[RFC 3/4] arm64: ftrace: add DYNAMIC_TRACE_WITH_REGS version
From: AKASHI Takahiro
Date: Thu Apr 23 2015 - 22:45:23 EST
CONFIG_DYNAMIC_TRACE_WITH_REGS is a prerequisite for ftrace-based kprobes
as well as livepatch.
This patch adds ftrace_regs_caller(), which will pass pt_regs info to
ftrace handlers, to enable this config.
Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/ftrace.h | 4 ++
arch/arm64/kernel/entry-ftrace.S | 124 ++++++++++++++++++++++++++++++++++++++
arch/arm64/kernel/ftrace.c | 24 +++++++-
4 files changed, 152 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1b8e973..c3678ed 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -54,6 +54,7 @@ config ARM64
select HAVE_DMA_ATTRS
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
+ select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_EFFICIENT_UNALIGNED_ACCESS
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_TRACER
diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index c5534fa..5a14269 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -16,6 +16,10 @@
#define MCOUNT_ADDR ((unsigned long)_mcount)
#define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE
+#ifdef CONFIG_DYNAMIC_FTRACE
+#define ARCH_SUPPORTS_FTRACE_OPS 1
+#endif
+
#ifndef __ASSEMBLY__
#include <linux/compat.h>
diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
index 08cafc5..fed28eb 100644
--- a/arch/arm64/kernel/entry-ftrace.S
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -10,6 +10,7 @@
*/
#include <linux/linkage.h>
+#include <asm/asm-offsets.h>
#include <asm/ftrace.h>
#include <asm/insn.h>
@@ -86,6 +87,95 @@
add \reg, \reg, #8
.endm
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+/*
+ * stack layout after mcount_save_regs in _mcount():
+ *
+ * current sp/fp => 0:+---------+
+ * in _mcount() |pt_regs |
+ * | |
+ * | +-----+
+ * | | x29 | -> instrumented function's fp
+ * | +-----+
+ * | | x30 | -> _mcount()'s lr
+ * | +-----+ (= instrumented function's pc)
+ * +S_FRAME_SIZE | |
+ * old sp => :+-----+---
+ * when instrumented | |
+ * function calls | ... |
+ * _mcount() | |
+ * | |
+ * instrumented => +xx:+-----+
+ * function's fp | x29 | -> parent's fp
+ * +-----+
+ * | x30 | -> instrumented function's lr (= parent's pc)
+ * +-----+
+ * | ... |
+ */
+ .macro mcount_save_regs
+ sub sp, sp, #S_FRAME_SIZE
+
+ stp x0, x1, [sp, #8 * 0]
+ stp x2, x3, [sp, #8 * 2]
+ stp x4, x5, [sp, #8 * 4]
+ stp x6, x7, [sp, #8 * 6]
+ stp x8, x9, [sp, #8 * 8]
+ stp x10, x11, [sp, #8 * 10]
+ stp x12, x13, [sp, #8 * 12]
+ stp x14, x15, [sp, #8 * 14]
+ stp x16, x17, [sp, #8 * 16]
+ stp x18, x19, [sp, #8 * 18]
+ stp x20, x21, [sp, #8 * 20]
+ stp x22, x23, [sp, #8 * 22]
+ stp x24, x25, [sp, #8 * 24]
+ stp x26, x27, [sp, #8 * 26]
+ stp x28, x29, [sp, #8 * 28]
+
+ ldr x0, [x29, #8]
+ mcount_adjust_addr x0, x0
+ str x0, [sp, #S_LR]
+
+ add x0, sp, #S_FRAME_SIZE
+ str x0, [sp, #S_SP]
+
+ mcount_adjust_addr x0, x30
+ str x0, [sp, #S_PC]
+
+ ldr x0, [sp, #8 * 0]
+
+ mov x29, sp
+ .endm
+
+ /* for instrumented function */
+ .macro mcount_get_lr1 reg
+ ldr \reg, [x29, #8 * 29]
