[compiler-rt] 1854594 - Hwasan InitPrctl check for error using internal_iserror

[Matthew Malcomson via llvm-commits]

Author: Matthew Malcomson
Date: 2021-01-13T11:35:09Z
New Revision: 1854594b80b444dc21b830b51e53e05d38fc7d60

URL: https://github.com/llvm/llvm-project/commit/1854594b80b444dc21b830b51e53e05d38fc7d60
DIFF: https://github.com/llvm/llvm-project/commit/1854594b80b444dc21b830b51e53e05d38fc7d60.diff

LOG: Hwasan InitPrctl check for error using internal_iserror

When adding this function in https://reviews.llvm.org/D68794 I did not
notice that internal_prctl has the API of the syscall to prctl rather
than the API of the glibc (posix) wrapper.

This means that the error return value is not necessarily -1 and that
errno is not set by the call.

For InitPrctl this means that the checks do not catch running on a
kernel *without* the required ABI (not caught since I only tested this
function correctly enables the ABI when it exists).
This commit updates the two calls which check for an error condition to
use `internal_iserror`.  That function sets a provided integer to an
equivalent errno value and returns a boolean to indicate success or not.

Tested by running on a kernel that has this ABI and on one that does
not.  Verified that running on the kernel without this ABI the current
code prints the provided error message and does not attempt to run the
program.  Verified that running on the kernel with this ABI the current
code does not print an error message and turns on the ABI.
All tests done on an AArch64 Linux machine.

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D94425

Added: 
    

Modified: 
    compiler-rt/lib/hwasan/hwasan_linux.cpp

Removed: 
    


################################################################################
diff  --git a/compiler-rt/lib/hwasan/hwasan_linux.cpp b/compiler-rt/lib/hwasan/hwasan_linux.cpp
index e99926d355cf..793fd2fab6bf 100644
--- a/compiler-rt/lib/hwasan/hwasan_linux.cpp
+++ b/compiler-rt/lib/hwasan/hwasan_linux.cpp
@@ -119,8 +119,10 @@ void InitPrctl() {
 #define PR_GET_TAGGED_ADDR_CTRL 56
 #define PR_TAGGED_ADDR_ENABLE (1UL << 0)
   // Check we're running on a kernel that can use the tagged address ABI.
-  if (internal_prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0) == (uptr)-1 &&
-      errno == EINVAL) {
+  int local_errno = 0;
+  if (internal_iserror(internal_prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0),
+                       &local_errno) &&
+      local_errno == EINVAL) {
 #if SANITIZER_ANDROID
     // Some older Android kernels have the tagged pointer ABI on
     // unconditionally, and hence don't have the tagged-addr prctl while still
@@ -137,8 +139,8 @@ void InitPrctl() {
   }
 
   // Turn on the tagged address ABI.
-  if (internal_prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0) ==
-          (uptr)-1 ||
+  if (internal_iserror(internal_prctl(PR_SET_TAGGED_ADDR_CTRL,
+                                      PR_TAGGED_ADDR_ENABLE, 0, 0, 0)) ||
       !internal_prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0)) {
     Printf(
         "FATAL: HWAddressSanitizer failed to enable tagged address syscall "