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

Steven Rostedt
2022-04-25T15:05:29Z

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