[LTP] [PATCH] syscalls/prctl10: Add basic test for PR_SET/GET_TSC
xuyang2018.jy@fujitsu.com
xuyang2018.jy@fujitsu.com
Tue Oct 11 04:41:08 CEST 2022
Hi Richard
I will accept these comment and send a v2.
Best Regards
Yang Xu
> Hello,
>
> "xuyang2018.jy@fujitsu.com" <xuyang2018.jy@fujitsu.com> writes:
>
>> Hi All
>>
>> Any comment?
>
> Ah, yes, better late than never.
>
>>
>> Best Regards
>> Yang Xu
>>> Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
>>> ---
>>> include/lapi/prctl.h | 7 ++
>>> runtest/syscalls | 1 +
>>> testcases/kernel/syscalls/prctl/.gitignore | 1 +
>>> testcases/kernel/syscalls/prctl/prctl10.c | 112 +++++++++++++++++++++
>>> 4 files changed, 121 insertions(+)
>>> create mode 100644 testcases/kernel/syscalls/prctl/prctl10.c
>>>
>>> diff --git a/include/lapi/prctl.h b/include/lapi/prctl.h
>>> index fa5922231..8d3ef5c32 100644
>>> --- a/include/lapi/prctl.h
>>> +++ b/include/lapi/prctl.h
>>> @@ -19,6 +19,13 @@
>>> # define PR_SET_SECCOMP 22
>>> #endif
>>>
>>> +#ifndef PR_SET_TSC
>>> +# define PR_GET_TSC 25
>>> +# define PR_SET_TSC 26
>>> +# define PR_TSC_ENABLE 1
>>> +# define PR_TSC_SIGSEGV 2
>>> +#endif
>>> +
>>> #ifndef PR_SET_TIMERSLACK
>>> # define PR_SET_TIMERSLACK 29
>>> # define PR_GET_TIMERSLACK 30
>>> diff --git a/runtest/syscalls b/runtest/syscalls
>>> index 36fc50aeb..a0935821a 100644
>>> --- a/runtest/syscalls
>>> +++ b/runtest/syscalls
>>> @@ -1004,6 +1004,7 @@ prctl06 prctl06
>>> prctl07 prctl07
>>> prctl08 prctl08
>>> prctl09 prctl09
>>> +prctl10 prctl10
>>>
>>> pread01 pread01
>>> pread01_64 pread01_64
>>> diff --git a/testcases/kernel/syscalls/prctl/.gitignore b/testcases/kernel/syscalls/prctl/.gitignore
>>> index 0f2c9b194..50ee4bf60 100644
>>> --- a/testcases/kernel/syscalls/prctl/.gitignore
>>> +++ b/testcases/kernel/syscalls/prctl/.gitignore
>>> @@ -8,3 +8,4 @@
>>> /prctl07
>>> /prctl08
>>> /prctl09
>>> +/prctl10
>>> diff --git a/testcases/kernel/syscalls/prctl/prctl10.c b/testcases/kernel/syscalls/prctl/prctl10.c
>>> new file mode 100644
>>> index 000000000..1b6791679
>>> --- /dev/null
>>> +++ b/testcases/kernel/syscalls/prctl/prctl10.c
>>> @@ -0,0 +1,112 @@
>>> +// SPDX-License-Identifier: GPL-2.0-or-later
>>> +/*
>>> + * Copyright (c) 2022 FUJITSU LIMITED. All rights reserved.
>>> + * Author: Yang Xu <xuyang2018.jy@fujitsu.com>
>>> + */
>>> +
>>> +/*\
>>> + * [Description]
>>> + *
>>> + * Basic test to test behaviour of PR_GET_TSC and PR_SET_TSC.
>>> + *
>>> + * Set the state of the flag determining whether the timestamp counter can
>>> + * be read by the process.
>>> + *
>>> + * - Pass PR_TSC_ENABLE to arg2 to allow it to be read.
>>> + * - Pass PR_TSC_SIGSEGV to arg2 to generate a SIGSEGV when reading TSC.
