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-rw-r--r--arch/powerpc/kernel/optprobes.c304
1 files changed, 304 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
new file mode 100644
index 000000000..3b1c2236c
--- /dev/null
+++ b/arch/powerpc/kernel/optprobes.c
@@ -0,0 +1,304 @@
+// 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(&regs, 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, &regs, ppc_inst_read(p->ainsn.insn)) == 1) {
+ emulate_update_regs(&regs, &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_no_resched();
+}
+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);
+}