Re: [PATCH bpf-next v3 2/7] ftrace: Fix deadloop caused by direct call in ftrace selftest

[Steven Rostedt <rostedt@goodmis.org>]

On Sun, 24 Apr 2022 11:40:23 -0400
Xu Kuohai <xukuohai@huawei.com> wrote:

> diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
> index abcadbe933bb..d2eff2b1d743 100644
> --- a/kernel/trace/trace_selftest.c
> +++ b/kernel/trace/trace_selftest.c
> @@ -785,8 +785,24 @@ static struct fgraph_ops fgraph_ops __initdata  = {
>  };
>  
>  #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> +#ifdef CONFIG_ARM64

Please find a way to add this in arm specific code. Do not add architecture
defines in generic code.

You could add:

#ifndef ARCH_HAVE_FTRACE_DIRECT_TEST_FUNC
noinline __noclone static void trace_direct_tramp(void) { }
#endif

here, and in arch/arm64/include/ftrace.h

#define ARCH_HAVE_FTRACE_DIRECT_TEST_FUNC

and define your test function in the arm64 specific code.

-- Steve




> +extern void trace_direct_tramp(void);
> +
> +asm (
> +"	.pushsection	.text, \"ax\", @progbits\n"
> +"	.type		trace_direct_tramp, %function\n"
> +"	.global		trace_direct_tramp\n"
> +"trace_direct_tramp:"
> +"	mov	x10, x30\n"
> +"	mov	x30, x9\n"
> +"	ret	x10\n"
> +"	.size		trace_direct_tramp, .-trace_direct_tramp\n"
> +"	.popsection\n"
> +);
> +#else
>  noinline __noclone static void trace_direct_tramp(void) { }
>  #endif
> +#endif
>  
>  /*
>   * Pretty much the same than for the function tracer from which the selftest