Re: [PATCH v6 4/5] arm64: ftrace: Add direct call trampoline samples support

Mark Rutland
2023-04-06T10:50:20Z

On Wed, Apr 05, 2023 at 08:02:49PM +0200, Florent Revest wrote:
> The ftrace samples need per-architecture trampoline implementations
> to save and restore argument registers around the calls to
> my_direct_func* and to restore polluted registers (eg: x30).
>
> These samples also include <asm/asm-offsets.h> which, on arm64, is not
> necessary and redefines previously defined macros (resulting in
> warnings) so these includes are guarded by !CONFIG_ARM64.
>
> Signed-off-by: Florent Revest <revest@chromium.org>

These all look good to me. I gave each module a spin in an 8-vCPU VM on an M1
Macbook Pro with a bunch of other work going on, and all of those worked as
expected with sensible output in /sys/kernel/tracing/trace, and no noticeable
failures elsewhere. So:

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

Mark.

> ---
> arch/arm64/Kconfig | 2 ++
> samples/ftrace/ftrace-direct-modify.c | 34 ++++++++++++++++++
> samples/ftrace/ftrace-direct-multi-modify.c | 40 +++++++++++++++++++++
> samples/ftrace/ftrace-direct-multi.c | 24 +++++++++++++
> samples/ftrace/ftrace-direct-too.c | 26 ++++++++++++++
> samples/ftrace/ftrace-direct.c | 24 +++++++++++++
> 6 files changed, 150 insertions(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index f3503d0cc1b8..c2bf28099abd 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -194,6 +194,8 @@ config ARM64
> !CC_OPTIMIZE_FOR_SIZE)
> select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY \
> if DYNAMIC_FTRACE_WITH_ARGS
> + select HAVE_SAMPLE_FTRACE_DIRECT
> + select HAVE_SAMPLE_FTRACE_DIRECT_MULTI
> select HAVE_EFFICIENT_UNALIGNED_ACCESS
> select HAVE_FAST_GUP
> select HAVE_FTRACE_MCOUNT_RECORD
> diff --git a/samples/ftrace/ftrace-direct-modify.c b/samples/ftrace/ftrace-direct-modify.c
> index 25fba66f61c0..98d1b7385f08 100644
> --- a/samples/ftrace/ftrace-direct-modify.c
> +++ b/samples/ftrace/ftrace-direct-modify.c
> @@ -2,7 +2,9 @@
> #include <linux/module.h>
> #include <linux/kthread.h>
> #include <linux/ftrace.h>
> +#ifndef CONFIG_ARM64
> #include <asm/asm-offsets.h>
> +#endif
>
> extern void my_direct_func1(void);
> extern void my_direct_func2(void);
> @@ -96,6 +98,38 @@ asm (
>
> #endif /* CONFIG_S390 */
>
> +#ifdef CONFIG_ARM64
> +
> +asm (
> +" .pushsection .text, \"ax\", @progbits\n"
> +" .type my_tramp1, @function\n"
> +" .globl my_tramp1\n"
> +" my_tramp1:"
> +" bti c\n"
> +" sub sp, sp, #16\n"
> +" stp x9, x30, [sp]\n"
> +" bl my_direct_func1\n"
> +" ldp x30, x9, [sp]\n"
> +" add sp, sp, #16\n"
> +" ret x9\n"
> +" .size my_tramp1, .-my_tramp1\n"
> +
> +" .type my_tramp2, @function\n"
> +" .globl my_tramp2\n"
> +" my_tramp2:"
> +" bti c\n"
> +" sub sp, sp, #16\n"
> +" stp x9, x30, [sp]\n"
> +" bl my_direct_func2\n"
> +" ldp x30, x9, [sp]\n"
> +" add sp, sp, #16\n"
> +" ret x9\n"
> +" .size my_tramp2, .-my_tramp2\n"
> +" .popsection\n"
> +);
> +
> +#endif /* CONFIG_ARM64 */
> +
> static struct ftrace_ops direct;
>
> static unsigned long my_tramp = (unsigned long)my_tramp1;
> diff --git a/samples/ftrace/ftrace-direct-multi-modify.c b/samples/ftrace/ftrace-direct-multi-modify.c
> index f72623899602..26956c8fc513 100644
> --- a/samples/ftrace/ftrace-direct-multi-modify.c
> +++ b/samples/ftrace/ftrace-direct-multi-modify.c
> @@ -2,7 +2,9 @@
> #include <linux/module.h>
> #include <linux/kthread.h>
> #include <linux/ftrace.h>
> +#ifndef CONFIG_ARM64
> #include <asm/asm-offsets.h>
> +#endif
>
> extern void my_direct_func1(unsigned long ip);
> extern void my_direct_func2(unsigned long ip);
> @@ -103,6 +105,44 @@ asm (
>
> #endif /* CONFIG_S390 */
>
> +#ifdef CONFIG_ARM64
> +
> +asm (
> +" .pushsection .text, \"ax\", @progbits\n"
> +" .type my_tramp1, @function\n"
> +" .globl my_tramp1\n"
> +" my_tramp1:"
> +" bti c\n"
> +" sub sp, sp, #32\n"
> +" stp x9, x30, [sp]\n"
> +" str x0, [sp, #16]\n"
> +" mov x0, x30\n"
> +" bl my_direct_func1\n"
