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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Kernel Probes Jump Optimization (Optprobes)
*
* Copyright (C) IBM Corporation, 2002, 2004
* Copyright (C) Hitachi Ltd., 2012
*/
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/hardirq.h>
#include <linux/preempt.h>
#include <linux/extable.h>
#include <linux/kdebug.h>
#include <linux/kallsyms.h>
#include <linux/ftrace.h>
#include <linux/frame.h>
#include <asm/text-patching.h>
#include <asm/cacheflush.h>
#include <asm/desc.h>
#include <asm/pgtable.h>
#include <linux/uaccess.h>
#include <asm/alternative.h>
#include <asm/insn.h>
#include <asm/debugreg.h>
#include <asm/set_memory.h>
#include <asm/sections.h>
#include <asm/nospec-branch.h>
#include "common.h"
unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
{
struct optimized_kprobe *op;
struct kprobe *kp;
long offs;
int i;
for (i = 0; i < RELATIVEJUMP_SIZE; i++) {
kp = get_kprobe((void *)addr - i);
/* This function only handles jump-optimized kprobe */
if (kp && kprobe_optimized(kp)) {
op = container_of(kp, struct optimized_kprobe, kp);
/* If op->list is not empty, op is under optimizing */
if (list_empty(&op->list))
goto found;
}
}
return addr;
found:
/*
* If the kprobe can be optimized, original bytes which can be
* overwritten by jump destination address. In this case, original
* bytes must be recovered from op->optinsn.copied_insn buffer.
*/
if (probe_kernel_read(buf, (void *)addr,
MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
return 0UL;
if (addr == (unsigned long)kp->addr) {
buf[0] = kp->opcode;
memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
} else {
offs = addr - (unsigned long)kp->addr - 1;
memcpy(buf, op->optinsn.copied_insn + offs, RELATIVE_ADDR_SIZE - offs);
}
return (unsigned long)buf;
}
/* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
static void synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)
{
#ifdef CONFIG_X86_64
*addr++ = 0x48;
*addr++ = 0xbf;
#else
*addr++ = 0xb8;
#endif
*(unsigned long *)addr = val;
}
asm (
".pushsection .rodata\n"
"optprobe_template_func:\n"
".global optprobe_template_entry\n"
"optprobe_template_entry:\n"
#ifdef CONFIG_X86_64
/* We don't bother saving the ss register */
" pushq %rsp\n"
" pushfq\n"
SAVE_REGS_STRING
" movq %rsp, %rsi\n"
".global optprobe_template_val\n"
"optprobe_template_val:\n"
ASM_NOP5
ASM_NOP5
".global optprobe_template_call\n"
"optprobe_template_call:\n"
ASM_NOP5
/* Move flags to rsp */
" movq 18*8(%rsp), %rdx\n"
" movq %rdx, 19*8(%rsp)\n"
RESTORE_REGS_STRING
/* Skip flags entry */
" addq $8, %rsp\n"
" popfq\n"
#else /* CONFIG_X86_32 */
" pushl %esp\n"
" pushfl\n"
SAVE_REGS_STRING
" movl %esp, %edx\n"
".global optprobe_template_val\n"
"optprobe_template_val:\n"
ASM_NOP5
".global optprobe_template_call\n"
"optprobe_template_call:\n"
ASM_NOP5
/* Move flags into esp */
" movl 14*4(%esp), %edx\n"
" movl %edx, 15*4(%esp)\n"
RESTORE_REGS_STRING
/* Skip flags entry */
" addl $4, %esp\n"
" popfl\n"
#endif
".global optprobe_template_end\n"
"optprobe_template_end:\n"
".popsection\n");
void optprobe_template_func(void);
STACK_FRAME_NON_STANDARD(optprobe_template_func);
#define TMPL_MOVE_IDX \
((long)optprobe_template_val - (long)optprobe_template_entry)
#define TMPL_CALL_IDX \
((long)optprobe_template_call - (long)optprobe_template_entry)
#define TMPL_END_IDX \
((long)optprobe_template_end - (long)optprobe_template_entry)
#define INT3_SIZE sizeof(kprobe_opcode_t)
/* Optimized kprobe call back function: called from optinsn */
static void
optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
{
/* This is possible if op is under delayed unoptimizing */
if (kprobe_disabled(&op->kp))
return;
preempt_disable();
if (kprobe_running()) {
kprobes_inc_nmissed_count(&op->kp);
} else {
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
/* Save skipped registers */
regs->cs = __KERNEL_CS;
#ifdef CONFIG_X86_32
regs->cs |= get_kernel_rpl();
regs->gs = 0;
#endif
regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
regs->orig_ax = ~0UL;
__this_cpu_write(current_kprobe, &op->kp);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
opt_pre_handler(&op->kp, regs);
__this_cpu_write(current_kprobe, NULL);
}
preempt_enable();
}
NOKPROBE_SYMBOL(optimized_callback);
static int copy_optimized_instructions(u8 *dest, u8 *src, u8 *real)
{
struct insn insn;
int len = 0, ret;
while (len < RELATIVEJUMP_SIZE) {
ret = __copy_instruction(dest + len, src + len, real + len, &insn);
if (!ret || !can_boost(&insn, src + len))
return -EINVAL;
len += ret;
}
/* Check whether the address range is reserved */
if (ftrace_text_reserved(src, src + len - 1) ||
alternatives_text_reserved(src, src + len - 1) ||
jump_label_text_reserved(src, src + len - 1))
return -EBUSY;
return len;
}
/* Check whether insn is indirect jump */
static int __insn_is_indirect_jump(struct insn *insn)
{
return ((insn->opcode.bytes[0] == 0xff &&
(X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
insn->opcode.bytes[0] == 0xea); /* Segment based jump */
}
/* Check whether insn jumps into specified address range */
static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
{
unsigned long target = 0;
switch (insn->opcode.bytes[0]) {
case 0xe0: /* loopne */
case 0xe1: /* loope */
case 0xe2: /* loop */
case 0xe3: /* jcxz */
case 0xe9: /* near relative jump */
case 0xeb: /* short relative jump */
break;
case 0x0f:
if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
break;
return 0;
default:
if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
break;
return 0;
}
target = (unsigned long)insn->next_byte + insn->immediate.value;
return (start <= target && target <= start + len);
}
static int insn_is_indirect_jump(struct insn *insn)
{
int ret = __insn_is_indirect_jump(insn);
#ifdef CONFIG_RETPOLINE
/*
* Jump to x86_indirect_thunk_* is treated as an indirect jump.
* Note that even with CONFIG_RETPOLINE=y, the kernel compiled with
* older gcc may use indirect jump. So we add this check instead of
* replace indirect-jump check.
*/
if (!ret)
ret = insn_jump_into_range(insn,
(unsigned long)__indirect_thunk_start,
(unsigned long)__indirect_thunk_end -
(unsigned long)__indirect_thunk_start);
#endif
return ret;
}
/* Decode whole function to ensure any instructions don't jump into target */
static int can_optimize(unsigned long paddr)
{
unsigned long addr, size = 0, offset = 0;
struct insn insn;
kprobe_opcode_t buf[MAX_INSN_SIZE];
/* Lookup symbol including addr */
if
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