riscv: probes: simulate c.jal instruction

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The c.jal instruction is currently marked REJECTED in kprobes
instruction decoding, but it should be SIMULATED like other
compressed jump instructions.

Add simulate_c_jal() which saves the return address to RA and
sets the program counter to the target offset, reusing
simulate_c_j for the common jump logic.

Although c.jal is RV32-only, the function compiles unconditionally.
On RV64, riscv_insn_is_c_jal() always returns 0, so the simulation
code is never invoked and the small overhead in kernel size is
acceptable.

Signed-off-by: Xiaofeng Yuan <xiaofengmian@163.com>
Reviewed-by: Charlie Jenkins <thecharlesjenkins@gmail.com>
Tested-by: Charlie Jenkins <thecharlesjenkins@gmail.com>
Reviewed-by: Nam Cao <namcao@linutronix.de>
Tested-by: Nam Cao <namcao@linutronix.de>
Link: https://patch.msgid.link/20260701081033.49871-2-xiaofengmian@163.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>

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Xiaofeng Yuan 2026-08-07 19:24:29 -06:00 • committed by Paul Walmsley

parent 6a48dea344

commit 540ad5ad05

3 changed files with 9 additions and 1 deletions

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2

arch/riscv/kernel/probes/decode-insn.c

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arch/riscv/kernel/probes/simulate-insn.c

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arch/riscv/kernel/probes/simulate-insn.h

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