// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Kernel Probes (KProbes)
*
* Copyright (C) IBM Corporation, 2002, 2004
*
* 2002-Oct Created by Vamsi Krishna S <[email protected]> Kernel
* Probes initial implementation ( includes contributions from
* Rusty Russell).
* 2004-July Suparna Bhattacharya <[email protected]> added jumper probes
* interface to access function arguments.
* 2004-Nov Ananth N Mavinakayanahalli <[email protected]> kprobes port
* for PPC64
*/
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/preempt.h>
#include <linux/extable.h>
#include <linux/kdebug.h>
#include <linux/slab.h>
#include <linux/set_memory.h>
#include <linux/execmem.h>
#include <asm/code-patching.h>
#include <asm/cacheflush.h>
#include <asm/sstep.h>
#include <asm/sections.h>
#include <asm/inst.h>
#include <linux/uaccess.h>
DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
bool arch_within_kprobe_blacklist(unsigned long addr)
{
return (addr >= (unsigned long)__kprobes_text_start &&
addr < (unsigned long)__kprobes_text_end) ||
(addr >= (unsigned long)_stext &&
addr < (unsigned long)__head_end);
}
kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
{
kprobe_opcode_t *addr = NULL;
#ifdef CONFIG_PPC64_ELF_ABI_V2
/* PPC64 ABIv2 needs local entry point */
addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
if (addr && !offset) {
#ifdef CONFIG_KPROBES_ON_FTRACE
unsigned long faddr;
/*
* Per livepatch.h, ftrace location is always within the first
* 16 bytes of a function on powerpc with -mprofile-kernel.
*/
faddr = ftrace_location_range((unsigned long)addr,
(unsigned long)addr + 16);
if (faddr)
addr = (kprobe_opcode_t *)faddr;
else
#endif
addr = (kprobe_opcode_t *)ppc_function_entry(addr);
}
#elif defined(CONFIG_PPC64_ELF_ABI_V1)
/*
* 64bit powerpc ABIv1 uses function descriptors:
* - Check for the dot variant of the symbol first.
* - If that fails, try looking up the symbol provided.
*
* This ensures we always get to the actual symbol and not
* the descriptor.
*
* Also handle <module:symbol> format.
*/
char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
bool dot_appended = false;
const char *c;
ssize_t ret = 0;
int len = 0;
if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
c++;
len = c - name;
memcpy(dot_name, name, len);
} else
c = name;
if (*c != '\0' && *c != '.') {
dot_name[len++] = '.';
dot_appended = true;
}
ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
if (ret > 0)
addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
/* Fallback to the original non-dot symbol lookup */
if (!addr && dot_appended)
addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
#else
addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
#endif
return addr;
}
static bool arch_kprobe_on_func_entry(unsigned long offset)
{
#ifdef CONFIG_PPC64_ELF_ABI_V2
#ifdef CONFIG_KPROBES_ON_FTRACE
return offset <= 16;
#else
return offset <= 8;
#endif
#else
return !offset;
#endif
}
/* XXX try and fold the magic of kprobe_lookup_name() in this */
kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offset,
bool *on_func_entry)
{
*on_func_entry = arch_kprobe_on_func_entry(offset);
return (kprobe_opcode_t *)(addr + offset);
}
int arch_prepare_kprobe(struct kprobe *p)
{
int ret = 0;
struct kprobe *prev;
ppc_inst_t insn = ppc_inst_read(p->addr);
if ((unsigned long)p->addr & 0x03) {
printk("Attempt to register kprobe at an unaligned address\n");
ret = -EINVAL;
} else if (!can_single_step(ppc_inst_val(insn))) {
printk("Cannot register a kprobe on instructions that can't be single stepped\n");
ret = -EINVAL;
} else if ((unsigned long)p->addr & ~PAGE_MASK &&
ppc_inst_prefixed(ppc_inst_read(p->addr - 1))) {
printk("Cannot register a kprobe on the second word of prefixed instruction\n");
ret = -EINVAL;
}
prev = get_kprobe(p->addr - 1);
/*
* When prev is a ftrace-based kprobe, we don't have an insn, and it
* doesn't probe for prefixed instruction.
