From: Wu Zhangjin <wuzhangjin@xxxxxxxxx>
(All of the stuff have been tested for kernel and module, including static
function tracer, dynamic function tracer and function graph tracer.)
Changes:
+ Reduce the runtime overhead
o Uses macros instead of variables for the fixed instructions to
reduce memory access
o Moves the Initilization of the instructions which will be fixed
after linking from ftrace_make_nop/ftrace_make_call to
ftrace_dyn_arch_init() and encodes the instructions through
uasm(arch/mips/include/asm/uasm.h).
o A common macro in_module() is defined to determine which space the
instruction pointer stays in and several related conditional
statements are converted to conditional operator(? :) statement.
+ Cleanup the whole stuff
Lots of comments/macros have been cleaned up to let it look better.
Signed-off-by: Wu Zhangjin <wuzhangjin@xxxxxxxxx>
---
arch/mips/include/asm/ftrace.h | 10 ++-
arch/mips/kernel/ftrace.c | 201 ++++++++++++++++++++++------------------
2 files changed, 119 insertions(+), 92 deletions(-)
diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h
index ce35c9a..e58f9ff 100644
--- a/arch/mips/include/asm/ftrace.h
+++ b/arch/mips/include/asm/ftrace.h
@@ -3,7 +3,7 @@
* License. See the file "COPYING" in the main directory of this archive for
* more details.
*
- * Copyright (C) 2009 DSLab, Lanzhou University, China
+ * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
* Author: Wu Zhangjin <wuzhangjin@xxxxxxxxx>
*/
@@ -19,6 +19,12 @@
extern void _mcount(void);
#define mcount _mcount
+/*
+ * If the Instruction Pointer is in module space (0xc0000000), return ture;
+ * otherwise, it is in kernel space (0x80000000), return false.
+ */
+#define in_module(ip) (unlikely((ip) & 0x40000000))
+
#define safe_load(load, src, dst, error) \
do { \
asm volatile ( \
@@ -83,8 +89,8 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
struct dyn_arch_ftrace {
};
+#endif /* CONFIG_DYNAMIC_FTRACE */
-#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* __ASSEMBLY__ */
#endif /* CONFIG_FUNCTION_TRACER */
#endif /* _ASM_MIPS_FTRACE_H */
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index e9e64e0..c38e3d9 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -2,7 +2,7 @@
* Code for replacing ftrace calls with jumps.
*
* Copyright (C) 2007-2008 Steven Rostedt <srostedt@xxxxxxxxxx>
- * Copyright (C) 2009 DSLab, Lanzhou University, China
+ * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
* Author: Wu Zhangjin <wuzhangjin@xxxxxxxxx>
*
* Thanks goes to Steven Rostedt for writing the original x86 version.
@@ -15,15 +15,50 @@
#include <asm/cacheflush.h>
#include <asm/asm.h>
#include <asm/asm-offsets.h>
+#include <asm/uasm.h>
#ifdef CONFIG_DYNAMIC_FTRACE
-#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
-#define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
-#define jump_insn_encode(op_code, addr) \
- ((unsigned int)((op_code) | (((addr) >> 2) & ADDR_MASK)))
+/* Before linking, the following instructions are fixed. */
+#ifdef CONFIG_CPU_LOONGSON2F
+/* insn: or at, at, zero */
+#define INSN_NOP 0x00200825
+#else
+/* insn: nop */
+#define INSN_NOP 0x00000000
+#endif
+
+/* insn: b 1f; offset = (16 >> 2) */
+#define INSN_B_1F 0x10000004
+
+/* After linking, the following instructions are fixed. */
+static unsigned int insn_jal_ftrace_caller __read_mostly;
+static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
+static unsigned int insn_j_ftrace_graph_caller __read_mostly;
-static unsigned int ftrace_nop = 0x00000000;
+/* The following instructions are encoded in the run-time */
+/* insn: jal func; op_code|addr : 31...26|25 ....0 */
+#define jal(addr) \
+ ((unsigned int)(0x0c000000 | (((addr) >> 2) & 0x03ffffff)))
+
+static inline void ftrace_dyn_arch_init_insns(void)
