linux/arch/arm/probes/uprobes/core.c
Fredrik Strupe d2f7eca60b ARM: 9071/1: uprobes: Don't hook on thumb instructions
Since uprobes is not supported for thumb, check that the thumb bit is
not set when matching the uprobes instruction hooks.

The Arm UDF instructions used for uprobes triggering
(UPROBE_SWBP_ARM_INSN and UPROBE_SS_ARM_INSN) coincidentally share the
same encoding as a pair of unallocated 32-bit thumb instructions (not
UDF) when the condition code is 0b1111 (0xf). This in effect makes it
possible to trigger the uprobes functionality from thumb, and at that
using two unallocated instructions which are not permanently undefined.

Signed-off-by: Fredrik Strupe <fredrik@strupe.net>
Cc: stable@vger.kernel.org
Fixes: c7edc9e326 ("ARM: add uprobes support")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
2021-04-18 19:14:45 +01:00

228 lines
5.0 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2012 Rabin Vincent <rabin at rab.in>
*/
#include <linux/kernel.h>
#include <linux/stddef.h>
#include <linux/errno.h>
#include <linux/highmem.h>
#include <linux/sched.h>
#include <linux/uprobes.h>
#include <linux/notifier.h>
#include <asm/opcodes.h>
#include <asm/traps.h>
#include "../decode.h"
#include "../decode-arm.h"
#include "core.h"
#define UPROBE_TRAP_NR UINT_MAX
bool is_swbp_insn(uprobe_opcode_t *insn)
{
return (__mem_to_opcode_arm(*insn) & 0x0fffffff) ==
(UPROBE_SWBP_ARM_INSN & 0x0fffffff);
}
int set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm,
unsigned long vaddr)
{
return uprobe_write_opcode(auprobe, mm, vaddr,
__opcode_to_mem_arm(auprobe->bpinsn));
}
bool arch_uprobe_ignore(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
if (!auprobe->asi.insn_check_cc(regs->ARM_cpsr)) {
regs->ARM_pc += 4;
return true;
}
return false;
}
bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
probes_opcode_t opcode;
if (!auprobe->simulate)
return false;
opcode = __mem_to_opcode_arm(*(unsigned int *) auprobe->insn);
auprobe->asi.insn_singlestep(opcode, &auprobe->asi, regs);
return true;
}
unsigned long
arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
struct pt_regs *regs)
{
unsigned long orig_ret_vaddr;
orig_ret_vaddr = regs->ARM_lr;
/* Replace the return addr with trampoline addr */
regs->ARM_lr = trampoline_vaddr;
return orig_ret_vaddr;
}
int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
unsigned long addr)
{
unsigned int insn;
unsigned int bpinsn;
enum probes_insn ret;
/* Thumb not yet support */
if (addr & 0x3)
return -EINVAL;
insn = __mem_to_opcode_arm(*(unsigned int *)auprobe->insn);
auprobe->ixol[0] = __opcode_to_mem_arm(insn);
auprobe->ixol[1] = __opcode_to_mem_arm(UPROBE_SS_ARM_INSN);
ret = arm_probes_decode_insn(insn, &auprobe->asi, false,
uprobes_probes_actions, NULL);
switch (ret) {
case INSN_REJECTED:
return -EINVAL;
case INSN_GOOD_NO_SLOT:
auprobe->simulate = true;
break;
case INSN_GOOD:
default:
break;
}
bpinsn = UPROBE_SWBP_ARM_INSN & 0x0fffffff;
if (insn >= 0xe0000000)
bpinsn |= 0xe0000000; /* Unconditional instruction */
else
bpinsn |= insn & 0xf0000000; /* Copy condition from insn */
auprobe->bpinsn = bpinsn;
return 0;
}
void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
void *src, unsigned long len)
{
void *xol_page_kaddr = kmap_atomic(page);
void *dst = xol_page_kaddr + (vaddr & ~PAGE_MASK);
preempt_disable();
/* Initialize the slot */
memcpy(dst, src, len);
/* flush caches (dcache/icache) */
flush_uprobe_xol_access(page, vaddr, dst, len);
preempt_enable();
kunmap_atomic(xol_page_kaddr);
}
int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
if (auprobe->prehandler)
auprobe->prehandler(auprobe, &utask->autask, regs);
utask->autask.saved_trap_no = current->thread.trap_no;
current->thread.trap_no = UPROBE_TRAP_NR;
regs->ARM_pc = utask->xol_vaddr;
return 0;
}
int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
WARN_ON_ONCE(current->thread.trap_no != UPROBE_TRAP_NR);
current->thread.trap_no = utask->autask.saved_trap_no;
regs->ARM_pc = utask->vaddr + 4;
if (auprobe->posthandler)
auprobe->posthandler(auprobe, &utask->autask, regs);
return 0;
}
bool arch_uprobe_xol_was_trapped(struct task_struct *t)
{
if (t->thread.trap_no != UPROBE_TRAP_NR)
return true;
return false;
}
void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
current->thread.trap_no = utask->autask.saved_trap_no;
instruction_pointer_set(regs, utask->vaddr);
}
int arch_uprobe_exception_notify(struct notifier_block *self,
unsigned long val, void *data)
{
return NOTIFY_DONE;
}
static int uprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
{
unsigned long flags;
local_irq_save(flags);
instr &= 0x0fffffff;
if (instr == (UPROBE_SWBP_ARM_INSN & 0x0fffffff))
uprobe_pre_sstep_notifier(regs);
else if (instr == (UPROBE_SS_ARM_INSN & 0x0fffffff))
uprobe_post_sstep_notifier(regs);
local_irq_restore(flags);
return 0;
}
unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
{
return instruction_pointer(regs);
}
static struct undef_hook uprobes_arm_break_hook = {
.instr_mask = 0x0fffffff,
.instr_val = (UPROBE_SWBP_ARM_INSN & 0x0fffffff),
.cpsr_mask = (PSR_T_BIT | MODE_MASK),
.cpsr_val = USR_MODE,
.fn = uprobe_trap_handler,
};
static struct undef_hook uprobes_arm_ss_hook = {
.instr_mask = 0x0fffffff,
.instr_val = (UPROBE_SS_ARM_INSN & 0x0fffffff),
.cpsr_mask = (PSR_T_BIT | MODE_MASK),
.cpsr_val = USR_MODE,
.fn = uprobe_trap_handler,
};
static int arch_uprobes_init(void)
{
register_undef_hook(&uprobes_arm_break_hook);
register_undef_hook(&uprobes_arm_ss_hook);
return 0;
}
device_initcall(arch_uprobes_init);