wasmer_vm/trap/traphandlers.rs
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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138
// This file contains code from external sources.
// Attributions: https://github.com/wasmerio/wasmer/blob/main/docs/ATTRIBUTIONS.md
#![allow(static_mut_refs)]
//! WebAssembly trap handling, which is built on top of the lower-level
//! signalhandling mechanisms.
use crate::vmcontext::{VMFunctionContext, VMTrampoline};
use crate::{Trap, VMContext, VMFunctionBody};
use backtrace::Backtrace;
use core::ptr::{read, read_unaligned};
use corosensei::stack::DefaultStack;
use corosensei::trap::{CoroutineTrapHandler, TrapHandlerRegs};
use corosensei::{Coroutine, CoroutineResult, Yielder};
use scopeguard::defer;
use std::any::Any;
use std::cell::Cell;
use std::error::Error;
use std::io;
use std::mem;
#[cfg(unix)]
use std::mem::MaybeUninit;
use std::ptr::{self, NonNull};
use std::sync::atomic::{compiler_fence, AtomicPtr, AtomicUsize, Ordering};
use std::sync::Once;
use wasmer_types::TrapCode;
/// Configuration for the runtime VM
/// Currently only the stack size is configurable
pub struct VMConfig {
/// Optionnal stack size (in byte) of the VM. Value lower than 8K will be rounded to 8K.
pub wasm_stack_size: Option<usize>,
}
// TrapInformation can be stored in the "Undefined Instruction" itself.
// On x86_64, 0xC? select a "Register" for the Mod R/M part of "ud1" (so with no other bytes after)
// On Arm64, the udf alows for a 16bits values, so we'll use the same 0xC? to store the trapinfo
static MAGIC: u8 = 0xc0;
static DEFAULT_STACK_SIZE: AtomicUsize = AtomicUsize::new(1024 * 1024);
// Current definition of `ucontext_t` in the `libc` crate is incorrect
// on aarch64-apple-drawin so it's defined here with a more accurate definition.
#[repr(C)]
#[cfg(all(target_arch = "aarch64", target_os = "macos"))]
#[allow(non_camel_case_types)]
struct ucontext_t {
uc_onstack: libc::c_int,
uc_sigmask: libc::sigset_t,
uc_stack: libc::stack_t,
uc_link: *mut libc::ucontext_t,
uc_mcsize: usize,
uc_mcontext: libc::mcontext_t,
}
// Current definition of `ucontext_t` in the `libc` crate is not present
// on aarch64-unknown-freebsd so it's defined here.
#[repr(C)]
#[cfg(all(target_arch = "aarch64", target_os = "freebsd"))]
#[allow(non_camel_case_types)]
struct ucontext_t {
uc_sigmask: libc::sigset_t,
uc_mcontext: libc::mcontext_t,
uc_link: *mut ucontext_t,
uc_stack: libc::stack_t,
uc_flags: libc::c_int,
spare: [libc::c_int; 4],
}
#[cfg(all(
unix,
not(all(target_arch = "aarch64", target_os = "macos")),
not(all(target_arch = "aarch64", target_os = "freebsd"))
))]
use libc::ucontext_t;
/// Default stack size is 1MB.
pub fn set_stack_size(size: usize) {
DEFAULT_STACK_SIZE.store(size.clamp(8 * 1024, 100 * 1024 * 1024), Ordering::Relaxed);
}
cfg_if::cfg_if! {
if #[cfg(unix)] {
/// Function which may handle custom signals while processing traps.
pub type TrapHandlerFn<'a> = dyn Fn(libc::c_int, *const libc::siginfo_t, *const libc::c_void) -> bool + Send + Sync + 'a;
} else if #[cfg(target_os = "windows")] {
/// Function which may handle custom signals while processing traps.
pub type TrapHandlerFn<'a> = dyn Fn(*mut windows_sys::Win32::System::Diagnostics::Debug::EXCEPTION_POINTERS) -> bool + Send + Sync + 'a;
}
}
// Process an IllegalOpcode to see if it has a TrapCode payload
unsafe fn process_illegal_op(addr: usize) -> Option<TrapCode> {
let mut val: Option<u8> = None;
if cfg!(target_arch = "x86_64") {
val = if read(addr as *mut u8) & 0xf0 == 0x40
&& read((addr + 1) as *mut u8) == 0x0f
&& read((addr + 2) as *mut u8) == 0xb9
{
Some(read((addr + 3) as *mut u8))
} else if read(addr as *mut u8) == 0x0f && read((addr + 1) as *mut u8) == 0xb9 {
Some(read((addr + 2) as *mut u8))
} else {
None
}
}
if cfg!(target_arch = "aarch64") {
val = if read_unaligned(addr as *mut u32) & 0xffff0000 == 0 {
Some(read(addr as *mut u8))
} else {
None
}
}
match val.and_then(|val| {
if val & MAGIC == MAGIC {
Some(val & 0xf)
} else {
None
}
}) {
None => None,
Some(val) => match val {
0 => Some(TrapCode::StackOverflow),
1 => Some(TrapCode::HeapAccessOutOfBounds),
2 => Some(TrapCode::HeapMisaligned),
3 => Some(TrapCode::TableAccessOutOfBounds),
4 => Some(TrapCode::IndirectCallToNull),
5 => Some(TrapCode::BadSignature),
6 => Some(TrapCode::IntegerOverflow),
7 => Some(TrapCode::IntegerDivisionByZero),
8 => Some(TrapCode::BadConversionToInteger),
9 => Some(TrapCode::UnreachableCodeReached),
10 => Some(TrapCode::UnalignedAtomic),
_ => None,
},
}
}
cfg_if::cfg_if! {
if #[cfg(unix)] {
static mut PREV_SIGSEGV: MaybeUninit<libc::sigaction> = MaybeUninit::uninit();
static mut PREV_SIGBUS: MaybeUninit<libc::sigaction> = MaybeUninit::uninit();
static mut PREV_SIGILL: MaybeUninit<libc::sigaction> = MaybeUninit::uninit();
static mut PREV_SIGFPE: MaybeUninit<libc::sigaction> = MaybeUninit::uninit();
unsafe fn platform_init() {
let register = |slot: &mut MaybeUninit<libc::sigaction>, signal: i32| {
let mut handler: libc::sigaction = mem::zeroed();
// The flags here are relatively careful, and they are...
