diff mbox series

[RFC,v3,2/2] selftests/x86: sysret_rip: Add more syscall tests with respect to `%rcx` and `%r11`

Message ID 20230124100926.637335-3-ammarfaizi2@gnuweeb.org
State Superseded
Headers show
Series None | expand

Commit Message

Ammar Faizi Jan. 24, 2023, 10:09 a.m. UTC 
From: Ammar Faizi <ammarfaizi2@gnuweeb.org>

Test that:

 - "syscall" in a FRED system doesn't clobber %rcx and %r11.
 - "syscall" in a non-FRED system sets %rcx=%rip and %r11=%rflags.

Test them out with a trivial system call like __NR_getppid and friends
which are extremely likely to return with SYSRET on an IDT system.

Link: https://lore.kernel.org/lkml/25b96960-a07e-a952-5c23-786b55054126@zytor.com
Co-developed-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Acked-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
---
 tools/testing/selftests/x86/sysret_rip.c | 9 +++++++++
 1 file changed, 9 insertions(+)
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Patch

diff --git a/tools/testing/selftests/x86/sysret_rip.c b/tools/testing/selftests/x86/sysret_rip.c
index b0d271c19ddd7834..bf90fac95a264e2d 100644
--- a/tools/testing/selftests/x86/sysret_rip.c
+++ b/tools/testing/selftests/x86/sysret_rip.c
@@ -267,8 +267,17 @@  static void test_syscall_fallthrough_to(unsigned long ip)
 	printf("[OK]\tWe survived\n");
 }
 
+static void test_syscall_rcx_r11(void)
+{
+	do_syscall(__NR_getpid, 0, 0, 0, 0, 0, 0);
+	do_syscall(__NR_gettid, 0, 0, 0, 0, 0, 0);
+	do_syscall(__NR_getppid, 0, 0, 0, 0, 0, 0);
+}
+
 int main()
 {
+	test_syscall_rcx_r11();
+
 	/*
 	 * When the kernel returns from a slow-path syscall, it will
 	 * detect whether SYSRET is appropriate.  If it incorrectly