[LTP] [PATCH v2 1/1] ptrace07: should not use a hard-coded xstate size and use CPUID specified instead

[Pengfei Xu]

Hi,

This patch fixes ptrace07 spurious failures when the platform xstate maxium
size is bigger than 4096bytes(512*8 bytes).

Thanks for comments!

BR.

On 2022-09-29 at 10:30:20 +0800, Pengfei Xu wrote:
> Should not use a hard-coded xstate size(512 * 8 = 4096 bytes) which is
> wrong, should use maximum XSAVE size specified by CPUID.(EAX=0DH, ECX=0H):EBX.
> If the CPU's maximum XSAVE size exceeds the hard-coded xstate size 4096 bytes,
> it will cause the ptrace07 case to fail as below:
> "
> ./ptrace07
> tst_test.c:1528: TINFO: Timeout per run is 0h 00m 30s
> ptrace07.c:142: TBROK: PTRACE_SETREGSET failed with unexpected error: EFAULT (14)
> tst_test.c:1571: TINFO: Killed the leftover descendant processes
> 
> Summary:
> passed   0
> failed   0
> broken   1
> skipped  0
> warnings 0
> "
> 
> Reported-by: Eric DeVolder <eric.devolder@oracle.com>
> Reviewed-by: Chang S. Bae <chang.seok.bae@intel.com>
> Signed-off-by: Pengfei Xu <pengfei.xu@intel.com>
> ---
>  testcases/kernel/syscalls/ptrace/ptrace07.c | 25 +++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/testcases/kernel/syscalls/ptrace/ptrace07.c b/testcases/kernel/syscalls/ptrace/ptrace07.c
> index da62cadb0..0accaceb5 100644
> --- a/testcases/kernel/syscalls/ptrace/ptrace07.c
> +++ b/testcases/kernel/syscalls/ptrace/ptrace07.c
> @@ -35,6 +35,7 @@
>  #include "config.h"
>  #include "ptrace.h"
>  #include "tst_test.h"
> +#include "ltp_cpuid.h"
>  
>  #ifndef PTRACE_GETREGSET
>  # define PTRACE_GETREGSET 0x4204
> @@ -48,6 +49,8 @@
>  # define NT_X86_XSTATE 0x202
>  #endif
>  
> +#define CPUID_LEAF_XSTATE 0xd
> +
>  static void check_regs_loop(uint32_t initval)
>  {
>  	const unsigned long num_iters = 1000000000;
> @@ -83,8 +86,15 @@ static void do_test(void)
>  	int i;
>  	int num_cpus = tst_ncpus();
>  	pid_t pid;
> -	uint64_t xstate[512];
> -	struct iovec iov = { .iov_base = xstate, .iov_len = sizeof(xstate) };
> +	uint32_t eax, ebx, ecx = 0, edx;
> +	uint64_t *xstate;
> +	/*
> +	 * CPUID.(EAX=0DH, ECX=0H):EBX: maximum size (bytes, from the beginning
> +	 * of the XSAVE/XRSTOR save area) required by enabled features in XCR0.
> +	 */
> +	cpuid(CPUID_LEAF_XSTATE, &eax, &ebx, &ecx, &edx);
> +	xstate = aligned_alloc(64, ebx);
> +	struct iovec iov = { .iov_base = xstate, .iov_len = ebx };
>  	int status;
>  	bool okay;
>  
> @@ -102,12 +112,15 @@ static void do_test(void)
>  	sched_yield();
>  
>  	TEST(ptrace(PTRACE_ATTACH, pid, 0, 0));
> -	if (TST_RET != 0)
> +	if (TST_RET != 0) {
> +		free(xstate);
>  		tst_brk(TBROK | TTERRNO, "PTRACE_ATTACH failed");
> +	}
>  
>  	SAFE_WAITPID(pid, NULL, 0);
>  	TEST(ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov));
>  	if (TST_RET != 0) {
> +		free(xstate);
>  		if (TST_ERR == EIO)
>  			tst_brk(TCONF, "GETREGSET/SETREGSET is unsupported");
>  
> @@ -138,6 +151,7 @@ static void do_test(void)
>  		tst_res(TINFO,
>  			"PTRACE_SETREGSET with reserved bits failed with EINVAL");
>  	} else {
> +		free(xstate);
>  		tst_brk(TBROK | TTERRNO,
>  			"PTRACE_SETREGSET failed with unexpected error");
>  	}
> @@ -152,8 +166,10 @@ static void do_test(void)
>  	 * worry about potential stops after this point.
>  	 */
>  	TEST(ptrace(PTRACE_DETACH, pid, 0, 0));
> -	if (TST_RET != 0)
> +	if (TST_RET != 0) {
> +		free(xstate);
>  		tst_brk(TBROK | TTERRNO, "PTRACE_DETACH failed");
> +	}
>  
>  	/* If child 'pid' crashes, only report it as info. */
>  	SAFE_WAITPID(pid, &status, 0);
> @@ -173,6 +189,7 @@ static void do_test(void)
>  	}
>  	if (okay)
>  		tst_res(TPASS, "wasn't able to set invalid FPU state");
> +	free(xstate);
>  }
>  
>  static struct tst_test test = {
> -- 
> 2.31.1
>