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std.debug: greatly expand target support for segfault handling/unwinding, and remove public ucontext_t completely #25516

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Merged
merged 6 commits into from
Oct 10, 2025
Merged

std.debug: greatly expand target support for segfault handling/unwinding, and remove public ucontext_t completely #25516

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c8efebc
std.os.linux: remove dead/wrong msghdr definitions in some arch bits
alexrp Oct 9, 2025
6c760d7
std.os.linux: define PROT.SEM for xtensa
alexrp Oct 9, 2025
98f0bf9
std.debug: fix SelfInfo default for freestanding ELF targets
alexrp Oct 9, 2025
3f5e782
std.debug: fix FP unwinding for LoongArch
alexrp Oct 9, 2025
f33d3a5
std.debug: greatly expand target support for segfault handling/unwinding
alexrp Oct 9, 2025
36dbe66
std: stop exposing anything having to do with ucontext_t
alexrp Oct 9, 2025
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107 changes: 1 addition & 106 deletions lib/std/c.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -1841,110 +1841,6 @@ pub const PROT = switch (native_os) {
else => void,
};

pub const REG = switch (native_os) {
.linux => linux.REG,
.emscripten => emscripten.REG,
.freebsd => switch (builtin.cpu.arch) {
.aarch64 => struct {
pub const FP = 29;
pub const SP = 31;
pub const PC = 32;
},
.arm => struct {
pub const FP = 11;
pub const SP = 13;
pub const PC = 15;
},
.x86_64 => struct {
pub const RBP = 12;
pub const RIP = 21;
pub const RSP = 24;
},
else => struct {},
},
.solaris, .illumos => struct {
pub const R15 = 0;
pub const R14 = 1;
pub const R13 = 2;
pub const R12 = 3;
pub const R11 = 4;
pub const R10 = 5;
pub const R9 = 6;
pub const R8 = 7;
pub const RDI = 8;
pub const RSI = 9;
pub const RBP = 10;
pub const RBX = 11;
pub const RDX = 12;
pub const RCX = 13;
pub const RAX = 14;
pub const RIP = 17;
pub const RSP = 20;
},
.netbsd => switch (builtin.cpu.arch) {
.aarch64, .aarch64_be => struct {
pub const FP = 29;
pub const SP = 31;
pub const PC = 32;
},
.arm, .armeb => struct {
pub const FP = 11;
pub const SP = 13;
pub const PC = 15;
},
.x86 => struct {
pub const GS = 0;
pub const FS = 1;
pub const ES = 2;
pub const DS = 3;
pub const EDI = 4;
pub const ESI = 5;
pub const EBP = 6;
pub const ESP = 7;
pub const EBX = 8;
pub const EDX = 9;
pub const ECX = 10;
pub const EAX = 11;
pub const TRAPNO = 12;
pub const ERR = 13;
pub const EIP = 14;
pub const CS = 15;
pub const EFL = 16;
pub const UESP = 17;
pub const SS = 18;
},
.x86_64 => struct {
pub const RDI = 0;
pub const RSI = 1;
pub const RDX = 2;
pub const RCX = 3;
pub const R8 = 4;
pub const R9 = 5;
pub const R10 = 6;
pub const R11 = 7;
pub const R12 = 8;
pub const R13 = 9;
pub const R14 = 10;
pub const R15 = 11;
pub const RBP = 12;
pub const RBX = 13;
pub const RAX = 14;
pub const GS = 15;
pub const FS = 16;
pub const ES = 17;
pub const DS = 18;
pub const TRAPNO = 19;
pub const ERR = 20;
pub const RIP = 21;
pub const CS = 22;
pub const RFLAGS = 23;
pub const RSP = 24;
pub const SS = 25;
},
else => struct {},
},
else => struct {},
};
pub const RLIM = switch (native_os) {
.linux => linux.RLIM,
.emscripten => emscripten.RLIM,
Expand Down Expand Up @@ -4553,7 +4449,7 @@ pub const rusage = switch (native_os) {
pub const siginfo_t = switch (native_os) {
.linux => linux.siginfo_t,
.emscripten => emscripten.siginfo_t,
.macos, .ios, .tvos, .watchos, .visionos => extern struct {
.driverkit, .macos, .ios, .tvos, .watchos, .visionos => extern struct {
signo: c_int,
errno: c_int,
code: c_int,
Expand Down Expand Up @@ -11084,7 +10980,6 @@ pub const SETUSTACK = solaris.GETUSTACK;
pub const SFD = solaris.SFD;
pub const ctid_t = solaris.ctid_t;
pub const file_obj = solaris.file_obj;
pub const fpregset_t = solaris.fpregset_t;
pub const id_t = solaris.id_t;
pub const lif_ifinfo_req = solaris.lif_ifinfo_req;
pub const lif_nd_req = solaris.lif_nd_req;
Expand Down
23 changes: 0 additions & 23 deletions lib/std/c/solaris.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -31,29 +31,6 @@ pub const poolid_t = id_t;
pub const zoneid_t = id_t;
pub const ctid_t = id_t;

