MIPS: Tracing: Make ftrace for MIPS work without -fno-omit-frame-pointer

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>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Nicholas Mc Guire <der.herr@hofr.at>
Cc: zhangfx@lemote.com
Cc: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/679/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

3 files changed, 106 insertions, 15 deletions

diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h
index 7094a40b96d8..3986cd8704f3 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 e981a497c98f..e363fc69aabd 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 98d469032506..bdfef2c24f16 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