arch/csky/kernel/ftrace.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
   3
   4 #include <linux/ftrace.h>
   5 #include <linux/uaccess.h>
   6 #include <asm/cacheflush.h>
   7
   8 #ifdef CONFIG_DYNAMIC_FTRACE
   9
  10 #define NOP             0x4000
  11 #define NOP32_HI        0xc400
  12 #define NOP32_LO        0x4820
  13 #define PUSH_LR         0x14d0
  14 #define MOVIH_LINK      0xea3a
  15 #define ORI_LINK        0xef5a
  16 #define JSR_LINK        0xe8fa
  17 #define BSR_LINK        0xe000
  18
  19 /*
  20  * Gcc-csky with -pg will insert stub in function prologue:
  21  *      push    lr
  22  *      jbsr    _mcount
  23  *      nop32
  24  *      nop32
  25  *
  26  * If the (callee - current_pc) is less then 64MB, we'll use bsr:
  27  *      push    lr
  28  *      bsr     _mcount
  29  *      nop32
  30  *      nop32
  31  * else we'll use (movih + ori + jsr):
  32  *      push    lr
  33  *      movih   r26, ...
  34  *      ori     r26, ...
  35  *      jsr     r26
  36  *
  37  * (r26 is our reserved link-reg)
  38  *
  39  */
  40 static inline void make_jbsr(unsigned long callee, unsigned long pc,
  41                              uint16_t *call, bool nolr)
  42 {
  43         long offset;
  44
  45         call[0] = nolr ? NOP : PUSH_LR;
  46
  47         offset = (long) callee - (long) pc;
  48
  49         if (unlikely(offset < -67108864 || offset > 67108864)) {
  50                 call[1] = MOVIH_LINK;
  51                 call[2] = callee >> 16;
  52                 call[3] = ORI_LINK;
  53                 call[4] = callee & 0xffff;
  54                 call[5] = JSR_LINK;
  55                 call[6] = 0;
  56         } else {
  57                 offset = offset >> 1;
  58
  59                 call[1] = BSR_LINK |
  60                          ((uint16_t)((unsigned long) offset >> 16) & 0x3ff);
  61                 call[2] = (uint16_t)((unsigned long) offset & 0xffff);
  62                 call[3] = call[5] = NOP32_HI;
  63                 call[4] = call[6] = NOP32_LO;
  64         }
  65 }
  66
  67 static uint16_t nops[7] = {NOP, NOP32_HI, NOP32_LO, NOP32_HI, NOP32_LO,
  68                                 NOP32_HI, NOP32_LO};
  69 static int ftrace_check_current_nop(unsigned long hook)
  70 {
  71         uint16_t olds[7];
  72         unsigned long hook_pos = hook - 2;
  73
  74         if (probe_kernel_read((void *)olds, (void *)hook_pos, sizeof(nops)))
  75                 return -EFAULT;
  76
  77         if (memcmp((void *)nops, (void *)olds, sizeof(nops))) {
  78                 pr_err("%p: nop but get (%04x %04x %04x %04x %04x %04x %04x)\n",
  79                         (void *)hook_pos,
  80                         olds[0], olds[1], olds[2], olds[3], olds[4], olds[5],
  81                         olds[6]);
  82
  83                 return -EINVAL;
  84         }
  85
  86         return 0;
  87 }
  88
  89 static int ftrace_modify_code(unsigned long hook, unsigned long target,
  90                               bool enable, bool nolr)
  91 {
  92         uint16_t call[7];
  93
  94         unsigned long hook_pos = hook - 2;
  95         int ret = 0;
  96
  97         make_jbsr(target, hook, call, nolr);
  98
  99         ret = probe_kernel_write((void *)hook_pos, enable ? call : nops,
 100                                  sizeof(nops));
 101         if (ret)
 102                 return -EPERM;
 103
 104         flush_icache_range(hook_pos, hook_pos + MCOUNT_INSN_SIZE);
 105
 106         return 0;
 107 }
 108
 109 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 110 {
 111         int ret = ftrace_check_current_nop(rec->ip);
 112
 113         if (ret)
 114                 return ret;
 115
 116         return ftrace_modify_code(rec->ip, addr, true, false);
 117 }
 118
 119 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 120                     unsigned long addr)
 121 {
 122         return ftrace_modify_code(rec->ip, addr, false, false);
 123 }
 124
 125 int ftrace_update_ftrace_func(ftrace_func_t func)
 126 {
 127         int ret = ftrace_modify_code((unsigned long)&ftrace_call,
 128                                 (unsigned long)func, true, true);
 129         return ret;
 130 }
 131
 132 int __init ftrace_dyn_arch_init(void)
 133 {
 134         return 0;
 135 }
 136 #endif /* CONFIG_DYNAMIC_FTRACE */
 137
 138 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 139 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 140                            unsigned long frame_pointer)
 141 {
 142         unsigned long return_hooker = (unsigned long)&return_to_handler;
 143         unsigned long old;
 144
 145         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 146                 return;
 147
 148         old = *parent;
 149
 150         if (!function_graph_enter(old, self_addr,
 151                         *(unsigned long *)frame_pointer, parent)) {
 152                 /*
 153                  * For csky-gcc function has sub-call:
 154                  * subi sp,     sp, 8
 155                  * stw  r8,     (sp, 0)
 156                  * mov  r8,     sp
 157                  * st.w r15,    (sp, 0x4)
 158                  * push r15
 159                  * jl   _mcount
 160                  * We only need set *parent for resume
 161                  *
 162                  * For csky-gcc function has no sub-call:
 163                  * subi sp,     sp, 4
 164                  * stw  r8,     (sp, 0)
 165                  * mov  r8,     sp
 166                  * push r15
 167                  * jl   _mcount
 168                  * We need set *parent and *(frame_pointer + 4) for resume,
 169                  * because lr is resumed twice.
 170                  */
 171                 *parent = return_hooker;
 172                 frame_pointer += 4;
 173                 if (*(unsigned long *)frame_pointer == old)
 174                         *(unsigned long *)frame_pointer = return_hooker;
 175         }
 176 }
 177
 178 #ifdef CONFIG_DYNAMIC_FTRACE
 179 int ftrace_enable_ftrace_graph_caller(void)
 180 {
 181         return ftrace_modify_code((unsigned long)&ftrace_graph_call,
 182                         (unsigned long)&ftrace_graph_caller, true, true);
 183 }
 184
 185 int ftrace_disable_ftrace_graph_caller(void)
 186 {
 187         return ftrace_modify_code((unsigned long)&ftrace_graph_call,
 188                         (unsigned long)&ftrace_graph_caller, false, true);
 189 }
 190 #endif /* CONFIG_DYNAMIC_FTRACE */
 191 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 192
 193 /* _mcount is defined in abi's mcount.S */
 194 EXPORT_SYMBOL(_mcount);