[libc-commits] [libc] [libc] major refactor of startup library (PR #76092)

via libc-commits libc-commits at lists.llvm.org
Wed Dec 20 10:56:23 PST 2023


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: Schrodinger ZHU Yifan (SchrodingerZhu)

<details>
<summary>Changes</summary>

* separate initialization routines into _start and do_start for all architectures.
* lift do_start as a separate object library to avoid code duplication.
* (addtionally) address the problem of building hermetic libc with -fstack-pointer-*

---

Patch is 37.11 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/76092.diff


11 Files Affected:

- (modified) libc/cmake/modules/LLVMLibCTestRules.cmake (+6) 
- (modified) libc/config/linux/app.h (+3) 
- (modified) libc/startup/linux/CMakeLists.txt (+23-1) 
- (modified) libc/startup/linux/aarch64/CMakeLists.txt (+1-5) 
- (modified) libc/startup/linux/aarch64/start.cpp (+15-141) 
- (added) libc/startup/linux/do_start.cpp (+141) 
- (added) libc/startup/linux/do_start.h (+14) 
- (modified) libc/startup/linux/riscv/CMakeLists.txt (+1-5) 
- (modified) libc/startup/linux/riscv/start.cpp (+14-152) 
- (modified) libc/startup/linux/x86_64/CMakeLists.txt (+2-8) 
- (modified) libc/startup/linux/x86_64/start.cpp (+18-147) 


``````````diff
diff --git a/libc/cmake/modules/LLVMLibCTestRules.cmake b/libc/cmake/modules/LLVMLibCTestRules.cmake
index 51d484b875aeff..b69839afebf8a1 100644
--- a/libc/cmake/modules/LLVMLibCTestRules.cmake
+++ b/libc/cmake/modules/LLVMLibCTestRules.cmake
@@ -498,6 +498,9 @@ function(add_integration_test test_name)
       libc.src.string.memcpy
       libc.src.string.memmove
       libc.src.string.memset
+      # __stack_chk_fail should always be included to allow building libc with
+      # stack protector.
+      libc.src.compiler.__stack_chk_fail
   )
   list(REMOVE_DUPLICATES fq_deps_list)
 
@@ -665,6 +668,9 @@ function(add_libc_hermetic_test test_name)
       libc.src.string.memmove
       libc.src.string.memset
       libc.src.__support.StringUtil.error_to_string
+      # __stack_chk_fail should always be included to allow building libc with
+      # stack protector.
+      libc.src.compiler.__stack_chk_fail
   )
 
   if(TARGET libc.src.time.clock)
diff --git a/libc/config/linux/app.h b/libc/config/linux/app.h
index 548c141fd70535..1b3523deb1b23e 100644
--- a/libc/config/linux/app.h
+++ b/libc/config/linux/app.h
@@ -119,6 +119,9 @@ void init_tls(TLSDescriptor &tls);
 // Cleanup the TLS area as described in |tls_descriptor|.
 void cleanup_tls(uintptr_t tls_addr, uintptr_t tls_size);
 
+// Set the thread pointer for the current thread.
+bool set_thread_ptr(uintptr_t val);
+
 } // namespace LIBC_NAMESPACE
 
 #endif // LLVM_LIBC_CONFIG_LINUX_APP_H
diff --git a/libc/startup/linux/CMakeLists.txt b/libc/startup/linux/CMakeLists.txt
index 2d55a365669718..e9bdc2dd4478e9 100644
--- a/libc/startup/linux/CMakeLists.txt
+++ b/libc/startup/linux/CMakeLists.txt
@@ -84,10 +84,32 @@ endif()
 
 add_subdirectory(${LIBC_TARGET_ARCHITECTURE})
 
+add_object_library(
+  do_start
+  SRCS
+    do_start.cpp
+  HDRS
+    do_start.h
+  DEPENDS
+    libc.config.linux.app_h
+    libc.include.sys_mman
+    libc.include.sys_syscall
+    libc.src.__support.threads.thread
+    libc.src.__support.OSUtil.osutil
+    libc.src.stdlib.exit
+    libc.src.stdlib.atexit
+    libc.src.unistd.environ
+  COMPILE_OPTIONS
+    -ffreestanding       # To avoid compiler warnings about calling the main function.
