[PATCH 8/8] arm64: ftrace: Add direct called trampoline samples support

Florent Revest
2023-02-01T16:38:09Z

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/nospec-branch.h> which does not exist on
arm64 and <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>
---
arch/arm64/Kconfig | 2 ++
samples/ftrace/ftrace-direct-modify.c | 32 ++++++++++++++++++
samples/ftrace/ftrace-direct-multi-modify.c | 36 +++++++++++++++++++++
samples/ftrace/ftrace-direct-multi.c | 22 +++++++++++++
samples/ftrace/ftrace-direct-too.c | 25 ++++++++++++++
samples/ftrace/ftrace-direct.c | 23 +++++++++++++
6 files changed, 140 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7deafd653c42..5480ef8eaa2a 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -194,6 +194,8 @@ config ARM64
if (DYNAMIC_FTRACE_WITH_ARGS && !CFI_CLANG)
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 0f1b8859e1e1..944b327e130c 100644
--- a/samples/ftrace/ftrace-direct-modify.c
+++ b/samples/ftrace/ftrace-direct-modify.c
@@ -2,8 +2,10 @@
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/ftrace.h>
+#ifndef CONFIG_ARM64
#include <asm/asm-offsets.h>
#include <asm/nospec-branch.h>
+#endif

extern void my_direct_func1(void);
extern void my_direct_func2(void);
@@ -96,6 +98,36 @@ asm (

#endif /* CONFIG_S390 */

+#ifdef CONFIG_ARM64
+
+asm (
+" .pushsection .text, \"ax\", @progbits\n"
+" .type my_tramp1, @function\n"
+" .globl my_tramp1\n"
+" my_tramp1:"
+" 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:"
+" 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 407c56325e65..ae1f97271d1a 100644
--- a/samples/ftrace/ftrace-direct-multi-modify.c
+++ b/samples/ftrace/ftrace-direct-multi-modify.c
@@ -2,8 +2,10 @@
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/ftrace.h>
+#ifndef CONFIG_ARM64
#include <asm/asm-offsets.h>
#include <asm/nospec-branch.h>
+#endif

extern void my_direct_func1(unsigned long ip);
extern void my_direct_func2(unsigned long ip);
@@ -103,6 +105,40 @@ asm (

#endif /* CONFIG_S390 */

+#ifdef CONFIG_ARM64
+
+asm (
+" .pushsection .text, \"ax\", @progbits\n"
+" .type my_tramp1, @function\n"
+" .globl my_tramp1\n"
+" my_tramp1:"
+" sub sp, sp, #32\n"
+" stp x9, x30, [sp]\n"
+" str x0, [sp, #16]\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:"
+" sub sp, sp, #32\n"
+" stp x9, x30, [sp]\n"
+" str x0, [sp, #16]\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 42a94806a446..84713fe28b74 100644
--- a/samples/ftrace/ftrace-direct-multi.c
+++ b/samples/ftrace/ftrace-direct-multi.c
@@ -4,8 +4,10 @@
#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>
#include <asm/nospec-branch.h>
+#endif

extern void my_direct_func(unsigned long ip);

@@ -66,6 +68,26 @@ asm (

#endif /* CONFIG_S390 */

+#ifdef CONFIG_ARM64
+
+asm (
+" .pushsection .text, \"ax\", @progbits\n"
+" .type my_tramp, @function\n"
+" .globl my_tramp\n"
+" my_tramp:"
+" 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_multi_init(void)
diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c
index 7ee5dd3cc61d..f46ee08caa2b 100644
--- a/samples/ftrace/ftrace-direct-too.c
+++ b/samples/ftrace/ftrace-direct-too.c
@@ -3,8 +3,10 @@

#include <linux/mm.h> /* for handle_mm_fault() */
#include <linux/ftrace.h>
+#ifndef CONFIG_ARM64
#include <asm/asm-offsets.h>
#include <asm/nospec-branch.h>
+#endif

extern void my_direct_func(struct vm_area_struct *vma,
unsigned long address, unsigned int flags);
@@ -70,6 +72,29 @@ asm (

#endif /* CONFIG_S390 */

+#ifdef CONFIG_ARM64
+
+asm (
+" .pushsection .text, \"ax\", @progbits\n"
+" .type my_tramp, @function\n"
+" .globl my_tramp\n"
+" my_tramp:"
+" sub sp, sp, #48\n"
+" stp x9, x30, [sp]\n"
+" stp x0, x1, [sp, #16]\n"
+" str x2, [sp, #32]\n"
+" bl my_direct_func\n"
+" ldp x30, x9, [sp]\n"
+" ldp x0, x1, [sp, #16]\n"
+" ldr x2, [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 5ffce87fa83e..e37e8d9e855c 100644
--- a/samples/ftrace/ftrace-direct.c
+++ b/samples/ftrace/ftrace-direct.c
@@ -3,8 +3,10 @@

#include <linux/sched.h> /* for wake_up_process() */
#include <linux/ftrace.h>
+#ifndef CONFIG_ARM64
#include <asm/asm-offsets.h>
#include <asm/nospec-branch.h>
+#endif

extern void my_direct_func(struct task_struct *p);

@@ -63,6 +65,27 @@ asm (

#endif /* CONFIG_S390 */

+#ifdef CONFIG_ARM64
+
+asm (
+" .pushsection .text, \"ax\", @progbits\n"
+" .type my_tramp, @function\n"
+" .globl my_tramp\n"
+" my_tramp:"
+" 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)
--
2.39.1.519.gcb327c4b5f-goog