pub const fpregset_t = extern union {
regs: [130]u32,
chip_state: extern struct {
cw: u16,
sw: u16,
fctw: u8,
__fx_rsvd: u8,
fop: u16,
rip: u64,
rdp: u64,
mxcsr: u32,
mxcsr_mask: u32,
st: [8]extern union {
fpr_16: [5]u16,
__fpr_pad: u128,
},
xmm: [16]u128,
__fx_ign2: [6]u128,
status: u32,
xstatus: u32,
},
};

pub const GETCONTEXT = 0;
pub const SETCONTEXT = 1;
pub const GETUSTACK = 2;
Expand Down
55 changes: 42 additions & 13 deletions lib/std/debug.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,10 @@ pub const SelfInfo = if (@hasDecl(root, "debug") and @hasDecl(root.debug, "SelfI
root.debug.SelfInfo
else switch (std.Target.ObjectFormat.default(native_os, native_arch)) {
.coff => if (native_os == .windows) @import("debug/SelfInfo/Windows.zig") else void,
.elf => @import("debug/SelfInfo/Elf.zig"),
.elf => switch (native_os) {
.freestanding, .other => void,
else => @import("debug/SelfInfo/Elf.zig"),
},
.macho => @import("debug/SelfInfo/MachO.zig"),
.goff, .plan9, .spirv, .wasm, .xcoff => void,
.c, .hex, .raw => unreachable,
Expand Down Expand Up @@ -985,15 +988,15 @@ const StackIterator = union(enum) {
// On RISC-V the frame pointer points to the top of the saved register
// area, on pretty much every other architecture it points to the stack
// slot where the previous frame pointer is saved.
if (native_arch.isRISCV()) break :off -2 * @sizeOf(usize);
if (native_arch.isLoongArch() or native_arch.isRISCV()) break :off -2 * @sizeOf(usize);
// On SPARC the previous frame pointer is stored at 14 slots past %fp+BIAS.
if (native_arch.isSPARC()) break :off 14 * @sizeOf(usize);
break :off 0;
};

/// Offset of the saved return address wrt the frame pointer.
const ra_offset = off: {
if (native_arch.isRISCV()) break :off -1 * @sizeOf(usize);
if (native_arch.isLoongArch() or native_arch.isRISCV()) break :off -1 * @sizeOf(usize);
if (native_arch.isSPARC()) break :off 15 * @sizeOf(usize);
if (native_arch.isPowerPC64()) break :off 2 * @sizeOf(usize);
// On s390x, r14 is the link register and we need to grab it from its customary slot in the
Expand Down Expand Up @@ -1312,15 +1315,26 @@ fn getDebugInfoAllocator() Allocator {

/// Whether or not the current target can print useful debug information when a segfault occurs.
pub const have_segfault_handling_support = switch (native_os) {
.haiku,
.linux,
.macos,
.serenity,