+    -fno-builtin         # avoid emit unexpected calls
+    -fno-stack-protector # stack protect canary is not available yet.
+)
+
 # TODO: factor out crt1 into multiple objects
 merge_relocatable_object(
   crt1
-  .${LIBC_TARGET_ARCHITECTURE}.crt1
+  .${LIBC_TARGET_ARCHITECTURE}.start
+  .do_start
 )
 
 add_startup_object(
diff --git a/libc/startup/linux/aarch64/CMakeLists.txt b/libc/startup/linux/aarch64/CMakeLists.txt
index b47db8eb5d23f3..868b755d38f519 100644
--- a/libc/startup/linux/aarch64/CMakeLists.txt
+++ b/libc/startup/linux/aarch64/CMakeLists.txt
@@ -1,17 +1,13 @@
 add_startup_object(
-  crt1
+  start
   SRC
     start.cpp
   DEPENDS
     libc.config.linux.app_h
     libc.include.sys_mman
     libc.include.sys_syscall
-    libc.src.__support.threads.thread
     libc.src.__support.OSUtil.osutil
-    libc.src.stdlib.exit
-    libc.src.stdlib.atexit
     libc.src.string.memory_utils.inline_memcpy
-    libc.src.unistd.environ
   COMPILE_OPTIONS
     -fno-omit-frame-pointer
     -ffreestanding # To avoid compiler warnings about calling the main function.
diff --git a/libc/startup/linux/aarch64/start.cpp b/libc/startup/linux/aarch64/start.cpp
index bc01582aeb49c7..0e1efdc1b04da9 100644
--- a/libc/startup/linux/aarch64/start.cpp
+++ b/libc/startup/linux/aarch64/start.cpp
@@ -6,23 +6,14 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "config/linux/app.h"
 #include "src/__support/OSUtil/syscall.h"
 #include "src/__support/threads/thread.h"
-#include "src/stdlib/atexit.h"
-#include "src/stdlib/exit.h"
 #include "src/string/memory_utils/inline_memcpy.h"
+#include "startup/linux/do_start.h"
 
 #include <arm_acle.h>
-
-#include <linux/auxvec.h>
-#include <linux/elf.h>
-#include <stdint.h>
 #include <sys/mman.h>
 #include <sys/syscall.h>
-#include <unistd.h>
-
-extern "C" int main(int, char **, char **);
 
 // Source documentation:
 // https://github.com/ARM-software/abi-aa/tree/main/sysvabi64
@@ -37,10 +28,6 @@ static constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap;
 #error "mmap and mmap2 syscalls not available."
 #endif
 
-AppProperties app;
-
-static ThreadAttributes main_thread_attrib;
-
 void init_tls(TLSDescriptor &tls_descriptor) {
   if (app.tls.size == 0) {
     tls_descriptor.size = 0;
@@ -69,18 +56,18 @@ void init_tls(TLSDescriptor &tls_descriptor) {
   // We cannot call the mmap function here as the functions set errno on
   // failure. Since errno is implemented via a thread local variable, we cannot
   // use errno before TLS is setup.
-  long mmap_ret_val = LIBC_NAMESPACE::syscall_impl<long>(
-      MMAP_SYSCALL_NUMBER, nullptr, alloc_size, PROT_READ | PROT_WRITE,
-      MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  long mmap_ret_val = syscall_impl<long>(MMAP_SYSCALL_NUMBER, nullptr,
+                                         alloc_size, PROT_READ | PROT_WRITE,
+                                         MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
   // We cannot check the return value with MAP_FAILED as that is the return
   // of the mmap function and not the mmap syscall.
