linux-kernel - Re: [RFC PATCH v5 2/7] selftests: x86: test_mremap

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Message-ID: <20250212135000-861e6353-6e0a-43c3-9b28-649ae4dfc607@linutronix.de>
Date: Wed, 12 Feb 2025 14:03:59 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: jeffxu@...omium.org
Cc: akpm@...ux-foundation.org, keescook@...omium.org, jannh@...gle.com, 
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Subject: Re: [RFC PATCH v5 2/7] selftests: x86: test_mremap_vdso: skip if
 vdso is msealed

On Wed, Feb 12, 2025 at 03:21:50AM +0000, jeffxu@...omium.org wrote:
> From: Jeff Xu <jeffxu@...omium.org>
> 
> Add code to detect if the vdso is memory sealed, skip the test
> if it is.
> 
> Signed-off-by: Jeff Xu <jeffxu@...omium.org>
> ---
>  .../testing/selftests/x86/test_mremap_vdso.c  | 38 +++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
> index d53959e03593..c68077c56b22 100644
> --- a/tools/testing/selftests/x86/test_mremap_vdso.c
> +++ b/tools/testing/selftests/x86/test_mremap_vdso.c
> @@ -14,6 +14,7 @@
>  #include <errno.h>
>  #include <unistd.h>
>  #include <string.h>
> +#include <stdbool.h>
>  
>  #include <sys/mman.h>
>  #include <sys/auxv.h>
> @@ -55,13 +56,50 @@ static int try_to_remap(void *vdso_addr, unsigned long size)
>  
>  }
>  
> +#define VDSO_NAME "[vdso]"
> +#define VMFLAGS "VmFlags:"
> +#define MSEAL_FLAGS "sl"
> +#define MAX_LINE_LEN 512
> +
> +bool vdso_sealed(FILE *maps)
> +{
> +	char line[MAX_LINE_LEN];
> +	bool has_vdso = false;
> +
> +	while (fgets(line, sizeof(line), maps)) {
> +		if (strstr(line, VDSO_NAME))
> +			has_vdso = true;
> +
> +		if (has_vdso && !strncmp(line, VMFLAGS, strlen(VMFLAGS))) {
> +			if (strstr(line, MSEAL_FLAGS))
> +				return true;
> +
> +			return false;

This only tests that any mapping after the vdso is sealed.
There is a real parser for /proc/self/smaps in
tools/testing/selftests/mm/vm_util.[ch], see check_vmflag_io().

> +		}
> +	}
> +
> +	return false;
> +}

<snip>