From d1a997ba4c1bf65497d956aea90de42a6398f73a Mon Sep 17 00:00:00 2001
From: Michael Jeanson <mjeanson@efficios.com>
Date: Tue, 14 Jun 2022 11:48:30 -0400
Subject: [PATCH] selftests/rseq: check if libc rseq support is registered
Git-commit: d1a997ba4c1bf65497d956aea90de42a6398f73a
Patch-mainline: v6.0-rc1
References: git-fixes

When checking for libc rseq support in the library constructor, don't
only depend on the symbols presence, check that the registration was
completed.

This targets a scenario where the libc has rseq support but it is not
wired for the current architecture in 'bits/rseq.h', we want to fallback
to our internal registration mechanism.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/r/20220614154830.1367382-4-mjeanson@efficios.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 tools/testing/selftests/rseq/rseq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c
index 986b9458efb2..4177f9507bbe 100644
--- a/tools/testing/selftests/rseq/rseq.c
+++ b/tools/testing/selftests/rseq/rseq.c
@@ -111,7 +111,8 @@ void rseq_init(void)
 	libc_rseq_offset_p = dlsym(RTLD_NEXT, "__rseq_offset");
 	libc_rseq_size_p = dlsym(RTLD_NEXT, "__rseq_size");
 	libc_rseq_flags_p = dlsym(RTLD_NEXT, "__rseq_flags");
-	if (libc_rseq_size_p && libc_rseq_offset_p && libc_rseq_flags_p) {
+	if (libc_rseq_size_p && libc_rseq_offset_p && libc_rseq_flags_p &&
+			*libc_rseq_size_p != 0) {
 		/* rseq registration owned by glibc */
 		rseq_offset = *libc_rseq_offset_p;
 		rseq_size = *libc_rseq_size_p;
-- 
2.35.3