> +" ldp x30, x9, [sp]\n"
> +" ldr x0, [sp, #16]\n"
> +" add sp, sp, #32\n"
> +" ret x9\n"
> +" .size my_tramp1, .-my_tramp1\n"
> +
> +" .type my_tramp2, @function\n"
> +" .globl my_tramp2\n"
> +" my_tramp2:"
> +" bti c\n"
> +" sub sp, sp, #32\n"
> +" stp x9, x30, [sp]\n"
> +" str x0, [sp, #16]\n"
> +" mov x0, x30\n"
> +" bl my_direct_func2\n"
> +" ldp x30, x9, [sp]\n"
> +" ldr x0, [sp, #16]\n"
> +" add sp, sp, #32\n"
> +" ret x9\n"
> +" .size my_tramp2, .-my_tramp2\n"
> +" .popsection\n"
> +);
> +
> +#endif /* CONFIG_ARM64 */
> +
> static unsigned long my_tramp = (unsigned long)my_tramp1;
> static unsigned long tramps[2] = {
> (unsigned long)my_tramp1,
> diff --git a/samples/ftrace/ftrace-direct-multi.c b/samples/ftrace/ftrace-direct-multi.c
> index 1547c2c6be02..b2ac90e0c02e 100644
> --- a/samples/ftrace/ftrace-direct-multi.c
> +++ b/samples/ftrace/ftrace-direct-multi.c
> @@ -4,7 +4,9 @@
> #include <linux/mm.h> /* for handle_mm_fault() */
> #include <linux/ftrace.h>
> #include <linux/sched/stat.h>
> +#ifndef CONFIG_ARM64
> #include <asm/asm-offsets.h>
> +#endif
>
> extern void my_direct_func(unsigned long ip);
>
> @@ -66,6 +68,28 @@ asm (
>
> #endif /* CONFIG_S390 */
>
> +#ifdef CONFIG_ARM64
> +
> +asm (
> +" .pushsection .text, \"ax\", @progbits\n"
> +" .type my_tramp, @function\n"
> +" .globl my_tramp\n"
> +" my_tramp:"
> +" bti c\n"
> +" sub sp, sp, #32\n"
> +" stp x9, x30, [sp]\n"
> +" str x0, [sp, #16]\n"
> +" mov x0, x30\n"
> +" bl my_direct_func\n"
> +" ldp x30, x9, [sp]\n"
> +" ldr x0, [sp, #16]\n"
> +" add sp, sp, #32\n"
> +" ret x9\n"
> +" .size my_tramp, .-my_tramp\n"
> +" .popsection\n"
> +);
> +
> +#endif /* CONFIG_ARM64 */
> static struct ftrace_ops direct;
>
> static int __init ftrace_direct_multi_init(void)
> diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c
> index 71ed4ee8cb4a..38f6f677f913 100644
> --- a/samples/ftrace/ftrace-direct-too.c
> +++ b/samples/ftrace/ftrace-direct-too.c
> @@ -3,7 +3,9 @@
>
> #include <linux/mm.h> /* for handle_mm_fault() */
> #include <linux/ftrace.h>
> +#ifndef CONFIG_ARM64
> #include <asm/asm-offsets.h>
> +#endif
>
> extern void my_direct_func(struct vm_area_struct *vma, unsigned long address,
> unsigned int flags, struct pt_regs *regs);
> @@ -72,6 +74,30 @@ asm (
>
> #endif /* CONFIG_S390 */
>
> +#ifdef CONFIG_ARM64
> +
> +asm (
> +" .pushsection .text, \"ax\", @progbits\n"
> +" .type my_tramp, @function\n"
> +" .globl my_tramp\n"
> +" my_tramp:"
> +" bti c\n"
> +" sub sp, sp, #48\n"
> +" stp x9, x30, [sp]\n"
> +" stp x0, x1, [sp, #16]\n"
> +" stp x2, x3, [sp, #32]\n"
> +" bl my_direct_func\n"
> +" ldp x30, x9, [sp]\n"
> +" ldp x0, x1, [sp, #16]\n"
> +" ldp x2, x3, [sp, #32]\n"
> +" add sp, sp, #48\n"
> +" ret x9\n"
> +" .size my_tramp, .-my_tramp\n"
> +" .popsection\n"
> +);
> +
> +#endif /* CONFIG_ARM64 */
> +
> static struct ftrace_ops direct;
>
> static int __init ftrace_direct_init(void)
> diff --git a/samples/ftrace/ftrace-direct.c b/samples/ftrace/ftrace-direct.c
> index d81a9473b585..e5312f9c15d3 100644
> --- a/samples/ftrace/ftrace-direct.c
> +++ b/samples/ftrace/ftrace-direct.c
> @@ -3,7 +3,9 @@
>
> #include <linux/sched.h> /* for wake_up_process() */
> #include <linux/ftrace.h>
> +#ifndef CONFIG_ARM64
> #include <asm/asm-offsets.h>
> +#endif
>
> extern void my_direct_func(struct task_struct *p);
>
> @@ -63,6 +65,28 @@ asm (
>
> #endif /* CONFIG_S390 */
>
> +#ifdef CONFIG_ARM64
> +
> +asm (
> +" .pushsection .text, \"ax\", @progbits\n"
> +" .type my_tramp, @function\n"
> +" .globl my_tramp\n"
> +" my_tramp:"
> +" bti c\n"
> +" sub sp, sp, #32\n"
> +" stp x9, x30, [sp]\n"
> +" str x0, [sp, #16]\n"
> +" bl my_direct_func\n"
> +" ldp x30, x9, [sp]\n"
> +" ldr x0, [sp, #16]\n"
> +" add sp, sp, #32\n"
> +" ret x9\n"
> +" .size my_tramp, .-my_tramp\n"
> +" .popsection\n"
> +);
> +
> +#endif /* CONFIG_ARM64 */
> +
> static struct ftrace_ops direct;
>
> static int __init ftrace_direct_init(void)
> --
> 2.40.0.577.gac1e443424-goog
>