>>> + */
>>> +
>>> +#include <sys/prctl.h>
>>> +#include <string.h>
>>> +#include <stdio.h>
>>> +#include <setjmp.h>
>>> +#include "tst_test.h"
>>> +#include "lapi/prctl.h"
>>> +
>>> +#define TCASE_ENTRY(tsc_read_stat) { .name = #tsc_read_stat, .read_stat = tsc_read_stat}
>>> +
>>> +static int pass;
>>> +static sigjmp_buf env;
>>> +
>>> +static const char *tsc_read_stat_names[] = {
>>> + [0] = "[not set]",
>>> + [PR_TSC_ENABLE] = "PR_TSC_ENABLE",
>>> + [PR_TSC_SIGSEGV] = "PR_TSC_SIGSEGV",
>>> +};
>>> +
>>> +static struct tcase {
>>> + char *name;
>>> + int read_stat;
>>> +} tcases[] = {
>>> + TCASE_ENTRY(PR_TSC_ENABLE),
>>> + TCASE_ENTRY(PR_TSC_SIGSEGV)
>>> +};
>>> +
>>> +static void sighandler(int sig LTP_ATTRIBUTE_UNUSED)
>>> +{
>>> + pass = 1;
>>> + TST_EXP_PASS_SILENT(prctl(PR_SET_TSC, PR_TSC_ENABLE));
>>> + siglongjmp(env, 1);
>>> +}
>>> +
>>> +static uint64_t rdtsc(void)
>>> +{
>>> + uint32_t lo, hi;
>>> + /* We cannot use "=A", since this would use %rax on x86_64 */
>>> + __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
>>> + return (uint64_t)hi << 32 | lo;
>>> +}
>>> +
>>> +static void verify_prctl(unsigned int n)
>>> +{
>>> + struct tcase *tc = &tcases[n];
>>> + unsigned long long time1, time2;
>>> + int tsc_val = 0;
>>> +
>>> + TST_EXP_PASS_SILENT(prctl(PR_SET_TSC, tc->read_stat));
>>> + TST_EXP_PASS_SILENT(prctl(PR_GET_TSC, &tsc_val));
>>> + if (tsc_val == tc->read_stat)
>>> + tst_res(TPASS, "current state is %s(%d)",
>>> + tc->name, tc->read_stat);
>>> + else
>>> + tst_res(TFAIL, "current state is %s(%d), expect %s(%d)",
>>> + tsc_read_stat_names[tsc_val], tsc_val, tc->name, tc->read_stat);
>>> +
>>> + if (tc->read_stat == PR_TSC_SIGSEGV) {
>>> + if (sigsetjmp(env, 1) == 0)
>>> + rdtsc();
>
> I think that because rdtsc is volatile, the load of 'pass' won't be
> moved before it by the compiler. OTOH pass itself is not marked volatile and we
> are relying on the compiler infering that it is volatile from the signal
> handler instead of assuming it is 0.
>
> To be on the safe side we could mark pass as volatile or use the atomic
> functions. However see below.
>
>>> +
>>> + if (pass)
>>> + tst_res(TPASS,
>>> + "get SIGSEGV signal under PR_TSC_SIGSEGV situation");
>>> + else
>>> + tst_res(TFAIL,
>>> + "don't get SIGSEGV signal under PR_TSC_SIGSEGV situation");
>>> + pass = 0;
>>> + }
>>> +
>>> + time1 = rdtsc();
>>> + time2 = rdtsc();
>>> + if (time2 > time1)
>>> + tst_res(TPASS, "rdtsc works correctly, %lld ->%lld",
>>> + time1, time2);
>>> + else
>>> + tst_res(TFAIL, "rdtsc works incorrectly, %lld ->%lld",
>>> + time1, time2);
>>> +}
>>> +
>>> +static void setup(void)
>>> +{
>>> + SAFE_SIGNAL(SIGSEGV, sighandler);
>
> So if we segfault for any other reason some wierd stuff could
> happen. Wouldn't it be easier to fork a child process and check if it is
> killed by SIGSEGV?
>
> It would be easier for me to reason about at least.
>
>>> +}
>>> +
>>> +static struct tst_test test = {
>>> + .setup = setup,
>>> + .test = verify_prctl,
>>> + .tcnt = ARRAY_SIZE(tcases),
>>> + .supported_archs = (const char *const []) {
>>> + "x86",
>>> + "x86_64",
>>> + NULL
>>> + },
>>> +};
>
>
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