + case SIGILL: sig_name =3D "SIGILL"; break; + case SIGABRT: sig_name =3D "SIGABRT"; break; + default: sig_name =3D "Unknown signal"; break; + } + + if (is_stack_overflow(info->si_addr)) { + msg_len =3D snprintf(msg, sizeof(msg), + "%s: error: %s: objtool stack overflow!\n", + objname, sig_name); + } else { + msg_len =3D snprintf(msg, sizeof(msg), + "%s: error: %s: objtool crash!\n", + objname, sig_name); + } + + msg_len =3D write(STDERR_FILENO, msg, msg_len); + + /* Re-raise the signal to trigger the core dump */ + sa_dfl.sa_handler =3D 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 =3D 0; + FILE *fp; + + if (getrlimit(RLIMIT_STACK, &rlim)) { + ERROR_GLIBC("getrlimit"); + return -1; + } + + fp =3D 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) !=3D 2) { + ERROR_GLIBC("sscanf"); + ret =3D -1; + goto done; + } + stack_limit =3D stack_end - rlim.rlim_cur; + goto done; + } + } + + ret =3D -1; + ERROR("/proc/self/maps: can't find [stack]"); + +done: + fclose(fp); + + return ret; +} + +int init_signal_handler(void) +{ + int signals[] =3D {SIGSEGV, SIGBUS, SIGILL, SIGABRT}; + struct sigaction sa; + stack_t ss; + + if (read_stack_limit()) + return -1; + + ss.ss_sp =3D malloc(SIGSTKSZ); + if (!ss.ss_sp) { + ERROR_GLIBC("malloc"); + return -1; + } + ss.ss_size =3D SIGSTKSZ; + ss.ss_flags =3D 0; + + if (sigaltstack(&ss, NULL) =3D=3D -1) { + ERROR_GLIBC("sigaltstack"); + return -1; + } + + sa.sa_sigaction =3D signal_handler; + sigemptyset(&sa.sa_mask); + + sa.sa_flags =3D SA_ONSTACK | SA_SIGINFO; + + for (int i =3D 0; i < ARRAY_SIZE(signals); i++) { + if (sigaction(signals[i], &sa, NULL) =3D=3D -1) { + ERROR_GLIBC("sigaction"); + return -1; + } + } + + return 0; +}