//
// SA_SIGINFO gives us access to information like the program
// counter from where the fault happened.
//
// SA_ONSTACK allows us to handle signals on an alternate stack,
// so that the handler can run in response to running out of
// stack space on the main stack. Rust installs an alternate
// stack with sigaltstack, so we rely on that.
//
// SA_NODEFER allows us to reenter the signal handler if we
// crash while handling the signal, and fall through to the
// Breakpad handler by testing handlingSegFault.
handler.sa_flags = libc::SA_SIGINFO | libc::SA_NODEFER | libc::SA_ONSTACK;
handler.sa_sigaction = trap_handler as usize;
libc::sigemptyset(&mut handler.sa_mask);
if libc::sigaction(signal, &handler, slot.as_mut_ptr()) != 0 {
panic!(
"unable to install signal handler: {}",
io::Error::last_os_error(),
);
}
};
// Allow handling OOB with signals on all architectures
register(&mut PREV_SIGSEGV, libc::SIGSEGV);
// Handle `unreachable` instructions which execute `ud2` right now
register(&mut PREV_SIGILL, libc::SIGILL);
// x86 uses SIGFPE to report division by zero
if cfg!(target_arch = "x86") || cfg!(target_arch = "x86_64") {
register(&mut PREV_SIGFPE, libc::SIGFPE);
}
// On ARM, handle Unaligned Accesses.
// On Darwin, guard page accesses are raised as SIGBUS.
if cfg!(target_arch = "arm") || cfg!(target_vendor = "apple") {
register(&mut PREV_SIGBUS, libc::SIGBUS);
}
// This is necessary to support debugging under LLDB on Darwin.
// For more details see https://github.com/mono/mono/commit/8e75f5a28e6537e56ad70bf870b86e22539c2fb7
#[cfg(target_vendor = "apple")]
{
use mach2::exception_types::*;
use mach2::kern_return::*;
use mach2::port::*;
use mach2::thread_status::*;
use mach2::traps::*;
use mach2::mach_types::*;
extern "C" {
fn task_set_exception_ports(
task: task_t,
exception_mask: exception_mask_t,
new_port: mach_port_t,
behavior: exception_behavior_t,
new_flavor: thread_state_flavor_t,
) -> kern_return_t;
}
#[allow(non_snake_case)]
#[cfg(target_arch = "x86_64")]
let MACHINE_THREAD_STATE = x86_THREAD_STATE64;
#[allow(non_snake_case)]
#[cfg(target_arch = "aarch64")]
let MACHINE_THREAD_STATE = 6;
task_set_exception_ports(
mach_task_self(),
EXC_MASK_BAD_ACCESS | EXC_MASK_ARITHMETIC | EXC_MASK_BAD_INSTRUCTION,
MACH_PORT_NULL,
EXCEPTION_STATE_IDENTITY as exception_behavior_t,
MACHINE_THREAD_STATE,
);
}
}
unsafe extern "C" fn trap_handler(
signum: libc::c_int,
siginfo: *mut libc::siginfo_t,
context: *mut libc::c_void,
) {
let previous = match signum {
libc::SIGSEGV => &PREV_SIGSEGV,
libc::SIGBUS => &PREV_SIGBUS,
libc::SIGFPE => &PREV_SIGFPE,
libc::SIGILL => &PREV_SIGILL,
_ => panic!("unknown signal: {}", signum),
};
// We try to get the fault address associated to this signal
let maybe_fault_address = match signum {
libc::SIGSEGV | libc::SIGBUS => {
Some((*siginfo).si_addr() as usize)
}
_ => None,
};
let trap_code = match signum {
// check if it was cased by a UD and if the Trap info is a payload to it
libc::SIGILL => {
let addr = (*siginfo).si_addr() as usize;
process_illegal_op(addr)
}
_ => None,
};
let ucontext = &mut *(context as *mut ucontext_t);
let (pc, sp) = get_pc_sp(ucontext);
let handled = TrapHandlerContext::handle_trap(
pc,
sp,
maybe_fault_address,
trap_code,
|regs| update_context(ucontext, regs),
|handler| handler(signum, siginfo, context),
);
if handled {
return;
}
// This signal is not for any compiled wasm code we expect, so we
// need to forward the signal to the next handler. If there is no
// next handler (SIG_IGN or SIG_DFL), then it's time to crash. To do
// this, we set the signal back to its original disposition and
// return. This will cause the faulting op to be re-executed which
// will crash in the normal way. If there is a next handler, call
// it. It will either crash synchronously, fix up the instruction
// so that execution can continue and return, or trigger a crash by
// returning the signal to it's original disposition and returning.
