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With the instruction decoder, we are now able to decode and recognize
instructions with opcode extensions. There are more instructions in
these groups that can be boosted:
Group 2: ROL, ROR, RCL, RCR, SHL/SAL, SHR, SAR
Group 3: TEST, NOT, NEG, MUL, IMUL, DIV, IDIV
Group 4: INC, DEC (byte operation)
Group 5: INC, DEC (word/doubleword/quadword operation)
These instructions are not boosted previously because there are reserved
opcodes within the groups, e.g., group 2 with ModR/M.nnn == 110 is
unmapped. As a result, kprobes attached to them requires two int3 traps
as being non-boostable also prevents jump-optimization.
Some simple tests on QEMU show that after boosting and jump-optimization
a single kprobe on these instructions with an empty pre-handler runs 10x
faster (~1000 cycles vs. ~100 cycles).
Since these instructions are mostly ALU operations and do not touch
special registers like RIP, let's boost them so that we get the
performance benefit.
Link: https://lore.kernel.org/all/20240204031300.830475-4-jinghao7@illinois.edu/
Signed-off-by: Jinghao Jia <jinghao7@illinois.edu>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
290eb13f1a