1 //===-- Internal header for Linux signals -----------------------*- C++ -*-===//
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 #ifndef LLVM_LIBC_SRC_SIGNAL_LINUX_SIGNAL_UTILS_H
10 #define LLVM_LIBC_SRC_SIGNAL_LINUX_SIGNAL_UTILS_H
11
12 #include "hdr/types/sigset_t.h"
13 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
14 #include "src/__support/common.h"
15 #include "src/__support/macros/config.h"
16
17 #include <signal.h> // sigaction
18 #include <stddef.h>
19 #include <sys/syscall.h> // For syscall numbers.
20
21 namespace LIBC_NAMESPACE_DECL {
22
23 // The POSIX definition of struct sigaction and the sigaction data structure
24 // expected by the rt_sigaction syscall differ in their definition. So, we
25 // define the equivalent of the what the kernel expects to help with making
26 // the rt_sigaction syscall.
27 //
28 // NOTE: Though the kernel definition does not have a union to include the
29 // handler taking siginfo_t * argument, one can set sa_handler to sa_sigaction
30 // if SA_SIGINFO is set in sa_flags.
31 struct KernelSigaction {
32 LIBC_INLINE KernelSigaction &operator=(const struct sigaction &sa) {
33 sa_flags = sa.sa_flags;
34 sa_restorer = sa.sa_restorer;
35 sa_mask = sa.sa_mask;
36 if (sa_flags & SA_SIGINFO) {
37 sa_sigaction = sa.sa_sigaction;
38 } else {
39 sa_handler = sa.sa_handler;
40 }
41 return *this;
42 }
43
sigactionKernelSigaction44 LIBC_INLINE operator struct sigaction() const {
45 struct sigaction sa;
46 sa.sa_flags = static_cast<int>(sa_flags);
47 sa.sa_mask = sa_mask;
48 sa.sa_restorer = sa_restorer;
49 if (sa_flags & SA_SIGINFO)
50 sa.sa_sigaction = sa_sigaction;
51 else
52 sa.sa_handler = sa_handler;
53 return sa;
54 }
55
56 union {
57 void (*sa_handler)(int);
58 void (*sa_sigaction)(int, siginfo_t *, void *);
59 };
60 unsigned long sa_flags;
61 void (*sa_restorer)(void);
62 // Our public definition of sigset_t matches that of the kernel's definition.
63 // So, we can use the public sigset_t type here.
64 sigset_t sa_mask;
65 };
66
67 static constexpr size_t BITS_PER_SIGWORD = sizeof(unsigned long) * 8;
68
full_set()69 LIBC_INLINE constexpr sigset_t full_set() { return sigset_t{{-1UL}}; }
70
empty_set()71 LIBC_INLINE constexpr sigset_t empty_set() { return sigset_t{{0}}; }
72
73 // Set the bit corresponding to |signal| in |set|. Return true on success
74 // and false on failure. The function will fail if |signal| is greater than
75 // NSIG or negative.
add_signal(sigset_t & set,int signal)76 LIBC_INLINE constexpr bool add_signal(sigset_t &set, int signal) {
77 if (signal > NSIG || signal <= 0)
78 return false;
79 size_t n = size_t(signal) - 1;
80 size_t word = n / BITS_PER_SIGWORD;
81 size_t bit = n % BITS_PER_SIGWORD;
82 set.__signals[word] |= (1UL << bit);
83 return true;
84 }
85
86 // Reset the bit corresponding to |signal| in |set|. Return true on success
87 // and false on failure. The function will fail if |signal| is greater than
88 // NSIG or negative.
delete_signal(sigset_t & set,int signal)89 LIBC_INLINE constexpr bool delete_signal(sigset_t &set, int signal) {
90 if (signal > NSIG || signal <= 0)
91 return false;
92 size_t n = size_t(signal) - 1;
93 size_t word = n / BITS_PER_SIGWORD;
94 size_t bit = n % BITS_PER_SIGWORD;
95 set.__signals[word] &= ~(1UL << bit);
96 return true;
97 }
98
block_all_signals(sigset_t & set)99 LIBC_INLINE int block_all_signals(sigset_t &set) {
100 sigset_t full = full_set();
101 return LIBC_NAMESPACE::syscall_impl<int>(SYS_rt_sigprocmask, SIG_BLOCK, &full,
102 &set, sizeof(sigset_t));
103 }
104
restore_signals(const sigset_t & set)105 LIBC_INLINE int restore_signals(const sigset_t &set) {
106 return LIBC_NAMESPACE::syscall_impl<int>(SYS_rt_sigprocmask, SIG_SETMASK,
107 &set, nullptr, sizeof(sigset_t));
108 }
109
110 } // namespace LIBC_NAMESPACE_DECL
111
112 #endif // LLVM_LIBC_SRC_SIGNAL_LINUX_SIGNAL_UTILS_H
113