[PATCH v6] riscv: selftests: Fix warnings pointer masking test

[Charlie Jenkins <charlie@xxxxxxxxxxxx>]

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@xxxxxxxxxxxx>
Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
---
Changes in v6:
- Add back ksft_test_result() (Samuel)
- Link to v5: https://lore.kernel.org/r/20241206-fix_warnings_pointer_masking_tests-v5-1-ed566c2f27e8@xxxxxxxxxxxx

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@xxxxxxxxxxxx

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@xxxxxxxxxxxx

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@xxxxxxxxxxxx

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@xxxxxxxxxxxx
---
 .../testing/selftests/riscv/abi/pointer_masking.c  | 28 +++++++++++++++++-----
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/riscv/abi/pointer_masking.c b/tools/testing/selftests/riscv/abi/pointer_masking.c
index dee41b7ee3e323150d55523c8acbf3ec38857b87..059d2e87eb1f737caf44f692b239bf3e49c233b4 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 +212,18 @@ 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);
+	else
+		ksft_test_result(set_tagged_addr_ctrl(min_pmlen, true) == -EINVAL,
+				 "sysctl disabled\n");
 
 	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);
+	else
+		ksft_test_result(set_tagged_addr_ctrl(min_pmlen, true) == 0,
+				 "sysctl enabled\n");
 
 	set_tagged_addr_ctrl(0, false);
 

---
base-commit: 40384c840ea1944d7c5a392e8975ed088ecf0b37
change-id: 20241204-fix_warnings_pointer_masking_tests-3860e4f35429
-- 
- Charlie