*/
if (prev && !kprobe_ftrace(prev) &&
ppc_inst_prefixed(ppc_inst_read(prev->ainsn.insn))) {
printk("Cannot register a kprobe on the second word of prefixed instruction\n");
ret = -EINVAL;
}
/* insn must be on a special executable page on ppc64. This is
* not explicitly required on ppc32 (right now), but it doesn't hurt */
if (!ret) {
p->ainsn.insn = get_insn_slot();
if (!p->ainsn.insn)
ret = -ENOMEM;
}
if (!ret) {
patch_instruction(p->ainsn.insn, insn);
p->opcode = ppc_inst_val(insn);
}
p->ainsn.boostable = 0;
return ret;
}
NOKPROBE_SYMBOL(arch_prepare_kprobe);
void arch_arm_kprobe(struct kprobe *p)
{
WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(BREAKPOINT_INSTRUCTION)));
}
NOKPROBE_SYMBOL(arch_arm_kprobe);
void arch_disarm_kprobe(struct kprobe *p)
{
WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(p->opcode)));
}
NOKPROBE_SYMBOL(arch_disarm_kprobe);
void arch_remove_kprobe(struct kprobe *p)
{
if (p->ainsn.insn) {
free_insn_slot(p->ainsn.insn, 0);
p->ainsn.insn = NULL;
}
}
NOKPROBE_SYMBOL(arch_remove_kprobe);
static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
enable_single_step(regs);
/*
* On powerpc we should single step on the original
* instruction even if the probed insn is a trap
* variant as values in regs could play a part in
* if the trap is taken or not
*/
regs_set_return_ip(regs, (unsigned long)p->ainsn.insn);
}
static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
{
kcb->prev_kprobe.kp = kprobe_running();
kcb->prev_kprobe.status = kcb->kprobe_status;
kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
}
static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
{
__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
kcb->kprobe_status = kcb->prev_kprobe.status;
kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
}
static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
__this_cpu_write(current_kprobe, p);
kcb->kprobe_saved_msr = regs->msr;
}
void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
{
ri->ret_addr = (kprobe_opcode_t *)regs->link;
ri->fp = NULL;
/* Replace the return addr with trampoline addr */
regs->link = (unsigned long)__kretprobe_trampoline;
}
NOKPROBE_SYMBOL(arch_prepare_kretprobe);
static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
{
int ret;
ppc_inst_t insn = ppc_inst_read(p->ainsn.insn);
/* regs->nip is also adjusted if emulate_step returns 1 */
ret = emulate_step(regs, insn);
if (ret > 0) {
/*
* Once this instruction has been boosted
* successfully, set the boostable flag
*/
if (unlikely(p->ainsn.boostable == 0))
p->ainsn.boostable = 1;
} else if (ret < 0) {
/*
* We don't allow kprobes on mtmsr(d)/rfi(d), etc.
* So, we should never get here... but, its still
* good to catch them, just in case...
*/
printk("Can't step on instruction %08lx\n", ppc_inst_as_ulong(insn));
BUG();
} else {
/*
* If we haven't previously emulated this instruction, then it
* can't be boosted. Note it down so we don't try to do so again.
*
* If, however, we had emulated this instruction in the past,
* then this is just an error with the current run (for
* instance, exceptions due to a load/store). We return 0 so
* that this is now single-stepped, but continue to try
* emulating it in subsequent probe hits.
*/
if (unlikely(p->ainsn.boostable != 1))
p->ainsn.boostable = -1;
}
return ret;
}
NOKPROBE_SYMBOL(try_to_emulate);
int kprobe_handler(struct pt_regs *regs)
{
struct kprobe *p;
int ret = 0;
unsigned int *addr = (unsigned int *)regs->nip;
struct kprobe_ctlblk *kcb;
if (user_mode(regs))
return 0;
if (!IS_ENABLED(CONFIG_BOOKE) &&
(!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)))
return 0;
/*
* We don't want to be preempted for the entire
* duration of kprobe processing
*/
preempt_disable();
kcb = get_kprobe_ctlblk();
p = get_kprobe(addr);
if (!p) {
unsigned int instr;
if (get_kernel_nofault(instr, addr))
goto no_kprobe;
if (instr != BREAKPOINT_INSTRUCTION) {
/*
* PowerPC has multiple variants of the "trap"
* instruction. If the current instruction is a
* trap variant, it could belong to someone else
*/
if (is_trap(instr))
goto no_kprobe;
/*
* The breakpoint instruction was removed right
* after we hit it. Another cpu has removed
* either a probepoint or a debugger breakpoint
* at this address. In either case, no further
* handling of this interrupt is appropriate.
*/
ret = 1;
}
/* Not one of ours: let kernel handle it */
goto no_kprobe;
}
/* Check we're not actually recursing */
if (kprobe_running()) {
kprobe_opcode_t insn = *p->ainsn.insn;
if (kcb->kprobe_status == KPROBE_HIT_SS && is_trap(insn)) {
/* Turn off 'trace' bits */
regs_set_return_msr(regs,
(regs->msr & ~MSR_SINGLESTEP) |
kcb->kprobe_saved_msr);
goto no_kprobe;
}
/*
* We have reentered the kprobe_handler(), since another probe
* was hit while within the handler. We here save the original
* kprobes variables and just single step on the instruction of
* the new probe without calling any user handlers.
