[libc-commits] [libc] [libc] fix sysconf test for rv32 (PR #162685)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: Schrodinger ZHU Yifan (SchrodingerZhu)

<details>
<summary>Changes</summary>

On 32-bit architectures, MMAP may return userspace virtual address with high bit set. This patch copy the err detection logic from existing mmap function implementation.

---
Full diff: https://github.com/llvm/llvm-project/pull/162685.diff


1 Files Affected:

- (modified) libc/src/__support/OSUtil/linux/auxv.h (+2-1) 


``````````diff
diff --git a/libc/src/__support/OSUtil/linux/auxv.h b/libc/src/__support/OSUtil/linux/auxv.h
index 894868ae5824d..cca0f358e2366 100644
--- a/libc/src/__support/OSUtil/linux/auxv.h
+++ b/libc/src/__support/OSUtil/linux/auxv.h
@@ -16,6 +16,7 @@
 
 #include <linux/auxvec.h> // For AT_ macros
 #include <linux/mman.h>   // For mmap flags
+#include <linux/param.h>  // For EXEC_PAGESIZE
 #include <linux/prctl.h>  // For prctl
 #include <sys/syscall.h>  // For syscall numbers
 
@@ -90,7 +91,7 @@ LIBC_INLINE void Vector::fallback_initialize_unsync() {
                                      PROT_READ | PROT_WRITE,
                                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
   // We do not proceed if mmap fails.
-  if (mmap_ret <= 0)
+  if (mmap_ret <= 0 && mmap_ret > -EXEC_PAGESIZE)
     return;
 
   // Initialize the auxv array with AT_NULL entries.

``````````

</details>


https://github.com/llvm/llvm-project/pull/162685