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Linux/arch/ia64/kernel/ftrace.c

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  1 /*
  2  * Dynamic function tracing support.
  3  *
  4  * Copyright (C) 2008 Shaohua Li <shaohua.li@intel.com>
  5  *
  6  * For licencing details, see COPYING.
  7  *
  8  * Defines low-level handling of mcount calls when the kernel
  9  * is compiled with the -pg flag. When using dynamic ftrace, the
 10  * mcount call-sites get patched lazily with NOP till they are
 11  * enabled. All code mutation routines here take effect atomically.
 12  */
 13 
 14 #include <linux/uaccess.h>
 15 #include <linux/ftrace.h>
 16 
 17 #include <asm/cacheflush.h>
 18 #include <asm/patch.h>
 19 
 20 /* In IA64, each function will be added below two bundles with -pg option */
 21 static unsigned char __attribute__((aligned(8)))
 22 ftrace_orig_code[MCOUNT_INSN_SIZE] = {
 23         0x02, 0x40, 0x31, 0x10, 0x80, 0x05, /* alloc r40=ar.pfs,12,8,0 */
 24         0xb0, 0x02, 0x00, 0x00, 0x42, 0x40, /* mov r43=r0;; */
 25         0x05, 0x00, 0xc4, 0x00,             /* mov r42=b0 */
 26         0x11, 0x48, 0x01, 0x02, 0x00, 0x21, /* mov r41=r1 */
 27         0x00, 0x00, 0x00, 0x02, 0x00, 0x00, /* nop.i 0x0 */
 28         0x08, 0x00, 0x00, 0x50              /* br.call.sptk.many b0 = _mcount;; */
 29 };
 30 
 31 struct ftrace_orig_insn {
 32         u64 dummy1, dummy2, dummy3;
 33         u64 dummy4:64-41+13;
 34         u64 imm20:20;
 35         u64 dummy5:3;
 36         u64 sign:1;
 37         u64 dummy6:4;
 38 };
 39 
 40 /* mcount stub will be converted below for nop */
 41 static unsigned char ftrace_nop_code[MCOUNT_INSN_SIZE] = {
 42         0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
 43         0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
 44         0x00, 0x00, 0x04, 0x00,             /* nop.i 0x0 */
 45         0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
 46         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* nop.x 0x0;; */
 47         0x00, 0x00, 0x04, 0x00
 48 };
 49 
 50 static unsigned char *ftrace_nop_replace(void)
 51 {
 52         return ftrace_nop_code;
 53 }
 54 
 55 /*
 56  * mcount stub will be converted below for call
 57  * Note: Just the last instruction is changed against nop
 58  * */
 59 static unsigned char __attribute__((aligned(8)))
 60 ftrace_call_code[MCOUNT_INSN_SIZE] = {
 61         0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
 62         0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
 63         0x00, 0x00, 0x04, 0x00,             /* nop.i 0x0 */
 64         0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
 65         0xff, 0xff, 0xff, 0xff, 0x7f, 0x00, /* brl.many .;;*/
 66         0xf8, 0xff, 0xff, 0xc8
 67 };
 68 
 69 struct ftrace_call_insn {
 70         u64 dummy1, dummy2;
 71         u64 dummy3:48;
 72         u64 imm39_l:16;
 73         u64 imm39_h:23;
 74         u64 dummy4:13;
 75         u64 imm20:20;
 76         u64 dummy5:3;
 77         u64 i:1;
 78         u64 dummy6:4;
 79 };
 80 
 81 static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
 82 {
 83         struct ftrace_call_insn *code = (void *)ftrace_call_code;
 84         unsigned long offset = addr - (ip + 0x10);
 85 
 86         code->imm39_l = offset >> 24;
 87         code->imm39_h = offset >> 40;
 88         code->imm20 = offset >> 4;
 89         code->i = offset >> 63;
 90         return ftrace_call_code;
 91 }
 92 
 93 static int
 94 ftrace_modify_code(unsigned long ip, unsigned char *old_code,
 95                    unsigned char *new_code, int do_check)
 96 {
 97         unsigned char replaced[MCOUNT_INSN_SIZE];
 98 
 99         /*
100          * Note:
101          * We are paranoid about modifying text, as if a bug was to happen, it
102          * could cause us to read or write to someplace that could cause harm.