+{
+ u32 *buf;
+ unsigned int v1;
+
+ /* lui v1, hi16_mcount */
+ v1 = 3;
+ buf = (u32 *)&insn_lui_v1_hi16_mcount;
+ UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
+
+ /* jal (ftrace_caller + 8), jump over the first two instruction */
+ buf = (u32 *)&insn_jal_ftrace_caller;
+ uasm_i_jal(&buf, (FTRACE_ADDR + 8));
+
+ /* j ftrace_graph_caller */
+ buf = (u32 *)&insn_j_ftrace_graph_caller;
+ uasm_i_j(&buf, (unsigned long)ftrace_graph_caller);
+}
static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
{
@@ -31,7 +66,6 @@ static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
/* *(unsigned int *)ip = new_code; */
safe_store_code(new_code, ip, faulted);
-
if (unlikely(faulted))
return -EFAULT;
@@ -40,117 +74,101 @@ static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
return 0;
}
-static int lui_v1;
-static int jal_mcount;
-
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int new;
- int faulted;
unsigned long ip = rec->ip;
- /* We have compiled module with -mlong-calls, but compiled the kernel
- * without it, we need to cope with them respectively. */
- if (ip & 0x40000000) {
- /* record it for ftrace_make_call */
- if (lui_v1 == 0) {
- /* lui_v1 = *(unsigned int *)ip; */
- safe_load_code(lui_v1, ip, faulted);
-
- if (unlikely(faulted))
- return -EFAULT;
- }
-
- /* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
- * addiu v1, v1, low_16bit_of_mcount
- * move at, ra
- * jalr v1
- * nop
- * 1f: (ip + 12)
- */
- new = 0x10000004;
- } else {
- /* record/calculate it for ftrace_make_call */
- if (jal_mcount == 0) {
- /* We can record it directly like this:
- * jal_mcount = *(unsigned int *)ip;
- * Herein, jump over the first two nop instructions */
- jal_mcount = jump_insn_encode(JAL, (MCOUNT_ADDR + 8));
- }
-
- /* move at, ra
- * jalr v1 --> nop
- */
- new = ftrace_nop;
- }
+ /*
+ * We have compiled modules with -mlong-calls, but compiled kernel
+ * without it, therefore, need to cope with them respectively.
+ *
+ * For module:
+ *
+ * lui v1, hi16_mcount --> b 1f
+ * addiu v1, v1, lo16_mcount
+ * move at, ra
+ * jalr v1
+ * nop
+ * 1f: (ip + 16)
+ * For kernel:
+ *
+ * move at, ra
+ * jal _mcount --> nop
+ *
+ */
+ new = in_module(ip) ? INSN_B_1F : INSN_NOP;
+
return ftrace_modify_code(ip, new);
}
-static int modified; /* initialized as 0 by default */
-
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int new;
unsigned long ip = rec->ip;
- /* We just need to remove the "b ftrace_stub" at the fist time! */
- if (modified == 0) {
- modified = 1;
- ftrace_modify_code(addr, ftrace_nop);
- }
- /* ip, module: 0xc0000000, kernel: 0x80000000 */
- new = (ip & 0x40000000) ? lui_v1 : jal_mcount;
+ new = in_module(ip) ? insn_lui_v1_hi16_mcount : insn_jal_ftrace_caller;
return ftrace_modify_code(ip, new);
}
-#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
-
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned int new;
- new = jump_insn_encode(JAL, (unsigned long)func);
+ new = jal((unsigned long)func);
- return ftrace_modify_code(FTRACE_CALL_IP, new);
+ return ftrace_modify_code((unsigned long)(&ftrace_call), new);
}
int __init ftrace_dyn_arch_init(void *data)
{
+ ftrace_dyn_arch_init_insns();
+
+ /*
+ * We are safe to remove the "b ftrace_stub" for the current
+ * ftrace_caller() is almost empty (only the stack operations), and
+ * most importantly, the calling to mcount will be disabled later in
+ * ftrace_init(), then there is no 'big' overhead. And in the future,
+ * we are hoping the function_trace_stop is initialized as 1 then we
+ * can eventually remove that 'useless' "b ftrace_stub" and the
+ * following nop. Currently, although we can call ftrace_stop() to set
+ * function_trace_stop as 1, but it will change the behavior of the
+ * Function Tracer.
