1//===-- Implementation of tls for riscv -----------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "src/__support/OSUtil/syscall.h"
10#include "src/__support/threads/thread.h"
11#include "src/string/memory_utils/inline_memcpy.h"
12#include "startup/linux/do_start.h"
13
14#include <sys/mman.h>
15#include <sys/syscall.h>
16
17namespace LIBC_NAMESPACE {
18
19#ifdef SYS_mmap2
20static constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap2;
21#elif SYS_mmap
22static constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap;
23#else
24#error "mmap and mmap2 syscalls not available."
25#endif
26
27void init_tls(TLSDescriptor &tls_descriptor) {
28 if (app.tls.size == 0) {
29 tls_descriptor.size = 0;
30 tls_descriptor.tp = 0;
31 return;
32 }
33
34 // riscv64 follows the variant 1 TLS layout:
35 const uintptr_t size_of_pointers = 2 * sizeof(uintptr_t);
36 uintptr_t padding = 0;
37 const uintptr_t ALIGNMENT_MASK = app.tls.align - 1;
38 uintptr_t diff = size_of_pointers & ALIGNMENT_MASK;
39 if (diff != 0)
40 padding += (ALIGNMENT_MASK - diff) + 1;
41
42 uintptr_t alloc_size = size_of_pointers + padding + app.tls.size;
43
44 // We cannot call the mmap function here as the functions set errno on
45 // failure. Since errno is implemented via a thread local variable, we cannot
46 // use errno before TLS is setup.
47 long mmap_ret_val = syscall_impl<long>(number: MMAP_SYSCALL_NUMBER, ts: nullptr,
48 ts: alloc_size, PROT_READ | PROT_WRITE,
49 MAP_ANONYMOUS | MAP_PRIVATE, ts: -1, ts: 0);
50 // We cannot check the return value with MAP_FAILED as that is the return
51 // of the mmap function and not the mmap syscall.
52 if (mmap_ret_val < 0 && static_cast<uintptr_t>(mmap_ret_val) > -app.page_size)
53 syscall_impl<long>(SYS_exit, ts: 1);
54 uintptr_t thread_ptr = uintptr_t(reinterpret_cast<uintptr_t *>(mmap_ret_val));
55 uintptr_t tls_addr = thread_ptr + size_of_pointers + padding;
56 inline_memcpy(dst: reinterpret_cast<char *>(tls_addr),
57 src: reinterpret_cast<const char *>(app.tls.address),
58 count: app.tls.init_size);
59 tls_descriptor.size = alloc_size;
60 tls_descriptor.addr = thread_ptr;
61 tls_descriptor.tp = tls_addr;
62}
63
64void cleanup_tls(uintptr_t addr, uintptr_t size) {
65 if (size == 0)
66 return;
67 syscall_impl<long>(SYS_munmap, ts: addr, ts: size);
68}
69
70bool set_thread_ptr(uintptr_t val) {
71 LIBC_INLINE_ASM("mv tp, %0\n\t" : : "r"(val));
72 return true;
73}
74} // namespace LIBC_NAMESPACE
75

source code of libc/startup/linux/riscv/tls.cpp