2 files changed, 7 insertions, 229 deletions

diff --git a/libc/src/sys/auxv/linux/CMakeLists.txt b/libc/src/sys/auxv/linux/CMakeLists.txt
index 4884184c..39cfb7b 100644
--- a/libc/src/sys/auxv/linux/CMakeLists.txt
+++ b/libc/src/sys/auxv/linux/CMakeLists.txt
@@ -5,15 +5,6 @@ add_entrypoint_object(
   HDRS
     ../getauxval.h
   DEPENDS
-    libc.src.sys.prctl.prctl
-    libc.src.sys.mman.mmap
-    libc.src.sys.mman.munmap
-    libc.src.__support.threads.callonce
-    libc.src.__support.common
-    libc.src.errno.errno
-    libc.config.app_h
-    libc.src.fcntl.open
-    libc.src.unistd.read
-    libc.src.unistd.close
-    libc.include.sys_auxv
+    libc.src.__support.OSUtil.linux.auxv
+    libc.src.__support.libc_errno
 )
diff --git a/libc/src/sys/auxv/linux/getauxval.cpp b/libc/src/sys/auxv/linux/getauxval.cpp
index b50c584..52d5a98 100644
--- a/libc/src/sys/auxv/linux/getauxval.cpp
+++ b/libc/src/sys/auxv/linux/getauxval.cpp
@@ -7,227 +7,14 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/sys/auxv/getauxval.h"
-#include "config/app.h"
-#include "hdr/fcntl_macros.h"
-#include "src/__support/OSUtil/fcntl.h"
-#include "src/__support/common.h"
+#include "src/__support/OSUtil/linux/auxv.h"
 #include "src/__support/libc_errno.h"
-#include "src/__support/macros/config.h"
-#include <linux/auxvec.h>
-
-// for guarded initialization
-#include "src/__support/threads/callonce.h"
-#include "src/__support/threads/linux/futex_word.h"
-
-// -----------------------------------------------------------------------------
-// TODO: This file should not include other public libc functions. Calling other
-// public libc functions is an antipattern within LLVM-libc. This needs to be
-// cleaned up. DO NOT COPY THIS.
-// -----------------------------------------------------------------------------
-
-// for mallocing the global auxv
-#include "src/sys/mman/mmap.h"
-#include "src/sys/mman/munmap.h"
-
-// for reading /proc/self/auxv
-#include "src/sys/prctl/prctl.h"
-#include "src/unistd/read.h"
-
-// getauxval will work either with or without __cxa_atexit support.
-// In order to detect if __cxa_atexit is supported, we define a weak symbol.
-// We prefer __cxa_atexit as it is always defined as a C symbol whileas atexit
-// may not be created via objcopy yet. Also, for glibc, atexit is provided via
-// libc_nonshared.a rather than libc.so. So, it is may not be made ready for
-// overlay builds.
-extern "C" [[gnu::weak]] int __cxa_atexit(void (*callback)(void *),
-                                          void *payload, void *);
 
 namespace LIBC_NAMESPACE_DECL {
-
-constexpr static size_t MAX_AUXV_ENTRIES = 64;
-
-// Helper to recover or set errno
-class AuxvErrnoGuard {
-public:
-  AuxvErrnoGuard() : saved(libc_errno), failure(false) {}
-  ~AuxvErrnoGuard() { libc_errno = failure ? ENOENT : saved; }
-  void mark_failure() { failure = true; }
-
-private:
-  int saved;
-  bool failure;
-};
-
-// Helper to manage the memory
-static AuxEntry *auxv = nullptr;
-
-class AuxvMMapGuard {
-public:
-  constexpr static size_t AUXV_MMAP_SIZE = sizeof(AuxEntry) * MAX_AUXV_ENTRIES;
-
-  AuxvMMapGuard()
-      : ptr(LIBC_NAMESPACE::mmap(nullptr, AUXV_MMAP_SIZE,
-                                 PROT_READ | PROT_WRITE,
-                                 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0)) {}
-  ~AuxvMMapGuard() {
-    if (ptr != MAP_FAILED)
-      LIBC_NAMESPACE::munmap(ptr, AUXV_MMAP_SIZE);
-  }
-  void submit_to_global() {
-    // atexit may fail, we do not set it to global in that case.
-    int ret = __cxa_atexit(
-        [](void *) {
-          LIBC_NAMESPACE::munmap(auxv, AUXV_MMAP_SIZE);
-          auxv = nullptr;
-        },
-        nullptr, nullptr);
-
-    if (ret != 0)
-      return;
-
-    auxv = reinterpret_cast<AuxEntry *>(ptr);
-    ptr = MAP_FAILED;
-  }
-  bool allocated() const { return ptr != MAP_FAILED; }
-  void *get() const { return ptr; }
-
-private:
-  void *ptr;
-};
-
-class AuxvFdGuard {
-public:
-  AuxvFdGuard() {
-    auto result = internal::open("/proc/self/auxv", O_RDONLY | O_CLOEXEC);
-    if (!result.has_value())
-      fd = -1;
-
-    fd = result.value();
-  }
-  ~AuxvFdGuard() {
-    if (fd != -1)
-      internal::close(fd);
-  }
-  bool valid() const { return fd != -1; }
-  int get() const { return fd; }
-
-private:
-  int fd;
-};
-
-static void initialize_auxv_once(void) {
-  // If we cannot get atexit, we cannot register the cleanup function.
