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Subject: Re: [PATCH 2/3] selftests: vdso: Use a header file to prototype
 parse_vdso API
To:     Mark Brown <broonie@kernel.org>
Cc:     linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
        shuah <shuah@kernel.org>
References: <20200505174728.46594-1-broonie@kernel.org>
 <20200505174728.46594-3-broonie@kernel.org>
From:   shuah <shuah@kernel.org>
Message-ID: <aaeb0619-68d2-18f8-f72a-b8b37f348b4e@kernel.org>
Date:   Tue, 19 May 2020 11:29:10 -0600
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On 5/5/20 11:47 AM, Mark Brown wrote:
> Both vdso_test_gettimeofday and vdso_standalone_test_x86 use the library in
> parse_vdso.c but each separately declares the API it offers which is not
> ideal. Create a header file with prototypes of the functions and use it in
> both the library and the tests to ensure that the same prototypes are used
> throughout.
> 
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
>   tools/testing/selftests/vDSO/parse_vdso.c     | 24 +-------------
>   tools/testing/selftests/vDSO/parse_vdso.h     | 31 +++++++++++++++++++
>   .../selftests/vDSO/vdso_standalone_test_x86.c |  4 +--
>   .../selftests/vDSO/vdso_test_gettimeofday.c   |  5 +--
>   4 files changed, 34 insertions(+), 30 deletions(-)
>   create mode 100644 tools/testing/selftests/vDSO/parse_vdso.h
> 
> diff --git a/tools/testing/selftests/vDSO/parse_vdso.c b/tools/testing/selftests/vDSO/parse_vdso.c
> index 1dbb4b87268f..413f75620a35 100644
> --- a/tools/testing/selftests/vDSO/parse_vdso.c
> +++ b/tools/testing/selftests/vDSO/parse_vdso.c
> @@ -21,29 +21,7 @@
>   #include <limits.h>
>   #include <elf.h>
>   
> -/*
> - * To use this vDSO parser, first call one of the vdso_init_* functions.
> - * If you've already parsed auxv, then pass the value of AT_SYSINFO_EHDR
> - * to vdso_init_from_sysinfo_ehdr.  Otherwise pass auxv to vdso_init_from_auxv.
> - * Then call vdso_sym for each symbol you want.  For example, to look up
> - * gettimeofday on x86_64, use:
> - *
> - *     <some pointer> = vdso_sym("LINUX_2.6", "gettimeofday");
> - * or
> - *     <some pointer> = vdso_sym("LINUX_2.6", "__vdso_gettimeofday");
> - *
> - * vdso_sym will return 0 if the symbol doesn't exist or if the init function
> - * failed or was not called.  vdso_sym is a little slow, so its return value
> - * should be cached.
> - *
> - * vdso_sym is threadsafe; the init functions are not.
> - *
> - * These are the prototypes:
> - */
> -extern void vdso_init_from_auxv(void *auxv);
> -extern void vdso_init_from_sysinfo_ehdr(uintptr_t base);
> -extern void *vdso_sym(const char *version, const char *name);
> -
> +#include "parse_vdso.h"
>   
>   /* And here's the code. */
>   #ifndef ELF_BITS
> diff --git a/tools/testing/selftests/vDSO/parse_vdso.h b/tools/testing/selftests/vDSO/parse_vdso.h
> new file mode 100644
> index 000000000000..ea4b8635bb0b
> --- /dev/null
> +++ b/tools/testing/selftests/vDSO/parse_vdso.h
> @@ -0,0 +1,31 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef PARSE_VDSO_H
> +#define PARSE_VDSO_H
> +
> +#include <stdint.h>
> +
> +/*
> + * To use this vDSO parser, first call one of the vdso_init_* functions.
> + * If you've already parsed auxv, then pass the value of AT_SYSINFO_EHDR
> + * to vdso_init_from_sysinfo_ehdr.  Otherwise pass auxv to vdso_init_from_auxv.
> + * Then call vdso_sym for each symbol you want.  For example, to look up
> + * gettimeofday on x86_64, use:
> + *
> + *     <some pointer> = vdso_sym("LINUX_2.6", "gettimeofday");
> + * or
> + *     <some pointer> = vdso_sym("LINUX_2.6", "__vdso_gettimeofday");
> + *
> + * vdso_sym will return 0 if the symbol doesn't exist or if the init function
> + * failed or was not called.  vdso_sym is a little slow, so its return value
> + * should be cached.
> + *
> + * vdso_sym is threadsafe; the init functions are not.
> + *
> + * These are the prototypes:
> + */
> +extern void *vdso_sym(const char *version, const char *name);
> +extern void vdso_init_from_sysinfo_ehdr(uintptr_t base);
> +extern void vdso_init_from_auxv(void *auxv);
> +

You don't need extern here - this should be in scope?

> +#endif
> diff --git a/tools/testing/selftests/vDSO/vdso_standalone_test_x86.c b/tools/testing/selftests/vDSO/vdso_standalone_test_x86.c
> index 5ac4b00acfbc..8a44ff973ee1 100644
> --- a/tools/testing/selftests/vDSO/vdso_standalone_test_x86.c
> +++ b/tools/testing/selftests/vDSO/vdso_standalone_test_x86.c
> @@ -16,9 +16,7 @@
>   #include <unistd.h>
>   #include <stdint.h>
>   
> -extern void *vdso_sym(const char *version, const char *name);
> -extern void vdso_init_from_sysinfo_ehdr(uintptr_t base);
> -extern void vdso_init_from_auxv(void *auxv);


thanks,
-- Shuah