[libc] Internal getrandom implementation (#144427)

Implemented an internal getrandom to avoid calls to the public one in
table.h

---------

Co-authored-by: Sriya Pratipati <sriyap@google.com>

libc/src/__support/HashTable/CMakeLists.txt

@@ -15,7 +15,8 @@ if (NOT ${getrandom_index} EQUAL -1)
   message(STATUS "Using getrandom for hashtable randomness")
   set(randomness_compile_flags -DLIBC_HASHTABLE_USE_GETRANDOM)
   set(randomness_extra_depends
-    libc.src.sys.random.getrandom libc.src.errno.errno)
+    libc.src.__support.OSUtil.linux.getrandom
+    libc.hdr.errno_macros)
 endif()
 
 

libc/src/__support/HashTable/randomness.h

@@ -14,8 +14,8 @@
 #include "src/__support/macros/attributes.h"
 #include "src/__support/macros/config.h"
 #if defined(LIBC_HASHTABLE_USE_GETRANDOM)
-#include "src/__support/libc_errno.h"
-#include "src/sys/random/getrandom.h"
+#include "hdr/errno_macros.h"
+#include "src/__support/OSUtil/linux/getrandom.h"
 #endif
 
 namespace LIBC_NAMESPACE_DECL {
@@ -35,20 +35,18 @@ LIBC_INLINE uint64_t next_random_seed() {
     entropy[0] = reinterpret_cast<uint64_t>(&entropy);
     entropy[1] = reinterpret_cast<uint64_t>(&state);
 #if defined(LIBC_HASHTABLE_USE_GETRANDOM)
-    int errno_backup = libc_errno;
     size_t count = sizeof(entropy);
     uint8_t *buffer = reinterpret_cast<uint8_t *>(entropy);
     while (count > 0) {
-      ssize_t len = getrandom(buffer, count, 0);
-      if (len == -1) {
-        if (libc_errno == ENOSYS)
+      auto len = internal::getrandom(buffer, count, 0);
+      if (!len.has_value()) {
+        if (len.error() == ENOSYS)
           break;
         continue;
       }
-      count -= len;
-      buffer += len;
+      count -= len.value();
+      buffer += len.value();
     }
-    libc_errno = errno_backup;
 #endif
     state.update(&entropy, sizeof(entropy));
   }

libc/src/__support/OSUtil/linux/CMakeLists.txt

@@ -24,6 +24,19 @@ add_object_library(
     libc.include.sys_syscall
 )
 
+add_header_library(
+  getrandom
+  HDRS
+    getrandom.h
+  DEPENDS
+    libc.src.__support.OSUtil.osutil
+    libc.src.__support.common
+    libc.src.__support.error_or
+    libc.src.__support.macros.config
+    libc.hdr.types.ssize_t
+    libc.include.sys_syscall
+)
+
 add_header_library(
   vdso_sym
   HDRS

libc/src/__support/OSUtil/linux/getrandom.h

@@ -0,0 +1,35 @@
+//===------------ Implementation of getrandom function ----------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_OSUTIL_GETRANDOM_H
+#define LLVM_LIBC_SRC___SUPPORT_OSUTIL_GETRANDOM_H
+
+#include "hdr/types/ssize_t.h"
+#include "src/__support/OSUtil/linux/syscall.h" // syscall_impl
+#include "src/__support/common.h"
+#include "src/__support/error_or.h"
+#include "src/__support/macros/config.h"
+#include <sys/syscall.h> // For syscall numbers
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+
+LIBC_INLINE static ErrorOr<ssize_t> getrandom(void *buf, size_t buflen,
+                                              unsigned int flags) {
+  ssize_t ret =
+      LIBC_NAMESPACE::syscall_impl<ssize_t>(SYS_getrandom, buf, buflen, flags);
+  if (ret < 0) {
+    return Error(-static_cast<int>(ret));
+  }
+  return ret;
+}
+
+} // namespace internal
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_OSUTIL_GETRANDOM_H

libc/src/sys/random/linux/getrandom.cpp

@@ -8,24 +8,23 @@
 
 #include "src/sys/random/getrandom.h"
 
+#include "src/__support/OSUtil/linux/getrandom.h"
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
-
+#include "src/__support/error_or.h"
 #include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
-#include <sys/syscall.h> // For syscall numbers.
 
 namespace LIBC_NAMESPACE_DECL {
 
 LLVM_LIBC_FUNCTION(ssize_t, getrandom,
                    (void *buf, size_t buflen, unsigned int flags)) {
-  ssize_t ret =
-      LIBC_NAMESPACE::syscall_impl<ssize_t>(SYS_getrandom, buf, buflen, flags);
-  if (ret < 0) {
-    libc_errno = static_cast<int>(-ret);
+  auto rand = internal::getrandom(buf, buflen, flags);
+  if (!rand.has_value()) {
+    libc_errno = static_cast<int>(rand.error());
     return -1;
   }
-  return ret;
+  return rand.value();
 }
 
 } // namespace LIBC_NAMESPACE_DECL