stack_overflow.rs.html -- source
Description: Source to the Rust file `src/libstd/sys/unix/stack_overflow.rs`.
Keywords: rust, rustlang, rust-lang

      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210

    #![cfg_attr(test, allow(dead_code))]

    use libc;
    use self::imp::{make_handler, drop_handler};

    pub use self::imp::cleanup;
    pub use self::imp::init;

    pub struct Handler {
        _data: *mut libc::c_void
    }

    impl Handler {
        pub unsafe fn new() -> Handler {
            make_handler()
        }
    }

    impl Drop for Handler {
        fn drop(&mut self) {
            unsafe {
                drop_handler(self);
            }
        }
    }

    #[cfg(any(target_os = "linux",
              target_os = "macos",
              target_os = "bitrig",
              target_os = "dragonfly",
              target_os = "freebsd",
              target_os = "solaris",
              all(target_os = "netbsd", not(target_vendor = "rumprun")),
              target_os = "openbsd"))]
    mod imp {
        use super::Handler;
        use mem;
        use ptr;
        use libc::{sigaltstack, SIGSTKSZ, SS_DISABLE};
        use libc::{sigaction, SIGBUS, SIG_DFL,
                   SA_SIGINFO, SA_ONSTACK, sighandler_t};
        use libc;
        use libc::{mmap, munmap};
        use libc::{SIGSEGV, PROT_READ, PROT_WRITE, MAP_PRIVATE, MAP_ANON};
        use libc::MAP_FAILED;

        use sys_common::thread_info;

        #[cfg(any(target_os = "linux", target_os = "android"))]
        unsafe fn siginfo_si_addr(info: *mut libc::siginfo_t) -> usize {
            #[repr(C)]
            struct siginfo_t {
                a: [libc::c_int; 3], // si_signo, si_errno, si_code
                si_addr: *mut libc::c_void,
            }

            (*(info as *const siginfo_t)).si_addr as usize
        }

        #[cfg(not(any(target_os = "linux", target_os = "android")))]
        unsafe fn siginfo_si_addr(info: *mut libc::siginfo_t) -> usize {
            (*info).si_addr as usize
        }

        // Signal handler for the SIGSEGV and SIGBUS handlers. We've got guard pages
        // (unmapped pages) at the end of every thread's stack, so if a thread ends
        // up running into the guard page it'll trigger this handler. We want to
        // detect these cases and print out a helpful error saying that the stack
        // has overflowed. All other signals, however, should go back to what they
        // were originally supposed to do.
        //
        // This handler currently exists purely to print an informative message
        // whenever a thread overflows its stack. We then abort to exit and
        // indicate a crash, but to avoid a misleading SIGSEGV that might lead
        // users to believe that unsafe code has accessed an invalid pointer; the
        // SIGSEGV encountered when overflowing the stack is expected and
        // well-defined.
        //
        // If this is not a stack overflow, the handler un-registers itself and
        // then returns (to allow the original signal to be delivered again).
        // Returning from this kind of signal handler is technically not defined
        // to work when reading the POSIX spec strictly, but in practice it turns
        // out many large systems and all implementations allow returning from a
        // signal handler to work. For a more detailed explanation see the
        // comments on #26458.
        unsafe extern fn signal_handler(signum: libc::c_int,
                                        info: *mut libc::siginfo_t,
                                        _data: *mut libc::c_void) {
            use sys_common::util::report_overflow;

            let guard = thread_info::stack_guard().unwrap_or(0..0);
            let addr = siginfo_si_addr(info);

            // If the faulting address is within the guard page, then we print a
            // message saying so and abort.
            if guard.start <= addr && addr < guard.end {
                report_overflow();
                rtabort!("stack overflow");
            } else {
                // Unregister ourselves by reverting back to the default behavior.
                let mut action: sigaction = mem::zeroed();
                action.sa_sigaction = SIG_DFL;
                sigaction(signum, &action, ptr::null_mut());

                // See comment above for why this function returns.
            }
        }

        static mut MAIN_ALTSTACK: *mut libc::c_void = ptr::null_mut();

        pub unsafe fn init() {
            let mut action: sigaction = mem::zeroed();
            action.sa_flags = SA_SIGINFO | SA_ONSTACK;
            action.sa_sigaction = signal_handler as sighandler_t;
            sigaction(SIGSEGV, &action, ptr::null_mut());
            sigaction(SIGBUS, &action, ptr::null_mut());

            let handler = make_handler();
            MAIN_ALTSTACK = handler._data;
            mem::forget(handler);
        }

        pub unsafe fn cleanup() {
            Handler { _data: MAIN_ALTSTACK };
        }

        unsafe fn get_stackp() -> *mut libc::c_void {
            let stackp = mmap(ptr::null_mut(),
                              SIGSTKSZ,
                              PROT_READ | PROT_WRITE,
                              MAP_PRIVATE | MAP_ANON | libc::MAP_STACK,
                              -1,
                              0);
            if stackp == MAP_FAILED {
                panic!("failed to allocate an alternative stack");
            }
            stackp
        }

        #[cfg(any(target_os = "linux",
                  target_os = "macos",
                  target_os = "bitrig",
                  target_os = "netbsd",
                  target_os = "openbsd",
                  target_os = "solaris"))]
        unsafe fn get_stack() -> libc::stack_t {
            libc::stack_t { ss_sp: get_stackp(), ss_flags: 0, ss_size: SIGSTKSZ }
        }

        #[cfg(any(target_os = "freebsd",
                  target_os = "dragonfly"))]
        unsafe fn get_stack() -> libc::stack_t {
            libc::stack_t { ss_sp: get_stackp() as *mut i8, ss_flags: 0, ss_size: SIGSTKSZ }
        }

        pub unsafe fn make_handler() -> Handler {
            let mut stack = mem::zeroed();
            sigaltstack(ptr::null(), &mut stack);
            // Configure alternate signal stack, if one is not already set.
            if stack.ss_flags & SS_DISABLE != 0 {
                stack = get_stack();
                sigaltstack(&stack, ptr::null_mut());
                Handler { _data: stack.ss_sp as *mut libc::c_void }
            } else {
                Handler { _data: ptr::null_mut() }
            }
        }

        pub unsafe fn drop_handler(handler: &mut Handler) {
            if !handler._data.is_null() {
                let stack =  libc::stack_t {
                    ss_sp: ptr::null_mut(),
                    ss_flags: SS_DISABLE,
                    // Workaround for bug in macOS implementation of sigaltstack
                    // UNIX2003 which returns ENOMEM when disabling a stack while
                    // passing ss_size smaller than MINSIGSTKSZ. According to POSIX
                    // both ss_sp and ss_size should be ignored in this case.
                    ss_size: SIGSTKSZ,
                };
                sigaltstack(&stack, ptr::null_mut());
                munmap(handler._data, SIGSTKSZ);
            }
        }
    }

    #[cfg(not(any(target_os = "linux",
                  target_os = "macos",
                  target_os = "bitrig",
                  target_os = "dragonfly",
                  target_os = "freebsd",
                  target_os = "solaris",
                  all(target_os = "netbsd", not(target_vendor = "rumprun")),
                  target_os = "openbsd")))]
    mod imp {
        use ptr;

        pub unsafe fn init() {
        }

        pub unsafe fn cleanup() {
        }

        pub unsafe fn make_handler() -> super::Handler {
            super::Handler { _data: ptr::null_mut() }
        }

        pub unsafe fn drop_handler(_handler: &mut super::Handler) {
        }
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)