Ah, right. I remembered there was something that made us use =q, but
could not remember what. I'll describe it correctly.
Therefore, this updated patch is bogus. The original one was ok, given
that we change the header to :
Immediate Values - x86 Optimization
x86 optimization of the immediate values which uses a movl with code patching
to set/unset the value used to populate the register used as variable source.
Note : a movb needs to get its value froma =q constraint.
Quoting "H. Peter Anvin" <hpa@zytor.com>
Using =r for single-byte values is incorrect for 32-bit code -- that would
permit %spl, %bpl, %sil, %dil which are illegal in 32-bit mode.
Changelog:
- Use text_poke_early with cr0 WP save/restore to patch the bypass. We are doing
non atomic writes to a code region only touched by us (nobody can execute it
since we are protected by the imv_mutex).
- Put imv_set and _imv_set in the architecture independent header.
- Use $0 instead of %2 with (0) operand.
- Add x86_64 support, ready for i386+x86_64 -> x86 merge.
- Use asm-x86/asm.h.
- Bugfix : 8 bytes 64 bits immediate value was declared as "4 bytes" in the
immediate structure.
- Change the immediate.c update code to support variable length opcodes.
- Vastly simplified, using a busy looping IPI with interrupts disabled.
Does not protect against NMI nor MCE.
- Pack the __imv section. Use smallest types required for size (char).
- Use imv_* instead of immediate_*.
Mathieu
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Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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