// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Code for Kernel probes Jump optimization.
*
* Copyright 2017, Anju T, IBM Corp.
*/
#include <linux/kprobes.h>
#include <linux/jump_label.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <asm/kprobes.h>
#include <asm/ptrace.h>
#include <asm/cacheflush.h>
#include <asm/code-patching.h>
#include <asm/sstep.h>
#include <asm/ppc-opcode.h>
#include <asm/inst.h>
#define TMPL_CALL_HDLR_IDX (optprobe_template_call_handler - optprobe_template_entry)
#define TMPL_EMULATE_IDX (optprobe_template_call_emulate - optprobe_template_entry)
#define TMPL_RET_IDX (optprobe_template_ret - optprobe_template_entry)
#define TMPL_OP_IDX (optprobe_template_op_address - optprobe_template_entry)
#define TMPL_INSN_IDX (optprobe_template_insn - optprobe_template_entry)
#define TMPL_END_IDX (optprobe_template_end - optprobe_template_entry)
static bool insn_page_in_use;
void *alloc_optinsn_page(void)
{
if (insn_page_in_use)
return NULL;
insn_page_in_use = true;
return &optinsn_slot;
}
void free_optinsn_page(void *page)
{
insn_page_in_use = false;
}
/*
* Check if we can optimize this probe. Returns NIP post-emulation if this can
* be optimized and 0 otherwise.
*/
static unsigned long can_optimize(struct kprobe *p)
{
struct pt_regs regs;
struct instruction_op op;
unsigned long nip = 0;
unsigned long addr = (unsigned long)p->addr;
/*
* kprobe placed for kretprobe during boot time
* has a 'nop' instruction, which can be emulated.
* So further checks can be skipped.
*/
if (p->addr == (kprobe_opcode_t *)&__kretprobe_trampoline)
return addr + sizeof(kprobe_opcode_t);
/*
* We only support optimizing kernel addresses, but not
* module addresses.
*
* FIXME: Optimize kprobes placed in module addresses.
*/
if (!is_kernel_addr(addr))
return 0;
memset(®s, 0, sizeof(struct pt_regs));
regs.nip = addr;
regs.trap = 0x0;
regs.msr = MSR_KERNEL;
/*
* Kprobe placed in conditional branch instructions are
* not optimized, as we can't predict the nip prior with
* dummy pt_regs and can not ensure that the return branch
* from detour buffer falls in the range of address (i.e 32MB).
* A branch back from trampoline is set up in the detour buffer
* to the nip returned by the analyse_instr() here.
*
* Ensure that the instruction is not a conditional branch,
* and that can be emulated.
*/
if (!is_conditional_branch(ppc_inst_read(p->ainsn.insn)) &&
analyse_instr(&op, ®s, ppc_inst_read(p->ainsn.insn)) == 1) {
emulate_update_regs(®s, &op);
nip = regs.nip;
}
return nip;
}
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 {
__this_cpu_write(current_kprobe, &op->kp);
regs_set_return_ip(regs, (unsigned long)op->kp.addr);
get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
opt_pre_handler(&op->kp, regs);
__this_cpu_write(current_kprobe, NULL);
}
preempt_enable();
}
NOKPROBE_SYMBOL(optimized_callback);
void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
{
if (op->optinsn.insn) {
free_optinsn_slot(op->optinsn.insn, 1);
op->optinsn.insn = NULL;
}
}
static void patch_imm32_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr)
{
patch_instruction(addr++, ppc_inst(PPC_RAW_LIS(reg, PPC_HI(val))));
patch_instruction(addr, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_LO(val))));
}
/*
* Generate instructions to load provided immediate 64-bit value
* to register 'reg' and patch these instructions at 'addr'.
*/
static void patch_imm64_load_insns(unsigned long long val, int reg, kprobe_opcode_t *addr)
{
patch_instruction(addr++, ppc_inst(PPC_RAW_LIS(reg, PPC_HIGHEST(val))));
patch_instruction(addr++, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_HIGHER(val))));
patch_instruction(addr++, ppc_inst(PPC_RAW_SLDI(reg, reg, 32)));
patch_instruction(addr++, ppc_inst(PPC_RAW_ORIS(reg, reg, PPC_HI(val))));
patch_instruction(addr, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_LO(val))));
}
static void patch_imm_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr)
{
if (IS_ENABLED(CONFIG_PPC64))
patch_imm64_load_insns(val, reg, addr);
else
patch_imm32_load_insns(val, reg, addr);
}
int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
{
ppc_inst_t branch_op_callback, branch_emulate_step, temp;
unsigned long op_callback_addr, emulate_step_addr;
kprobe_opcode_t *buff;
long b_offset;
unsigned long nip, size;
int rc, i;
nip = can_optimize(p);
if (!nip)
return -EILSEQ;
/* Allocate instruction slot for detour buffer */
buff = get_optinsn_slot();
if (!buff)
return -ENOMEM;
/*
* OPTPROBE uses 'b' instruction to branch to optinsn.insn.
