linux-kernel - Re: [PATCH v4 1/5] selftests/x86: Use getauxval() to simplify the code in sgx

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Date:   Wed, 3 Feb 2021 00:02:49 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Shuah Khan <shuah@...nel.org>, x86@...nel.org,
        linux-sgx@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Jia Zhang <zhang.jia@...ux.alibaba.com>
Subject: Re: [PATCH v4 1/5] selftests/x86: Use getauxval() to simplify the
 code in sgx

On Mon, Feb 01, 2021 at 09:26:49PM +0800, Tianjia Zhang wrote:
> Simplify the sgx code implemntation by using library function
> getauxval() instead of a custom function to get the base address
> of vDSO.
> 
> Signed-off-by: Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>

Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>

This needs also ack from Shuah.

/Jarkko

> ---
>  tools/testing/selftests/sgx/main.c | 24 ++++--------------------
>  1 file changed, 4 insertions(+), 20 deletions(-)
> 
> diff --git a/tools/testing/selftests/sgx/main.c b/tools/testing/selftests/sgx/main.c
> index 724cec700926..5167505fbb46 100644
> --- a/tools/testing/selftests/sgx/main.c
> +++ b/tools/testing/selftests/sgx/main.c
> @@ -15,6 +15,7 @@
>  #include <sys/stat.h>
>  #include <sys/time.h>
>  #include <sys/types.h>
> +#include <sys/auxv.h>
>  #include "defines.h"
>  #include "main.h"
>  #include "../kselftest.h"
> @@ -28,24 +29,6 @@ struct vdso_symtab {
>  	Elf64_Word *elf_hashtab;
>  };
>  
> -static void *vdso_get_base_addr(char *envp[])
> -{
> -	Elf64_auxv_t *auxv;
> -	int i;
> -
> -	for (i = 0; envp[i]; i++)
> -		;
> -
> -	auxv = (Elf64_auxv_t *)&envp[i + 1];
> -
> -	for (i = 0; auxv[i].a_type != AT_NULL; i++) {
> -		if (auxv[i].a_type == AT_SYSINFO_EHDR)
> -			return (void *)auxv[i].a_un.a_val;
> -	}
> -
> -	return NULL;
> -}
> -
>  static Elf64_Dyn *vdso_get_dyntab(void *addr)
>  {
>  	Elf64_Ehdr *ehdr = addr;
> @@ -162,7 +145,7 @@ static int user_handler(long rdi, long rsi, long rdx, long ursp, long r8, long r
>  	return 0;
>  }
>  
> -int main(int argc, char *argv[], char *envp[])
> +int main(int argc, char *argv[])
>  {
>  	struct sgx_enclave_run run;
>  	struct vdso_symtab symtab;
> @@ -203,7 +186,8 @@ int main(int argc, char *argv[], char *envp[])
>  	memset(&run, 0, sizeof(run));
>  	run.tcs = encl.encl_base;
>  
> -	addr = vdso_get_base_addr(envp);
> +	/* Get vDSO base address */
> +	addr = (void *)getauxval(AT_SYSINFO_EHDR);
>  	if (!addr)
>  		goto err;
>  
> -- 
> 2.19.1.3.ge56e4f7
> 
>