Blackfin: add support for dynamic ftrace

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

5 files changed, 181 insertions, 9 deletions

diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig
index 0f63ed4fe143..10bdd8de0253 100644
--- a/arch/blackfin/Kconfig
+++ b/arch/blackfin/Kconfig
@@ -25,6 +25,8 @@ config BLACKFIN
         def_bool y
         select HAVE_ARCH_KGDB
         select HAVE_ARCH_TRACEHOOK
+        select HAVE_DYNAMIC_FTRACE
+        select HAVE_FTRACE_MCOUNT_RECORD
         select HAVE_FUNCTION_GRAPH_TRACER
         select HAVE_FUNCTION_TRACER
         select HAVE_FUNCTION_TRACE_MCOUNT_TEST
diff --git a/arch/blackfin/include/asm/ftrace.h b/arch/blackfin/include/asm/ftrace.h
index 4cfe2d9ba7e8..8a029505d7b7 100644
--- a/arch/blackfin/include/asm/ftrace.h
+++ b/arch/blackfin/include/asm/ftrace.h
@@ -12,6 +12,22 @@
 
 #ifndef __ASSEMBLY__
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+extern void _mcount(void);
+#define MCOUNT_ADDR ((unsigned long)_mcount)
+
+static inline unsigned long ftrace_call_adjust(unsigned long addr)
+{
+        return addr;
+}
+
+struct dyn_arch_ftrace {
+        /* No extra data needed for Blackfin */
+};
+
+#endif
+
 #ifdef CONFIG_FRAME_POINTER
 #include <linux/mm.h>
 
diff --git a/arch/blackfin/kernel/Makefile b/arch/blackfin/kernel/Makefile
index 30d0d1f01dc7..ca5ccc777772 100644
--- a/arch/blackfin/kernel/Makefile
+++ b/arch/blackfin/kernel/Makefile
@@ -16,6 +16,7 @@ else
     obj-y += time.o
 endif
 
+obj-$(CONFIG_DYNAMIC_FTRACE)         += ftrace.o
 obj-$(CONFIG_FUNCTION_TRACER)        += ftrace-entry.o
 obj-$(CONFIG_FUNCTION_GRAPH_TRACER)  += ftrace.o
 CFLAGS_REMOVE_ftrace.o = -pg
diff --git a/arch/blackfin/kernel/ftrace-entry.S b/arch/blackfin/kernel/ftrace-entry.S
index d66446b572c0..7eed00bbd26d 100644
--- a/arch/blackfin/kernel/ftrace-entry.S
+++ b/arch/blackfin/kernel/ftrace-entry.S
@@ -10,6 +10,18 @@
 
 .text
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+/* Simple stub so we can boot the kernel until runtime patching has
+ * disabled all calls to this.  Then it'll be unused.
+ */
+ENTRY(__mcount)
+# if ANOMALY_05000371
+        nop; nop; nop; nop;
+# endif
+        rts;
+ENDPROC(__mcount)
+
 /* GCC will have called us before setting up the function prologue, so we
  * can clobber the normal scratch registers, but we need to make sure to
  * save/restore the registers used for argument passing (R0-R2) in case
@@ -20,15 +32,65 @@
  * function.  And since GCC pushed the previous RETS for us, the previous
  * function will be waiting there.  mmmm pie.
  */
+ENTRY(_ftrace_caller)
+# ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
+        /* optional micro optimization: return if stopped */
+        p1.l = _function_trace_stop;
+        p1.h = _function_trace_stop;
+        r3 = [p1];
+        cc = r3 == 0;
+        if ! cc jump _ftrace_stub (bp);
+# endif
+
+        /* save first/second/third function arg and the return register */
+        [--sp] = r2;
+        [--sp] = r0;
+        [--sp] = r1;
+        [--sp] = rets;
+
+        /* function_trace_call(unsigned long ip, unsigned long parent_ip):
+         *  ip: this point was called by ...
+         *  parent_ip: ... this function
+         * the ip itself will need adjusting for the mcount call
+         */
+        r0 = rets;
+        r1 = [sp + 16]; /* skip the 4 local regs on stack */
+        r0 += -MCOUNT_INSN_SIZE;
+
+.globl _ftrace_call
+_ftrace_call:
+        call _ftrace_stub
+
+# ifdef CONFIG_FUNCTION_GRAPH_TRACER
+.globl _ftrace_graph_call
+_ftrace_graph_call:
+        nop;    /* jump _ftrace_graph_caller; */
+# endif
+
+        /* restore state and get out of dodge */
+.Lfinish_trace:
+        rets = [sp++];
+        r1 = [sp++];
+        r0 = [sp++];
+        r2 = [sp++];
+
+.globl _ftrace_stub
+_ftrace_stub:
+        rts;
+ENDPROC(_ftrace_caller)
+
+#else
+
+/* See documentation for _ftrace_caller */
 ENTRY(__mcount)
-#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
+# ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
         /* optional micro optimization: return if stopped */
         p1.l = _function_trace_stop;
         p1.h = _function_trace_stop;
         r3 = [p1];
         cc = r3 == 0;
         if ! cc jump _ftrace_stub (bp);
-#endif
+# endif
 
         /* save third function arg early so we can do testing below */
         [--sp] = r2;
@@ -44,7 +106,7 @@ ENTRY(__mcount)
         cc = r2 == r3;
         if ! cc jump .Ldo_trace;
 