   if (mmap_ret_val < 0 && static_cast<uintptr_t>(mmap_ret_val) > -app.page_size)
-    LIBC_NAMESPACE::syscall_impl<long>(SYS_exit, 1);
+    syscall_impl<long>(SYS_exit, 1);
   uintptr_t thread_ptr = uintptr_t(reinterpret_cast<uintptr_t *>(mmap_ret_val));
   uintptr_t tls_addr = thread_ptr + size_of_pointers + padding;
-  LIBC_NAMESPACE::inline_memcpy(reinterpret_cast<char *>(tls_addr),
-                                reinterpret_cast<const char *>(app.tls.address),
-                                app.tls.init_size);
+  inline_memcpy(reinterpret_cast<char *>(tls_addr),
+                reinterpret_cast<const char *>(app.tls.address),
+                app.tls.init_size);
   tls_descriptor.size = alloc_size;
   tls_descriptor.addr = thread_ptr;
   tls_descriptor.tp = thread_ptr;
@@ -89,127 +76,12 @@ void init_tls(TLSDescriptor &tls_descriptor) {
 void cleanup_tls(uintptr_t addr, uintptr_t size) {
   if (size == 0)
     return;
-  LIBC_NAMESPACE::syscall_impl<long>(SYS_munmap, addr, size);
-}
-
-static void set_thread_ptr(uintptr_t val) { __arm_wsr64("tpidr_el0", val); }
-
-using InitCallback = void(int, char **, char **);
-using FiniCallback = void(void);
-
-extern "C" {
-// These arrays are present in the .init_array and .fini_array sections.
-// The symbols are inserted by linker when it sees references to them.
-extern uintptr_t __preinit_array_start[];
-extern uintptr_t __preinit_array_end[];
-extern uintptr_t __init_array_start[];
-extern uintptr_t __init_array_end[];
-extern uintptr_t __fini_array_start[];
-extern uintptr_t __fini_array_end[];
-}
-
-static void call_init_array_callbacks(int argc, char **argv, char **env) {
-  size_t preinit_array_size = __preinit_array_end - __preinit_array_start;
-  for (size_t i = 0; i < preinit_array_size; ++i)
-    reinterpret_cast<InitCallback *>(__preinit_array_start[i])(argc, argv, env);
-  size_t init_array_size = __init_array_end - __init_array_start;
-  for (size_t i = 0; i < init_array_size; ++i)
-    reinterpret_cast<InitCallback *>(__init_array_start[i])(argc, argv, env);
+  syscall_impl<long>(SYS_munmap, addr, size);
 }
 
-static void call_fini_array_callbacks() {
-  size_t fini_array_size = __fini_array_end - __fini_array_start;
-  for (size_t i = fini_array_size; i > 0; --i)
-    reinterpret_cast<FiniCallback *>(__fini_array_start[i - 1])();
-}
-
-} // namespace LIBC_NAMESPACE
-
-using LIBC_NAMESPACE::app;
-using LIBC_NAMESPACE::AuxEntry;
-
-__attribute__((noinline)) static void do_start() {
-  auto tid = LIBC_NAMESPACE::syscall_impl<long>(SYS_gettid);
-  if (tid <= 0)
-    LIBC_NAMESPACE::syscall_impl<long>(SYS_exit, 1);
-  LIBC_NAMESPACE::main_thread_attrib.tid = static_cast<int>(tid);
-
-  // After the argv array, is a 8-byte long NULL value before the array of env
-  // values. The end of the env values is marked by another 8-byte long NULL
-  // value. We step over it (the "+ 1" below) to get to the env values.
-  uint64_t *env_ptr = app.args->argv + app.args->argc + 1;
-  uint64_t *env_end_marker = env_ptr;
-  app.env_ptr = env_ptr;
-  while (*env_end_marker)
-    ++env_end_marker;
-
-  // Initialize the POSIX global declared in unistd.h
-  environ = reinterpret_cast<char **>(env_ptr);
-
-  // After the env array, is the aux-vector. The end of the aux-vector is
-  // denoted by an AT_NULL entry.
-  Elf64_Phdr *program_hdr_table = nullptr;
-  uintptr_t program_hdr_count;
-  app.auxv_ptr = reinterpret_cast<AuxEntry *>(env_end_marker + 1);
-  for (auto *aux_entry = app.auxv_ptr; aux_entry->id != AT_NULL; ++aux_entry) {
-    switch (aux_entry->id) {
-    case AT_PHDR:
-      program_hdr_table = reinterpret_cast<Elf64_Phdr *>(aux_entry->value);
-      break;
-    case AT_PHNUM:
-      program_hdr_count = aux_entry->value;
-      break;
-    case AT_PAGESZ:
-      app.page_size = aux_entry->value;
-      break;
-    default:
-      break; // TODO: Read other useful entries from the aux vector.
-    }
-  }
-
-  app.tls.size = 0;
-  for (uintptr_t i = 0; i < program_hdr_count; ++i) {
-    Elf64_Phdr *phdr = program_hdr_table + i;
-    if (phdr->p_type != PT_TLS)
-      continue;
-    // TODO: p_vaddr value has to be adjusted for static-pie executables.
-    app.tls.address = phdr->p_vaddr;
-    app.tls.size = phdr->p_memsz;
-    app.tls.init_size = phdr->p_filesz;
-    app.tls.align = phdr->p_align;
-  }
-
-  // This descriptor has to be static since its cleanup function cannot
-  // capture the context.
-  static LIBC_NAMESPACE::TLSDescriptor tls;
-  LIBC_NAMESPACE::init_tls(tls);
-  if (tls.size != 0)
-    LIBC_NAMESPACE::set_thread_ptr(tls.tp);
-
-  LIBC_NAMESPACE::self.attrib = &LIBC_NAMESPACE::main_thread_attrib;
-  LIBC_NAMESPACE::main_thread_attrib.atexit_callback_mgr =
-      LIBC_NAMESPACE::internal::get_thread_atexit_callback_mgr();
-  // We register the cleanup_tls function to be the last atexit callback to be
-  // invoked. It will tear down the TLS. Other callbacks may depend on TLS (such
-  // as the stack protector canary).
-  LIBC_NAMESPACE::atexit(
-      []() { LIBC_NAMESPACE::cleanup_tls(tls.tp, tls.size); });
-  // We want the fini array callbacks to be run after other atexit
-  // callbacks are run. So, we register them before running the init
-  // array callbacks as they can potentially register their own atexit
-  // callbacks.
-  LIBC_NAMESPACE::atexit(&LIBC_NAMESPACE::call_fini_array_callbacks);
-
-  LIBC_NAMESPACE::call_init_array_callbacks(
-      static_cast<int>(app.args->argc),
-      reinterpret_cast<char **>(app.args->argv),
-      reinterpret_cast<char **>(env_ptr));
-
-  int retval = main(static_cast<int>(app.args->argc),
-                    reinterpret_cast<char **>(app.args->argv),
-                    reinterpret_cast<char **>(env_ptr));
-
-  LIBC_NAMESPACE::exit(retval);
+bool set_thread_ptr(uintptr_t val) {
+  __arm_wsr64("tpidr_el0", val);
+  return true;
 }
 
 extern "C" void _start() {
@@ -223,7 +95,9 @@ extern "C" void _start() {
   // will take us to the previous stack pointer. That is the reason why the
   // actual business logic of the startup code is pushed into a non-inline
   // function do_start so that this function is free of any stack usage.
-  app.args = reinterpret_cast<LIBC_NAMESPACE::Args *>(
+  app.args = reinterpret_cast<Args *>(
       reinterpret_cast<uintptr_t *>(__builtin_frame_address(0)) + 2);
   do_start();
 }
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/startup/linux/do_start.cpp b/libc/startup/linux/do_start.cpp
new file mode 100644
index 00000000000000..4a86bc385a7c8b
--- /dev/null
+++ b/libc/startup/linux/do_start.cpp
@@ -0,0 +1,141 @@
+//===-- Implementation file of do_start -----------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+#include "startup/linux/do_start.h"
+#include "src/__support/OSUtil/syscall.h"
+#include "src/__support/threads/thread.h"
+#include "src/stdlib/atexit.h"
+#include "src/stdlib/exit.h"
+#include "src/unistd/environ.h"
+
+#include <linux/auxvec.h>
+#include <linux/elf.h>
+#include <stdint.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+
+namespace LIBC_NAMESPACE {
+
+// TODO: this symbol will be moved to config.linux.app
+AppProperties app;
+
+using InitCallback = void(int, char **, char **);
+using FiniCallback = void(void);
+
+extern "C" int main(int argc, char **argv, char **envp);
+
+extern "C" {
+// These arrays are present in the .init_array and .fini_array sections.
+// The symbols are inserted by linker when it sees references to them.
+extern uintptr_t __preinit_array_start[];
+extern uintptr_t __preinit_array_end[];
+extern uintptr_t __init_array_start[];
+extern uintptr_t __init_array_end[];
+extern uintptr_t __fini_array_start[];
+extern uintptr_t __fini_array_end[];
+}
+
+static void call_init_array_callbacks(int argc, char **argv, char **env) {
+  size_t preinit_array_size = __preinit_array_end - __preinit_array_start;
+  for (size_t i = 0; i < preinit_array_size; ++i)
+    reinterpret_cast<InitCallback *>(__preinit_array_start[i])(argc, argv, env);
+  size_t init_array_size = __init_array_end - __init_array_start;
+  for (size_t i = 0; i < init_array_size; ++i)
+    reinterpret_cast<InitCallback *>(__init_array_start[i])(argc, argv, env);
+}
+
+static void call_fini_array_callbacks() {
+  size_t fini_array_size = __fini_array_end - __fini_array_start;
+  for (size_t i = fini_array_size; i > 0; --i)
+    reinterpret_cast<FiniCallback *>(__fini_array_start[i - 1])();
+}
+
+static ThreadAttributes main_thread_attrib;
+
+[[noreturn]] void do_start() {
+  auto tid = syscall_impl<long>(SYS_gettid);
+  if (tid <= 0)
+    syscall_impl<long>(SYS_exit, 1);
+  main_thread_attrib.tid = static_cast<int>(tid);
+
+  // After the argv array, is a 8-byte long NULL value before the array of env
+  // values. The end of the env values is marked by another 8-byte long NULL
+  // value. We step over it (the "+ 1" below) to get to the env values.
+  uint64_t *env_ptr = app.args->argv + app.args->argc + 1;
+  uint64_t *env_end_marker = env_ptr;
+  app.env_ptr = env_ptr;
+  while (*env_end_marker)
+    ++env_end_marker;
+
+  // Initialize the POSIX global declared in unistd.h
+  environ = reinterpret_cast<char **>(env_ptr);
+
+  // After the env array, is the aux-vector. The end of the aux-vector is
+  // denoted by an AT_NULL entry.
+  Elf64_Phdr *program_hdr_table = nullptr;
+  uintptr_t program_hdr_count = 0;
+  app.auxv_ptr = reinterpret_cast<AuxEntry *>(env_end_marker + 1);
+  for (auto *aux_entry = app.auxv_ptr; aux_entry->id != AT_NULL; ++aux_entry) {
+    switch (aux_entry->id) {
+    case AT_PHDR:
+      program_hdr_table = reinterpret_cast<Elf64_Phdr *>(aux_entry->value);
+      break;
+    case AT_PHNUM:
+      program_hdr_count = aux_entry->value;
+      break;
+    case AT_PAGESZ:
+      app.page_size = aux_entry->value;
+      break;
+    default:
+      break; // TODO: Read other useful entries from the aux vector.
+    }
+  }
+
+  app.tls.size = 0;
+  for (uintptr_t i = 0; i < program_hdr_count; ++i) {
+    Elf64_Phdr *phdr = program_hdr_table + i;
+    if (phdr->p_type != PT_TLS)
+      continue;
+    // TODO: p_vaddr value has to be adjusted for static-pie executables.
+    app.tls.address = phdr->p_vaddr;
+    app.tls.size = phdr->p_memsz;
+    app.tls.init_size = phdr->p_filesz;
+    app.tls.align = phdr->p_align;
+  }
+
+  // This descriptor has to be static since its cleanup function cannot
+  // capture the context.
+  static TLSDescriptor tls;
+  init_tls(tls);
+  if (tls.size != 0 && !set_thread_ptr(tls.tp))
+    syscall_impl<long>(SYS_exit, 1);
+
+  self.attrib = &main_thread_attrib;
+  main_thread_attrib.atexit_callback_mgr =
+      internal::get_thread_atexit_callback_mgr();
+  // We register the cleanup_tls function to be the last atexit callback to be
+  // invoked. It will tear down the TLS. Other callbacks may depend on TLS (such
+  // as the stack protector canary).
