linux-kernel - Re: [PATCH v6 11/13] riscv/kprobe: Fix instruction simulation of JALR

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Message-ID: <877cx26f57.fsf@all.your.base.are.belong.to.us>
Date:   Tue, 31 Jan 2023 13:51:32 +0100
From:   Björn Töpel <bjorn@...nel.org>
To:     Chen Guokai <chenguokai17@...ls.ucas.ac.cn>,
        paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, rostedt@...dmis.org, mingo@...hat.com,
        sfr@...b.auug.org.au
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        liaochang1@...wei.com
Subject: Re: [PATCH v6 11/13] riscv/kprobe: Fix instruction simulation of JALR

Chen Guokai <chenguokai17@...ls.ucas.ac.cn> writes:

> From: Liao Chang <liaochang1@...wei.com>
>
> Set kprobe at 'jalr 1140(ra)' of vfs_write results in the following
> crash:
>
> [   32.092235] Unable to handle kernel access to user memory without uaccess routines at virtual address 00aaaaaad77b1170
> [   32.093115] Oops [#1]
> [   32.093251] Modules linked in:
> [   32.093626] CPU: 0 PID: 135 Comm: ftracetest Not tainted 6.2.0-rc2-00013-gb0aa5e5df0cb-dirty #16
> [   32.093985] Hardware name: riscv-virtio,qemu (DT)
> [   32.094280] epc : ksys_read+0x88/0xd6
> [   32.094855]  ra : ksys_read+0xc0/0xd6
> [   32.095016] epc : ffffffff801cda80 ra : ffffffff801cdab8 sp : ff20000000d7bdc0
> [   32.095227]  gp : ffffffff80f14000 tp : ff60000080f9cb40 t0 : ffffffff80f13e80
> [   32.095500]  t1 : ffffffff8000c29c t2 : ffffffff800dbc54 s0 : ff20000000d7be60
> [   32.095716]  s1 : 0000000000000000 a0 : ffffffff805a64ae a1 : ffffffff80a83708
> [   32.095921]  a2 : ffffffff80f160a0 a3 : 0000000000000000 a4 : f229b0afdb165300
> [   32.096171]  a5 : f229b0afdb165300 a6 : ffffffff80eeebd0 a7 : 00000000000003ff
> [   32.096411]  s2 : ff6000007ff76800 s3 : fffffffffffffff7 s4 : 00aaaaaad77b1170
> [   32.096638]  s5 : ffffffff80f160a0 s6 : ff6000007ff76800 s7 : 0000000000000030
> [   32.096865]  s8 : 00ffffffc3d97be0 s9 : 0000000000000007 s10: 00aaaaaad77c9410
> [   32.097092]  s11: 0000000000000000 t3 : ffffffff80f13e48 t4 : ffffffff8000c29c
> [   32.097317]  t5 : ffffffff8000c29c t6 : ffffffff800dbc54
> [   32.097505] status: 0000000200000120 badaddr: 00aaaaaad77b1170 cause: 000000000000000d
> [   32.098011] [<ffffffff801cdb72>] ksys_write+0x6c/0xd6
> [   32.098222] [<ffffffff801cdc06>] sys_write+0x2a/0x38
> [   32.098405] [<ffffffff80003c76>] ret_from_syscall+0x0/0x2
>
> Since the rs1 and rd might be the same one, such as 'jalr 1140(ra)',
> hence it requires obtaining the target address from rs1 followed by
> updating rd.
>
> Fixes: c22b0bcb1dd0 ("riscv: Add kprobes supported")
> Signed-off-by: Liao Chang <liaochang1@...wei.com>

This has already been picked up to riscv-fixes:
https://lore.kernel.org/linux-riscv/167462581691.3015.5045414056306333462.git-patchwork-notify@kernel.org/

No need to have this patch in the series (and dito to
https://lore.kernel.org/linux-riscv/20230127130541.1250865-11-chenguokai17@mails.ucas.ac.cn/
that Guo submitted a fix for).


Björn