let previous = &*previous.as_ptr();
if previous.sa_flags & libc::SA_SIGINFO != 0 {
mem::transmute::<
usize,
extern "C" fn(libc::c_int, *mut libc::siginfo_t, *mut libc::c_void),
>(previous.sa_sigaction)(signum, siginfo, context)
} else if previous.sa_sigaction == libc::SIG_DFL
{
libc::sigaction(signum, previous, ptr::null_mut());
} else if previous.sa_sigaction != libc::SIG_IGN {
mem::transmute::<usize, extern "C" fn(libc::c_int)>(
previous.sa_sigaction
)(signum)
}
}
unsafe fn get_pc_sp(context: &ucontext_t) -> (usize, usize) {
let (pc, sp);
cfg_if::cfg_if! {
if #[cfg(all(
any(target_os = "linux", target_os = "android"),
target_arch = "x86_64",
))] {
pc = context.uc_mcontext.gregs[libc::REG_RIP as usize] as usize;
sp = context.uc_mcontext.gregs[libc::REG_RSP as usize] as usize;
} else if #[cfg(all(
any(target_os = "linux", target_os = "android"),
target_arch = "x86",
))] {
pc = context.uc_mcontext.gregs[libc::REG_EIP as usize] as usize;
sp = context.uc_mcontext.gregs[libc::REG_ESP as usize] as usize;
} else if #[cfg(all(target_os = "freebsd", target_arch = "x86"))] {
pc = context.uc_mcontext.mc_eip as usize;
sp = context.uc_mcontext.mc_esp as usize;
} else if #[cfg(all(target_os = "freebsd", target_arch = "x86_64"))] {
pc = context.uc_mcontext.mc_rip as usize;
sp = context.uc_mcontext.mc_rsp as usize;
} else if #[cfg(all(target_vendor = "apple", target_arch = "x86_64"))] {
pc = (*context.uc_mcontext).__ss.__rip as usize;
sp = (*context.uc_mcontext).__ss.__rsp as usize;
} else if #[cfg(all(
any(target_os = "linux", target_os = "android"),
target_arch = "aarch64",
))] {
pc = context.uc_mcontext.pc as usize;
sp = context.uc_mcontext.sp as usize;
} else if #[cfg(all(
any(target_os = "linux", target_os = "android"),
target_arch = "arm",
))] {
pc = context.uc_mcontext.arm_pc as usize;
sp = context.uc_mcontext.arm_sp as usize;
} else if #[cfg(all(
any(target_os = "linux", target_os = "android"),
any(target_arch = "riscv64", target_arch = "riscv32"),
))] {
pc = context.uc_mcontext.__gregs[libc::REG_PC] as usize;
sp = context.uc_mcontext.__gregs[libc::REG_SP] as usize;
} else if #[cfg(all(target_vendor = "apple", target_arch = "aarch64"))] {
pc = (*context.uc_mcontext).__ss.__pc as usize;
sp = (*context.uc_mcontext).__ss.__sp as usize;
} else if #[cfg(all(target_os = "freebsd", target_arch = "aarch64"))] {
pc = context.uc_mcontext.mc_gpregs.gp_elr as usize;
sp = context.uc_mcontext.mc_gpregs.gp_sp as usize;
} else if #[cfg(all(target_os = "linux", target_arch = "loongarch64"))] {
pc = context.uc_mcontext.__gregs[1] as usize;
sp = context.uc_mcontext.__gregs[3] as usize;
} else {
compile_error!("Unsupported platform");
}
};
(pc, sp)
}
unsafe fn update_context(context: &mut ucontext_t, regs: TrapHandlerRegs) {
cfg_if::cfg_if! {
if #[cfg(all(
any(target_os = "linux", target_os = "android"),
target_arch = "x86_64",
))] {
let TrapHandlerRegs { rip, rsp, rbp, rdi, rsi } = regs;
context.uc_mcontext.gregs[libc::REG_RIP as usize] = rip as i64;
context.uc_mcontext.gregs[libc::REG_RSP as usize] = rsp as i64;
context.uc_mcontext.gregs[libc::REG_RBP as usize] = rbp as i64;
context.uc_mcontext.gregs[libc::REG_RDI as usize] = rdi as i64;
context.uc_mcontext.gregs[libc::REG_RSI as usize] = rsi as i64;
} else if #[cfg(all(
any(target_os = "linux", target_os = "android"),
target_arch = "x86",
))] {
let TrapHandlerRegs { eip, esp, ebp, ecx, edx } = regs;
context.uc_mcontext.gregs[libc::REG_EIP as usize] = eip as i32;
context.uc_mcontext.gregs[libc::REG_ESP as usize] = esp as i32;
context.uc_mcontext.gregs[libc::REG_EBP as usize] = ebp as i32;
context.uc_mcontext.gregs[libc::REG_ECX as usize] = ecx as i32;
context.uc_mcontext.gregs[libc::REG_EDX as usize] = edx as i32;
} else if #[cfg(all(target_vendor = "apple", target_arch = "x86_64"))] {
let TrapHandlerRegs { rip, rsp, rbp, rdi, rsi } = regs;
(*context.uc_mcontext).__ss.__rip = rip;
(*context.uc_mcontext).__ss.__rsp = rsp;
(*context.uc_mcontext).__ss.__rbp = rbp;
(*context.uc_mcontext).__ss.__rdi = rdi;
(*context.uc_mcontext).__ss.__rsi = rsi;
} else if #[cfg(all(target_os = "freebsd", target_arch = "x86"))] {
