[RFC PATCH 3/5] livepatch: ftrace: arm64: Add support for -mfentry on arm64
From: Li Bin
Date: Thu May 28 2015 - 01:56:02 EST
This patch depends on the compiler's mfentry feature for arm64 that
proposed by this patchset. If the kernel is compiled with this feature,
the entry of each function like:
foo:
mov x9, x30
bl __fentry__
mov x30, x9
When -mfentry is used, the call is to '__fentry__' and not '_mcount'
and is done before the function's stack frame is set up. So __fentry__
is responsibel to protect parameter registers and corruptible registers.
Signed-off-by: Li Bin <huawei.libin@xxxxxxxxxx>
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/ftrace.h | 5 +++
arch/arm64/kernel/arm64ksyms.c | 4 ++
arch/arm64/kernel/entry-ftrace.S | 59 +++++++++++++++++++++++++++++++++++--
scripts/recordmcount.pl | 2 +-
5 files changed, 66 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index ea435c9..7bb2468 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -60,6 +60,7 @@ config ARM64
select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE
select HAVE_EFFICIENT_UNALIGNED_ACCESS
select HAVE_FTRACE_MCOUNT_RECORD
+ select HAVE_FENTRY
select HAVE_FUNCTION_TRACER
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_GENERIC_DMA_COHERENT
diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index a7722b9..08eab52 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -13,7 +13,11 @@
#include <asm/insn.h>
+#ifdef CC_USING_FENTRY
+#define MCOUNT_ADDR ((unsigned long)__fentry__)
+#else
#define MCOUNT_ADDR ((unsigned long)_mcount)
+#endif
#define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE
#ifdef CONFIG_DYNAMIC_FTRACE
@@ -24,6 +28,7 @@
#include <linux/compat.h>
extern void _mcount(unsigned long);
+extern void __fentry__(unsigned long);
extern void *return_address(unsigned int);
struct dyn_arch_ftrace {
diff --git a/arch/arm64/kernel/arm64ksyms.c b/arch/arm64/kernel/arm64ksyms.c
index a85843d..f0455d3 100644
--- a/arch/arm64/kernel/arm64ksyms.c
+++ b/arch/arm64/kernel/arm64ksyms.c
@@ -63,5 +63,9 @@ EXPORT_SYMBOL(change_bit);
EXPORT_SYMBOL(test_and_change_bit);
#ifdef CONFIG_FUNCTION_TRACER
+#ifdef CC_USING_FENTRY
+EXPORT_SYMBOL(__fentry__);
+#else
EXPORT_SYMBOL(_mcount);
#endif
+#endif
diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
index fde793b..18cfe5b 100644
--- a/arch/arm64/kernel/entry-ftrace.S
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -93,27 +93,57 @@
ldr \reg, [\reg]
.endm
+ /* for instrumented function's parent */
+ .macro fentry_get_parent_fp reg
+ ldr \reg, [x29]
+ .endm
+
/* for instrumented function */
.macro mcount_get_pc0 reg
mcount_adjust_addr \reg, x30
.endm
+ /* for instrumented function */
+ .macro fentry_get_pc0 reg
+ mcount_adjust_addr \reg, x30
+ .endm
+
.macro mcount_get_pc reg
ldr \reg, [x29, #8]
mcount_adjust_addr \reg, \reg
.endm
+ .macro fentry_get_pc reg
+ ldr \reg, [x29, #8]
+ mcount_adjust_addr \reg, \reg
+ .endm
+
.macro mcount_get_lr reg
ldr \reg, [x29]
ldr \reg, [\reg, #8]
mcount_adjust_addr \reg, \reg
.endm
+ .macro fentry_get_lr reg, base
+ ldr \reg, [\base, #72] //S_X9
+ mcount_adjust_addr \reg, \reg
+ .endm
+
.macro mcount_get_lr_addr reg
ldr \reg, [x29]
