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

[Charlie Jenkins]

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 <char...@rivosinc.com>
---
 tools/testing/selftests/riscv/abi/pointer_masking.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/riscv/abi/pointer_masking.c 
b/tools/testing/selftests/riscv/abi/pointer_masking.c
index dee41b7ee3e3..5ae941e9ac73 100644
--- a/tools/testing/selftests/riscv/abi/pointer_masking.c
+++ b/tools/testing/selftests/riscv/abi/pointer_masking.c
@@ -189,6 +189,7 @@ static void test_tagged_addr_abi_sysctl(void)
 {
        char value;
        int fd;
+       int ret;
 
        ksft_print_msg("Testing tagged address ABI sysctl\n");
 
@@ -200,14 +201,24 @@ 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_fail("Write to 
/proc/sys/abi/tagged_addr_disabled failed.\n");
+               return;
+       }
+
        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");
+       ret = pwrite(fd, &value, 1, 0);
+       if (ret != 2) {
+               ksft_test_result_fail("Write to 
/proc/sys/abi/tagged_addr_disabled failed.\n");
+               return;
+       }
+
+       ksft_test_result(set_tagged_addr_ctrl(min_pmlen, true) == -EINVAL,
+                        "sysctl disabled\n");
 
        set_tagged_addr_ctrl(0, false);
 

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