let TrapHandlerRegs { eip, esp, ebp, ecx, edx } = regs;
context.uc_mcontext.mc_eip = eip as libc::register_t;
context.uc_mcontext.mc_esp = esp as libc::register_t;
context.uc_mcontext.mc_ebp = ebp as libc::register_t;
context.uc_mcontext.mc_ecx = ecx as libc::register_t;
context.uc_mcontext.mc_edx = edx as libc::register_t;
} else if #[cfg(all(target_os = "freebsd", target_arch = "x86_64"))] {
let TrapHandlerRegs { rip, rsp, rbp, rdi, rsi } = regs;
context.uc_mcontext.mc_rip = rip as libc::register_t;
context.uc_mcontext.mc_rsp = rsp as libc::register_t;
context.uc_mcontext.mc_rbp = rbp as libc::register_t;
context.uc_mcontext.mc_rdi = rdi as libc::register_t;
context.uc_mcontext.mc_rsi = rsi as libc::register_t;
} else if #[cfg(all(
any(target_os = "linux", target_os = "android"),
target_arch = "aarch64",
))] {
let TrapHandlerRegs { pc, sp, x0, x1, x29, lr } = regs;
context.uc_mcontext.pc = pc;
context.uc_mcontext.sp = sp;
context.uc_mcontext.regs[0] = x0;
context.uc_mcontext.regs[1] = x1;
context.uc_mcontext.regs[29] = x29;
context.uc_mcontext.regs[30] = lr;
} else if #[cfg(all(
any(target_os = "linux", target_os = "android"),
target_arch = "arm",
))] {
let TrapHandlerRegs {
pc,
r0,
r1,
r7,
r11,
r13,
r14,
cpsr_thumb,
cpsr_endian,
} = regs;
context.uc_mcontext.arm_pc = pc;
context.uc_mcontext.arm_r0 = r0;
context.uc_mcontext.arm_r1 = r1;
context.uc_mcontext.arm_r7 = r7;
context.uc_mcontext.arm_fp = r11;
context.uc_mcontext.arm_sp = r13;
context.uc_mcontext.arm_lr = r14;
if cpsr_thumb {
context.uc_mcontext.arm_cpsr |= 0x20;
} else {
context.uc_mcontext.arm_cpsr &= !0x20;
}
if cpsr_endian {
context.uc_mcontext.arm_cpsr |= 0x200;
} else {
context.uc_mcontext.arm_cpsr &= !0x200;
}
} else if #[cfg(all(
any(target_os = "linux", target_os = "android"),
any(target_arch = "riscv64", target_arch = "riscv32"),
))] {
let TrapHandlerRegs { pc, ra, sp, a0, a1, s0 } = regs;
context.uc_mcontext.__gregs[libc::REG_PC] = pc as libc::c_ulong;
context.uc_mcontext.__gregs[libc::REG_RA] = ra as libc::c_ulong;
context.uc_mcontext.__gregs[libc::REG_SP] = sp as libc::c_ulong;
context.uc_mcontext.__gregs[libc::REG_A0] = a0 as libc::c_ulong;
context.uc_mcontext.__gregs[libc::REG_A0 + 1] = a1 as libc::c_ulong;
context.uc_mcontext.__gregs[libc::REG_S0] = s0 as libc::c_ulong;
} else if #[cfg(all(target_vendor = "apple", target_arch = "aarch64"))] {
let TrapHandlerRegs { pc, sp, x0, x1, x29, lr } = regs;
(*context.uc_mcontext).__ss.__pc = pc;
(*context.uc_mcontext).__ss.__sp = sp;
(*context.uc_mcontext).__ss.__x[0] = x0;
(*context.uc_mcontext).__ss.__x[1] = x1;
(*context.uc_mcontext).__ss.__fp = x29;
(*context.uc_mcontext).__ss.__lr = lr;
} else if #[cfg(all(target_os = "freebsd", target_arch = "aarch64"))] {
let TrapHandlerRegs { pc, sp, x0, x1, x29, lr } = regs;
context.uc_mcontext.mc_gpregs.gp_elr = pc as libc::register_t;
context.uc_mcontext.mc_gpregs.gp_sp = sp as libc::register_t;
context.uc_mcontext.mc_gpregs.gp_x[0] = x0 as libc::register_t;
context.uc_mcontext.mc_gpregs.gp_x[1] = x1 as libc::register_t;
context.uc_mcontext.mc_gpregs.gp_x[29] = x29 as libc::register_t;
context.uc_mcontext.mc_gpregs.gp_x[30] = lr as libc::register_t;
} else if #[cfg(all(target_os = "linux", target_arch = "loongarch64"))] {
let TrapHandlerRegs { pc, sp, a0, a1, fp, ra } = regs;
context.uc_mcontext.__pc = pc;
context.uc_mcontext.__gregs[1] = ra;
context.uc_mcontext.__gregs[3] = sp;
context.uc_mcontext.__gregs[4] = a0;
context.uc_mcontext.__gregs[5] = a1;
context.uc_mcontext.__gregs[22] = fp;
} else {
compile_error!("Unsupported platform");
}
};
}
} else if #[cfg(target_os = "windows")] {
use windows_sys::Win32::System::Diagnostics::Debug::{
AddVectoredExceptionHandler,
CONTEXT,
EXCEPTION_CONTINUE_EXECUTION,
EXCEPTION_CONTINUE_SEARCH,
EXCEPTION_POINTERS,
};
use windows_sys::Win32::Foundation::{
EXCEPTION_ACCESS_VIOLATION,
EXCEPTION_ILLEGAL_INSTRUCTION,
EXCEPTION_INT_DIVIDE_BY_ZERO,
EXCEPTION_INT_OVERFLOW,
EXCEPTION_STACK_OVERFLOW,
};
unsafe fn platform_init() {
// our trap handler needs to go first, so that we can recover from
// wasm faults and continue execution, so pass `1` as a true value
// here.
