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