linux-kernel - Re: [PATCH] riscv: traps: handle uprobe event in software-check exception

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Message-ID: <2453d5e6-cd47-4a4e-8636-3a1524be0589@ghiti.fr>
Date: Tue, 25 Mar 2025 10:42:15 +0100
From: Alexandre Ghiti <alex@...ti.fr>
To: Zong Li <zong.li@...ive.com>, paul.walmsley@...ive.com,
 palmer@...belt.com, aou@...s.berkeley.edu, debug@...osinc.com,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] riscv: traps: handle uprobe event in software-check
 exception

Hi,

On 14/03/2025 10:26, Zong Li wrote:
> Handle the uprobe event first before handling the CFI violation in
> software-check exception handler. Because when the landing pad is
> activated, if the uprobe point is set at the lpad instruction at
> the beginning of a function, the system triggers a software-check
> exception instead of an ebreak exception due to the exception
> priority, then uprobe can't work successfully.
>
> Co-developed-by: Deepak Gupta <debug@...osinc.com>
> Signed-off-by: Deepak Gupta <debug@...osinc.com>
> Signed-off-by: Zong Li <zong.li@...ive.com>
> ---
>
> This patch is based on top of the following series
> [PATCH v11 00/27] riscv control-flow integrity for usermode
>
>   arch/riscv/kernel/traps.c | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index 3f7709f4595a..ef5a92111ee1 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -386,9 +386,12 @@ asmlinkage __visible __trap_section void do_trap_software_check(struct pt_regs *
>   	if (user_mode(regs)) {
>   		irqentry_enter_from_user_mode(regs);
>   
> -		/* not a cfi violation, then merge into flow of unknown trap handler */
> -		if (!handle_user_cfi_violation(regs))
> -			do_trap_unknown(regs);
> +		/* handle uprobe event frist */
> +		if (!probe_breakpoint_handler(regs)) {
> +			/* not a cfi violation, then merge into flow of unknown trap handler */
> +			if (!handle_user_cfi_violation(regs))
> +				do_trap_unknown(regs);
> +		}
>   
>   		irqentry_exit_to_user_mode(regs);
>   	} else {


Deepak, can you take this patch in your next spin of your CFI series? 
Otherwise, I'm pretty sure we will forget about it :)

Thanks,

Alex