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 <linux/stop_machine.h>
   7 #include <asm/cacheflush.h>
   8
   9 #ifdef CONFIG_DYNAMIC_FTRACE
  10
  11 #define NOP             0x4000
  12 #define NOP32_HI        0xc400
  13 #define NOP32_LO        0x4820
  14 #define PUSH_LR         0x14d0
  15 #define MOVIH_LINK      0xea3a
  16 #define ORI_LINK        0xef5a
  17 #define JSR_LINK        0xe8fa
  18 #define BSR_LINK        0xe000
  19
  20 /*
  21  * Gcc-csky with -pg will insert stub in function prologue:
  22  *      push    lr
  23  *      jbsr    _mcount
  24  *      nop32
  25  *      nop32
  26  *
  27  * If the (callee - current_pc) is less then 64MB, we'll use bsr:
  28  *      push    lr
  29  *      bsr     _mcount
  30  *      nop32
  31  *      nop32
  32  * else we'll use (movih + ori + jsr):
  33  *      push    lr
  34  *      movih   r26, ...
  35  *      ori     r26, ...
  36  *      jsr     r26
  37  *
  38  * (r26 is our reserved link-reg)
  39  *
  40  */
  41 static inline void make_jbsr(unsigned long callee, unsigned long pc,
  42                              uint16_t *call, bool nolr)
  43 {
  44         long offset;
  45
  46         call[0] = nolr ? NOP : PUSH_LR;
  47
  48         offset = (long) callee - (long) pc;
  49
  50         if (unlikely(offset < -67108864 || offset > 67108864)) {
  51                 call[1] = MOVIH_LINK;
  52                 call[2] = callee >> 16;
  53                 call[3] = ORI_LINK;
  54                 call[4] = callee & 0xffff;
  55                 call[5] = JSR_LINK;
  56                 call[6] = 0;
  57         } else {
  58                 offset = offset >> 1;
  59
  60                 call[1] = BSR_LINK |
  61                          ((uint16_t)((unsigned long) offset >> 16) & 0x3ff);
  62                 call[2] = (uint16_t)((unsigned long) offset & 0xffff);
  63                 call[3] = call[5] = NOP32_HI;
  64                 call[4] = call[6] = NOP32_LO;
  65         }
  66 }
  67
  68 static uint16_t nops[7] = {NOP, NOP32_HI, NOP32_LO, NOP32_HI, NOP32_LO,
  69                                 NOP32_HI, NOP32_LO};
  70 static int ftrace_check_current_nop(unsigned long hook)
  71 {
  72         uint16_t olds[7];
  73         unsigned long hook_pos = hook - 2;
  74
  75         if (probe_kernel_read((void *)olds, (void *)hook_pos, sizeof(nops)))
  76                 return -EFAULT;
  77
  78         if (memcmp((void *)nops, (void *)olds, sizeof(nops))) {
  79                 pr_err("%p: nop but get (%04x %04x %04x %04x %04x %04x %04x)\n",
  80                         (void *)hook_pos,
  81                         olds[0], olds[1], olds[2], olds[3], olds[4], olds[5],
  82                         olds[6]);
  83
  84                 return -EINVAL;
  85         }
  86
  87         return 0;
  88 }
  89
  90 static int ftrace_modify_code(unsigned long hook, unsigned long target,
  91                               bool enable, bool nolr)
  92 {
  93         uint16_t call[7];
  94
  95         unsigned long hook_pos = hook - 2;
  96         int ret = 0;
  97
  98         make_jbsr(target, hook, call, nolr);
  99
 100         ret = probe_kernel_write((void *)hook_pos, enable ? call : nops,
 101                                  sizeof(nops));
 102         if (ret)
 103                 return -EPERM;
 104
 105         flush_icache_range(hook_pos, hook_pos + MCOUNT_INSN_SIZE);
 106
 107         return 0;
 108 }
 109
 110 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 111 {
 112         int ret = ftrace_check_current_nop(rec->ip);
 113
 114         if (ret)
 115                 return ret;
 116
 117         return ftrace_modify_code(rec->ip, addr, true, false);
 118 }
 119
 120 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 121                     unsigned long addr)
 122 {
 123         return ftrace_modify_code(rec->ip, addr, false, false);
 124 }
 125
 126 int ftrace_update_ftrace_func(ftrace_func_t func)
 127 {
