Re: [LTP] [PATCH v2] syscalls/prctl10: Add basic test for PR_SET/GET_TSC

[Richard Palethorpe <rpalethorpe@suse.de>]

Hello,

Yang Xu <xuyang2018.jy@fujitsu.com> writes:

> 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  | 108 +++++++++++++++++++++
>  4 files changed, 117 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 61a7b7677..51de0a614 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..01307ecd7
> --- /dev/null
> +++ b/testcases/kernel/syscalls/prctl/prctl10.c
> @@ -0,0 +1,108 @@
> +// 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 read.
> + */
> +
> +#include <sys/prctl.h>
> +#include <string.h>
> +#include <stdio.h>
> +#include <stdlib.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 const char * const 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 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 int expected_status(int status, int exp_status)
> +{
> +	if (!exp_status && WIFEXITED(status))
> +		return 0;
> +
> +	if (exp_status && WIFSIGNALED(status) && WTERMSIG(status) == exp_status)
> +		return 0;
> +
> +	return 1;
> +}
> +
> +static void verify_prctl(unsigned int n)
> +{
> +	struct tcase *tc = &tcases[n];
> +	unsigned long long time1, time2;
> +	int tsc_val = 0, pid, status;
> +
> +	pid = SAFE_FORK();
> +	if (!pid) {
> +		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);
> +
> +		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);
> +		exit(0);
> +	}
> +	SAFE_WAITPID(pid, &status, 0);
> +
> +	if (expected_status(status, tc->read_stat == PR_TSC_SIGSEGV ? SIGSEGV : 0))
> +		tst_res(TFAIL, "Test %s failed", tc->name);
> +	else
> +		tst_res(TPASS, "Test %s succeeded", tc->name);
> +}
> +
> +static struct tst_test test = {
> +	.needs_root = 1,

Why did you add this?

It doesn't require root, but it could be denied with seccomp or an
LSM. In some cases having root won't help (e.g. in a container). If
you want to handle scenarios like these, then it would be better to
check the return status of prctl.

> +	.forks_child = 1,
> +	.test = verify_prctl,
> +	.tcnt = ARRAY_SIZE(tcases),
> +	.supported_archs = (const char *const []) {
> +		"x86",
> +		"x86_64",
> +		NULL
> +	},
> +};

Otherwise LGTM.

-- 
Thank you,
Richard.

-- 
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