if AddVectoredExceptionHandler(1, Some(exception_handler)).is_null() {
panic!("failed to add exception handler: {}", io::Error::last_os_error());
}
}
unsafe extern "system" fn exception_handler(
exception_info: *mut EXCEPTION_POINTERS
) -> i32 {
// Check the kind of exception, since we only handle a subset within
// wasm code. If anything else happens we want to defer to whatever
// the rest of the system wants to do for this exception.
let record = &*(*exception_info).ExceptionRecord;
if record.ExceptionCode != EXCEPTION_ACCESS_VIOLATION &&
record.ExceptionCode != EXCEPTION_ILLEGAL_INSTRUCTION &&
record.ExceptionCode != EXCEPTION_STACK_OVERFLOW &&
record.ExceptionCode != EXCEPTION_INT_DIVIDE_BY_ZERO &&
record.ExceptionCode != EXCEPTION_INT_OVERFLOW
{
return EXCEPTION_CONTINUE_SEARCH;
}
// FIXME: this is what the previous C++ did to make sure that TLS
// works by the time we execute this trap handling code. This isn't
// exactly super easy to call from Rust though and it's not clear we
// necessarily need to do so. Leaving this here in case we need this
// in the future, but for now we can probably wait until we see a
// strange fault before figuring out how to reimplement this in
// Rust.
//
// if (!NtCurrentTeb()->Reserved1[sThreadLocalArrayPointerIndex]) {
// return EXCEPTION_CONTINUE_SEARCH;
// }
let context = &mut *(*exception_info).ContextRecord;
let (pc, sp) = get_pc_sp(context);
// We try to get the fault address associated to this exception.
let maybe_fault_address = match record.ExceptionCode {
EXCEPTION_ACCESS_VIOLATION => Some(record.ExceptionInformation[1]),
EXCEPTION_STACK_OVERFLOW => Some(sp),
_ => None,
};
let trap_code = match record.ExceptionCode {
// check if it was cased by a UD and if the Trap info is a payload to it
EXCEPTION_ILLEGAL_INSTRUCTION => {
process_illegal_op(pc)
}
_ => None,
};
// This is basically the same as the unix version above, only with a
// few parameters tweaked here and there.
let handled = TrapHandlerContext::handle_trap(
pc,
sp,
maybe_fault_address,
trap_code,
|regs| update_context(context, regs),
|handler| handler(exception_info),
);
if handled {
EXCEPTION_CONTINUE_EXECUTION
} else {
EXCEPTION_CONTINUE_SEARCH
}
}
unsafe fn get_pc_sp(context: &CONTEXT) -> (usize, usize) {
let (pc, sp);
cfg_if::cfg_if! {
if #[cfg(target_arch = "x86_64")] {
pc = context.Rip as usize;
sp = context.Rsp as usize;
} else if #[cfg(target_arch = "x86")] {
pc = context.Rip as usize;
sp = context.Rsp as usize;
} else {
compile_error!("Unsupported platform");
}
};
(pc, sp)
}
unsafe fn update_context(context: &mut CONTEXT, regs: TrapHandlerRegs) {
cfg_if::cfg_if! {
if #[cfg(target_arch = "x86_64")] {
let TrapHandlerRegs { rip, rsp, rbp, rdi, rsi } = regs;
context.Rip = rip;
context.Rsp = rsp;
context.Rbp = rbp;
context.Rdi = rdi;
context.Rsi = rsi;
} else if #[cfg(target_arch = "x86")] {
let TrapHandlerRegs { eip, esp, ebp, ecx, edx } = regs;
context.Eip = eip;
context.Esp = esp;
context.Ebp = ebp;
context.Ecx = ecx;
context.Edx = edx;
} else {
compile_error!("Unsupported platform");
}
};
}
}
}
/// This function is required to be called before any WebAssembly is entered.
/// This will configure global state such as signal handlers to prepare the
/// process to receive wasm traps.
///
/// This function must not only be called globally once before entering
/// WebAssembly but it must also be called once-per-thread that enters
/// WebAssembly. Currently in wasmer's integration this function is called on
/// creation of a `Store`.
pub fn init_traps() {
static INIT: Once = Once::new();
INIT.call_once(|| unsafe {
platform_init();
});
}
/// Raises a user-defined trap immediately.
///
/// This function performs as-if a wasm trap was just executed, only the trap
/// has a dynamic payload associated with it which is user-provided. This trap
/// payload is then returned from `catch_traps` below.
///
/// # Safety
///
/// Only safe to call when wasm code is on the stack, aka `catch_traps` must
/// have been previous called and not yet returned.
/// Additionally no Rust destructors may be on the stack.
/// They will be skipped and not executed.
pub unsafe fn raise_user_trap(data: Box<dyn Error + Send + Sync>) -> ! {
unwind_with(UnwindReason::UserTrap(data))
}
/// Raises a trap from inside library code immediately.
