mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-27 19:29:37 +00:00
![Nathan Lynch](/assets/img/avatar_default.png)
Place VDSO-related user-space code in arch/arm/kernel/vdso/. It is almost completely written in C with some assembly helpers to load the data page address, sample the counter, and fall back to system calls when necessary. The VDSO can service gettimeofday and clock_gettime when CONFIG_ARM_ARCH_TIMER is enabled and the architected timer is present (and correctly configured). It reads the CP15-based virtual counter to compute high-resolution timestamps. Of particular note is that a post-processing step ("vdsomunge") is necessary to produce a shared object which is architecturally allowed to be used by both soft- and hard-float EABI programs. The 2012 edition of the ARM ABI defines Tag_ABI_VFP_args = 3 "Code is compatible with both the base and VFP variants; the user did not permit non-variadic functions to pass FP parameters/results." Unfortunately current toolchains do not support this tag, which is ideally what we would use. The best available option is to ensure that both EF_ARM_ABI_FLOAT_SOFT and EF_ARM_ABI_FLOAT_HARD are unset in the ELF header's e_flags, indicating that the shared object is "old" and should be accepted for backward compatibility's sake. While binutils < 2.24 appear to produce a vdso.so with both flags clear, 2.24 always sets EF_ARM_ABI_FLOAT_SOFT, with no way to inhibit this behavior. So we have to fix things up with a custom post-processing step. In fact, the VDSO code in glibc does much less validation (including checking these flags) than the code for handling conventional file-backed shared libraries, so this is a bit moot unless glibc's VDSO code becomes more strict. Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
282 lines
5.5 KiB
C
282 lines
5.5 KiB
C
/*
|
|
* Copyright 2015 Mentor Graphics Corporation.
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License
|
|
* as published by the Free Software Foundation; version 2 of the
|
|
* License.
|
|
*
|
|
* This program is distributed in the hope that it will be useful, but
|
|
* WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
#include <linux/compiler.h>
|
|
#include <linux/hrtimer.h>
|
|
#include <linux/time.h>
|
|
#include <asm/arch_timer.h>
|
|
#include <asm/barrier.h>
|
|
#include <asm/bug.h>
|
|
#include <asm/page.h>
|
|
#include <asm/unistd.h>
|
|
#include <asm/vdso_datapage.h>
|
|
|
|
#ifndef CONFIG_AEABI
|
|
#error This code depends on AEABI system call conventions
|
|
#endif
|
|
|
|
extern struct vdso_data *__get_datapage(void);
|
|
|
|
static notrace u32 __vdso_read_begin(const struct vdso_data *vdata)
|
|
{
|
|
u32 seq;
|
|
repeat:
|
|
seq = ACCESS_ONCE(vdata->seq_count);
|
|
if (seq & 1) {
|
|
cpu_relax();
|
|
goto repeat;
|
|
}
|
|
return seq;
|
|
}
|
|
|
|
static notrace u32 vdso_read_begin(const struct vdso_data *vdata)
|
|
{
|
|
u32 seq;
|
|
|
|
seq = __vdso_read_begin(vdata);
|
|
|
|
smp_rmb(); /* Pairs with smp_wmb in vdso_write_end */
|
|
return seq;
|
|
}
|
|
|
|
static notrace int vdso_read_retry(const struct vdso_data *vdata, u32 start)
|
|
{
|
|
smp_rmb(); /* Pairs with smp_wmb in vdso_write_begin */
|
|
return vdata->seq_count != start;
|
|
}
|
|
|
|
static notrace long clock_gettime_fallback(clockid_t _clkid,
|
|
struct timespec *_ts)
|
|
{
|
|
register struct timespec *ts asm("r1") = _ts;
|
|
register clockid_t clkid asm("r0") = _clkid;
|
|
register long ret asm ("r0");
|
|
register long nr asm("r7") = __NR_clock_gettime;
|
|
|
|
asm volatile(
|
|
" swi #0\n"
|
|
: "=r" (ret)
|
|
: "r" (clkid), "r" (ts), "r" (nr)
|
|
: "memory");
|
|
|
|
return ret;
|
|
}
|
|
|
|
static notrace int do_realtime_coarse(struct timespec *ts,
|
|
struct vdso_data *vdata)
|
|
{
|
|
u32 seq;
|
|
|
|
do {
|
|
seq = vdso_read_begin(vdata);
|
|
|
|
ts->tv_sec = vdata->xtime_coarse_sec;
|
|
ts->tv_nsec = vdata->xtime_coarse_nsec;
|
|
|
|
} while (vdso_read_retry(vdata, seq));
|
|
|
|
return 0;
|
|
}
|
|
|
|
