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cranelift-jit: Fix arm64 adrp relocations #11734

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merged 1 commit into from
Sep 23, 2025
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cranelift-jit: Fix arm64 adrp relocations #11734

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14 changes: 10 additions & 4 deletions cranelift/jit/src/compiled_blob.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -101,11 +101,17 @@ impl CompiledBlob {
let base = get_address(name);
let what = unsafe { base.offset(isize::try_from(addend).unwrap()) };
let get_page = |x| x & (!0xfff);
let pcrel = i32::try_from(get_page(what as isize) - get_page(at as isize))
.unwrap()
.cast_unsigned();
// NOTE: This should technically be i33 given that this relocation type allows
// a range from -4GB to +4GB, not -2GB to +2GB. But this doesn't really matter
// as the target is unlikely to be more than 2GB from the adrp instruction. We
// need to be careful to not cast to an unsigned int until after doing >> 12 to
// compute the upper 21bits of the pcrel address however as otherwise the top
// bit of the 33bit pcrel address would be forced 0 through zero extension
// instead of being sign extended as it should be.
let pcrel =
i32::try_from(get_page(what as isize) - get_page(at as isize)).unwrap();
let iptr = at as *mut u32;
let hi21 = pcrel >> 12;
let hi21 = (pcrel >> 12).cast_unsigned();
let lo = (hi21 & 0x3) << 29;
let hi = (hi21 & 0x1ffffc) << 3;
unsafe { modify_inst32(iptr, |inst| inst | lo | hi) };
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