*
* The target address has to be relatively nearby, to permit use
* of branch instruction in powerpc, because the address is specified
* in an immediate field in the instruction opcode itself, ie 24 bits
* in the opcode specify the address. Therefore the address should
* be within 32MB on either side of the current instruction.
*/
b_offset = (unsigned long)buff - (unsigned long)p->addr;
if (!is_offset_in_branch_range(b_offset))
goto error;
/* Check if the return address is also within 32MB range */
b_offset = (unsigned long)(buff + TMPL_RET_IDX) - nip;
if (!is_offset_in_branch_range(b_offset))
goto error;
/* Setup template */
/* We can optimize this via patch_instruction_window later */
size = (TMPL_END_IDX * sizeof(kprobe_opcode_t)) / sizeof(int);
pr_devel("Copying template to %p, size %lu\n", buff, size);
for (i = 0; i < size; i++) {
rc = patch_instruction(buff + i, ppc_inst(*(optprobe_template_entry + i)));
if (rc < 0)
goto error;
}
/*
* Fixup the template with instructions to:
* 1. load the address of the actual probepoint
*/
patch_imm_load_insns((unsigned long)op, 3, buff + TMPL_OP_IDX);
/*
* 2. branch to optimized_callback() and emulate_step()
*/
op_callback_addr = ppc_kallsyms_lookup_name("optimized_callback");
emulate_step_addr = ppc_kallsyms_lookup_name("emulate_step");
if (!op_callback_addr || !emulate_step_addr) {
WARN(1, "Unable to lookup optimized_callback()/emulate_step()\n");
goto error;
}
rc = create_branch(&branch_op_callback, buff + TMPL_CALL_HDLR_IDX,
op_callback_addr, BRANCH_SET_LINK);
rc |= create_branch(&branch_emulate_step, buff + TMPL_EMULATE_IDX,
emulate_step_addr, BRANCH_SET_LINK);
if (rc)
goto error;
patch_instruction(buff + TMPL_CALL_HDLR_IDX, branch_op_callback);
patch_instruction(buff + TMPL_EMULATE_IDX, branch_emulate_step);
/*
* 3. load instruction to be emulated into relevant register, and
*/
temp = ppc_inst_read(p->ainsn.insn);
patch_imm_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX);
/*
* 4. branch back from trampoline
*/
patch_branch(buff + TMPL_RET_IDX, nip, 0);
flush_icache_range((unsigned long)buff, (unsigned long)(&buff[TMPL_END_IDX]));
op->optinsn.insn = buff;
return 0;
error:
free_optinsn_slot(buff, 0);
return -ERANGE;
}
int arch_prepared_optinsn(struct arch_optimized_insn *optinsn)
{
return optinsn->insn != NULL;
}
/*
* On powerpc, Optprobes always replaces one instruction (4 bytes
* aligned and 4 bytes long). It is impossible to encounter another
* kprobe in this address range. So always return 0.
*/
int arch_check_optimized_kprobe(struct optimized_kprobe *op)
{
return 0;
}
void arch_optimize_kprobes(struct list_head *oplist)
{
ppc_inst_t instr;
struct optimized_kprobe *op;
struct optimized_kprobe *tmp;
list_for_each_entry_safe(op, tmp, oplist, list) {
/*
* Backup instructions which will be replaced
* by jump address
*/
memcpy(op->optinsn.copied_insn, op->kp.addr, RELATIVEJUMP_SIZE);
create_branch(&instr, op->kp.addr, (unsigned long)op->optinsn.insn, 0);
patch_instruction(op->kp.addr, instr);
list_del_init(&op->list);
}
}
void arch_unoptimize_kprobe(struct optimized_kprobe *op)
{
arch_arm_kprobe(&op->kp);
}
void arch_unoptimize_kprobes(struct list_head *oplist, struct list_head *done_list)
{
struct optimized_kprobe *op;
struct optimized_kprobe *tmp;
list_for_each_entry_safe(op, tmp, oplist, list) {
arch_unoptimize_kprobe(op);
list_move(&op->list, done_list);
}
}
int arch_within_optimized_kprobe(struct optimized_kprobe *op, kprobe_opcode_t *addr)
{
return (op->kp.addr <= addr &&
op->kp.addr + (RELATIVEJUMP_SIZE / sizeof(kprobe_opcode_t)) > addr);
}
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