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 } 116