linux-kernel - Re: [PATCH v5] riscv: selftests: Fix warnings pointer masking test

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Message-ID: <41025b15-2f66-481b-a2da-dbf86e2bfc10@sifive.com>
Date: Tue, 10 Dec 2024 23:46:24 -0600
From: Samuel Holland <samuel.holland@...ive.com>
To: Charlie Jenkins <charlie@...osinc.com>,
 Andrew Jones <ajones@...tanamicro.com>
Cc: linux-kselftest@...r.kernel.org, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org, Palmer Dabbelt <palmer@...osinc.com>,
 Shuah Khan <shuah@...nel.org>, Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Alexandre Ghiti <alex@...ti.fr>
Subject: Re: [PATCH v5] riscv: selftests: Fix warnings pointer masking test

Hi Charlie,

On 2024-12-06 11:52 AM, Charlie Jenkins wrote:
> When compiling the pointer masking tests with -Wall this warning
> is present:
> 
> pointer_masking.c: In function ‘test_tagged_addr_abi_sysctl’:
> pointer_masking.c:203:9: warning: ignoring return value of ‘pwrite’
> declared with attribute ‘warn_unused_result’ [-Wunused-result]
>   203 |         pwrite(fd, &value, 1, 0); |
>       ^~~~~~~~~~~~~~~~~~~~~~~~ pointer_masking.c:208:9: warning:
> ignoring return value of ‘pwrite’ declared with attribute
> ‘warn_unused_result’ [-Wunused-result]
>   208 |         pwrite(fd, &value, 1, 0);
> 
> I came across this on riscv64-linux-gnu-gcc (Ubuntu
> 11.4.0-1ubuntu1~22.04).
> 
> Fix this by checking that the number of bytes written equal the expected
> number of bytes written.
> 
> Fixes: 7470b5afd150 ("riscv: selftests: Add a pointer masking test")
> Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
> ---
> Changes in v5:
> - No longer skip second pwrite if first one fails
> - Use wrapper function instead of goto (Drew)
> - Link to v4: https://lore.kernel.org/r/20241205-fix_warnings_pointer_masking_tests-v4-1-0c77eb725486@rivosinc.com
> 
> Changes in v4:
> - Skip sysctl_enabled test if first pwrite failed
> - Link to v3: https://lore.kernel.org/r/20241205-fix_warnings_pointer_masking_tests-v3-1-5c28b0f9640d@rivosinc.com
> 
> Changes in v3:
> - Fix sysctl enabled test case (Drew/Alex)
> - Move pwrite err condition into goto (Drew)
> - Link to v2: https://lore.kernel.org/r/20241204-fix_warnings_pointer_masking_tests-v2-1-1bf0c5095f58@rivosinc.com
> 
> Changes in v2:
> - I had ret != 2 for testing, I changed it to be ret != 1.
> - Link to v1: https://lore.kernel.org/r/20241204-fix_warnings_pointer_masking_tests-v1-1-ea1e9665ce7a@rivosinc.com
> ---
>  .../testing/selftests/riscv/abi/pointer_masking.c  | 22 ++++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/testing/selftests/riscv/abi/pointer_masking.c b/tools/testing/selftests/riscv/abi/pointer_masking.c
> index dee41b7ee3e3..50c4d1bc7570 100644
> --- a/tools/testing/selftests/riscv/abi/pointer_masking.c
> +++ b/tools/testing/selftests/riscv/abi/pointer_masking.c
> @@ -185,8 +185,20 @@ static void test_fork_exec(void)
>  	}
>  }
>  
> +static bool pwrite_wrapper(int fd, void *buf, size_t count, const char *msg)
> +{
> +	int ret = pwrite(fd, buf, count, 0);
> +
> +	if (ret != count) {
> +		ksft_perror(msg);
> +		return false;
> +	}
> +	return true;
> +}
> +
>  static void test_tagged_addr_abi_sysctl(void)
>  {
> +	char *err_pwrite_msg = "failed to write to /proc/sys/abi/tagged_addr_disabled\n";
>  	char value;
>  	int fd;
>  
> @@ -200,14 +212,12 @@ static void test_tagged_addr_abi_sysctl(void)
>  	}
>  
>  	value = '1';
> -	pwrite(fd, &value, 1, 0);
> -	ksft_test_result(set_tagged_addr_ctrl(min_pmlen, true) == -EINVAL,
> -			 "sysctl disabled\n");
> +	if (!pwrite_wrapper(fd, &value, 1, "write '1'"))
> +		ksft_test_result_fail(err_pwrite_msg);
>  
>  	value = '0';
> -	pwrite(fd, &value, 1, 0);
> -	ksft_test_result(set_tagged_addr_ctrl(min_pmlen, true) == 0,
> -			 "sysctl enabled\n");
> +	if (!pwrite_wrapper(fd, &value, 1, "write '0'"))
> +		ksft_test_result_fail(err_pwrite_msg);

You've removed the ksft_test_result() calls, which contain the actual behavioral
tests (set_tagged_addr_ctrl()), so the test no longer does anything but toggle
the sysctl:

# Testing fork/exec behavior
ok 55 dereference after fork
ok 56 dereference after fork+exec
# Testing tagged address ABI sysctl
# Testing tagged address ABI
ok 57 PMLEN=0 tagged address ABI
ok 58 PMLEN=7 tagged address ABI
ok 59 PMLEN=16 tagged address ABI
# Planned tests != run tests (61 != 59)
# Totals: pass:59 fail:0 xfail:0 xpass:0 skip:0 error:0

It does do the right thing if I `mount --bind /dev/full
/proc/sys/abi/tagged_addr_disabled`:

# Testing fork/exec behavior
ok 55 dereference after fork
ok 56 dereference after fork+exec
# Testing tagged address ABI sysctl
# write '1': No space left on device (28)
not ok 57 failed to write to /proc/sys/abi/tagged_addr_disabled
# write '0': No space left on device (28)
not ok 58 failed to write to /proc/sys/abi/tagged_addr_disabled
# Testing tagged address ABI
ok 59 PMLEN=0 tagged address ABI
ok 60 PMLEN=7 tagged address ABI
ok 61 PMLEN=16 tagged address ABI
# Totals: pass:59 fail:2 xfail:0 xpass:0 skip:0 error:0

So I guess the "ksft_test_result(set_tagged_addr_ctrl..." needs to go in the
else case of the pwrite_wrapper() call.

Regards,
Samuel

>  
>  	set_tagged_addr_ctrl(0, false);
>  
> 
> ---
> base-commit: 40384c840ea1944d7c5a392e8975ed088ecf0b37
> change-id: 20241204-fix_warnings_pointer_masking_tests-3860e4f35429