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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* dwarf-regs.c : Mapping of DWARF debug register numbers into register names.
* Extracted from probe-finder.c
*
* Written by Masami Hiramatsu <mhiramat@redhat.com>
*/
#include <stddef.h>
#include <errno.h> /* for EINVAL */
#include <string.h> /* for strcmp */
#include <linux/ptrace.h> /* for struct pt_regs */
#include <linux/kernel.h> /* for offsetof */
#include <dwarf-regs.h>
/*
* See arch/x86/kernel/ptrace.c.
* Different from it:
*
* - Since struct pt_regs is defined differently for user and kernel,
* but we want to use 'ax, bx' instead of 'rax, rbx' (which is struct
* field name of user's pt_regs), we make REG_OFFSET_NAME to accept
* both string name and reg field name.
*
* - Since accessing x86_32's pt_regs from x86_64 building is difficult
* and vise versa, we simply fill offset with -1, so
* get_arch_regstr() still works but regs_query_register_offset()
* returns error.
* The only inconvenience caused by it now is that we are not allowed
* to generate BPF prologue for a x86_64 kernel if perf is built for
* x86_32. This is really a rare usecase.
*
* - Order is different from kernel's ptrace.c for get_arch_regstr(). Use
* the order defined by dwarf.
*/
struct pt_regs_offset {
const char *name;
int offset;
};
#define REG_OFFSET_END {.name = NULL, .offset = 0}
#ifdef __x86_64__
# define REG_OFFSET_NAME_64(n, r) {.name = n, .offset = offsetof(struct pt_regs, r)}
# define REG_OFFSET_NAME_32(n, r) {.name = n, .offset = -1}
#else
# define REG_OFFSET_NAME_64(n, r) {.name = n, .offset = -1}
# define REG_OFFSET_NAME_32(n, r) {.name = n, .offset = offsetof(struct pt_regs, r)}
#endif
/* TODO: switching by dwarf address size */
#ifndef __x86_64__
static const struct pt_regs_offset x86_32_regoffset_table[] = {
REG_OFFSET_NAME_32("%ax", eax),
REG_OFFSET_NAME_32("%cx", ecx),
REG_OFFSET_NAME_32("%dx", edx),
REG_OFFSET_NAME_32("%bx", ebx),
REG_OFFSET_NAME_32("$stack", esp), /* Stack address instead of %sp */
REG_OFFSET_NAME_32("%bp", ebp),
REG_OFFSET_NAME_32("%si", esi),
REG_OFFSET_NAME_32("%di", edi),
REG_OFFSET_END,
};
#define regoffset_table x86_32_regoffset_table
#else
static const struct pt_regs_offset x86_64_regoffset_table[] = {
REG_OFFSET_NAME_64("%ax", rax),
REG_OFFSET_NAME_64("%dx", rdx),
REG_OFFSET_NAME_64("%cx", rcx),
REG_OFFSET_NAME_64("%bx", rbx),
REG_OFFSET_NAME_64("%si", rsi),
REG_OFFSET_NAME_64("%di", rdi),
REG_OFFSET_NAME_64("%bp", rbp),
REG_OFFSET_NAME_64("%sp", rsp),
REG_OFFSET_NAME_64("%r8", r8),
REG_OFFSET_NAME_64("%r9", r9),
REG_OFFSET_NAME_64("%r10", r10),
REG_OFFSET_NAME_64("%r11", r11),
REG_OFFSET_NAME_64("%r12", r12),
REG_OFFSET_NAME_64("%r13", r13),
REG_OFFSET_NAME_64("%r14", r14),
REG_OFFSET_NAME_64("%r15", r15),
REG_OFFSET_END,
};
#define regoffset_table x86_64_regoffset_table
#endif
/* Minus 1 for the ending REG_OFFSET_END */
#define ARCH_MAX_REGS ((sizeof(regoffset_table) / sizeof(regoffset_table[0])) - 1)
/* Return architecture dependent register string (for kprobe-tracer) */
const char *get_arch_regstr(unsigned int n)
{
return (n < ARCH_MAX_REGS) ? regoffset_table[n].name : NULL;
}
/* Reuse code from arch/x86/kernel/ptrace.c */
/**
* regs_query_register_offset() - query register offset from its name
* @name: the name of a register
*
* regs_query_register_offset() returns the offset of a register in struct
* pt_regs from its name. If the name is invalid, this returns -EINVAL;
*/
int regs_query_register_offset(const char *name)
{
const struct pt_regs_offset *roff;
for (roff = regoffset_table; roff->name != NULL; roff++)
if (!strcmp(roff->name, name))
return roff->offset;
return -EINVAL;
}
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