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

[Charlie Jenkins <charlie@rivosinc.com>]

On Fri, Dec 06, 2024 at 09:21:50AM -0800, Charlie Jenkins wrote:
> 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.

I guess it is sufficient to leave out the skip here, if the first one
fails we can just continue and let the second one fail too.

- Charlie

> 
> > 
> > > +		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