///
/// This function performs as-if a wasm trap was just executed. This trap
/// payload is then returned from `catch_traps` below.
///
/// # Safety
///
/// Only safe to call when wasm code is on the stack, aka `catch_traps` must
/// have been previous called and not yet returned.
/// Additionally no Rust destructors may be on the stack.
/// They will be skipped and not executed.
pub unsafe fn raise_lib_trap(trap: Trap) -> ! {
unwind_with(UnwindReason::LibTrap(trap))
}
/// Carries a Rust panic across wasm code and resumes the panic on the other
/// side.
///
/// # Safety
///
/// Only safe to call when wasm code is on the stack, aka `catch_traps` must
/// have been previously called and not returned. Additionally no Rust destructors may be on the
/// stack. They will be skipped and not executed.
pub unsafe fn resume_panic(payload: Box<dyn Any + Send>) -> ! {
unwind_with(UnwindReason::Panic(payload))
}
/// Call the wasm function pointed to by `callee`.
///
/// * `vmctx` - the callee vmctx argument
/// * `caller_vmctx` - the caller vmctx argument
/// * `trampoline` - the jit-generated trampoline whose ABI takes 4 values, the
/// callee vmctx, the caller vmctx, the `callee` argument below, and then the
/// `values_vec` argument.
/// * `callee` - the third argument to the `trampoline` function
/// * `values_vec` - points to a buffer which holds the incoming arguments, and to
/// which the outgoing return values will be written.
///
/// # Safety
///
/// Wildly unsafe because it calls raw function pointers and reads/writes raw
/// function pointers.
pub unsafe fn wasmer_call_trampoline(
trap_handler: Option<*const TrapHandlerFn<'static>>,
config: &VMConfig,
vmctx: VMFunctionContext,
trampoline: VMTrampoline,
callee: *const VMFunctionBody,
values_vec: *mut u8,
) -> Result<(), Trap> {
catch_traps(trap_handler, config, move || {
mem::transmute::<
unsafe extern "C" fn(
*mut VMContext,
*const VMFunctionBody,
*mut wasmer_types::RawValue,
),
extern "C" fn(VMFunctionContext, *const VMFunctionBody, *mut u8),
>(trampoline)(vmctx, callee, values_vec);
})
}
/// Catches any wasm traps that happen within the execution of `closure`,
/// returning them as a `Result`.
///
/// # Safety
///
/// Highly unsafe since `closure` won't have any dtors run.
pub unsafe fn catch_traps<F, R: 'static>(
trap_handler: Option<*const TrapHandlerFn<'static>>,
config: &VMConfig,
closure: F,
) -> Result<R, Trap>
where
F: FnOnce() -> R + 'static,
{
// Ensure that per-thread initialization is done.
lazy_per_thread_init()?;
let stack_size = config
.wasm_stack_size
.unwrap_or_else(|| DEFAULT_STACK_SIZE.load(Ordering::Relaxed));
on_wasm_stack(stack_size, trap_handler, closure).map_err(UnwindReason::into_trap)
}
// We need two separate thread-local variables here:
// - YIELDER is set within the new stack and is used to unwind back to the root
// of the stack from inside it.
// - TRAP_HANDLER is set from outside the new stack and is solely used from
// signal handlers. It must be atomic since it is used by signal handlers.
//
// We also do per-thread signal stack initialization on the first time
// TRAP_HANDLER is accessed.
thread_local! {
static YIELDER: Cell<Option<NonNull<Yielder<(), UnwindReason>>>> = const { Cell::new(None) };
static TRAP_HANDLER: AtomicPtr<TrapHandlerContext> = const { AtomicPtr::new(ptr::null_mut()) };
}
/// Read-only information that is used by signal handlers to handle and recover
/// from traps.
#[allow(clippy::type_complexity)]
struct TrapHandlerContext {
inner: *const u8,
handle_trap: fn(
*const u8,
usize,
usize,
Option<usize>,
Option<TrapCode>,
&mut dyn FnMut(TrapHandlerRegs),
) -> bool,
custom_trap: Option<*const TrapHandlerFn<'static>>,
}
struct TrapHandlerContextInner<T> {
/// Information about the currently running coroutine. This is used to
/// reset execution to the root of the coroutine when a trap is handled.
coro_trap_handler: CoroutineTrapHandler<Result<T, UnwindReason>>,
}
impl TrapHandlerContext {
/// Runs the given function with a trap handler context. The previous
/// trap handler context is preserved and restored afterwards.
fn install<T, R>(
custom_trap: Option<*const TrapHandlerFn<'static>>,
coro_trap_handler: CoroutineTrapHandler<Result<T, UnwindReason>>,
f: impl FnOnce() -> R,
) -> R {
// Type-erase the trap handler function so that it can be placed in TLS.
fn func<T>(
ptr: *const u8,
pc: usize,
sp: usize,
maybe_fault_address: Option<usize>,
trap_code: Option<TrapCode>,
update_regs: &mut dyn FnMut(TrapHandlerRegs),
) -> bool {
unsafe {
(*(ptr as *const TrapHandlerContextInner<T>)).handle_trap(
pc,
sp,
maybe_fault_address,
trap_code,
update_regs,
)
}
}
let inner = TrapHandlerContextInner { coro_trap_handler };
let ctx = Self {
inner: &inner as *const _ as *const u8,
handle_trap: func::<T>,
custom_trap,
};
compiler_fence(Ordering::Release);
let prev = TRAP_HANDLER.with(|ptr| {
let prev = ptr.load(Ordering::Relaxed);
ptr.store(&ctx as *const Self as *mut Self, Ordering::Relaxed);
prev
});
defer! {
TRAP_HANDLER.with(|ptr| ptr.store(prev, Ordering::Relaxed));
compiler_fence(Ordering::Acquire);
}
f()
}
/// Attempts to handle the trap if it's a wasm trap.
