[PATCH v2] selftests/ptrace/get_syscall_info: fix for MIPS n32

[Shuah Khan]

On 1/15/25 16:37, Dmitry V. Levin wrote:
> MIPS n32 is one of two ILP32 architectures supported by the kernel
> that have 64-bit syscall arguments (another one is x32).
> 
> When this test passed 32-bit arguments to syscall(), they were
> sign-extended in libc, PTRACE_GET_SYSCALL_INFO reported these
> sign-extended 64-bit values, and the test complained about the mismatch.
> 
> Fix this by passing arguments of the appropriate type to syscall(),
> which is "unsigned long long" on MIPS n32, and __kernel_ulong_t on other
> architectures.
> 
> As a side effect, this also extends the test on all 64-bit architectures
> by choosing constants that don't fit into 32-bit integers.
> 
> Signed-off-by: Dmitry V. Levin <ldv at strace.io>
> ---
> 
> v2: Fixed MIPS #ifdef.
> 
>   .../selftests/ptrace/get_syscall_info.c       | 53 +++++++++++--------
>   1 file changed, 32 insertions(+), 21 deletions(-)
> 
> diff --git a/tools/testing/selftests/ptrace/get_syscall_info.c b/tools/testing/selftests/ptrace/get_syscall_info.c
> index 5bcd1c7b5be6..2970f72d66d3 100644
> --- a/tools/testing/selftests/ptrace/get_syscall_info.c
> +++ b/tools/testing/selftests/ptrace/get_syscall_info.c
> @@ -11,8 +11,19 @@
>   #include <err.h>
>   #include <signal.h>
>   #include <asm/unistd.h>
> +#include <linux/types.h>
>   #include "linux/ptrace.h"
>   
> +#if defined(_MIPS_SIM) && _MIPS_SIM == _MIPS_SIM_NABI32
> +/*
> + * MIPS N32 is the only architecture where __kernel_ulong_t
> + * does not match the bitness of syscall arguments.
> + */
> +typedef unsigned long long kernel_ulong_t;
> +#else
> +typedef __kernel_ulong_t kernel_ulong_t;
> +#endif
> +

What's the reason for adding these typedefs? checkpatch should
have warned you about adding new typedefs.

Also this introduces kernel_ulong_t in user-space test code.
Something to avoid.

>   static int
>   kill_tracee(pid_t pid)
>   {
> @@ -42,37 +53,37 @@ sys_ptrace(int request, pid_t pid, unsigned long addr, unsigned long data)
>   
>   TEST(get_syscall_info)
>   {
> -	static const unsigned long args[][7] = {
> +	const kernel_ulong_t args[][7] = {
>   		/* a sequence of architecture-agnostic syscalls */
>   		{
>   			__NR_chdir,
> -			(unsigned long) "",
> -			0xbad1fed1,
> -			0xbad2fed2,
> -			0xbad3fed3,
> -			0xbad4fed4,
> -			0xbad5fed5
> +			(uintptr_t) "",

You could use ifdef here.

> +			(kernel_ulong_t) 0xdad1bef1bad1fed1ULL,
> +			(kernel_ulong_t) 0xdad2bef2bad2fed2ULL,
> +			(kernel_ulong_t) 0xdad3bef3bad3fed3ULL,
> +			(kernel_ulong_t) 0xdad4bef4bad4fed4ULL,
> +			(kernel_ulong_t) 0xdad5bef5bad5fed5ULL
>   		},
>   		{
>   			__NR_gettid,
> -			0xcaf0bea0,
> -			0xcaf1bea1,
> -			0xcaf2bea2,
> -			0xcaf3bea3,
> -			0xcaf4bea4,
> -			0xcaf5bea5
> +			(kernel_ulong_t) 0xdad0bef0caf0bea0ULL,
> +			(kernel_ulong_t) 0xdad1bef1caf1bea1ULL,
> +			(kernel_ulong_t) 0xdad2bef2caf2bea2ULL,
> +			(kernel_ulong_t) 0xdad3bef3caf3bea3ULL,
> +			(kernel_ulong_t) 0xdad4bef4caf4bea4ULL,
> +			(kernel_ulong_t) 0xdad5bef5caf5bea5ULL
>   		},
>   		{
>   			__NR_exit_group,
>   			0,
> -			0xfac1c0d1,
> -			0xfac2c0d2,
> -			0xfac3c0d3,
> -			0xfac4c0d4,
> -			0xfac5c0d5
> +			(kernel_ulong_t) 0xdad1bef1fac1c0d1ULL,
> +			(kernel_ulong_t) 0xdad2bef2fac2c0d2ULL,
> +			(kernel_ulong_t) 0xdad3bef3fac3c0d3ULL,
> +			(kernel_ulong_t) 0xdad4bef4fac4c0d4ULL,
> +			(kernel_ulong_t) 0xdad5bef5fac5c0d5ULL
>   		}
>   	};
> -	const unsigned long *exp_args;
> +	const kernel_ulong_t *exp_args;
>   
>   	pid_t pid = fork();
>   
> @@ -154,7 +165,7 @@ TEST(get_syscall_info)
>   			}
>   			ASSERT_LT(0, (rc = sys_ptrace(PTRACE_GET_SYSCALL_INFO,
>   						      pid, size,
> -						      (unsigned long) &info))) {
> +						      (uintptr_t) &info))) {
>   				LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO: %m");
>   			}
>   			ASSERT_EQ(expected_none_size, rc) {
> @@ -177,7 +188,7 @@ TEST(get_syscall_info)
>   		case SIGTRAP | 0x80:
>   			ASSERT_LT(0, (rc = sys_ptrace(PTRACE_GET_SYSCALL_INFO,
>   						      pid, size,
> -						      (unsigned long) &info))) {
> +						      (uintptr_t) &info))) {
>   				LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO: %m");
>   			}
>   			switch (ptrace_stop) {

thanks,
-- Shuah