Re: [PATCH v4] riscv: selftests: Fix warnings pointer masking test

[Charlie Jenkins <charlie@rivosinc.com>]

On Fri, Dec 06, 2024 at 10:15:17AM +0100, Andrew Jones wrote:
> On Thu, Dec 05, 2024 at 01:49:31PM -0800, 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@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
> > ---
> >  tools/testing/selftests/riscv/abi/pointer_masking.c | 20 ++++++++++++++++++--
> >  1 file changed, 18 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/riscv/abi/pointer_masking.c b/tools/testing/selftests/riscv/abi/pointer_masking.c
> > index dee41b7ee3e3..759445d5f265 100644
> > --- a/tools/testing/selftests/riscv/abi/pointer_masking.c
> > +++ b/tools/testing/selftests/riscv/abi/pointer_masking.c
> > @@ -189,6 +189,8 @@ static void test_tagged_addr_abi_sysctl(void)
> >  {
> >  	char value;
> >  	int fd;
> > +	int ret;
> > +	char *err_pwrite_msg = "failed to write to /proc/sys/abi/tagged_addr_disabled\n";
> >  
> >  	ksft_print_msg("Testing tagged address ABI sysctl\n");
> >  
> > @@ -200,18 +202,32 @@ static void test_tagged_addr_abi_sysctl(void)
> >  	}
> >  
> >  	value = '1';
> > -	pwrite(fd, &value, 1, 0);
> > +	ret = pwrite(fd, &value, 1, 0);
> > +	if (ret != 1) {
> > +		ksft_test_result_skip(err_pwrite_msg);
> 
> It seems like we should have a better way to keep the count balanced than
> to require a ksft_test_result_skip() call for each test on each error
> path. Every time we add a test we'll have to go add skips everywhere else.

It's only a problem if there are multiple tests in a single test
function like there is here. Since the tests disable then reenable it
makes sense to have them in one function, but does require us to do the
skipping.

> 
> > +		goto err_pwrite;
> > +	}
> > +
> >  	ksft_test_result(set_tagged_addr_ctrl(min_pmlen, true) == -EINVAL,
> >  			 "sysctl disabled\n");
> >  
> >  	value = '0';
> > -	pwrite(fd, &value, 1, 0);
> > +	ret = pwrite(fd, &value, 1, 0);
> > +	if (ret != 1)
> > +		goto err_pwrite;
> > +
> >  	ksft_test_result(set_tagged_addr_ctrl(min_pmlen, true) == 0,
> >  			 "sysctl enabled\n");
> >  
> >  	set_tagged_addr_ctrl(0, false);
> >  
> >  	close(fd);
> > +
> > +	return;
> > +
> > +err_pwrite:
> > +	close(fd);
> > +	ksft_test_result_fail(err_pwrite_msg);
> >  }
> 
> I don't think the goto reduces much code or improves readability much. A
> wrapper function should do better. I was thinking something like
> 
>  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;
>  }
> 
> 
>  value = '1';
>  if (!pwrite_wrapper(fd, &value, 1, "write '1'"))
>     ksft_test_result_fail(...);
> 
>  value = '0';
>  if (!pwrite_wrapper(fd, &value, 1, "write '0'"))
>     ksft_test_result_fail(...);
> 
> 

Will do, thanks!

- Charlie

> >  
> >  static void test_tagged_addr_abi_pmlen(int pmlen)
> > 
> > ---
> > base-commit: 40384c840ea1944d7c5a392e8975ed088ecf0b37
> > change-id: 20241204-fix_warnings_pointer_masking_tests-3860e4f35429
> > -- 
> > - Charlie
> > 
> 
> Thanks,
> drew