unsafe fn handle_trap(
pc: usize,
sp: usize,
maybe_fault_address: Option<usize>,
trap_code: Option<TrapCode>,
mut update_regs: impl FnMut(TrapHandlerRegs),
call_handler: impl Fn(&TrapHandlerFn<'static>) -> bool,
) -> bool {
let ptr = TRAP_HANDLER.with(|ptr| ptr.load(Ordering::Relaxed));
if ptr.is_null() {
return false;
}
let ctx = &*ptr;
// Check if this trap is handled by a custom trap handler.
if let Some(trap_handler) = ctx.custom_trap {
if call_handler(&*trap_handler) {
return true;
}
}
(ctx.handle_trap)(
ctx.inner,
pc,
sp,
maybe_fault_address,
trap_code,
&mut update_regs,
)
}
}
impl<T> TrapHandlerContextInner<T> {
unsafe fn handle_trap(
&self,
pc: usize,
sp: usize,
maybe_fault_address: Option<usize>,
trap_code: Option<TrapCode>,
update_regs: &mut dyn FnMut(TrapHandlerRegs),
) -> bool {
// Check if this trap occurred while executing on the Wasm stack. We can
// only recover from traps if that is the case.
if !self.coro_trap_handler.stack_ptr_in_bounds(sp) {
return false;
}
let signal_trap = trap_code.or_else(|| {
maybe_fault_address.map(|addr| {
if self.coro_trap_handler.stack_ptr_in_bounds(addr) {
TrapCode::StackOverflow
} else {
TrapCode::HeapAccessOutOfBounds
}
})
});
// Don't try to generate a backtrace for stack overflows: unwinding
// information is often not precise enough to properly describe what is
// happenning during a function prologue, which can lead the unwinder to
// read invalid memory addresses.
//
// See: https://github.com/rust-lang/backtrace-rs/pull/357
let backtrace = if signal_trap == Some(TrapCode::StackOverflow) {
Backtrace::from(vec![])
} else {
Backtrace::new_unresolved()
};
// Set up the register state for exception return to force the
// coroutine to return to its caller with UnwindReason::WasmTrap.
let unwind = UnwindReason::WasmTrap {
backtrace,
signal_trap,
pc,
};
let regs = self
.coro_trap_handler
.setup_trap_handler(move || Err(unwind));
update_regs(regs);
true
}
}
enum UnwindReason {
/// A panic caused by the host
Panic(Box<dyn Any + Send>),
/// A custom error triggered by the user
UserTrap(Box<dyn Error + Send + Sync>),
/// A Trap triggered by a wasm libcall
LibTrap(Trap),
/// A trap caused by the Wasm generated code
WasmTrap {
backtrace: Backtrace,
pc: usize,
signal_trap: Option<TrapCode>,
},
}
impl UnwindReason {
fn into_trap(self) -> Trap {
match self {
Self::UserTrap(data) => Trap::User(data),
Self::LibTrap(trap) => trap,
Self::WasmTrap {
backtrace,
pc,
signal_trap,
} => Trap::wasm(pc, backtrace, signal_trap),
Self::Panic(panic) => std::panic::resume_unwind(panic),
}
}
}
unsafe fn unwind_with(reason: UnwindReason) -> ! {
let yielder = YIELDER
.with(|cell| cell.replace(None))
.expect("not running on Wasm stack");
yielder.as_ref().suspend(reason);
// on_wasm_stack will forcibly reset the coroutine stack after yielding.
unreachable!();
}
/// Runs the given function on a separate stack so that its stack usage can be
/// bounded. Stack overflows and other traps can be caught and execution
/// returned to the root of the stack.
fn on_wasm_stack<F: FnOnce() -> T + 'static, T: 'static>(
stack_size: usize,
trap_handler: Option<*const TrapHandlerFn<'static>>,
f: F,
) -> Result<T, UnwindReason> {
// Allocating a new stack is pretty expensive since it involves several
// system calls. We therefore keep a cache of pre-allocated stacks which
// allows them to be reused multiple times.
// FIXME(Amanieu): We should refactor this to avoid the lock.
lazy_static::lazy_static! {
static ref STACK_POOL: crossbeam_queue::SegQueue<DefaultStack> = crossbeam_queue::SegQueue::new();
}
let stack = STACK_POOL
.pop()
.unwrap_or_else(|| DefaultStack::new(stack_size).unwrap());
let mut stack = scopeguard::guard(stack, |stack| STACK_POOL.push(stack));
// Create a coroutine with a new stack to run the function on.
let mut coro = Coroutine::with_stack(&mut *stack, move |yielder, ()| {
// Save the yielder to TLS so that it can be used later.
YIELDER.with(|cell| cell.set(Some(yielder.into())));
Ok(f())
});
// Ensure that YIELDER is reset on exit even if the coroutine panics,
defer! {
YIELDER.with(|cell| cell.set(None));
}
// Set up metadata for the trap handler for the duration of the coroutine
// execution. This is restored to its previous value afterwards.