-  if (&__cxa_atexit == nullptr)
-    return;
-
-  AuxvMMapGuard mmap_guard;
-  if (!mmap_guard.allocated())
-    return;
-  auto *ptr = reinterpret_cast<AuxEntry *>(mmap_guard.get());
-
-  // We get one less than the max size to make sure the search always
-  // terminates. MMAP private pages are zeroed out already.
-  size_t available_size = AuxvMMapGuard::AUXV_MMAP_SIZE - sizeof(AuxEntryType);
-  // PR_GET_AUXV is only available on Linux kernel 6.1 and above. If this is not
-  // defined, we direcly fall back to reading /proc/self/auxv. In case the libc
-  // is compiled and run on separate kernels, we also check the return value of
-  // prctl.
-#ifdef PR_GET_AUXV
-  int ret = prctl(PR_GET_AUXV, reinterpret_cast<unsigned long>(ptr),
-                  available_size, 0, 0);
-  if (ret >= 0) {
-    mmap_guard.submit_to_global();
-    return;
-  }
-#endif
-  AuxvFdGuard fd_guard;
-  if (!fd_guard.valid())
-    return;
-  auto *buf = reinterpret_cast<char *>(ptr);
-  libc_errno = 0;
-  bool error_detected = false;
-  // Read until we use up all the available space or we finish reading the file.
-  while (available_size != 0) {
-    ssize_t bytes_read =
-        LIBC_NAMESPACE::read(fd_guard.get(), buf, available_size);
-    if (bytes_read <= 0) {
-      if (libc_errno == EINTR)
-        continue;
-      // Now, we either have an non-recoverable error or we have reached the end
-      // of the file. Mark `error_detected` accordingly.
-      if (bytes_read == -1)
-        error_detected = true;
-      break;
-    }
-    buf += bytes_read;
-    available_size -= bytes_read;
-  }
-  // If we get out of the loop without an error, the auxv is ready.
-  if (!error_detected)
-    mmap_guard.submit_to_global();
-}
-
-static AuxEntry read_entry(int fd) {
-  AuxEntry buf;
-  size_t size = sizeof(AuxEntry);
-  char *ptr = reinterpret_cast<char *>(&buf);
-  while (size > 0) {
-    ssize_t ret = LIBC_NAMESPACE::read(fd, ptr, size);
-    if (ret < 0) {
-      if (libc_errno == EINTR)
-        continue;
-      // Error detected, return AT_NULL
-      buf.id = AT_NULL;
-      buf.value = AT_NULL;
-      break;
-    }
-    ptr += ret;
-    size -= ret;
-  }
-  return buf;
-}
-
 LLVM_LIBC_FUNCTION(unsigned long, getauxval, (unsigned long id)) {
-  // Fast path when libc is loaded by its own initialization code. In this case,
-  // app.auxv_ptr is already set to the auxv passed on the initial stack of the
-  // process.
-  AuxvErrnoGuard errno_guard;
-
-  auto search_auxv = [&errno_guard](AuxEntry *auxv,
-                                    unsigned long id) -> AuxEntryType {
-    for (auto *ptr = auxv; ptr->id != AT_NULL; ptr++)
-      if (ptr->id == id)
-        return ptr->value;
-
-    errno_guard.mark_failure();
-    return AT_NULL;
-  };
-
-  // App is a weak symbol that is only defined if libc is linked to its own
-  // initialization routine. We need to check if it is null.
-  if (&app != nullptr)
-    return search_auxv(app.auxv_ptr, id);
-
-  static FutexWordType once_flag;
-  LIBC_NAMESPACE::callonce(reinterpret_cast<CallOnceFlag *>(&once_flag),
-                           initialize_auxv_once);
-  if (auxv != nullptr)
-    return search_auxv(auxv, id);
-
-  // Fallback to use read without mmap
-  AuxvFdGuard fd_guard;
-  if (fd_guard.valid()) {
-    while (true) {
-      AuxEntry buf = read_entry(fd_guard.get());
-      if (buf.id == AT_NULL)
-        break;
-      if (buf.id == id)
-        return buf.value;
-    }
-  }
-
-  // cannot find the entry after all methods, mark failure and return 0
-  errno_guard.mark_failure();
-  return AT_NULL;
+  if (cpp::optional<unsigned long> val = auxv::get(id))
+    return *val;
+  libc_errno = ENOENT;
+  return 0;
 }
 } // namespace LIBC_NAMESPACE_DECL