 128         int ret = ftrace_modify_code((unsigned long)&ftrace_call,
 129                                 (unsigned long)func, true, true);
 130         if (!ret)
 131                 ret = ftrace_modify_code((unsigned long)&ftrace_regs_call,
 132                                 (unsigned long)func, true, true);
 133         return ret;
 134 }
 135
 136 int __init ftrace_dyn_arch_init(void)
 137 {
 138         return 0;
 139 }
 140 #endif /* CONFIG_DYNAMIC_FTRACE */
 141
 142 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 143 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 144                        unsigned long addr)
 145 {
 146         return ftrace_modify_code(rec->ip, addr, true, true);
 147 }
 148 #endif
 149
 150 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 151 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 152                            unsigned long frame_pointer)
 153 {
 154         unsigned long return_hooker = (unsigned long)&return_to_handler;
 155         unsigned long old;
 156
 157         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 158                 return;
 159
 160         old = *parent;
 161
 162         if (!function_graph_enter(old, self_addr,
 163                         *(unsigned long *)frame_pointer, parent)) {
 164                 /*
 165                  * For csky-gcc function has sub-call:
 166                  * subi sp,     sp, 8
 167                  * stw  r8,     (sp, 0)
 168                  * mov  r8,     sp
 169                  * st.w r15,    (sp, 0x4)
 170                  * push r15
 171                  * jl   _mcount
 172                  * We only need set *parent for resume
 173                  *
 174                  * For csky-gcc function has no sub-call:
 175                  * subi sp,     sp, 4
 176                  * stw  r8,     (sp, 0)
 177                  * mov  r8,     sp
 178                  * push r15
 179                  * jl   _mcount
 180                  * We need set *parent and *(frame_pointer + 4) for resume,
 181                  * because lr is resumed twice.
 182                  */
 183                 *parent = return_hooker;
 184                 frame_pointer += 4;
 185                 if (*(unsigned long *)frame_pointer == old)
 186                         *(unsigned long *)frame_pointer = return_hooker;
 187         }
 188 }
 189
 190 #ifdef CONFIG_DYNAMIC_FTRACE
 191 int ftrace_enable_ftrace_graph_caller(void)
 192 {
 193         return ftrace_modify_code((unsigned long)&ftrace_graph_call,
 194                         (unsigned long)&ftrace_graph_caller, true, true);
 195 }
 196
 197 int ftrace_disable_ftrace_graph_caller(void)
 198 {
 199         return ftrace_modify_code((unsigned long)&ftrace_graph_call,
 200                         (unsigned long)&ftrace_graph_caller, false, true);
 201 }
 202 #endif /* CONFIG_DYNAMIC_FTRACE */
 203 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 204
 205 #ifdef CONFIG_DYNAMIC_FTRACE
 206 #ifndef CONFIG_CPU_HAS_ICACHE_INS
 207 struct ftrace_modify_param {
 208         int command;
 209         atomic_t cpu_count;
 210 };
 211
 212 static int __ftrace_modify_code(void *data)
 213 {
 214         struct ftrace_modify_param *param = data;
 215
 216         if (atomic_inc_return(&param->cpu_count) == 1) {
 217                 ftrace_modify_all_code(param->command);
 218                 atomic_inc(&param->cpu_count);
 219         } else {
 220                 while (atomic_read(&param->cpu_count) <= num_online_cpus())
 221                         cpu_relax();
 222                 local_icache_inv_all(NULL);
 223         }
 224
 225         return 0;
 226 }
 227
 228 void arch_ftrace_update_code(int command)
 229 {
 230         struct ftrace_modify_param param = { command, ATOMIC_INIT(0) };
 231
 232         stop_machine(__ftrace_modify_code, &param, cpu_online_mask);
 233 }
 234 #endif
 235 #endif /* CONFIG_DYNAMIC_FTRACE */
 236
 237 /* _mcount is defined in abi's mcount.S */
 238 EXPORT_SYMBOL(_mcount);