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authorKonstantin Belousov <kib@FreeBSD.org>2017-01-04 16:10:52 +0000
committerKonstantin Belousov <kib@FreeBSD.org>2017-01-04 16:10:52 +0000
commit4f64c5b3cf891e5046e67526c9b52cd79b09a7a0 (patch)
treee65ea251283831139a717e53bc4e12bc79444fc6 /lib/libc/x86/sys/__vdso_gettc.c
parent6c4338f2ef3b36c050a85514eb2b67f48066687b (diff)
downloadsrc-4f64c5b3cf891e5046e67526c9b52cd79b09a7a0.tar.gz
src-4f64c5b3cf891e5046e67526c9b52cd79b09a7a0.zip
__vdso_gettc(): be extra careful with /dev/hpet mappings, never unmap
the mapping which might be accessed by other threads. If a pointer to the /dev/hpet register page mapping was stored into the hpet_dev_map, other threads might access the page at any time. Never unmap it, instead, keep track of mappings for all hpet units in smal array. Store pointer to the newly mapped registers page using CAS, to detect parallel mappings. It appeared relatively easy to demonstrate the problem by arranging two threads which perform gettimeofday(2) concurently, first time in the process address space, when HPET is used for timecounter. PR: 215715 Sponsored by: The FreeBSD Foundation MFC after: 1 week
Notes
Notes: svn path=/head/; revision=311287
Diffstat (limited to 'lib/libc/x86/sys/__vdso_gettc.c')
-rw-r--r--lib/libc/x86/sys/__vdso_gettc.c54
1 files changed, 35 insertions, 19 deletions
diff --git a/lib/libc/x86/sys/__vdso_gettc.c b/lib/libc/x86/sys/__vdso_gettc.c
index 5097ad515650..723db6e0874e 100644
--- a/lib/libc/x86/sys/__vdso_gettc.c
+++ b/lib/libc/x86/sys/__vdso_gettc.c
@@ -1,6 +1,6 @@
/*-
* Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
- * Copyright (c) 2016 The FreeBSD Foundation
+ * Copyright (c) 2016, 2017 The FreeBSD Foundation
* All rights reserved.
*
* Portions of this software were developed by Konstantin Belousov
@@ -42,11 +42,11 @@ __FBSDID("$FreeBSD$");
#include <string.h>
#include <unistd.h>
#include "un-namespace.h"
+#include <machine/atomic.h>
#include <machine/cpufunc.h>
#include <machine/specialreg.h>
#include <dev/acpica/acpi_hpet.h>
#ifdef __amd64__
-#include <machine/atomic.h>
#include <dev/hyperv/hyperv.h>
#endif
#include "libc_private.h"
@@ -115,37 +115,47 @@ __vdso_rdtsc32(void)
return (rdtsc32());
}
-static char *hpet_dev_map = NULL;
-static uint32_t hpet_idx = 0xffffffff;
+#define HPET_DEV_MAP_MAX 10
+static volatile char *hpet_dev_map[HPET_DEV_MAP_MAX];
static void
__vdso_init_hpet(uint32_t u)
{
static const char devprefix[] = "/dev/hpet";
char devname[64], *c, *c1, t;
+ volatile char *new_map, *old_map;
+ uint32_t u1;
int fd;
c1 = c = stpcpy(devname, devprefix);
- u = hpet_idx;
+ u1 = u;
do {
- *c++ = u % 10 + '0';
- u /= 10;
- } while (u != 0);
+ *c++ = u1 % 10 + '0';
+ u1 /= 10;
+ } while (u1 != 0);
*c = '\0';
for (c--; c1 != c; c1++, c--) {
t = *c1;
*c1 = *c;
*c = t;
}
+
+ old_map = hpet_dev_map[u];
+ if (old_map != NULL)
+ return;
+
fd = _open(devname, O_RDONLY);
if (fd == -1) {
- hpet_dev_map = MAP_FAILED;
+ atomic_cmpset_rel_ptr((volatile uintptr_t *)&hpet_dev_map[u],
+ (uintptr_t)old_map, (uintptr_t)MAP_FAILED);
return;
}
- if (hpet_dev_map != NULL && hpet_dev_map != MAP_FAILED)
- munmap(hpet_dev_map, PAGE_SIZE);
- hpet_dev_map = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_SHARED, fd, 0);
+ new_map = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_SHARED, fd, 0);
_close(fd);
+ if (atomic_cmpset_rel_ptr((volatile uintptr_t *)&hpet_dev_map[u],
+ (uintptr_t)old_map, (uintptr_t)new_map) == 0 &&
+ new_map != MAP_FAILED)
+ munmap((void *)new_map, PAGE_SIZE);
}
#ifdef __amd64__
@@ -213,7 +223,8 @@ __vdso_hyperv_tsc(struct hyperv_reftsc *tsc_ref, u_int *tc)
int
__vdso_gettc(const struct vdso_timehands *th, u_int *tc)
{
- uint32_t tmp;
+ volatile char *map;
+ uint32_t idx;
switch (th->th_algo) {
case VDSO_TH_ALGO_X86_TSC:
@@ -221,14 +232,19 @@ __vdso_gettc(const struct vdso_timehands *th, u_int *tc)
__vdso_rdtsc32();
return (0);
case VDSO_TH_ALGO_X86_HPET:
- tmp = th->th_x86_hpet_idx;
- if (hpet_dev_map == NULL || tmp != hpet_idx) {
- hpet_idx = tmp;
- __vdso_init_hpet(hpet_idx);
+ idx = th->th_x86_hpet_idx;
+ if (idx >= HPET_DEV_MAP_MAX)
+ return (ENOSYS);
+ map = (volatile char *)atomic_load_acq_ptr(
+ (volatile uintptr_t *)&hpet_dev_map[idx]);
+ if (map == NULL) {
+ __vdso_init_hpet(idx);
+ map = (volatile char *)atomic_load_acq_ptr(
+ (volatile uintptr_t *)&hpet_dev_map[idx]);
}
- if (hpet_dev_map == MAP_FAILED)
+ if (map == MAP_FAILED)
return (ENOSYS);
- *tc = *(volatile uint32_t *)(hpet_dev_map + HPET_MAIN_COUNTER);
+ *tc = *(volatile uint32_t *)(map + HPET_MAIN_COUNTER);
return (0);
#ifdef __amd64__
case VDSO_TH_ALGO_X86_HVTSC: