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-rw-r--r--libc/startup/linux/aarch64/start.cpp215
1 files changed, 5 insertions, 210 deletions
diff --git a/libc/startup/linux/aarch64/start.cpp b/libc/startup/linux/aarch64/start.cpp
index bc01582aeb49..d0a852687339 100644
--- a/libc/startup/linux/aarch64/start.cpp
+++ b/libc/startup/linux/aarch64/start.cpp
@@ -1,4 +1,4 @@
-//===-- Implementation of crt for aarch64 ---------------------------------===//
+//===-- Implementation of _start for aarch64 ------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
@@ -6,213 +6,8 @@
//
//===----------------------------------------------------------------------===//
-#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 <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
-
-namespace LIBC_NAMESPACE {
-
-#ifdef SYS_mmap2
-static constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap2;
-#elif SYS_mmap
-static constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap;
-#else
-#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;
- tls_descriptor.tp = 0;
- return;
- }
-
- // aarch64 follows the variant 1 TLS layout:
- //
- // 1. First entry is the dynamic thread vector pointer
- // 2. Second entry is a 8-byte reserved word.
- // 3. Padding for alignment.
- // 4. The TLS data from the ELF image.
- //
- // The thread pointer points to the first entry.
-
- const uintptr_t size_of_pointers = 2 * sizeof(uintptr_t);
- uintptr_t padding = 0;
- const uintptr_t ALIGNMENT_MASK = app.tls.align - 1;
- uintptr_t diff = size_of_pointers & ALIGNMENT_MASK;
- if (diff != 0)
- padding += (ALIGNMENT_MASK - diff) + 1;
-
- uintptr_t alloc_size = size_of_pointers + padding + app.tls.size;
-
- // 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);
- // 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);
- 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);
- tls_descriptor.size = alloc_size;
- tls_descriptor.addr = thread_ptr;
- tls_descriptor.tp = thread_ptr;
-}
-
-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);
-}
-
-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);
-}
-
-extern "C" void _start() {
+#include "startup/linux/do_start.h"
+extern "C" [[noreturn]] void _start() {
// Skip the Frame Pointer and the Link Register
// https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst
// Section 6.2.3. Note that this only works if the current function
@@ -223,7 +18,7 @@ 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 *>(
+ LIBC_NAMESPACE::app.args = reinterpret_cast<LIBC_NAMESPACE::Args *>(
reinterpret_cast<uintptr_t *>(__builtin_frame_address(0)) + 2);
- do_start();
+ LIBC_NAMESPACE::do_start();
}
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