103          * Carefully read and modify the code with probe_kernel_*(), and make
104          * sure what we read is what we expected it to be before modifying it.
105          */
106 
107         if (!do_check)
108                 goto skip_check;
109 
110         /* read the text we want to modify */
111         if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
112                 return -EFAULT;
113 
114         /* Make sure it is what we expect it to be */
115         if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
116                 return -EINVAL;
117 
118 skip_check:
119         /* replace the text with the new text */
120         if (probe_kernel_write(((void *)ip), new_code, MCOUNT_INSN_SIZE))
121                 return -EPERM;
122         flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
123 
124         return 0;
125 }
126 
127 static int ftrace_make_nop_check(struct dyn_ftrace *rec, unsigned long addr)
128 {
129         unsigned char __attribute__((aligned(8))) replaced[MCOUNT_INSN_SIZE];
130         unsigned long ip = rec->ip;
131 
132         if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
133                 return -EFAULT;
134         if (rec->flags & FTRACE_FL_CONVERTED) {
135                 struct ftrace_call_insn *call_insn, *tmp_call;
136 
137                 call_insn = (void *)ftrace_call_code;
138                 tmp_call = (void *)replaced;
139                 call_insn->imm39_l = tmp_call->imm39_l;
140                 call_insn->imm39_h = tmp_call->imm39_h;
141                 call_insn->imm20 = tmp_call->imm20;
142                 call_insn->i = tmp_call->i;
143                 if (memcmp(replaced, ftrace_call_code, MCOUNT_INSN_SIZE) != 0)
144                         return -EINVAL;
145                 return 0;
146         } else {
147                 struct ftrace_orig_insn *call_insn, *tmp_call;
148 
149                 call_insn = (void *)ftrace_orig_code;
150                 tmp_call = (void *)replaced;
151                 call_insn->sign = tmp_call->sign;
152                 call_insn->imm20 = tmp_call->imm20;
153                 if (memcmp(replaced, ftrace_orig_code, MCOUNT_INSN_SIZE) != 0)
154                         return -EINVAL;
155                 return 0;
156         }
157 }
158 
159 int ftrace_make_nop(struct module *mod,
160                     struct dyn_ftrace *rec, unsigned long addr)
161 {
162         int ret;
163         char *new;
164 
165         ret = ftrace_make_nop_check(rec, addr);
166         if (ret)
167                 return ret;
168         new = ftrace_nop_replace();
169         return ftrace_modify_code(rec->ip, NULL, new, 0);
170 }
171 
172 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
173 {
174         unsigned long ip = rec->ip;
175         unsigned char *old, *new;
176 
177         old=  ftrace_nop_replace();
178         new = ftrace_call_replace(ip, addr);
179         return ftrace_modify_code(ip, old, new, 1);
180 }
181 
182 /* in IA64, _mcount can't directly call ftrace_stub. Only jump is ok */
183 int ftrace_update_ftrace_func(ftrace_func_t func)
184 {
185         unsigned long ip;
186         unsigned long addr = ((struct fnptr *)ftrace_call)->ip;
187 
188         if (func == ftrace_stub)
189                 return 0;
190         ip = ((struct fnptr *)func)->ip;
191 
192         ia64_patch_imm64(addr + 2, ip);
193 
194         flush_icache_range(addr, addr + 16);
195         return 0;
196 }
197 
198 /* run from kstop_machine */
199 int __init ftrace_dyn_arch_init(void)
200 {
201         return 0;
202 }
203 

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