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

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * dwarf-regs.c : Mapping of DWARF debug register numbers into register names.
   4  * Extracted from probe-finder.c
   5  *
   6  * Written by Masami Hiramatsu <mhiramat@redhat.com>
   7  */
   8
   9 #include <stddef.h>
  10 #include <errno.h> /* for EINVAL */
  11 #include <string.h> /* for strcmp */
  12 #include <linux/ptrace.h> /* for struct pt_regs */
  13 #include <linux/kernel.h> /* for offsetof */
  14 #include <dwarf-regs.h>
  15
  16 /*
  17  * See arch/x86/kernel/ptrace.c.
  18  * Different from it:
  19  *
  20  *  - Since struct pt_regs is defined differently for user and kernel,
  21  *    but we want to use 'ax, bx' instead of 'rax, rbx' (which is struct
  22  *    field name of user's pt_regs), we make REG_OFFSET_NAME to accept
  23  *    both string name and reg field name.
  24  *
  25  *  - Since accessing x86_32's pt_regs from x86_64 building is difficult
  26  *    and vise versa, we simply fill offset with -1, so
  27  *    get_arch_regstr() still works but regs_query_register_offset()
  28  *    returns error.
  29  *    The only inconvenience caused by it now is that we are not allowed
  30  *    to generate BPF prologue for a x86_64 kernel if perf is built for
  31  *    x86_32. This is really a rare usecase.
  32  *
  33  *  - Order is different from kernel's ptrace.c for get_arch_regstr(). Use
  34  *    the order defined by dwarf.
  35  */
  36
  37 struct pt_regs_offset {
  38         const char *name;
  39         int offset;
  40 };
  41
  42 #define REG_OFFSET_END {.name = NULL, .offset = 0}
  43
  44 #ifdef __x86_64__
  45 # define REG_OFFSET_NAME_64(n, r) {.name = n, .offset = offsetof(struct pt_regs, r)}
  46 # define REG_OFFSET_NAME_32(n, r) {.name = n, .offset = -1}
  47 #else
  48 # define REG_OFFSET_NAME_64(n, r) {.name = n, .offset = -1}
  49 # define REG_OFFSET_NAME_32(n, r) {.name = n, .offset = offsetof(struct pt_regs, r)}
  50 #endif
  51
  52 /* TODO: switching by dwarf address size */
  53 #ifndef __x86_64__
  54 static const struct pt_regs_offset x86_32_regoffset_table[] = {
  55         REG_OFFSET_NAME_32("%ax",       eax),
  56         REG_OFFSET_NAME_32("%cx",       ecx),
  57         REG_OFFSET_NAME_32("%dx",       edx),
  58         REG_OFFSET_NAME_32("%bx",       ebx),
  59         REG_OFFSET_NAME_32("$stack",    esp),   /* Stack address instead of %sp */
  60         REG_OFFSET_NAME_32("%bp",       ebp),
  61         REG_OFFSET_NAME_32("%si",       esi),
  62         REG_OFFSET_NAME_32("%di",       edi),
  63         REG_OFFSET_END,
  64 };
  65
  66 #define regoffset_table x86_32_regoffset_table
  67 #else
  68 static const struct pt_regs_offset x86_64_regoffset_table[] = {
  69         REG_OFFSET_NAME_64("%ax",       rax),
  70         REG_OFFSET_NAME_64("%dx",       rdx),
  71         REG_OFFSET_NAME_64("%cx",       rcx),
  72         REG_OFFSET_NAME_64("%bx",       rbx),
  73         REG_OFFSET_NAME_64("%si",       rsi),
  74         REG_OFFSET_NAME_64("%di",       rdi),
  75         REG_OFFSET_NAME_64("%bp",       rbp),
  76         REG_OFFSET_NAME_64("%sp",       rsp),
  77         REG_OFFSET_NAME_64("%r8",       r8),
  78         REG_OFFSET_NAME_64("%r9",       r9),
  79         REG_OFFSET_NAME_64("%r10",      r10),
  80         REG_OFFSET_NAME_64("%r11",      r11),
  81         REG_OFFSET_NAME_64("%r12",      r12),
  82         REG_OFFSET_NAME_64("%r13",      r13),
  83         REG_OFFSET_NAME_64("%r14",      r14),
  84         REG_OFFSET_NAME_64("%r15",      r15),
  85         REG_OFFSET_END,
  86 };
  87
  88 #define regoffset_table x86_64_regoffset_table
  89 #endif
  90
  91 /* Minus 1 for the ending REG_OFFSET_END */
  92 #define ARCH_MAX_REGS ((sizeof(regoffset_table) / sizeof(regoffset_table[0])) - 1)
  93
  94 /* Return architecture dependent register string (for kprobe-tracer) */
  95 const char *get_arch_regstr(unsigned int n)
  96 {
  97         return (n < ARCH_MAX_REGS) ? regoffset_table[n].name : NULL;
  98 }
  99
 100 /* Reuse code from arch/x86/kernel/ptrace.c */
 101 /**
 102  * regs_query_register_offset() - query register offset from its name
 103  * @name:       the name of a register
 104  *
 105  * regs_query_register_offset() returns the offset of a register in struct
 106  * pt_regs from its name. If the name is invalid, this returns -EINVAL;
 107  */
 108 int regs_query_register_offset(const char *name)
 109 {
 110         const struct pt_regs_offset *roff;
 111         for (roff = regoffset_table; roff->name != NULL; roff++)
 112                 if (!strcmp(roff->name, name))
 113                         return roff->offset;
 114         return -EINVAL;
 115 }