proc: fix PIE proc-empty-vm, proc-pid-vm tests

vsyscall detection code uses direct call to the beginning of
the vsyscall page:

	asm ("call %P0" :: "i" (0xffffffffff600000))

It generates "call rel32" instruction but it is not relocated if binary
is PIE, so binary segfaults into random userspace address and vsyscall
page status is detected incorrectly.

Do more direct:

	asm ("call *%rax")

which doesn't do need any relocaltions.

Mark g_vsyscall as volatile for a good measure, I didn't find instruction
setting it to 0. Now the code is obviously correct:

	xor	eax, eax
	mov	rdi, rbp
	mov	rsi, rbp
	mov	DWORD PTR [rip+0x2d15], eax      # g_vsyscall = 0
	mov	rax, 0xffffffffff600000
	call	rax
	mov	DWORD PTR [rip+0x2d02], 1        # g_vsyscall = 1
	mov	eax, DWORD PTR ds:0xffffffffff600000
	mov	DWORD PTR [rip+0x2cf1], 2        # g_vsyscall = 2
	mov	edi, [rip+0x2ceb]                # exit(g_vsyscall)
	call	exit

Note: fixed proc-empty-vm test oopses 5.19.0-28-generic kernel
	but this is separate story.

Link: https://lkml.kernel.org/r/Y7h2xvzKLg36DSq8@p183
Fixes: 5bc73bb3451b9 ("proc: test how it holds up with mapping'less process")
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reported-by: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Tested-by: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/proc/proc-empty-vm.c b/tools/testing/selftests/proc/proc-empty-vm.c
index d95b1cb43d9d08cb6c41eaef267b992082705910..7588428b8fcd7de0791a3fc66e45503a2bc95247 100644 (file)
--- a/tools/testing/selftests/proc/proc-empty-vm.c
+++ b/tools/testing/selftests/proc/proc-empty-vm.c
@@ -25,6 +25,7 @@
 #undef NDEBUG
 #include <assert.h>
 #include <errno.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -41,7 +42,7 @@
  * 1: vsyscall VMA is --xp             vsyscall=xonly
  * 2: vsyscall VMA is r-xp             vsyscall=emulate
  */
-static int g_vsyscall;
+static volatile int g_vsyscall;
 static const char *g_proc_pid_maps_vsyscall;
 static const char *g_proc_pid_smaps_vsyscall;
 
@@ -147,11 +148,12 @@ static void vsyscall(void)
 
                g_vsyscall = 0;
                /* gettimeofday(NULL, NULL); */
+               uint64_t rax = 0xffffffffff600000;
                asm volatile (
-                       "call %P0"
-                       :
-                       : "i" (0xffffffffff600000), "D" (NULL), "S" (NULL)
-                       : "rax", "rcx", "r11"
+                       "call *%[rax]"
+                       : [rax] "+a" (rax)
+                       : "D" (NULL), "S" (NULL)
+                       : "rcx", "r11"
                );
 
                g_vsyscall = 1;

diff --git a/tools/testing/selftests/proc/proc-pid-vm.c b/tools/testing/selftests/proc/proc-pid-vm.c
index 69551bfa215c4e8321a1971f405e602a67940148..cacbd2a4aec9120b06285a47688cf4b4decc6a2d 100644 (file)
--- a/tools/testing/selftests/proc/proc-pid-vm.c
+++ b/tools/testing/selftests/proc/proc-pid-vm.c
@@ -257,11 +257,12 @@ static void vsyscall(void)
 
                g_vsyscall = 0;
                /* gettimeofday(NULL, NULL); */
+               uint64_t rax = 0xffffffffff600000;
                asm volatile (
-                       "call %P0"
-                       :
-                       : "i" (0xffffffffff600000), "D" (NULL), "S" (NULL)
-                       : "rax", "rcx", "r11"
+                       "call *%[rax]"
+                       : [rax] "+a" (rax)
+                       : "D" (NULL), "S" (NULL)
+                       : "rcx", "r11"
                );
 
                g_vsyscall = 1;