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Add support for environments with the FPU disabled #25

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merged 3 commits into from
Jun 13, 2024
Merged

Add support for environments with the FPU disabled #25

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32a81bb
fix(aarch64): add support for environments without fp-armv8
lylythechosenone Jun 10, 2024
29bf345
style(aarch64): move comment inside the macro
lylythechosenone Jun 10, 2024
24ca420
fix(aarch64): replace `fp-armv8` with `neon`
lylythechosenone Jun 12, 2024
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89 changes: 59 additions & 30 deletions src/unwinder/arch/aarch64.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -58,22 +58,18 @@ impl ops::IndexMut<gimli::Register> for Context {
}
}

#[naked]
pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), ptr: *mut ()) {
// No need to save caller-saved registers here.
unsafe {
macro_rules! save {
(gp$(, $fp:ident)?) => {
// No need to save caller-saved registers here.
asm!(
"
stp x29, x30, [sp, -16]!
sub sp, sp, 512
mov x8, x0
mov x0, sp

stp d8, d9, [sp, 0x140]
stp d10, d11, [sp, 0x150]
stp d12, d13, [sp, 0x160]
stp d14, d15, [sp, 0x170]

",
save!(maybesavefp($($fp)?)),
"
str x19, [sp, 0x98]
stp x20, x21, [sp, 0xA0]
stp x22, x23, [sp, 0xB0]
Expand All @@ -91,30 +87,33 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
",
options(noreturn)
);
}
};
(maybesavefp(fp)) => {
"
stp d8, d9, [sp, 0x140]
stp d10, d11, [sp, 0x150]
stp d12, d13, [sp, 0x160]
stp d14, d15, [sp, 0x170]
"
};
(maybesavefp()) => { "" };
}

pub unsafe fn restore_context(ctx: &Context) -> ! {
#[naked]
pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), ptr: *mut ()) {
unsafe {
#[cfg(target_feature = "fp-armv8")]
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AFAIK there is no such a target feature in aarch64 (at least on the Rust side):

$ rustc +nightly --print cfg --target aarch64-unknown-linux-gnu | grep target_feature
target_feature="neon"
$ rustc +nightly --print cfg --target aarch64-unknown-none | grep target_feature
target_feature="neon"
$ rustc +nightly --print cfg --target aarch64-unknown-none-softfloat | grep target_feature

https://github.com/rust-lang/rust/blob/b5b13568fb5da4ac988bde370008d6134d3dfe6c/compiler/rustc_target/src/target_features.rs#L87

arm has it though: https://github.com/rust-lang/rust/blob/b5b13568fb5da4ac988bde370008d6134d3dfe6c/compiler/rustc_target/src/target_features.rs#L62

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Oh, weird—the error when I tried to use unwinding mentioned fp-armv8 explicitly. I'll fix that.

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To be more clear: when I tried to use the current unwinding master branch on aarch64-unknown-none-softfloat, I got a compile error saying that the registers d[n] require target feature fp-armv8. This is likely a diagnostic issue, and I'll see if I can reproduce it to send that over to rustc.

save!(gp, fp);
#[cfg(not(target_feature = "fp-armv8"))]
save!(gp);
}
}

macro_rules! restore {
($ctx:expr, gp$(, $fp:ident)?) => {
asm!(
restore!(mayberestore($($fp)?)),
"
ldp d0, d1, [x0, 0x100]
ldp d2, d3, [x0, 0x110]
ldp d4, d5, [x0, 0x120]
ldp d6, d7, [x0, 0x130]
ldp d8, d9, [x0, 0x140]
ldp d10, d11, [x0, 0x150]
ldp d12, d13, [x0, 0x160]
ldp d14, d15, [x0, 0x170]
ldp d16, d17, [x0, 0x180]
ldp d18, d19, [x0, 0x190]
ldp d20, d21, [x0, 0x1A0]
ldp d22, d23, [x0, 0x1B0]
ldp d24, d25, [x0, 0x1C0]
ldp d26, d27, [x0, 0x1D0]
ldp d28, d29, [x0, 0x1E0]
ldp d30, d31, [x0, 0x1F0]

ldp x2, x3, [x0, 0x10]
ldp x4, x5, [x0, 0x20]
ldp x6, x7, [x0, 0x30]
Expand All @@ -135,8 +134,38 @@ pub unsafe fn restore_context(ctx: &Context) -> ! {
ldp x0, x1, [x0, 0x00]
ret
",
in("x0") ctx,
in("x0") $ctx,
options(noreturn)
);
};
(mayberestore(fp)) => {
"
ldp d0, d1, [x0, 0x100]
ldp d2, d3, [x0, 0x110]
ldp d4, d5, [x0, 0x120]
ldp d6, d7, [x0, 0x130]
ldp d8, d9, [x0, 0x140]
ldp d10, d11, [x0, 0x150]
ldp d12, d13, [x0, 0x160]
ldp d14, d15, [x0, 0x170]
ldp d16, d17, [x0, 0x180]
ldp d18, d19, [x0, 0x190]
ldp d20, d21, [x0, 0x1A0]
ldp d22, d23, [x0, 0x1B0]
ldp d24, d25, [x0, 0x1C0]
ldp d26, d27, [x0, 0x1D0]
ldp d28, d29, [x0, 0x1E0]
ldp d30, d31, [x0, 0x1F0]
"
};
(mayberestore()) => { "" };
}

pub unsafe fn restore_context(ctx: &Context) -> ! {
unsafe {
#[cfg(target_feature = "fp-armv8")]
restore!(ctx, gp, fp);
#[cfg(not(target_feature = "fp-armv8"))]
restore!(ctx, gp);
}
}