static notrace int do_monotonic_coarse(struct timespec *ts,
|
|
struct vdso_data *vdata)
|
|
{
|
|
struct timespec tomono;
|
|
u32 seq;
|
|
|
|
do {
|
|
seq = vdso_read_begin(vdata);
|
|
|
|
ts->tv_sec = vdata->xtime_coarse_sec;
|
|
ts->tv_nsec = vdata->xtime_coarse_nsec;
|
|
|
|
tomono.tv_sec = vdata->wtm_clock_sec;
|
|
tomono.tv_nsec = vdata->wtm_clock_nsec;
|
|
|
|
} while (vdso_read_retry(vdata, seq));
|
|
|
|
ts->tv_sec += tomono.tv_sec;
|
|
timespec_add_ns(ts, tomono.tv_nsec);
|
|
|
|
return 0;
|
|
}
|
|
|
|
#ifdef CONFIG_ARM_ARCH_TIMER
|
|
|
|
static notrace u64 get_ns(struct vdso_data *vdata)
|
|
{
|
|
u64 cycle_delta;
|
|
u64 cycle_now;
|
|
u64 nsec;
|
|
|
|
cycle_now = arch_counter_get_cntvct();
|
|
|
|
cycle_delta = (cycle_now - vdata->cs_cycle_last) & vdata->cs_mask;
|
|
|
|
nsec = (cycle_delta * vdata->cs_mult) + vdata->xtime_clock_snsec;
|
|
nsec >>= vdata->cs_shift;
|
|
|
|
return nsec;
|
|
}
|
|
|
|
static notrace int do_realtime(struct timespec *ts, struct vdso_data *vdata)
|
|
{
|
|
u64 nsecs;
|
|
u32 seq;
|
|
|
|
do {
|
|
seq = vdso_read_begin(vdata);
|
|
|
|
if (!vdata->tk_is_cntvct)
|
|
return -1;
|
|
|
|
ts->tv_sec = vdata->xtime_clock_sec;
|
|
nsecs = get_ns(vdata);
|
|
|
|
} while (vdso_read_retry(vdata, seq));
|
|
|
|
ts->tv_nsec = 0;
|
|
timespec_add_ns(ts, nsecs);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static notrace int do_monotonic(struct timespec *ts, struct vdso_data *vdata)
|
|
{
|
|
struct timespec tomono;
|
|
u64 nsecs;
|
|
u32 seq;
|
|
|
|
do {
|
|
seq = vdso_read_begin(vdata);
|
|
|
|
if (!vdata->tk_is_cntvct)
|
|
return -1;
|
|
|
|
ts->tv_sec = vdata->xtime_clock_sec;
|
|
nsecs = get_ns(vdata);
|
|
|
|
tomono.tv_sec = vdata->wtm_clock_sec;
|
|
tomono.tv_nsec = vdata->wtm_clock_nsec;
|
|
|
|
} while (vdso_read_retry(vdata, seq));
|
|
|
|
ts->tv_sec += tomono.tv_sec;
|
|
ts->tv_nsec = 0;
|
|
timespec_add_ns(ts, nsecs + tomono.tv_nsec);
|
|
|
|
return 0;
|
|
}
|
|
|
|
#else /* CONFIG_ARM_ARCH_TIMER */
|
|
|
|
static notrace int do_realtime(struct timespec *ts, struct vdso_data *vdata)
|
|
{
|
|
return -1;
|
|
}
|
|
|
|
static notrace int do_monotonic(struct timespec *ts, struct vdso_data *vdata)
|
|
{
|
|
return -1;
|
|
}
|
|
|
|
#endif /* CONFIG_ARM_ARCH_TIMER */
|
|
|
|
notrace int __vdso_clock_gettime(clockid_t clkid, struct timespec *ts)
|
|
{
|
|
struct vdso_data *vdata;
|
|
int ret = -1;
|
|
|
|
vdata = __get_datapage();
|
|
|
|
switch (clkid) {
|
|
case CLOCK_REALTIME_COARSE:
|
|
ret = do_realtime_coarse(ts, vdata);
|
|
break;
|
|
case CLOCK_MONOTONIC_COARSE:
|
|
ret = do_monotonic_coarse(ts, vdata);
|
|
break;
|
|
case CLOCK_REALTIME:
|
|
ret = do_realtime(ts, vdata);
|
|
break;
|
|
case CLOCK_MONOTONIC:
|
|
ret = do_monotonic(ts, vdata);
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
if (ret)
|
|
ret = clock_gettime_fallback(clkid, ts);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static notrace long gettimeofday_fallback(struct timeval *_tv,
|
|
struct timezone *_tz)
|
|
{
|
|
register struct timezone *tz asm("r1") = _tz;
|
|
register struct timeval *tv asm("r0") = _tv;
|
|
register long ret asm ("r0");
|
|
register long nr asm("r7") = __NR_gettimeofday;
|
|
|
|
asm volatile(
|
|
" swi #0\n"
|
|
: "=r" (ret)
|
|
: "r" (tv), "r" (tz), "r" (nr)
|
|
: "memory");
|
|
|
|
return ret;
|
|
}
|
|
|
|
notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
|
|
{
|
|
struct timespec ts;
|
|
struct vdso_data *vdata;
|
|
int ret;
|
|
|
|
vdata = __get_datapage();
|
|
|
|
ret = do_realtime(&ts, vdata);
|
|
if (ret)
|
|
return gettimeofday_fallback(tv, tz);
|
|
|
|
if (tv) {
|
|
tv->tv_sec = ts.tv_sec;
|
|
tv->tv_usec = ts.tv_nsec / 1000;
|
|
}
|
|
if (tz) {
|
|
tz->tz_minuteswest = vdata->tz_minuteswest;
|
|
tz->tz_dsttime = vdata->tz_dsttime;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
/* Avoid unresolved references emitted by GCC */
|
|
|
|
void __aeabi_unwind_cpp_pr0(void)
|
|
{
|
|
}
|
|
|
|
void __aeabi_unwind_cpp_pr1(void)
|
|
{
|
|
}
|
|
|
|
void __aeabi_unwind_cpp_pr2(void)
|
|
{
|
|
}
|