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Subject[PATCH v9 08/10] tracing: make ftrace for MIPS work without -fno-omit-frame-pointer
Date
From: Wu Zhangjin <wuzhangjin@gmail.com>

When remove the -fno-omit-frame-pointer, gcc will not save the frame
pointer for us, we need to save one ourselves.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
---
arch/mips/include/asm/ftrace.h | 57 ++++++++++++++++++++++++++++++++++++++++
arch/mips/kernel/ftrace.c | 56 ++++++++++++++++++++++++++++----------
arch/mips/kernel/mcount.S | 8 +++++
3 files changed, 106 insertions(+), 15 deletions(-)
diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h
index 7094a40..3986cd8 100644
--- a/arch/mips/include/asm/ftrace.h
+++ b/arch/mips/include/asm/ftrace.h
@@ -19,6 +19,62 @@
extern void _mcount(void);
#define mcount _mcount

+#define safe_load(load, src, dst, error) \
+do { \
+ asm volatile ( \
+ "1: " load " %[" STR(dst) "], 0(%[" STR(src) "])\n"\
+ " li %[" STR(error) "], 0\n" \
+ "2:\n" \
+ \
+ ".section .fixup, \"ax\"\n" \
+ "3: li %[" STR(error) "], 1\n" \
+ " j 2b\n" \
+ ".previous\n" \
+ \
+ ".section\t__ex_table,\"a\"\n\t" \
+ STR(PTR) "\t1b, 3b\n\t" \
+ ".previous\n" \
+ \
+ : [dst] "=&r" (dst), [error] "=r" (error)\
+ : [src] "r" (src) \
+ : "memory" \
+ ); \
+} while (0)
+
+#define safe_store(store, src, dst, error) \
+do { \
+ asm volatile ( \
+ "1: " store " %[" STR(src) "], 0(%[" STR(dst) "])\n"\
+ " li %[" STR(error) "], 0\n" \
+ "2:\n" \
+ \
+ ".section .fixup, \"ax\"\n" \
+ "3: li %[" STR(error) "], 1\n" \
+ " j 2b\n" \
+ ".previous\n" \
+ \
+ ".section\t__ex_table,\"a\"\n\t"\
+ STR(PTR) "\t1b, 3b\n\t" \
+ ".previous\n" \
+ \
+ : [error] "=r" (error) \
+ : [dst] "r" (dst), [src] "r" (src)\
+ : "memory" \
+ ); \
+} while (0)
+
+#define safe_load_code(dst, src, error) \
+ safe_load(STR(lw), src, dst, error)
+#define safe_store_code(src, dst, error) \
+ safe_store(STR(sw), src, dst, error)
+
+#define safe_load_stack(dst, src, error) \
+ safe_load(STR(PTR_L), src, dst, error)
+
+#define safe_store_stack(src, dst, error) \
+ safe_store(STR(PTR_S), src, dst, error)
+
+
#ifdef CONFIG_DYNAMIC_FTRACE
static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
@@ -27,6 +83,7 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)

struct dyn_arch_ftrace {
};
+
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* __ASSEMBLY__ */
#endif /* CONFIG_FUNCTION_TRACER */
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index e981a49..e363fc6 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -27,7 +27,13 @@ static unsigned int ftrace_nop = 0x00000000;

static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
{
- *(unsigned int *)ip = new_code;
+ int faulted;
+
+ /* *(unsigned int *)ip = new_code; */
+ safe_store_code(new_code, ip, faulted);
+
+ if (unlikely(faulted))
+ return -EFAULT;

flush_icache_range(ip, ip + 8);

@@ -41,14 +47,20 @@ 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;
+ 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
@@ -147,6 +159,7 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
{
unsigned long sp, ip, ra;
unsigned int code;
+ int faulted;

/* in module or kernel? */
if (self_addr & 0x40000000) {
@@ -162,8 +175,11 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
do {
ip -= 4;

- /* get the code at "ip" */
- code = *(unsigned int *)ip;
+ /* 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
* ra is stored, then this is a leaf function and it does not
@@ -174,11 +190,14 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
} while (((code & S_RA_SP) != S_RA_SP));

sp = fp + (code & OFFSET_MASK);
- ra = *(unsigned long *)sp;
+
+ /* ra = *(unsigned long *)sp; */
+ safe_load_stack(ra, sp, faulted);
+ if (unlikely(faulted))
+ return 0;

if (ra == parent)
return sp;
-
return 0;
}

@@ -193,6 +212,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
struct ftrace_graph_ent trace;
unsigned long return_hooker = (unsigned long)
&return_to_handler;
+ int faulted;

if (unlikely(atomic_read(&current->tracing_graph_pause)))
return;
@@ -206,21 +226,23 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
* ftrace_get_parent_addr() does it!
*/

- old = *parent;
+ /* old = *parent; */
+ safe_load_stack(old, parent, faulted);
+ if (unlikely(faulted))
+ goto out;

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) {
- ftrace_graph_stop();
- WARN_ON(1);
- return;
- }
+ if (parent == 0)
+ goto out;

- *parent = return_hooker;
+ /* *parent = return_hooker; */
+ safe_store_stack(return_hooker, parent, faulted);
+ if (unlikely(faulted))
+ goto out;

if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) ==
-EBUSY) {
@@ -235,5 +257,9 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
current->curr_ret_stack--;
*parent = old;
}
+ return;
+out:
+ ftrace_graph_stop();
+ WARN_ON(1);
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
index 98d4690..bdfef2c 100644
--- a/arch/mips/kernel/mcount.S
+++ b/arch/mips/kernel/mcount.S
@@ -139,7 +139,15 @@ NESTED(ftrace_graph_caller, PT_SIZE, ra)
#endif
PTR_LA a0, PT_R1(sp) /* arg1: &AT -> a0 */
jal prepare_ftrace_return
+#ifdef CONFIG_FRAME_POINTER
move a2, fp /* arg3: frame pointer */
+#else
+#ifdef CONFIG_64BIT
+ PTR_LA a2, PT_SIZE(sp)
+#else
+ PTR_LA a2, (PT_SIZE+8)(sp)
+#endif
+#endif

MCOUNT_RESTORE_REGS
RETURN_BACK
--
1.6.2.1


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