*/
save_previous_kprobe(kcb);
set_current_kprobe(p, regs, kcb);
kprobes_inc_nmissed_count(p);
kcb->kprobe_status = KPROBE_REENTER;
if (p->ainsn.boostable >= 0) {
ret = try_to_emulate(p, regs);
if (ret > 0) {
restore_previous_kprobe(kcb);
preempt_enable();
return 1;
}
}
prepare_singlestep(p, regs);
return 1;
}
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
set_current_kprobe(p, regs, kcb);
if (p->pre_handler && p->pre_handler(p, regs)) {
/* handler changed execution path, so skip ss setup */
reset_current_kprobe();
preempt_enable();
return 1;
}
if (p->ainsn.boostable >= 0) {
ret = try_to_emulate(p, regs);
if (ret > 0) {
if (p->post_handler)
p->post_handler(p, regs, 0);
kcb->kprobe_status = KPROBE_HIT_SSDONE;
reset_current_kprobe();
preempt_enable();
return 1;
}
}
prepare_singlestep(p, regs);
kcb->kprobe_status = KPROBE_HIT_SS;
return 1;
no_kprobe:
preempt_enable();
return ret;
}
NOKPROBE_SYMBOL(kprobe_handler);
/*
* Function return probe trampoline:
* - init_kprobes() establishes a probepoint here
* - When the probed function returns, this probe
* causes the handlers to fire
*/
asm(".global __kretprobe_trampoline\n"
".type __kretprobe_trampoline, @function\n"
"__kretprobe_trampoline:\n"
"nop\n"
"blr\n"
".size __kretprobe_trampoline, .-__kretprobe_trampoline\n");
/*
* Called when the probe at kretprobe trampoline is hit
*/
static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
{
unsigned long orig_ret_address;
orig_ret_address = __kretprobe_trampoline_handler(regs, NULL);
/*
* We get here through one of two paths:
* 1. by taking a trap -> kprobe_handler() -> here
* 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
*
* When going back through (1), we need regs->nip to be setup properly
* as it is used to determine the return address from the trap.
* For (2), since nip is not honoured with optprobes, we instead setup
* the link register properly so that the subsequent 'blr' in
* __kretprobe_trampoline jumps back to the right instruction.
*
* For nip, we should set the address to the previous instruction since
* we end up emulating it in kprobe_handler(), which increments the nip
* again.
*/
regs_set_return_ip(regs, orig_ret_address - 4);
regs->link = orig_ret_address;
return 0;
}
NOKPROBE_SYMBOL(trampoline_probe_handler);
/*
* Called after single-stepping. p->addr is the address of the
* instruction whose first byte has been replaced by the "breakpoint"
* instruction. To avoid the SMP problems that can occur when we
* temporarily put back the original opcode to single-step, we
* single-stepped a copy of the instruction. The address of this
* copy is p->ainsn.insn.
*/
int kprobe_post_handler(struct pt_regs *regs)
{
int len;
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
if (!cur || user_mode(regs))
return 0;
len = ppc_inst_len(ppc_inst_read(cur->ainsn.insn));
/* make sure we got here for instruction we have a kprobe on */
if (((unsigned long)cur->ainsn.insn + len) != regs->nip)
return 0;
if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
kcb->kprobe_status = KPROBE_HIT_SSDONE;
cur->post_handler(cur, regs, 0);
}
/* Adjust nip to after the single-stepped instruction */
regs_set_return_ip(regs, (unsigned long)cur->addr + len);
regs_set_return_msr(regs, regs->msr | kcb->kprobe_saved_msr);
/*Restore back the original saved kprobes variables and continue. */
if (kcb->kprobe_status == KPROBE_REENTER) {
restore_previous_kprobe(kcb);
goto out;
}
reset_current_kprobe();
out:
preempt_enable();
/*
* if somebody else is singlestepping across a probe point, msr
* will have DE/SE set, in which case, continue the remaining processing
* of do_debug, as if this is not a probe hit.
*/
if (regs->msr & MSR_SINGLESTEP)
return 0;
return 1;
}
NOKPROBE_SYMBOL(kprobe_post_handler);
int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
const struct exception_table_entry *entry;
switch(kcb->kprobe_status) {
case KPROBE_HIT_SS:
case KPROBE_REENTER:
/*
* We are here because the instruction being single
* stepped caused a page fault. We reset the current
* kprobe and the nip points back to the probe address
* and allow the page fault handler to continue as a
* normal page fault.
*/
regs_set_return_ip(regs, (unsigned long)cur->addr);
/* Turn off 'trace' bits */
regs_set_return_msr(regs,
(regs->msr & ~MSR_SINGLESTEP) |
kcb->kprobe_saved_msr);
if (kcb->kprobe_status == KPROBE_REENTER)
restore_previous_kprobe(kcb);
else
reset_current_kprobe();
preempt_enable();
break;
case KPROBE_HIT_ACTIVE:
case KPROBE_HIT_SSDONE:
/*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
if ((entry = search_exception_tables(regs->nip)) != NULL) {
regs_set_return_ip(regs, extable_fixup(entry));
return 1;
}
/*
* fixup_exception() could not handle it,
* Let do_page_fault() fix it.
*/
break;
default:
break;
}
return 0;
}
NOKPROBE_SYMBOL(kprobe_fault_handler);
static struct kprobe trampoline_p = {
.addr = (kprobe_opcode_t *) &__kretprobe_trampoline,
.pre_handler = trampoline_probe_handler
};
int __init arch_init_kprobes(void)
{
return register_kprobe(&trampoline_p);
}
int arch_trampoline_kprobe(struct kprobe *p)
{
if (p->addr == (kprobe_opcode_t *)&__kretprobe_trampoline)
return 1;
return 0;
}
NOKPROBE_SYMBOL(arch_trampoline_kprobe);
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