Re: [PATCH] linux-user/arm: Deliver SIGTRAP for UDF patterns used as breakpoints

[Richard Henderson]

On 11/17/20 7:56 AM, Peter Maydell wrote:
> The Linux kernel doesn't use the official bkpt insn for breakpoints;
> instead it uses three instructions in the guaranteed-to-UNDEF space,
> and generates SIGTRAP for these rather than the SIGILL that most
> UNDEF insns generate:
> 
> https://elixir.bootlin.com/linux/v5.9.8/source/arch/arm/kernel/ptrace.c#L197
> 
> Make QEMU treat these insns specially too.  The main benefit of this
> is that if you're running a debugger on a guest program that runs
> into a GCC __builtin_trap() or LLVM "trap because execution should
> never reach here" then you'll get the expected signal rather than a
> SIGILL.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> This is not a "fix" for LP:1904210, but it does bring QEMU's
> behaviour into line with that of the real kernel on that binary.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~