arch/sparc/kernel/ftrace.c

   1 #include <linux/spinlock.h>
   2 #include <linux/hardirq.h>
   3 #include <linux/ftrace.h>
   4 #include <linux/percpu.h>
   5 #include <linux/init.h>
   6 #include <linux/list.h>
   7
   8 #include <asm/ftrace.h>
   9
  10 static const u32 ftrace_nop = 0x01000000;
  11
  12 unsigned char *ftrace_nop_replace(void)
  13 {
  14         return (char *)&ftrace_nop;
  15 }
  16
  17 unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
  18 {
  19         static u32 call;
  20         s32 off;
  21
  22         off = ((s32)addr - (s32)ip);
  23         call = 0x40000000 | ((u32)off >> 2);
  24
  25         return (unsigned char *) &call;
  26 }
  27
  28 int
  29 ftrace_modify_code(unsigned long ip, unsigned char *old_code,
  30                    unsigned char *new_code)
  31 {
  32         u32 old = *(u32 *)old_code;
  33         u32 new = *(u32 *)new_code;
  34         u32 replaced;
  35         int faulted;
  36
  37         __asm__ __volatile__(
  38         "1:     cas     [%[ip]], %[old], %[new]\n"
  39         "       flush   %[ip]\n"
  40         "       mov     0, %[faulted]\n"
  41         "2:\n"
  42         "       .section .fixup,#alloc,#execinstr\n"
  43         "       .align  4\n"
  44         "3:     sethi   %%hi(2b), %[faulted]\n"
  45         "       jmpl    %[faulted] + %%lo(2b), %%g0\n"
  46         "        mov    1, %[faulted]\n"
  47         "       .previous\n"
  48         "       .section __ex_table,\"a\"\n"
  49         "       .align  4\n"
  50         "       .word   1b, 3b\n"
  51         "       .previous\n"
  52         : "=r" (replaced), [faulted] "=r" (faulted)
  53         : [new] "0" (new), [old] "r" (old), [ip] "r" (ip)
  54         : "memory");
  55
  56         if (replaced != old && replaced != new)
  57                 faulted = 2;
  58
  59         return faulted;
  60 }
  61
  62 int ftrace_update_ftrace_func(ftrace_func_t func)
  63 {
  64         unsigned long ip = (unsigned long)(&ftrace_call);
  65         unsigned char old[MCOUNT_INSN_SIZE], *new;
  66
  67         memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
  68         new = ftrace_call_replace(ip, (unsigned long)func);
  69         return ftrace_modify_code(ip, old, new);
  70 }
  71
  72 int __init ftrace_dyn_arch_init(void *data)
  73 {
  74         ftrace_mcount_set(data);
  75         return 0;
  76 }