linux-kernel - Re: [PATCH 8/8] ftrace/samples: Add multi direct interface test module

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Date:   Tue, 26 Oct 2021 12:23:09 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>
Subject: Re: [PATCH 8/8] ftrace/samples: Add multi direct interface test
 module

On Fri, Oct 08, 2021 at 11:13:36AM +0200, Jiri Olsa wrote:
> Adding simple module that uses multi direct interface:
> 
>   register_ftrace_direct_multi
>   unregister_ftrace_direct_multi
> 
> The init function registers trampoline for 2 functions,
> and exit function unregisters them.
> 
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>

Building s390:defconfig ... failed
--------------
Error log:
<stdin>:1559:2: warning: #warning syscall futex_waitv not implemented [-Wcpp]
{standard input}: Assembler messages:
{standard input}:11: Error: Unrecognized opcode: `pushq'
{standard input}:12: Error: Unrecognized opcode: `movq'
{standard input}:13: Error: Unrecognized opcode: `pushq'
{standard input}:14: Error: Unrecognized opcode: `movq'
{standard input}:15: Error: Unrecognized opcode: `call'
{standard input}:16: Error: Unrecognized opcode: `popq'
{standard input}:17: Error: Unrecognized opcode: `leave'
{standard input}:18: Error: Unrecognized opcode: `ret'
make[3]: *** [scripts/Makefile.build:288: samples/ftrace/ftrace-direct-multi.o] Error 1
make[2]: *** [scripts/Makefile.build:571: samples/ftrace] Error 2
make[1]: *** [Makefile:1993: samples] Error 2
make[1]: *** Waiting for unfinished jobs....
make: *** [Makefile:226: __sub-make] Error 2

Guenter

> ---
>  samples/ftrace/Makefile              |  1 +
>  samples/ftrace/ftrace-direct-multi.c | 52 ++++++++++++++++++++++++++++
>  2 files changed, 53 insertions(+)
>  create mode 100644 samples/ftrace/ftrace-direct-multi.c
> 
> diff --git a/samples/ftrace/Makefile b/samples/ftrace/Makefile
> index 4ce896e10b2e..ab1d1c05c288 100644
> --- a/samples/ftrace/Makefile
> +++ b/samples/ftrace/Makefile
> @@ -3,6 +3,7 @@
>  obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct.o
>  obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct-too.o
>  obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct-modify.o
> +obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct-multi.o
>  
>  CFLAGS_sample-trace-array.o := -I$(src)
>  obj-$(CONFIG_SAMPLE_TRACE_ARRAY) += sample-trace-array.o
> diff --git a/samples/ftrace/ftrace-direct-multi.c b/samples/ftrace/ftrace-direct-multi.c
> new file mode 100644
> index 000000000000..2a5b1fb7ac14
> --- /dev/null
> +++ b/samples/ftrace/ftrace-direct-multi.c
> @@ -0,0 +1,52 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#include <linux/module.h>
> +
> +#include <linux/mm.h> /* for handle_mm_fault() */
> +#include <linux/ftrace.h>
> +#include <linux/sched/stat.h>
> +
> +void my_direct_func(unsigned long ip)
> +{
> +	trace_printk("ip %lx\n", ip);
> +}
> +
> +extern void my_tramp(void *);
> +
> +asm (
> +"	.pushsection    .text, \"ax\", @progbits\n"
> +"	.type		my_tramp, @function\n"
> +"	.globl		my_tramp\n"
> +"   my_tramp:"
> +"	pushq %rbp\n"
> +"	movq %rsp, %rbp\n"
> +"	pushq %rdi\n"
> +"	movq 8(%rbp), %rdi\n"
> +"	call my_direct_func\n"
> +"	popq %rdi\n"
> +"	leave\n"
> +"	ret\n"
> +"	.size		my_tramp, .-my_tramp\n"
> +"	.popsection\n"
> +);
> +
> +static struct ftrace_ops direct;
> +
> +static int __init ftrace_direct_multi_init(void)
> +{
> +	ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
> +	ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
> +
> +	return register_ftrace_direct_multi(&direct, (unsigned long) my_tramp);
> +}
> +
> +static void __exit ftrace_direct_multi_exit(void)
> +{
> +	unregister_ftrace_direct_multi(&direct, (unsigned long) my_tramp);
> +}
> +
> +module_init(ftrace_direct_multi_init);
> +module_exit(ftrace_direct_multi_exit);
> +
> +MODULE_AUTHOR("Jiri Olsa");
> +MODULE_DESCRIPTION("Example use case of using register_ftrace_direct_multi()");
> +MODULE_LICENSE("GPL");
> -- 
> 2.31.1
>