+  atexit([]() { cleanup_tls(tls.tp, tls.size); });
+  // We want the fini array callbacks to be run after other atexit
+  // callbacks are run. So, we register them before running the init
+  // array callbacks as they can potentially register their own atexit
+  // callbacks.
+  atexit(&call_fini_array_callbacks);
+
+  call_init_array_callbacks(static_cast<int>(app.args->argc),
+                            reinterpret_cast<char **>(app.args->argv),
+                            reinterpret_cast<char **>(env_ptr));
+
+  int retval = main(static_cast<int>(app.args->argc),
+                    reinterpret_cast<char **>(app.args->argv),
+                    reinterpret_cast<char **>(env_ptr));
+
+  exit(retval);
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/startup/linux/do_start.h b/libc/startup/linux/do_start.h
new file mode 100644
index 00000000000000..a0e7a3cd695627
--- /dev/null
+++ b/libc/startup/linux/do_start.h
@@ -0,0 +1,14 @@
+//===-- Header file of do_start -------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "config/linux/app.h"
+
+namespace LIBC_NAMESPACE {
+// setup the libc runtime and invoke the main routine.
+[[noreturn]] void do_start();
+} // namespace LIBC_NAMESPACE
diff --git a/libc/startup/linux/riscv/CMakeLists.txt b/libc/startup/linux/riscv/CMakeLists.txt
index b47db8eb5d23f3..868b755d38f519 100644
--- a/libc/startup/linux/riscv/CMakeLists.txt
+++ b/libc/startup/linux/riscv/CMakeLists.txt
@@ -1,17 +1,13 @@
 add_startup_object(
-  crt1
+  start
   SRC
     start.cpp
   DEPENDS
     libc.config.linux.app_h
     libc.include.sys_mman
     libc.include.sys_syscall
-    libc.src.__support.threads.thread
     libc.src.__support.OSUtil.osutil
-    libc.src.stdlib.exit
-    libc.src.stdlib.atexit
     libc.src.string.memory_utils.inline_memcpy
-    libc.src.unistd.environ
   COMPILE_OPTIONS
     -fno-omit-frame-pointer
     -ffreestanding # To avoid compiler warnings about calling the main function.
diff --git a/libc/startup/linux/riscv/start.cpp b/libc/startup/linux/riscv/start.cpp
index 5b6e5bde8da81d..57c83b502e9c94 100644
--- a/libc/startup/linux/riscv/start.cpp
+++ b/libc/startup/linux/riscv/start.cpp
@@ -6,21 +6,13 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "config/linux/app.h"
 #include "src/__support/OSUtil/syscall.h"
 #include "src/__support/threads/thread.h"
-#include "src/stdlib/atexit.h"
-#include "src/stdlib/exit.h"
 #include "src/string/memory_utils/inline_memcpy.h"
+#include "startup/linux/do_start.h"
 
-#include <linux/auxvec.h>
-#include <linux/elf.h>
-#include <stdint.h>
 #include <sys/mman.h>
 #include <sys/syscall.h>
-#include <unistd.h>
-
-extern "C" int main(int, char **, char **);
 
 namespace LIBC_NAMESPACE {
 
@@ -32,10 +24,6 @@ static constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap;
 #error "mmap and mmap2 syscalls not available."
 #endif
 
-AppProperties app;
-
-static ThreadAttributes main_thread_attrib;
-
 void init_tls(TLSDescriptor &tls_descriptor) {
   if (app.tls.size == 0) {
     tls_descriptor.size = 0;
@@ -56,18 +44,18 @@ void init_tls(TLSDescriptor &tls_descriptor) {
   // We cannot call the mmap function here as the functions set errno on
   // failure. Since errno is implemented via a thread local variable, we cannot
   // use errno before TLS is setup.
-  long mmap_ret_val = LIBC_NAMESPACE::syscall_impl<long>(
-      MMAP_SYSCALL_NUMBER, nullptr, alloc_size, PROT_READ | PROT_WRITE,
-      MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  long mmap_ret_val = syscall_impl<long>(MMAP_SYSCALL_NUMBER, nullptr,
+                                         alloc_size, PROT_READ | PROT_WRITE,
+                                         MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
   // We cannot check the return...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/76092


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