[libc-commits] [libc] be6af89 - [libc] Add TLS image initialization to aarch64 startup code.
Siva Chandra via libc-commits
libc-commits at lists.llvm.org
Fri Jun 17 22:51:15 PDT 2022
Author: Siva Chandra
Date: 2022-06-17T22:50:14-07:00
New Revision: be6af89f85ebd04646b5704301470f02b70a0447
URL: https://github.com/llvm/llvm-project/commit/be6af89f85ebd04646b5704301470f02b70a0447
DIFF: https://github.com/llvm/llvm-project/commit/be6af89f85ebd04646b5704301470f02b70a0447.diff
LOG: [libc] Add TLS image initialization to aarch64 startup code.
The TLS loader test has been enabled for aarch64.
Handling of PT_TLS' filesz and memsz for x86_64 has also been fixed.
Reviewed By: jeffbailey
Differential Revision: https://reviews.llvm.org/D128032
Added:
Modified:
libc/config/linux/app.h
libc/loader/linux/aarch64/CMakeLists.txt
libc/loader/linux/aarch64/start.cpp
libc/loader/linux/x86_64/start.cpp
libc/test/integration/loader/linux/CMakeLists.txt
Removed:
################################################################################
diff --git a/libc/config/linux/app.h b/libc/config/linux/app.h
index 024aed0dcdd71..e835367413abc 100644
--- a/libc/config/linux/app.h
+++ b/libc/config/linux/app.h
@@ -20,9 +20,16 @@ struct TLS {
// The load address of the TLS.
uintptr_t address;
- // The bytes size of the TLS.
+ // The byte size of the TLS image consisting of both initialized and
+ // uninitialized memory. In ELF executables, it is size of .tdata + size of
+ // .tbss. Put in another way, it is the memsz field of the PT_TLS header.
uintptr_t size;
+ // The byte size of initialized memory in the TLS image. In ELF exectubles,
+ // this is the size of .tdata. Put in another way, it is the filesz of the
+ // PT_TLS header.
+ uintptr_t init_size;
+
// The alignment of the TLS layout. It assumed that the alignment
// value is a power of 2.
uintptr_t align;
diff --git a/libc/loader/linux/aarch64/CMakeLists.txt b/libc/loader/linux/aarch64/CMakeLists.txt
index 716930aa70990..6c2e615290fa1 100644
--- a/libc/loader/linux/aarch64/CMakeLists.txt
+++ b/libc/loader/linux/aarch64/CMakeLists.txt
@@ -4,8 +4,10 @@ add_loader_object(
start.cpp
DEPENDS
libc.config.linux.app_h
+ libc.include.sys_mman
libc.include.sys_syscall
libc.src.__support.OSUtil.osutil
+ libc.src.string.memory_utils.memcpy_implementation
COMPILE_OPTIONS
-fno-omit-frame-pointer
-ffreestanding # To avoid compiler warnings about calling the main function.