TrapHandlerContext::install(trap_handler, coro.trap_handler(), || {
match coro.resume(()) {
CoroutineResult::Yield(trap) => {
// This came from unwind_with which requires that there be only
// Wasm code on the stack.
unsafe {
coro.force_reset();
}
Err(trap)
}
CoroutineResult::Return(result) => result,
}
})
}
/// When executing on the Wasm stack, temporarily switch back to the host stack
/// to perform an operation that should not be constrainted by the Wasm stack
/// limits.
///
/// This is particularly important since the usage of the Wasm stack is under
/// the control of untrusted code. Malicious code could artificially induce a
/// stack overflow in the middle of a sensitive host operations (e.g. growing
/// a memory) which would be hard to recover from.
pub fn on_host_stack<F: FnOnce() -> T, T>(f: F) -> T {
// Reset YIEDER to None for the duration of this call to indicate that we
// are no longer on the Wasm stack.
let yielder_ptr = YIELDER.with(|cell| cell.replace(None));
// If we are already on the host stack, execute the function directly. This
// happens if a host function is called directly from the API.
let yielder = match yielder_ptr {
Some(ptr) => unsafe { ptr.as_ref() },
None => return f(),
};
// Restore YIELDER upon exiting normally or unwinding.
defer! {
YIELDER.with(|cell| cell.set(yielder_ptr));
}
// on_parent_stack requires the closure to be Send so that the Yielder
// cannot be called from the parent stack. This is not a problem for us
// since we don't expose the Yielder.
struct SendWrapper<T>(T);
unsafe impl<T> Send for SendWrapper<T> {}
let wrapped = SendWrapper(f);
yielder.on_parent_stack(move || {
let wrapped = wrapped;
(wrapped.0)()
})
}
#[cfg(windows)]
pub fn lazy_per_thread_init() -> Result<(), Trap> {
// We need additional space on the stack to handle stack overflow
// exceptions. Rust's initialization code sets this to 0x5000 but this
// seems to be insufficient in practice.
use windows_sys::Win32::System::Threading::SetThreadStackGuarantee;
if unsafe { SetThreadStackGuarantee(&mut 0x10000) } == 0 {
panic!("failed to set thread stack guarantee");
}
Ok(())
}
/// A module for registering a custom alternate signal stack (sigaltstack).
///
/// Rust's libstd installs an alternate stack with size `SIGSTKSZ`, which is not
/// always large enough for our signal handling code. Override it by creating
/// and registering our own alternate stack that is large enough and has a guard
/// page.
#[cfg(unix)]
pub fn lazy_per_thread_init() -> Result<(), Trap> {
use std::ptr::null_mut;
thread_local! {
/// Thread-local state is lazy-initialized on the first time it's used,
/// and dropped when the thread exits.
static TLS: Tls = unsafe { init_sigstack() };
}
/// The size of the sigaltstack (not including the guard, which will be
/// added). Make this large enough to run our signal handlers.
const MIN_STACK_SIZE: usize = 16 * 4096;
enum Tls {
OutOfMemory,
Allocated {
mmap_ptr: *mut libc::c_void,
mmap_size: usize,
},
BigEnough,
}
unsafe fn init_sigstack() -> Tls {
// Check to see if the existing sigaltstack, if it exists, is big
// enough. If so we don't need to allocate our own.
let mut old_stack = mem::zeroed();
let r = libc::sigaltstack(ptr::null(), &mut old_stack);
assert_eq!(r, 0, "learning about sigaltstack failed");
if old_stack.ss_flags & libc::SS_DISABLE == 0 && old_stack.ss_size >= MIN_STACK_SIZE {
return Tls::BigEnough;
}
// ... but failing that we need to allocate our own, so do all that
// here.
let page_size: usize = region::page::size();
let guard_size = page_size;
let alloc_size = guard_size + MIN_STACK_SIZE;
let ptr = libc::mmap(
null_mut(),
alloc_size,
libc::PROT_NONE,
libc::MAP_PRIVATE | libc::MAP_ANON,
-1,
0,
);
if ptr == libc::MAP_FAILED {
return Tls::OutOfMemory;
}
// Prepare the stack with readable/writable memory and then register it
// with `sigaltstack`.
let stack_ptr = (ptr as usize + guard_size) as *mut libc::c_void;
let r = libc::mprotect(
stack_ptr,
MIN_STACK_SIZE,
libc::PROT_READ | libc::PROT_WRITE,
);
assert_eq!(r, 0, "mprotect to configure memory for sigaltstack failed");
let new_stack = libc::stack_t {
ss_sp: stack_ptr,
ss_flags: 0,
ss_size: MIN_STACK_SIZE,
};
let r = libc::sigaltstack(&new_stack, ptr::null_mut());
assert_eq!(r, 0, "registering new sigaltstack failed");
Tls::Allocated {
mmap_ptr: ptr,
mmap_size: alloc_size,
}
}
// Ensure TLS runs its initializer and return an error if it failed to
// set up a separate stack for signal handlers.
return TLS.with(|tls| {
if let Tls::OutOfMemory = tls {
Err(Trap::oom())
} else {
Ok(())
}
});
impl Drop for Tls {
fn drop(&mut self) {
let (ptr, size) = match self {
Self::Allocated {
mmap_ptr,
mmap_size,
} => (*mmap_ptr, *mmap_size),
_ => return,
};
unsafe {
// Deallocate the stack memory.
let r = libc::munmap(ptr, size);
debug_assert_eq!(r, 0, "munmap failed during thread shutdown");
}
}
}
}