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+# ifdef CONFIG_FUNCTION_GRAPH_TRACER
         /* if the ftrace_graph_return function pointer is not set to
          * the ftrace_stub entry, call prepare_ftrace_return().
          */
@@ -64,7 +126,7 @@ ENTRY(__mcount)
         r3 = [p0];
         cc = r2 == r3;
         if ! cc jump _ftrace_graph_caller;
-#endif
+# endif
 
         r2 = [sp++];
         rts;
@@ -103,6 +165,8 @@ _ftrace_stub:
         rts;
 ENDPROC(__mcount)
 
+#endif
+
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 /* The prepare_ftrace_return() function is similar to the trace function
  * except it takes a pointer to the location of the frompc.  This is so
@@ -110,6 +174,7 @@ ENDPROC(__mcount)
  * purposes.
  */
 ENTRY(_ftrace_graph_caller)
+# ifndef CONFIG_DYNAMIC_FTRACE
         /* save first/second function arg and the return register */
         [--sp] = r0;
         [--sp] = r1;
@@ -118,9 +183,13 @@ ENTRY(_ftrace_graph_caller)
         /* prepare_ftrace_return(parent, self_addr, frame_pointer) */
         r0 = sp;        /* unsigned long *parent */
         r1 = rets;      /* unsigned long self_addr */
-#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
+# else
+        r0 = sp;        /* unsigned long *parent */
+        r1 = [sp];      /* unsigned long self_addr */
+# endif
+# ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
         r2 = fp;        /* unsigned long frame_pointer */
-#endif
+# endif
         r0 += 16;       /* skip the 4 local regs on stack */
         r1 += -MCOUNT_INSN_SIZE;
         call _prepare_ftrace_return;
@@ -139,9 +208,9 @@ ENTRY(_return_to_handler)
         [--sp] = r1;
 
         /* get original return address */
-#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
+# ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
         r0 = fp;        /* Blackfin is sane, so omit this */
-#endif
+# endif
         call _ftrace_return_to_handler;
         rets = r0;
 
diff --git a/arch/blackfin/kernel/ftrace.c b/arch/blackfin/kernel/ftrace.c
index a61d948ea925..48808a12b427 100644
--- a/arch/blackfin/kernel/ftrace.c
+++ b/arch/blackfin/kernel/ftrace.c
@@ -1,17 +1,101 @@
 /*
  * ftrace graph code
  *
- * Copyright (C) 2009 Analog Devices Inc.
+ * Copyright (C) 2009-2010 Analog Devices Inc.
  * Licensed under the GPL-2 or later.
  */
 
 #include <linux/ftrace.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
+#include <linux/uaccess.h>
 #include <asm/atomic.h>
+#include <asm/cacheflush.h>
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+static const unsigned char mnop[] = {
+        0x03, 0xc0, 0x00, 0x18, /* MNOP; */
+        0x03, 0xc0, 0x00, 0x18, /* MNOP; */
+};
+
+static void bfin_make_pcrel24(unsigned char *insn, unsigned long src,
+                              unsigned long dst)
+{
+        uint32_t pcrel = (dst - src) >> 1;
+        insn[0] = pcrel >> 16;
+        insn[1] = 0xe3;
+        insn[2] = pcrel;
+        insn[3] = pcrel >> 8;
+}
+#define bfin_make_pcrel24(insn, src, dst) bfin_make_pcrel24(insn, src, (unsigned long)(dst))
+
+static int ftrace_modify_code(unsigned long ip, const unsigned char *code,
+                              unsigned long len)
+{
+        int ret = probe_kernel_write((void *)ip, (void *)code, len);
+        flush_icache_range(ip, ip + len);
+        return ret;
+}
+
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
+                    unsigned long addr)
+{
+        /* Turn the mcount call site into two MNOPs as those are 32bit insns */
+        return ftrace_modify_code(rec->ip, mnop, sizeof(mnop));
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+        /* Restore the mcount call site */
+        unsigned char call[8];
+        call[0] = 0x67; /* [--SP] = RETS; */
+        call[1] = 0x01;
+        bfin_make_pcrel24(&call[2], rec->ip + 2, addr);
+        call[6] = 0x27; /* RETS = [SP++]; */
+        call[7] = 0x01;
+        return ftrace_modify_code(rec->ip, call, sizeof(call));
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+        unsigned char call[4];
+        unsigned long ip = (unsigned long)&ftrace_call;
+        bfin_make_pcrel24(call, ip, func);
+        return ftrace_modify_code(ip, call, sizeof(call));
+}
+
+int __init ftrace_dyn_arch_init(void *data)
+{
+        /* return value is done indirectly via data */
+        *(unsigned long *)data = 0;
+
+        return 0;
+}
+
+#endif
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
+# ifdef CONFIG_DYNAMIC_FTRACE
+
+extern void ftrace_graph_call(void);
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+        unsigned long ip = (unsigned long)&ftrace_graph_call;
+        uint16_t jump_pcrel12 = ((unsigned long)&ftrace_graph_caller - ip) >> 1;
+        jump_pcrel12 |= 0x2000;
+        return ftrace_modify_code(ip, (void *)&jump_pcrel12, sizeof(jump_pcrel12));
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+        return ftrace_modify_code((unsigned long)&ftrace_graph_call, empty_zero_page, 2);
+}
+
+# endif
+
 /*
  * Hook the return address and push it in the stack of return addrs
  * in current thread info.