tools/perf/arch/x86/util/dwarf-regs.c

   1 /*
   2  * dwarf-regs.c : Mapping of DWARF debug register numbers into register names.
   3  * Extracted from probe-finder.c
   4  *
   5  * Written by Masami Hiramatsu <mhiramat@redhat.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  20  *
  21  */
  22
  23 #include <stddef.h>
  24 #include <errno.h> /* for EINVAL */
  25 #include <string.h> /* for strcmp */
  26 #include <linux/ptrace.h> /* for struct pt_regs */
  27 #include <linux/kernel.h> /* for offsetof */
  28 #include <dwarf-regs.h>
  29
  30 /*
  31  * See arch/x86/kernel/ptrace.c.
  32  * Different from it:
  33  *
  34  *  - Since struct pt_regs is defined differently for user and kernel,
  35  *    but we want to use 'ax, bx' instead of 'rax, rbx' (which is struct
  36  *    field name of user's pt_regs), we make REG_OFFSET_NAME to accept
  37  *    both string name and reg field name.
  38  *
  39  *  - Since accessing x86_32's pt_regs from x86_64 building is difficult
  40  *    and vise versa, we simply fill offset with -1, so
  41  *    get_arch_regstr() still works but regs_query_register_offset()
  42  *    returns error.
  43  *    The only inconvenience caused by it now is that we are not allowed
  44  *    to generate BPF prologue for a x86_64 kernel if perf is built for
  45  *    x86_32. This is really a rare usecase.
  46  *
  47  *  - Order is different from kernel's ptrace.c for get_arch_regstr(). Use
  48  *    the order defined by dwarf.
  49  */
  50
  51 struct pt_regs_offset {
  52         const char *name;
  53         int offset;
  54 };
  55
  56 #define REG_OFFSET_END {.name = NULL, .offset = 0}
  57
  58 #ifdef __x86_64__
  59 # define REG_OFFSET_NAME_64(n, r) {.name = n, .offset = offsetof(struct pt_regs, r)}
  60 # define REG_OFFSET_NAME_32(n, r) {.name = n, .offset = -1}
  61 #else
  62 # define REG_OFFSET_NAME_64(n, r) {.name = n, .offset = -1}
  63 # define REG_OFFSET_NAME_32(n, r) {.name = n, .offset = offsetof(struct pt_regs, r)}
  64 #endif
  65
  66 static const struct pt_regs_offset x86_32_regoffset_table[] = {
  67         REG_OFFSET_NAME_32("%ax",       eax),
  68         REG_OFFSET_NAME_32("%cx",       ecx),
  69         REG_OFFSET_NAME_32("%dx",       edx),
  70         REG_OFFSET_NAME_32("%bx",       ebx),
  71         REG_OFFSET_NAME_32("$stack",    esp),   /* Stack address instead of %sp */
  72         REG_OFFSET_NAME_32("%bp",       ebp),
  73         REG_OFFSET_NAME_32("%si",       esi),
  74         REG_OFFSET_NAME_32("%di",       edi),
  75         REG_OFFSET_END,
  76 };
  77
  78 static const struct pt_regs_offset x86_64_regoffset_table[] = {
  79         REG_OFFSET_NAME_64("%ax",       rax),
  80         REG_OFFSET_NAME_64("%dx",       rdx),
  81         REG_OFFSET_NAME_64("%cx",       rcx),
  82         REG_OFFSET_NAME_64("%bx",       rbx),
  83         REG_OFFSET_NAME_64("%si",       rsi),
  84         REG_OFFSET_NAME_64("%di",       rdi),
  85         REG_OFFSET_NAME_64("%bp",       rbp),
  86         REG_OFFSET_NAME_64("%sp",       rsp),
  87         REG_OFFSET_NAME_64("%r8",       r8),
  88         REG_OFFSET_NAME_64("%r9",       r9),
  89         REG_OFFSET_NAME_64("%r10",      r10),
  90         REG_OFFSET_NAME_64("%r11",      r11),
  91         REG_OFFSET_NAME_64("%r12",      r12),
  92         REG_OFFSET_NAME_64("%r13",      r13),
  93         REG_OFFSET_NAME_64("%r14",      r14),
  94         REG_OFFSET_NAME_64("%r15",      r15),
  95         REG_OFFSET_END,
  96 };
  97
  98 /* TODO: switching by dwarf address size */
  99 #ifdef __x86_64__
 100 #define regoffset_table x86_64_regoffset_table
 101 #else
 102 #define regoffset_table x86_32_regoffset_table
 103 #endif
 104
 105 /* Minus 1 for the ending REG_OFFSET_END */
 106 #define ARCH_MAX_REGS ((sizeof(regoffset_table) / sizeof(regoffset_table[0])) - 1)
 107
 108 /* Return architecture dependent register string (for kprobe-tracer) */
 109 const char *get_arch_regstr(unsigned int n)
 110 {
 111         return (n < ARCH_MAX_REGS) ? regoffset_table[n].name : NULL;
 112 }
 113
 114 /* Reuse code from arch/x86/kernel/ptrace.c */
 115 /**
 116  * regs_query_register_offset() - query register offset from its name
 117  * @name:       the name of a register
 118  *
 119  * regs_query_register_offset() returns the offset of a register in struct
 120  * pt_regs from its name. If the name is invalid, this returns -EINVAL;
 121  */
 122 int regs_query_register_offset(const char *name)
 123 {
 124         const struct pt_regs_offset *roff;
 125         for (roff = regoffset_table; roff->name != NULL; roff++)
 126                 if (!strcmp(roff->name, name))
 127                         return roff->offset;
 128         return -EINVAL;
 129 }