+ */
+ ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
+
/* The return code is retured via data */
*(unsigned long *)data = 0;
return 0;
}
-#endif /* CONFIG_DYNAMIC_FTRACE */
+#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
#ifdef CONFIG_DYNAMIC_FTRACE
extern void ftrace_graph_call(void);
-#define JMP 0x08000000 /* jump to target directly */
-#define CALL_FTRACE_GRAPH_CALLER \
- jump_insn_encode(JMP, (unsigned long)(&ftrace_graph_caller))
#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
int ftrace_enable_ftrace_graph_caller(void)
{
return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
- CALL_FTRACE_GRAPH_CALLER);
+ insn_j_ftrace_graph_caller);
}
int ftrace_disable_ftrace_graph_caller(void)
{
- return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, ftrace_nop);
+ return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
}
-#endif /* !CONFIG_DYNAMIC_FTRACE */
+#endif /* !CONFIG_DYNAMIC_FTRACE */
#ifndef KBUILD_MCOUNT_RA_ADDRESS
-#define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
-#define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
+#define S_RA_SP 0xafbf0000 /* s{d,w} ra, offset(sp) */
+#define S_R_SP 0xafb00000 /* s{d,w} R, offset(sp) */
#define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */
unsigned long ftrace_get_parent_addr(unsigned long self_addr,
@@ -162,32 +180,32 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
unsigned int code;
int faulted;
- /* in module or kernel? */
- if (self_addr & 0x40000000) {
- /* module: move to the instruction "lui v1, HI_16BIT_OF_MCOUNT" */
- ip = self_addr - 20;
- } else {
- /* kernel: move to the instruction "move ra, at" */
- ip = self_addr - 12;
- }
+ /*
+ * For module, move the ip from calling site of mcount to the
+ * instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for
+ * kernel, move to the instruction "move ra, at"(offset is 12)
+ */
+ ip = self_addr - (in_module(self_addr) ? 20 : 12);
- /* search the text until finding the non-store instruction or "s{d,w}
- * ra, offset(sp)" instruction */
+ /*
+ * search the text until finding the non-store instruction or "s{d,w}
+ * ra, offset(sp)" instruction
+ */
do {
ip -= 4;
/* get the code at "ip": code = *(unsigned int *)ip; */
safe_load_code(code, ip, faulted);
-
if (unlikely(faulted))
return 0;
- /* If we hit the non-store instruction before finding where the
+ /*
+ * If we hit the non-store instruction before finding where the
* ra is stored, then this is a leaf function and it does not
- * store the ra on the stack. */
+ * store the ra on the stack.
+ */
if ((code & S_R_SP) != S_R_SP)
return parent_addr;
-
} while (((code & S_RA_SP) != S_RA_SP));
sp = fp + (code & OFFSET_MASK);
@@ -211,16 +229,17 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
unsigned long fp)
{
+ int faulted;
unsigned long old;
struct ftrace_graph_ent trace;
unsigned long return_hooker = (unsigned long)
&return_to_handler;
- int faulted;
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
return;
- /* "parent" is the stack address saved the return address of the caller
+ /*
+ * "parent" is the stack address saved the return address of the caller
* of _mcount.
*
* if the gcc < 4.5, a leaf function does not save the return address
@@ -241,12 +260,14 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
if (unlikely(faulted))
goto out;
#ifndef KBUILD_MCOUNT_RA_ADDRESS
- parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
- (unsigned long)parent,
- fp);
- /* If fails when getting the stack address of the non-leaf function's
- * ra, stop function graph tracer and return */
- if (parent == 0)
+ parent = (unsigned long *)ftrace_get_parent_addr(
+ self_addr, old, (unsigned long)parent, fp);
+
+ /*
+ * If fails on getting the stack address of the non-leaf function's ra,
+ * stop function graph tracer and return
+ */
+ if (unlikely(parent == 0))
goto out;
#endif
/* *parent = return_hooker; */
@@ -272,4 +293,4 @@ out:
ftrace_graph_stop();
WARN_ON(1);
}
-#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
--
1.7.0.1