+ ldr \reg, [\reg, #8]
+ mcount_adjust_addr \reg, \reg
+ .endm
+
+ .macro mcount_restore_rest_regs
+ ldp x0, x1, [sp, #8 * 0]
+ ldp x2, x3, [sp, #8 * 2]
+ ldp x4, x5, [sp, #8 * 4]
+ ldp x6, x7, [sp, #8 * 6]
+ ldp x8, x9, [sp, #8 * 8]
+ ldp x10, x11, [sp, #8 * 10]
+ ldp x12, x13, [sp, #8 * 12]
+ ldp x14, x15, [sp, #8 * 14]
+ ldp x16, x17, [sp, #8 * 16]
+ ldp x18, x19, [sp, #8 * 18]
+ ldp x20, x21, [sp, #8 * 20]
+ ldp x22, x23, [sp, #8 * 22]
+ ldp x24, x25, [sp, #8 * 24]
+ ldp x26, x27, [sp, #8 * 26]
+ ldp x28, x29, [sp, #8 * 28]
+ ldr x30, [sp, #S_LR]
+ add sp, sp, #S_FRAME_SIZE
+
+ mcount_enter
+ .endm
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
+
#ifndef CONFIG_DYNAMIC_FTRACE
/*
* void _mcount(unsigned long return_address)
@@ -156,6 +246,10 @@ ENTRY(ftrace_caller)
mcount_get_pc0 x0 // function's pc
mcount_get_lr x1 // function's lr
+ adrp x2, function_trace_op
+ add x2, x2, #:lo12:function_trace_op
+ ldr x2, [x2] // current ftrace_ops
+ mov x3, xzr // pt_regs (NULL)
.global ftrace_call
ftrace_call: // tracer(pc, lr);
@@ -171,6 +265,36 @@ ftrace_graph_call: // ftrace_graph_caller();
mcount_exit
ENDPROC(ftrace_caller)
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+/*
+ * void ftrace_regs_caller()
+ */
+ENTRY(ftrace_regs_caller)
+ mcount_save_regs
+
+ mcount_get_pc0 x0 // function's pc
+ mcount_get_lr1 x1 // function's lr
+ adrp x2, function_trace_op
+ add x2, x2, #:lo12:function_trace_op
+ ldr x2, [x2] // current ftrace_ops
+ mov x3, sp // pt_regs
+
+ .global ftrace_regs_call
+ftrace_regs_call: // tracer(pc, lr, ops, regs);
+ nop // This will be replaced with "bl xxx"
+ // where xxx can be any kind of tracer.
+
+ mcount_restore_rest_regs
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ b ftrace_graph_call
+#endif
+
+ mcount_exit
+ENDPROC(ftrace_regs_caller)
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
+
#endif /* CONFIG_DYNAMIC_FTRACE */
ENTRY(ftrace_stub)
diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index c851be7..5440673 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -56,12 +56,21 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long pc;
u32 new;
+ int ret;
pc = (unsigned long)&ftrace_call;
new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func,
AARCH64_INSN_BRANCH_LINK);
+ ret = ftrace_modify_code(pc, 0, new, false);
- return ftrace_modify_code(pc, 0, new, false);
+ if (!ret) {
+ pc = (unsigned long)&ftrace_regs_call;
+ new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func,
+ AARCH64_INSN_BRANCH_LINK);
+ ret = ftrace_modify_code(pc, 0, new, false);
+ }
+
+ return ret;
}
/*
@@ -97,6 +106,19 @@ int __init ftrace_dyn_arch_init(void)
{
return 0;
}
+
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+ unsigned long addr)
+{
+ unsigned long pc = rec->ip;
+ u32 old, new;
+
+ old = aarch64_insn_gen_branch_imm(pc, old_addr,
+ AARCH64_INSN_BRANCH_LINK);
+ new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
+
+ return ftrace_modify_code(pc, old, new, true);
+}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
--
1.7.9.5
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