Re: [PATCH v3 02/13] arm64: refactor aarch32_break_handler()

[Mark Rutland <mark.rutland@arm.com>]

On Mon, Jun 09, 2025 at 06:34:02PM +0100, Ada Couprie Diaz wrote:
> `aarch32_break_handler()` is called in `do_el0_undef()` when we
> are trying to handle an exception whose Exception Syndrome is unknown.
> It checks if the instruction hit might be a 32-bit arm break (be it
> A32 or T2), and sends a SIGTRAP to userspace if it is so that it can
> be handled.
> 
> However, this is badly represented in the naming of the function, and
> is not consistent with the other functions called with the same logic
> in `do_el0_undef()`.
> 
> Rename it `try_handle_aarch32_break()` and change the return value to
> a boolean to align with the logic of the other tentative handlers in
> `do_el0_undef()`, the previous error code being ignored anyway.
> 
> Signed-off-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
>  arch/arm64/include/asm/debug-monitors.h |  2 +-
>  arch/arm64/kernel/debug-monitors.c      | 10 +++++-----
>  arch/arm64/kernel/traps.c               |  2 +-
>  3 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h
> index 8f6ba31b8658..e1caf6a8380c 100644
> --- a/arch/arm64/include/asm/debug-monitors.h
> +++ b/arch/arm64/include/asm/debug-monitors.h
> @@ -116,7 +116,7 @@ static inline int reinstall_suspended_bps(struct pt_regs *regs)
>  }
>  #endif
>  
> -int aarch32_break_handler(struct pt_regs *regs);
> +bool try_handle_aarch32_break(struct pt_regs *regs);
>  
>  void debug_traps_init(void);
>  
> diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
> index 676fa0231935..9e69f2e915e8 100644
> --- a/arch/arm64/kernel/debug-monitors.c
> +++ b/arch/arm64/kernel/debug-monitors.c
> @@ -334,7 +334,7 @@ static int brk_handler(unsigned long unused, unsigned long esr,
>  }
>  NOKPROBE_SYMBOL(brk_handler);
[>  
> -int aarch32_break_handler(struct pt_regs *regs)
> +bool try_handle_aarch32_break(struct pt_regs *regs)
>  {
>  	u32 arm_instr;
>  	u16 thumb_instr;
> @@ -342,7 +342,7 @@ int aarch32_break_handler(struct pt_regs *regs)
>  	void __user *pc = (void __user *)instruction_pointer(regs);
>  
>  	if (!compat_user_mode(regs))
> -		return -EFAULT;
> +		return false;
>  
>  	if (compat_thumb_mode(regs)) {
>  		/* get 16-bit Thumb instruction */
> @@ -366,12 +366,12 @@ int aarch32_break_handler(struct pt_regs *regs)
>  	}
>  
>  	if (!bp)
> -		return -EFAULT;
> +		return false;
>  
>  	send_user_sigtrap(TRAP_BRKPT);
> -	return 0;
> +	return true;
>  }
> -NOKPROBE_SYMBOL(aarch32_break_handler);
> +NOKPROBE_SYMBOL(try_handle_aarch32_break);
>  
>  void __init debug_traps_init(void)
>  {
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index 9bfa5c944379..685c11b2c553 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -454,7 +454,7 @@ void do_el0_undef(struct pt_regs *regs, unsigned long esr)
>  	u32 insn;
>  
>  	/* check for AArch32 breakpoint instructions */
> -	if (!aarch32_break_handler(regs))
> +	if (try_handle_aarch32_break(regs))
>  		return;
>  
>  	if (user_insn_read(regs, &insn))
> -- 
> 2.43.0
>