x64: Fix encoding of RIP-relative addressing #10819
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This commit fixes a bug in the new assembler which was surfaced through the changes in bytecodealliance#10782 but was a pre-existing issue. Specifically the encoding of a RIP-relative addressing mode required knowing the number of bytes at the end of an instruction but this was accidentally hardcoded to 0. In bytecodealliance#10782 `imul` instructions were added where a RIP-relative address mode can be used in conjunction with an immediate which cause the RIP-relative addressing to load from the wrong address. This bug can in theory affect other instructions in the new assembler as well, but auditing the list of instructions it looks like `imul` is the only one that can possibly have an immediate after a RIP-relative addressing mode. That means that prior instructions using the new assembler should not be affected.
abrown
approved these changes
May 20, 2025
|
@abrown mind double-checking the last commit I just added? |
abrown
approved these changes
May 20, 2025
Co-authored-by: Andrew Brown <[email protected]>
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This commit fixes a bug in the new assembler which was surfaced through the changes in #10782 but was a pre-existing issue. Specifically the encoding of a RIP-relative addressing mode required knowing the number of bytes at the end of an instruction but this was accidentally hardcoded to 0. In #10782
imulinstructions were added where a RIP-relative address mode can be used in conjunction with an immediate which cause the RIP-relative addressing to load from the wrong address.This bug can in theory affect other instructions in the new assembler as well, but auditing the list of instructions it looks like
imulis the only one that can possibly have an immediate after a RIP-relative addressing mode. That means that prior instructions using the new assembler should not be affected.