linux-kernel - Re: [PATCHv7 bpf-next 8/9] selftests/bpf: Add uretprobe shadow stack test

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Date: Tue, 11 Jun 2024 07:02:12 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Jiri Olsa <jolsa@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>, Oleg Nesterov <oleg@...hat.com>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
 <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 linux-api@...r.kernel.org, linux-man@...r.kernel.org, x86@...nel.org,
 bpf@...r.kernel.org, Song Liu <songliubraving@...com>, Yonghong Song
 <yhs@...com>, John Fastabend <john.fastabend@...il.com>, Peter Zijlstra
 <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>,
 "Borislav Petkov (AMD)" <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
 Andy Lutomirski <luto@...nel.org>, "Edgecombe, Rick P"
 <rick.p.edgecombe@...el.com>, Deepak Gupta <debug@...osinc.com>
Subject: Re: [PATCHv7 bpf-next 8/9] selftests/bpf: Add uretprobe shadow
 stack test

On Thu, 23 May 2024 14:11:48 +0200
Jiri Olsa <jolsa@...nel.org> wrote:

> Adding uretprobe shadow stack test that runs all existing
> uretprobe tests with shadow stack enabled if it's available.
> 

According to the document and sample code, this looks good to me.

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thanks,

> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  .../selftests/bpf/prog_tests/uprobe_syscall.c | 60 +++++++++++++++++++
>  1 file changed, 60 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> index 3ef324c2db50..fda456401284 100644
> --- a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> @@ -9,6 +9,9 @@
>  #include <linux/compiler.h>
>  #include <linux/stringify.h>
>  #include <sys/wait.h>
> +#include <sys/syscall.h>
> +#include <sys/prctl.h>
> +#include <asm/prctl.h>
>  #include "uprobe_syscall.skel.h"
>  #include "uprobe_syscall_executed.skel.h"
>  
> @@ -297,6 +300,56 @@ static void test_uretprobe_syscall_call(void)
>  	close(go[1]);
>  	close(go[0]);
>  }
> +
> +/*
> + * Borrowed from tools/testing/selftests/x86/test_shadow_stack.c.
> + *
> + * For use in inline enablement of shadow stack.
> + *
> + * The program can't return from the point where shadow stack gets enabled
> + * because there will be no address on the shadow stack. So it can't use
> + * syscall() for enablement, since it is a function.
> + *
> + * Based on code from nolibc.h. Keep a copy here because this can't pull
> + * in all of nolibc.h.
> + */
> +#define ARCH_PRCTL(arg1, arg2)					\
> +({								\
> +	long _ret;						\
> +	register long _num  asm("eax") = __NR_arch_prctl;	\
> +	register long _arg1 asm("rdi") = (long)(arg1);		\
> +	register long _arg2 asm("rsi") = (long)(arg2);		\
> +								\
> +	asm volatile (						\
> +		"syscall\n"					\
> +		: "=a"(_ret)					\
> +		: "r"(_arg1), "r"(_arg2),			\
> +		  "0"(_num)					\
> +		: "rcx", "r11", "memory", "cc"			\
> +	);							\
> +	_ret;							\
> +})
> +
> +#ifndef ARCH_SHSTK_ENABLE
> +#define ARCH_SHSTK_ENABLE	0x5001
> +#define ARCH_SHSTK_DISABLE	0x5002
> +#define ARCH_SHSTK_SHSTK	(1ULL <<  0)
> +#endif
> +
> +static void test_uretprobe_shadow_stack(void)
> +{
> +	if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK)) {
> +		test__skip();
> +		return;
> +	}
> +
> +	/* Run all of the uretprobe tests. */
> +	test_uretprobe_regs_equal();
> +	test_uretprobe_regs_change();
> +	test_uretprobe_syscall_call();
> +
> +	ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK);
> +}
>  #else
>  static void test_uretprobe_regs_equal(void)
>  {
> @@ -312,6 +365,11 @@ static void test_uretprobe_syscall_call(void)
>  {
>  	test__skip();
>  }
> +
> +static void test_uretprobe_shadow_stack(void)
> +{
> +	test__skip();
> +}
>  #endif
>  
>  void test_uprobe_syscall(void)
> @@ -322,4 +380,6 @@ void test_uprobe_syscall(void)
>  		test_uretprobe_regs_change();
>  	if (test__start_subtest("uretprobe_syscall_call"))
>  		test_uretprobe_syscall_call();
> +	if (test__start_subtest("uretprobe_shadow_stack"))
> +		test_uretprobe_shadow_stack();
>  }
> -- 
> 2.45.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>