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Date: Tue, 8 Aug 2023 18:06:55 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Nam Cao <namcaov@...il.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] riscv: kprobes: simulate c.jr and c.jalr instructions
On Sun, Jul 30, 2023 at 10:27:08AM +0200, Nam Cao wrote:
> kprobes currently rejects c.jr and c.jalr instructions. Implement them.
>
> Signed-off-by: Nam Cao <namcaov@...il.com>
> ---
> arch/riscv/kernel/probes/decode-insn.c | 4 +--
> arch/riscv/kernel/probes/simulate-insn.c | 37 ++++++++++++++++++++++++
> arch/riscv/kernel/probes/simulate-insn.h | 2 ++
> 3 files changed, 41 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/kernel/probes/decode-insn.c b/arch/riscv/kernel/probes/decode-insn.c
> index 39adb07a342d..6dba23a55ac7 100644
> --- a/arch/riscv/kernel/probes/decode-insn.c
> +++ b/arch/riscv/kernel/probes/decode-insn.c
> @@ -29,14 +29,14 @@ riscv_probe_decode_insn(probe_opcode_t *addr, struct arch_probe_insn *api)
> * TODO: the REJECTED ones below need to be implemented
> */
> #ifdef CONFIG_RISCV_ISA_C
> - RISCV_INSN_REJECTED(c_jr, insn);
> RISCV_INSN_REJECTED(c_jal, insn);
> - RISCV_INSN_REJECTED(c_jalr, insn);
> RISCV_INSN_REJECTED(c_beqz, insn);
> RISCV_INSN_REJECTED(c_bnez, insn);
> RISCV_INSN_REJECTED(c_ebreak, insn);
>
> RISCV_INSN_SET_SIMULATE(c_j, insn);
> + RISCV_INSN_SET_SIMULATE(c_jr, insn);
> + RISCV_INSN_SET_SIMULATE(c_jalr, insn);
> #endif
>
> RISCV_INSN_SET_SIMULATE(jal, insn);
> diff --git a/arch/riscv/kernel/probes/simulate-insn.c b/arch/riscv/kernel/probes/simulate-insn.c
> index 3ba45c612cd8..1ead6f4951f9 100644
> --- a/arch/riscv/kernel/probes/simulate-insn.c
> +++ b/arch/riscv/kernel/probes/simulate-insn.c
> @@ -212,3 +212,40 @@ bool __kprobes simulate_c_j(u32 opcode, unsigned long addr, struct pt_regs *regs
>
> return true;
> }
> +
> +static bool __kprobes simulate_c_jr_jalr(u32 opcode, unsigned long addr, struct pt_regs *regs,
> + bool is_jalr)
> +{
> + /*
> + * 15 12 11 7 6 2 1 0
> + * | funct4 | rs1 | rs2 | op |
> + * 4 5 5 2
> + */
> +
> + unsigned long jump_addr;
> +
> + u32 rs1 = (opcode >> 7) & 0x1f;
> +
> + if (rs1 == 0) /* C.JR is only valid when rs1 != x0 */
> + return false;
> +
> + if (!rv_insn_reg_get_val(regs, rs1, &jump_addr))
> + return false;
> +
> + if (is_jalr && !rv_insn_reg_set_val(regs, 1, addr + 2))
> + return false;
> +
> + instruction_pointer_set(regs, jump_addr);
> +
> + return true;
> +}
> +
> +bool __kprobes simulate_c_jr(u32 opcode, unsigned long addr, struct pt_regs *regs)
> +{
> + return simulate_c_jr_jalr(opcode, addr, regs, false);
> +}
> +
> +bool __kprobes simulate_c_jalr(u32 opcode, unsigned long addr, struct pt_regs *regs)
> +{
> + return simulate_c_jr_jalr(opcode, addr, regs, true);
> +}
> diff --git a/arch/riscv/kernel/probes/simulate-insn.h b/arch/riscv/kernel/probes/simulate-insn.h
> index 4bd6c266e7d3..472a1948ec4f 100644
> --- a/arch/riscv/kernel/probes/simulate-insn.h
> +++ b/arch/riscv/kernel/probes/simulate-insn.h
> @@ -25,5 +25,7 @@ bool simulate_branch(u32 opcode, unsigned long addr, struct pt_regs *regs);
> bool simulate_jal(u32 opcode, unsigned long addr, struct pt_regs *regs);
> bool simulate_jalr(u32 opcode, unsigned long addr, struct pt_regs *regs);
> bool simulate_c_j(u32 opcode, unsigned long addr, struct pt_regs *regs);
> +bool simulate_c_jr(u32 opcode, unsigned long addr, struct pt_regs *regs);
> +bool simulate_c_jalr(u32 opcode, unsigned long addr, struct pt_regs *regs);
>
> #endif /* _RISCV_KERNEL_PROBES_SIMULATE_INSN_H */
> --
> 2.34.1
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
You can add:
Reviewed-by: Charlie Jenkins <charlie@...osinc.com>
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