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Subject[PATCH 4.18 21/44] x86/vdso: Fix vDSO syscall fallback asm constraint regression
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Lutomirski <luto@kernel.org>

commit 02e425668f5c9deb42787d10001a3b605993ad15 upstream.

When I added the missing memory outputs, I failed to update the
index of the first argument (ebx) on 32-bit builds, which broke the
fallbacks. Somehow I must have screwed up my testing or gotten
lucky.

Add another test to cover gettimeofday() as well.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: 715bd9d12f84 ("x86/vdso: Fix asm constraints on vDSO syscall fallbacks")
Link: http://lkml.kernel.org/r/21bd45ab04b6d838278fa5bebfa9163eceffa13c.1538608971.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/entry/vdso/vclock_gettime.c | 8 +--
tools/testing/selftests/x86/test_vdso.c | 73 ++++++++++++++++++++++++++++++++
2 files changed, 77 insertions(+), 4 deletions(-)

--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -68,11 +68,11 @@ notrace static long vdso_fallback_gettim

asm (
"mov %%ebx, %%edx \n"
- "mov %2, %%ebx \n"
+ "mov %[clock], %%ebx \n"
"call __kernel_vsyscall \n"
"mov %%edx, %%ebx \n"
: "=a" (ret), "=m" (*ts)
- : "0" (__NR_clock_gettime), "g" (clock), "c" (ts)
+ : "0" (__NR_clock_gettime), [clock] "g" (clock), "c" (ts)
: "memory", "edx");
return ret;
}
@@ -83,11 +83,11 @@ notrace static long vdso_fallback_gtod(s

asm (
"mov %%ebx, %%edx \n"
- "mov %2, %%ebx \n"
+ "mov %[tv], %%ebx \n"
"call __kernel_vsyscall \n"
"mov %%edx, %%ebx \n"
: "=a" (ret), "=m" (*tv), "=m" (*tz)
- : "0" (__NR_gettimeofday), "g" (tv), "c" (tz)
+ : "0" (__NR_gettimeofday), [tv] "g" (tv), "c" (tz)
: "memory", "edx");
return ret;
}
--- a/tools/testing/selftests/x86/test_vdso.c
+++ b/tools/testing/selftests/x86/test_vdso.c
@@ -36,6 +36,10 @@ typedef int (*vgettime_t)(clockid_t, str

vgettime_t vdso_clock_gettime;

+typedef long (*vgtod_t)(struct timeval *tv, struct timezone *tz);
+
+vgtod_t vdso_gettimeofday;
+
typedef long (*getcpu_t)(unsigned *, unsigned *, void *);

getcpu_t vgetcpu;
@@ -104,6 +108,11 @@ static void fill_function_pointers()
vdso_clock_gettime = (vgettime_t)dlsym(vdso, "__vdso_clock_gettime");
if (!vdso_clock_gettime)
printf("Warning: failed to find clock_gettime in vDSO\n");
+
+ vdso_gettimeofday = (vgtod_t)dlsym(vdso, "__vdso_gettimeofday");
+ if (!vdso_gettimeofday)
+ printf("Warning: failed to find gettimeofday in vDSO\n");
+
}

static long sys_getcpu(unsigned * cpu, unsigned * node,
@@ -117,6 +126,11 @@ static inline int sys_clock_gettime(cloc
return syscall(__NR_clock_gettime, id, ts);
}

+static inline int sys_gettimeofday(struct timeval *tv, struct timezone *tz)
+{
+ return syscall(__NR_gettimeofday, tv, tz);
+}
+
static void test_getcpu(void)
{
printf("[RUN]\tTesting getcpu...\n");
@@ -177,6 +191,14 @@ static bool ts_leq(const struct timespec
return a->tv_nsec <= b->tv_nsec;
}

+static bool tv_leq(const struct timeval *a, const struct timeval *b)
+{
+ if (a->tv_sec != b->tv_sec)
+ return a->tv_sec < b->tv_sec;
+ else
+ return a->tv_usec <= b->tv_usec;
+}
+
static char const * const clocknames[] = {
[0] = "CLOCK_REALTIME",
[1] = "CLOCK_MONOTONIC",
@@ -248,11 +270,62 @@ static void test_clock_gettime(void)
test_one_clock_gettime(INT_MAX, "invalid");
}

+static void test_gettimeofday(void)
+{
+ struct timeval start, vdso, end;
+ struct timezone sys_tz, vdso_tz;
+ int vdso_ret, end_ret;
+
+ if (!vdso_gettimeofday)
+ return;
+
+ printf("[RUN]\tTesting gettimeofday...\n");
+
+ if (sys_gettimeofday(&start, &sys_tz) < 0) {
+ printf("[FAIL]\tsys_gettimeofday failed (%d)\n", errno);
+ nerrs++;
+ return;
+ }
+
+ vdso_ret = vdso_gettimeofday(&vdso, &vdso_tz);
+ end_ret = sys_gettimeofday(&end, NULL);
+
+ if (vdso_ret != 0 || end_ret != 0) {
+ printf("[FAIL]\tvDSO returned %d, syscall errno=%d\n",
+ vdso_ret, errno);
+ nerrs++;
+ return;
+ }
+
+ printf("\t%llu.%06ld %llu.%06ld %llu.%06ld\n",
+ (unsigned long long)start.tv_sec, start.tv_usec,
+ (unsigned long long)vdso.tv_sec, vdso.tv_usec,
+ (unsigned long long)end.tv_sec, end.tv_usec);
+
+ if (!tv_leq(&start, &vdso) || !tv_leq(&vdso, &end)) {
+ printf("[FAIL]\tTimes are out of sequence\n");
+ nerrs++;
+ }
+
+ if (sys_tz.tz_minuteswest == vdso_tz.tz_minuteswest &&
+ sys_tz.tz_dsttime == vdso_tz.tz_dsttime) {
+ printf("[OK]\ttimezones match: minuteswest=%d, dsttime=%d\n",
+ sys_tz.tz_minuteswest, sys_tz.tz_dsttime);
+ } else {
+ printf("[FAIL]\ttimezones do not match\n");
+ nerrs++;
+ }
+
+ /* And make sure that passing NULL for tz doesn't crash. */
+ vdso_gettimeofday(&vdso, NULL);
+}
+
int main(int argc, char **argv)
{
fill_function_pointers();

test_clock_gettime();
+ test_gettimeofday();

/*
* Test getcpu() last so that, if something goes wrong setting affinity,

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