From: Guo Ren <guoren@kernel.org>
To: "Björn Töpel" <bjorn@kernel.org>
Cc: "Paul Walmsley" <paul.walmsley@sifive.com>,
"Palmer Dabbelt" <palmer@dabbelt.com>,
"Albert Ou" <aou@eecs.berkeley.edu>,
linux-riscv@lists.infradead.org,
"Björn Töpel" <bjorn@rivosinc.com>,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv, kprobes: Stricter c.jr/c.jalr decoding
Date: Tue, 3 Jan 2023 17:59:33 +0800 [thread overview]
Message-ID: <CAJF2gTTF9_J__Qk+ppg5c1V+1PeFbZ-xf7DEbo=DXBRpQu1L=A@mail.gmail.com> (raw)
In-Reply-To: <20230102160748.1307289-1-bjorn@kernel.org>
Thx for catching it.
On Tue, Jan 3, 2023 at 12:07 AM Björn Töpel <bjorn@kernel.org> wrote:
>
> From: Björn Töpel <bjorn@rivosinc.com>
>
> In the compressed instruction extension, c.jr, c.jalr, c.mv, and c.add
> is encoded the following way (each instruction is 16b):
>
> ---+-+-----------+-----------+--
> 100 0 rs1[4:0]!=0 00000 10 : c.jr
> 100 1 rs1[4:0]!=0 00000 10 : c.jalr
> 100 0 rd[4:0]!=0 rs2[4:0]!=0 10 : c.mv
> 100 1 rd[4:0]!=0 rs2[4:0]!=0 10 : c.add
Yes, I forgot the c.mv & c.add effect.
Reviewed-by: Guo Ren <guoren@kernel.org>
>
> The following logic is used to decode c.jr and c.jalr:
>
> insn & 0xf007 == 0x8002 => instruction is an c.jr
> insn & 0xf007 == 0x9002 => instruction is an c.jalr
>
> When 0xf007 is used to mask the instruction, c.mv can be incorrectly
> decoded as c.jr, and c.add as c.jalr.
>
> Correct the decoding by changing the mask from 0xf007 to 0xf07f.
>
> Fixes: c22b0bcb1dd0 ("riscv: Add kprobes supported")
> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
> ---
> arch/riscv/kernel/probes/simulate-insn.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/kernel/probes/simulate-insn.h b/arch/riscv/kernel/probes/simulate-insn.h
> index cb6ff7dccb92..de8474146a9b 100644
> --- a/arch/riscv/kernel/probes/simulate-insn.h
> +++ b/arch/riscv/kernel/probes/simulate-insn.h
> @@ -31,9 +31,9 @@ __RISCV_INSN_FUNCS(fence, 0x7f, 0x0f);
> } while (0)
>
> __RISCV_INSN_FUNCS(c_j, 0xe003, 0xa001);
> -__RISCV_INSN_FUNCS(c_jr, 0xf007, 0x8002);
> +__RISCV_INSN_FUNCS(c_jr, 0xf07f, 0x8002);
> __RISCV_INSN_FUNCS(c_jal, 0xe003, 0x2001);
> -__RISCV_INSN_FUNCS(c_jalr, 0xf007, 0x9002);
> +__RISCV_INSN_FUNCS(c_jalr, 0xf07f, 0x9002);
> __RISCV_INSN_FUNCS(c_beqz, 0xe003, 0xc001);
> __RISCV_INSN_FUNCS(c_bnez, 0xe003, 0xe001);
> __RISCV_INSN_FUNCS(c_ebreak, 0xffff, 0x9002);
>
> base-commit: 1b929c02afd37871d5afb9d498426f83432e71c2
> --
> 2.37.2
>
--
Best Regards
Guo Ren
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next prev parent reply other threads:[~2023-01-03 10:08 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-02 16:07 [PATCH] riscv, kprobes: Stricter c.jr/c.jalr decoding Björn Töpel
2023-01-02 20:31 ` Conor Dooley
2023-01-03 6:44 ` Björn Töpel
2023-01-03 10:33 ` Conor Dooley
2023-01-03 9:59 ` Guo Ren [this message]
2023-01-05 22:52 ` Palmer Dabbelt
2023-01-05 23:00 ` patchwork-bot+linux-riscv
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