2021-01-18 13:40:40

by Tianjia Zhang

Subject: [PATCH] selftests/x86: Simplify the code of getting vdso base address in sgx

The base address of vDSO can be obtained through the library function
`getauxval()`, so use `getauxval(AT_SYSINFO_EHDR)` instead of a custom
implementation to simplify the code.

Reported-by: Jia Zhang <[email protected]>
Signed-off-by: Tianjia Zhang <[email protected]>
---
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..365d01dea67b 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 *)(uintptr_t)getauxval(AT_SYSINFO_EHDR);
if (!addr)
goto err;

--
2.19.1.3.ge56e4f7

2021-01-20 15:40:37

by Jarkko Sakkinen

Subject: Re: [PATCH] selftests/x86: Simplify the code of getting vdso base address in sgx

On Mon, Jan 18, 2021 at 09:33:21PM +0800, Tianjia Zhang wrote:
> The base address of vDSO can be obtained through the library function
> `getauxval()`, so use `getauxval(AT_SYSINFO_EHDR)` instead of a custom
> implementation to simplify the code.
>
> Reported-by: Jia Zhang <[email protected]>
> Signed-off-by: Tianjia Zhang <[email protected]>

- Remove reported-by, as there is no regression.
- Please write to the long description what the commit does.
It's lacking that. I.e. instead of passive form: "Obtain the
base address...".

/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..365d01dea67b 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 *)(uintptr_t)getauxval(AT_SYSINFO_EHDR);
> if (!addr)
> goto err;
>
> --
> 2.19.1.3.ge56e4f7
>
>