From: Chenghao Duan <duanchenghao@kylinos.cn>
To: Hengqi Chen <hengqi.chen@gmail.com>
Cc: yangtiezhu@loongson.cn, chenhuacai@kernel.org, kernel@xen0n.name,
zhangtianyang@loongson.cn, masahiroy@kernel.org,
linux-kernel@vger.kernel.org, loongarch@lists.linux.dev,
bpf@vger.kernel.org, guodongtai@kylinos.cn,
youling.tang@linux.dev, jianghaoran@kylinos.cn,
vincent.mc.li@gmail.com
Subject: Re: [PATCH v1 2/2] LoongArch: Enable BPF exception fixup for specific ADE subcode
Date: Wed, 10 Dec 2025 13:43:29 +0800 [thread overview]
Message-ID: <20251210054329.GA691118@chenghao-pc> (raw)
In-Reply-To: <CAEyhmHTtEE6cnm18_WC+d+o4RnLUw+BUUNL54R6d9W2b868+LA@mail.gmail.com>
On Wed, Dec 10, 2025 at 01:20:12PM +0800, Hengqi Chen wrote:
> On Tue, Dec 9, 2025 at 5:34 PM Chenghao Duan <duanchenghao@kylinos.cn> wrote:
> >
> > This patch allows the LoongArch BPF JIT to handle recoverable memory
> > access errors generated by BPF_PROBE_MEM* instructions.
> >
> > When a BPF program performs memory access operations, the instructions
> > it executes may trigger ADEM exceptions. The kernel’s built-in BPF
> > exception table mechanism (EX_TYPE_BPF) will generate corresponding
> > exception fixup entries in the JIT compilation phase; however, the
> > architecture-specific trap handling function needs to proactively call
> > the common fixup routine to achieve exception recovery.
> >
> > do_ade(): fix EX_TYPE_BPF memory access exceptions for BPF programs,
> > ensure safe execution.
> >
>
> Which bpf prog triggers this code path ? Why didn't we trigger it before ?
module_attach and subprogs_extable trigger ADE exception via illegal address
access in BPF programs, leading to kernel panic without this patch.
>
> > Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
> > ---
> > arch/loongarch/kernel/traps.c | 7 ++++++-
> > 1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
> > index da5926fead4a..9ca8aacc82b8 100644
> > --- a/arch/loongarch/kernel/traps.c
> > +++ b/arch/loongarch/kernel/traps.c
> > @@ -534,8 +534,13 @@ asmlinkage void noinstr do_fpe(struct pt_regs *regs, unsigned long fcsr)
> >
> > asmlinkage void noinstr do_ade(struct pt_regs *regs)
> > {
> > - irqentry_state_t state = irqentry_enter(regs);
> > + irqentry_state_t state;
> > + unsigned int esubcode = FIELD_GET(CSR_ESTAT_ESUBCODE, regs->csr_estat);
> > +
> > + if ((esubcode == 1) && fixup_exception(regs))
> > + return;
> >
> > + state = irqentry_enter(regs);
> > die_if_kernel("Kernel ade access", regs);
> > force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)regs->csr_badvaddr);
> >
> > --
> > 2.25.1
> >
next prev parent reply other threads:[~2025-12-10 5:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-09 9:34 [PATCH v1 0/2] Fix the failure issue of the module_attach test case Chenghao Duan
2025-12-09 9:34 ` [PATCH v1 1/2] LoongArch: Modify the jump logic of the trampoline Chenghao Duan
2025-12-10 0:48 ` Tiezhu Yang
2025-12-10 4:15 ` Hengqi Chen
2025-12-10 6:16 ` Chenghao Duan
2025-12-09 9:34 ` [PATCH v1 2/2] LoongArch: Enable BPF exception fixup for specific ADE subcode Chenghao Duan
2025-12-10 1:02 ` Tiezhu Yang
2025-12-10 5:20 ` Hengqi Chen
2025-12-10 5:43 ` Chenghao Duan [this message]
2025-12-10 3:18 ` [PATCH v1 0/2] Fix the failure issue of the module_attach test case Vincent Li
2025-12-10 4:10 ` Hengqi Chen
2025-12-10 6:08 ` Chenghao Duan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20251210054329.GA691118@chenghao-pc \
--to=duanchenghao@kylinos.cn \
--cc=bpf@vger.kernel.org \
--cc=chenhuacai@kernel.org \
--cc=guodongtai@kylinos.cn \
--cc=hengqi.chen@gmail.com \
--cc=jianghaoran@kylinos.cn \
--cc=kernel@xen0n.name \
--cc=linux-kernel@vger.kernel.org \
--cc=loongarch@lists.linux.dev \
--cc=masahiroy@kernel.org \
--cc=vincent.mc.li@gmail.com \
--cc=yangtiezhu@loongson.cn \
--cc=youling.tang@linux.dev \
--cc=zhangtianyang@loongson.cn \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).