.dragonfly,
.freebsd,
.netbsd,
.solaris,
.openbsd,

.driverkit,
.ios,
.macos,
.tvos,
.visionos,
.watchos,

.illumos,
.solaris,

.windows,
.freebsd,
.openbsd,
.serenity,
=> true,

else => false,
Expand Down Expand Up @@ -1403,11 +1417,26 @@ fn handleSegfaultPosix(sig: i32, info: *const posix.siginfo_t, ctx_ptr: ?*anyopa
}
}
const addr: usize = switch (native_os) {
.linux => @intFromPtr(info.fields.sigfault.addr),
.freebsd, .macos, .serenity => @intFromPtr(info.addr),
.netbsd => @intFromPtr(info.info.reason.fault.addr),
.openbsd => @intFromPtr(info.data.fault.addr),
.solaris, .illumos => @intFromPtr(info.reason.fault.addr),
.serenity,
.dragonfly,
.freebsd,
.driverkit,
.ios,
.macos,
.tvos,
.visionos,
.watchos,
=> @intFromPtr(info.addr),
.linux,
=> @intFromPtr(info.fields.sigfault.addr),
.netbsd,
=> @intFromPtr(info.info.reason.fault.addr),
.haiku,
.openbsd,
=> @intFromPtr(info.data.fault.addr),
.illumos,
.solaris,
=> @intFromPtr(info.reason.fault.addr),
else => comptime unreachable,
};
const name = switch (sig) {
Expand Down
50 changes: 41 additions & 9 deletions lib/std/debug/SelfInfo/Elf.zig
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Expand Up @@ -94,6 +94,15 @@ pub const can_unwind: bool = s: {
// Notably, we are yet to support unwinding on ARM. There, unwinding is not done through
// `.eh_frame`, but instead with the `.ARM.exidx` section, which has a different format.
const archs: []const std.Target.Cpu.Arch = switch (builtin.target.os.tag) {
// Not supported yet: arm, m68k, sparc64
.haiku => &.{
.aarch64,
.powerpc,
.riscv64,
.x86,
.x86_64,
},
// Not supported yet: arc, arm/armeb/thumb/thumbeb, csky, m68k, or1k, sparc/sparc64, xtensa
.linux => &.{
.aarch64,
.aarch64_be,
Expand All @@ -113,31 +122,54 @@ pub const can_unwind: bool = s: {
.x86,
.x86_64,
},
.netbsd => &.{
.serenity => &.{
.aarch64,
.aarch64_be,
.x86,
.x86_64,
.riscv64,
},
.freebsd => &.{

.dragonfly => &.{
.x86_64,
},
// Not supported yet: arm
.freebsd => &.{
.aarch64,
.powerpc64,
.powerpc64le,
.riscv64,
.x86_64,
},
.openbsd => &.{
// Not supported yet: arm/armeb, m68k, mips64/mips64el, sparc/sparc64
.netbsd => &.{
.aarch64,
.aarch64_be,
.mips,
.mipsel,
.powerpc,
.x86,
.x86_64,
},
.solaris => &.{
// Not supported yet: arm, sparc64
.openbsd => &.{
.aarch64,
.mips64,
.mips64el,
.powerpc,
.powerpc64,
.riscv64,
.x86,
.x86_64,
},

.illumos => &.{
.x86,
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Illumos and Solaris haven't supported x86 for a while now. You can run old binaries but it's discouraged to create new ones.

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I know Solaris hasn't, but illumos seems to still support userspace 32-bit applications? http://www.tribblix.org/32bit.html

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It only matters how you define can_unwind:

  1. Does this arch-os-abi combo support unwinding?
  2. Does the Zig compiler emit code for this combo?

If 2 doesn't matter then you may as well add x86 to Solaris as well. It seems like it doesn't since sparc64-solaris isn't there.

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sparc64-solaris is just a to-do along with sparc64-linux and others; I'll do a later pull request that adds full SPARC unwinding to all of std.debug (unless @mlugg beats me to it?).

In general, I'm going off test/llvm_targets.zig for what targets are relevant here. That file in turn boils down to which targets are still supported by the developers/vendor of the OS. If a target is missing here, it's probably because it's missing in test/llvm_targets.zig, while a @compileError represents work to be done.

That said, I'm not sure I entirely understand point 2; the Zig compiler should in theory be able to emit code for x86-solaris, sparc-solaris, sparc64-solaris, etc. It's just that if a target is effectively dead and no one cares about it, we're not going to bother maintaining code paths for it.

.x86_64,
},
.serenity => &.{
// Not supported yet: sparc64
.solaris => &.{
.x86_64,
.aarch64,
.riscv64,
},

else => unreachable,
};
for (archs) |a| {
Expand Down
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