diff --git a/libc/loader/linux/aarch64/start.cpp b/libc/loader/linux/aarch64/start.cpp
index ecff48f3235de..53308c1e74723 100644
--- a/libc/loader/linux/aarch64/start.cpp
+++ b/libc/loader/linux/aarch64/start.cpp
@@ -8,10 +8,15 @@
#include "config/linux/app.h"
#include "src/__support/OSUtil/syscall.h"
+#include "src/string/memory_utils/memcpy_implementations.h"
+
+#include <arm_acle.h>
#include <linux/auxvec.h>
#include <linux/elf.h>
+#include <stddef.h>
#include <stdint.h>
+#include <sys/mman.h>
#include <sys/syscall.h>
extern "C" int main(int, char **, char **);
@@ -21,8 +26,56 @@ extern "C" int main(int, char **, char **);
namespace __llvm_libc {
+#ifdef SYS_mmap2
+static constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap2;
+#elif SYS_mmap
+static constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap;
+#else
+#error "Target platform does not have SYS_mmap or SYS_mmap2 defined"
+#endif
+
AppProperties app;
+void initTLS() {
+ if (app.tls.size == 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 size_t size_of_pointers = 2 * sizeof(uintptr_t);
+ size_t padding = 0;
+ const size_t ALIGNMENT_MASK = app.tls.align - 1;
+ size_t
diff = size_of_pointers & ALIGNMENT_MASK;
+ if (
diff != 0)
+ padding += (ALIGNMENT_MASK -
diff ) + 1;
+
+ size_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 = __llvm_libc::syscall(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.pageSize)
+ __llvm_libc::syscall(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;
+ __llvm_libc::inline_memcpy(reinterpret_cast<char *>(tls_addr),
+ reinterpret_cast<const char *>(app.tls.address),
+ app.tls.init_size);
+ __arm_wsr64("tpidr_el0", thread_ptr);
+}
+
} // namespace __llvm_libc
using __llvm_libc::app;
@@ -50,9 +103,17 @@ extern "C" void _start() {
// After the env array, is the aux-vector. The end of the aux-vector is
// denoted by an AT_NULL entry.
+ Elf64_Phdr *programHdrTable = nullptr;
+ uintptr_t programHdrCount;
for (AuxEntry *aux_entry = reinterpret_cast<AuxEntry *>(env_end_marker + 1);
aux_entry->type != AT_NULL; ++aux_entry) {
switch (aux_entry->type) {
+ case AT_PHDR:
+ programHdrTable = reinterpret_cast<Elf64_Phdr *>(aux_entry->value);
+ break;
+ case AT_PHNUM:
+ programHdrCount = aux_entry->value;
+ break;
case AT_PAGESZ:
app.pageSize = aux_entry->value;
break;
@@ -61,7 +122,19 @@ extern "C" void _start() {
}
}
- // TODO: Init TLS
+ app.tls.size = 0;
+ for (uintptr_t i = 0; i < programHdrCount; ++i) {
+ Elf64_Phdr *phdr = programHdrTable + 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;
+ }
+
+ __llvm_libc::initTLS();
__llvm_libc::syscall(SYS_exit, main(app.args->argc,
reinterpret_cast<char **>(app.args->argv),
diff --git a/libc/loader/linux/x86_64/start.cpp b/libc/loader/linux/x86_64/start.cpp
index ef413c0e5ffb2..dae0d970f221b 100644
--- a/libc/loader/linux/x86_64/start.cpp
+++ b/libc/loader/linux/x86_64/start.cpp
@@ -66,7 +66,7 @@ void initTLS() {
__llvm_libc::inline_memcpy(reinterpret_cast<char *>(tlsAddr),
reinterpret_cast<const char *>(app.tls.address),
- app.tls.size);
+ app.tls.init_size);
if (__llvm_libc::syscall(SYS_arch_prctl, ARCH_SET_FS, endPtr) == -1)
__llvm_libc::syscall(SYS_exit, 1);
}
@@ -132,6 +132,7 @@ extern "C" void _start() {
}
}
+ app.tls.size = 0;
for (uintptr_t i = 0; i < programHdrCount; ++i) {
Elf64_Phdr *phdr = programHdrTable + i;
if (phdr->p_type != PT_TLS)
@@ -139,6 +140,7 @@ extern "C" void _start() {
// 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;
}
diff --git a/libc/test/integration/loader/linux/CMakeLists.txt b/libc/test/integration/loader/linux/CMakeLists.txt
index 564046372064f..137b46ac78f1c 100644
--- a/libc/test/integration/loader/linux/CMakeLists.txt
+++ b/libc/test/integration/loader/linux/CMakeLists.txt
@@ -38,10 +38,6 @@ add_integration_test(
main_without_args.cpp
)
-if(NOT (${LIBC_TARGET_ARCHITECTURE} STREQUAL "x86_64"))
- return()
-endif()
-
add_integration_test(
loader_tls_test
SUITE libc-loader-tests
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