The clone.S patch fixes 2 elfutils testsuite unwind failures, where the
backtrace gets stuck repeating __thread_start until we hit the backtrace
limit. This was confirmed by building and installing a patched glibc and
then building elfutils and running its testsuite.
Unfortunately, the testcase isn't working as expected and I don't know why.
The testcase passes even when my clone.S patch is not installed. The testcase
looks logically similarly to the elfutils testcases that are failing. Maybe
there is a subtle difference in how the glibc unwinding works versus the
elfutils unwinding? I don't have good gdb pthread support yet, so I haven't
found a way to debug this. Anyways, I don't know if the testcase is useful or
not. If the testcase isn't useful then maybe the clone.S patch is OK without
a testcase?
Jim
[BZ #24040]
* elf/Makefile (CFLAGS-tst-unwind-main.c): Add -DUSE_PTHREADS=0.
* elf/tst-unwind-main.c: If USE_PTHEADS, include pthread.h and error.h
(func): New.
(main): If USE_PTHREADS, call pthread_create to run func. Otherwise
call func directly.
* nptl/Makefile (tests): Add tst-unwind-thread.
(CFLAGS-tst-unwind-thread.c): Define.
* nptl/tst-unwind-thread.c: New file.
* sysdeps/unix/sysv/linux/riscv/clone.S (__thread_start): Mark ra
as undefined.
---
elf/Makefile | 2 +-
elf/tst-unwind-main.c | 28 ++++++++++++++++++++++++---
nptl/Makefile | 4 +++-
nptl/tst-unwind-thread.c | 2 ++
sysdeps/unix/sysv/linux/riscv/clone.S | 5 +++++
5 files changed, 36 insertions(+), 5 deletions(-)
create mode 100644 nptl/tst-unwind-thread.c
diff --git a/elf/Makefile b/elf/Makefile
index 9cf5cd8dfd..815bbd2041 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -1497,4 +1497,4 @@ $(objpfx)tst-big-note: $(objpfx)tst-big-note-lib.so
$(objpfx)tst-unwind-ctor: $(objpfx)tst-unwind-ctor-lib.so
-CFLAGS-tst-unwind-main.c += -funwind-tables
+CFLAGS-tst-unwind-main.c += -funwind-tables -DUSE_PTHREADS=0
diff --git a/elf/tst-unwind-main.c b/elf/tst-unwind-main.c
index 4089e7e907..0c345dc31f 100644
--- a/elf/tst-unwind-main.c
+++ b/elf/tst-unwind-main.c
@@ -20,19 +20,41 @@
#include <unistd.h>
#include <support/test-driver.h>
+#if USE_PTHREADS
+# include <pthread.h>
+# include <error.h>
+#endif
+
static _Unwind_Reason_Code
callback (struct _Unwind_Context *ctx, void *arg)
{
return _URC_NO_REASON;
}
-int
-main (void)
+static void *
+func (void *a)
{
/* Arrange for this test to be killed if _Unwind_Backtrace runs into an
endless loop. We cannot use the test driver because the complete
call chain needs to be compiled with -funwind-tables so that
- _Unwind_Backtrace is able to reach _start. */
+ _Unwind_Backtrace is able to reach the start routine. */
alarm (DEFAULT_TIMEOUT);
_Unwind_Backtrace (callback, 0);
+ return a;
+}
+
+int
+main (void)
+{
+#if USE_PTHREADS
+ pthread_t thr;
+ int rc = pthread_create (&thr, NULL, &func, NULL);
+ if (rc)
+ error (1, rc, "pthread_create");
+ rc = pthread_join (thr, NULL);
+ if (rc)
+ error (1, rc, "pthread_join");
+#else
+ func (NULL);
+#endif
}
diff --git a/nptl/Makefile b/nptl/Makefile
index 340282c6cb..07c2f49235 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -319,7 +319,7 @@ tests = tst-attr1 tst-attr2 tst-attr3 tst-default-attr \
tst-cnd-basic tst-mtx-trylock tst-cnd-broadcast \
tst-cnd-timedwait tst-thrd-detach tst-mtx-basic tst-thrd-sleep \
tst-mtx-recursive tst-tss-basic tst-call-once tst-mtx-timedlock \
- tst-rwlock-pwn
+ tst-rwlock-pwn tst-unwind-thread
tests-internal := tst-rwlock19 tst-rwlock20 \
tst-sem11 tst-sem12 tst-sem13 \
@@ -709,6 +709,8 @@ $(objpfx)tst-audit-threads: $(objpfx)tst-audit-threads-mod2.so
$(objpfx)tst-audit-threads.out: $(objpfx)tst-audit-threads-mod1.so
tst-audit-threads-ENV = LD_AUDIT=$(objpfx)tst-audit-threads-mod1.so
+CFLAGS-tst-unwind-thread.c += -funwind-tables
+
# The tests here better do not run in parallel
ifneq ($(filter %tests,$(MAKECMDGOALS)),)
.NOTPARALLEL:
diff --git a/nptl/tst-unwind-thread.c b/nptl/tst-unwind-thread.c
new file mode 100644
index 0000000000..d5c38e3709
--- /dev/null
+++ b/nptl/tst-unwind-thread.c
@@ -0,0 +1,2 @@
+#define USE_PTHREADS 1
+#include "../elf/tst-unwind-main.c"
diff --git a/sysdeps/unix/sysv/linux/riscv/clone.S b/sysdeps/unix/sysv/linux/riscv/clone.S
index c079c1fb9f..0ff9ab3fd9 100644
--- a/sysdeps/unix/sysv/linux/riscv/clone.S
+++ b/sysdeps/unix/sysv/linux/riscv/clone.S
@@ -69,6 +69,11 @@ L (error):
ENTRY (__thread_start)
L (thread_start):
+ /* Terminate call stack by noting ra is undefined. Use a dummy
+ .cfi_label to force starting the FDE. */
+ .cfi_label .Ldummy
+ cfi_undefined (ra)
+
/* Restore the arg for user's function. */
REG_L a1,0(sp) /* Function pointer. */
REG_L a0,SZREG(sp) /* Argument pointer. */