add \reg, \reg, #8
.endm
+ .macro fentry_get_lr_addr reg, base
+ add \reg, \base, #72 //S_X9
+ .endm
+
+#ifdef CC_USING_FENTRY
+#define function_hook __fentry__
+#else
+#define function_hook _mcount
+#endif
+
#ifndef CONFIG_DYNAMIC_FTRACE
/*
* void _mcount(unsigned long return_address)
@@ -123,7 +153,7 @@
* - tracer function to probe instrumented function's entry,
* - ftrace_graph_caller to set up an exit hook
*/
-ENTRY(_mcount)
+ENTRY(function_hook)
mcount_enter
save_mcount_regs
@@ -133,8 +163,13 @@ ENTRY(_mcount)
cmp x0, x2 // if (ftrace_trace_function
b.eq skip_ftrace_call // != ftrace_stub) {
+#ifdef CC_USING_FENTRY
+ fentry_get_pc x0 // function's pc
+ fentry_get_lr x1, sp // function's lr (= parent's pc)
+#else
mcount_get_pc x0 // function's pc
mcount_get_lr x1 // function's lr (= parent's pc)
+#endif
blr x2 // (*ftrace_trace_function)(pc, lr);
#ifndef CONFIG_FUNCTION_GRAPH_TRACER
@@ -161,7 +196,7 @@ skip_ftrace_call:
restore_mcount_regs
mcount_exit
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
-ENDPROC(_mcount)
+ENDPROC(function_hook)
#else /* CONFIG_DYNAMIC_FTRACE */
/*
@@ -170,9 +205,9 @@ ENDPROC(_mcount)
* and later on, NOP to branch to ftrace_caller() when enabled or branch to
* NOP when disabled per-function base.
*/
-ENTRY(_mcount)
+ENTRY(function_hook)
ret
-ENDPROC(_mcount)
+ENDPROC(function_hook)
/*
* void ftrace_caller(unsigned long return_address)
@@ -189,8 +224,13 @@ ENTRY(ftrace_caller)
adrp x0, function_trace_op
ldr x2, [x0, #:lo12:function_trace_op]
+#ifdef CC_USING_FENTRY
+ fentry_get_pc0 x0 // function's pc
+ fentry_get_lr x1, sp // function's lr
+#else
mcount_get_pc0 x0 // function's pc
mcount_get_lr x1 // function's lr
+#endif
mov x3, #0
.global ftrace_call
@@ -237,8 +277,13 @@ ENTRY(ftrace_regs_caller)
adrp x0, function_trace_op
ldr x2, [x0, #:lo12:function_trace_op]
+#ifdef CC_USING_FENTRY
+ fentry_get_pc0 x0 // function's pc
+ fentry_get_lr x1, sp // function's lr
+#else
mcount_get_pc0 x0 // function's pc
mcount_get_lr x1 // function's lr
+#endif
mov x3, sp
.global ftrace_regs_call
@@ -282,9 +327,15 @@ ENDPROC(ftrace_stub)
* and run return_to_handler() later on its exit.
*/
ENTRY(ftrace_graph_caller)
+#ifdef CC_USING_FENTRY
+ fentry_get_lr_addr x0, sp // pointer to function's saved lr
+ fentry_get_pc x1 // function's pc
+ fentry_get_parent_fp x2 // parent's fp
+#else
mcount_get_lr_addr x0 // pointer to function's saved lr
mcount_get_pc x1 // function's pc
mcount_get_parent_fp x2 // parent's fp
+#endif
bl prepare_ftrace_return // prepare_ftrace_return(&lr, pc, fp)
restore_mcount_regs
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index 826470d..5020d96 100755
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -279,7 +279,7 @@ if ($arch eq "x86_64") {
} elsif ($arch eq "arm64") {
$alignment = 3;
$section_type = '%progbits';
- $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_AARCH64_CALL26\\s+_mcount\$";
+ $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_AARCH64_CALL26\\s+(_mcount|__fentry__)\$";
$type = ".quad";
} elsif ($arch eq "ia64") {
$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
--
1.7.1
--
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