--- vrfc
+++ v4
@@ -1,68 +1,125 @@
-Detour buffer contains instructions to create an in memory pt_regs.
-After the execution of prehandler a call is made for instruction emulation.
-The NIP is decided after the probed instruction is executed. Hence a branch
-instruction is created to the NIP returned by emulate_step().
+Current infrastructure of kprobe uses the unconditional trap instruction
+to probe a running kernel. Optprobe allows kprobe to replace the trap with
+a branch instruction to a detour buffer. Detour buffer contains instructions
+to create an in memory pt_regs. Detour buffer also has a call to
+optimized_callback() which in turn call the pre_handler().
+After the execution of the pre-handler, a call is made for instruction
+emulation. The NIP is determined in advanced through dummy instruction
+emulation and a branch instruction is created to the NIP at the end of
+the trampoline.
-Signed-off-by: Anju T <anju@linux.vnet.ibm.com>
+To address the limitation of branch instruction in POWER architecture,
+detour buffer slot is allocated from a reserved area. For the time being,
+64KB is reserved in memory for this purpose.
+
+Instructions which can be emulated using analyse_instr() are the candidates
+for optimization. Before optimization ensure that the address range
+between the detour buffer allocated and the instruction being probed
+is within +/- 32MB.
+
+Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
+Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
+Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
---
- arch/powerpc/include/asm/kprobes.h | 25 +++++++++
- arch/powerpc/kernel/optprobes_head.S | 104 +++++++++++++++++++++++++++++++++++
- 2 files changed, 129 insertions(+)
+ arch/powerpc/Kconfig | 1 +
+ arch/powerpc/include/asm/code-patching.h | 1 +
+ arch/powerpc/include/asm/kprobes.h | 24 ++-
+ arch/powerpc/kernel/Makefile | 1 +
+ arch/powerpc/kernel/optprobes.c | 348 +++++++++++++++++++++++++++++++
+ arch/powerpc/kernel/optprobes_head.S | 135 ++++++++++++
+ arch/powerpc/lib/code-patching.c | 21 ++
+ 7 files changed, 530 insertions(+), 1 deletion(-)
+ create mode 100644 arch/powerpc/kernel/optprobes.c
create mode 100644 arch/powerpc/kernel/optprobes_head.S
+diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
+index a8ee573..e4d352e 100644
+--- a/arch/powerpc/Kconfig
++++ b/arch/powerpc/Kconfig
+@@ -99,6 +99,7 @@ config PPC
+ select HAVE_IOREMAP_PROT
+ select HAVE_EFFICIENT_UNALIGNED_ACCESS if !(CPU_LITTLE_ENDIAN && POWER7_CPU)
+ select HAVE_KPROBES
++ select HAVE_OPTPROBES if PPC64
+ select HAVE_ARCH_KGDB
+ select HAVE_KRETPROBES
+ select HAVE_ARCH_TRACEHOOK
+diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
+index 75ee4f4..8ab9377 100644
+--- a/arch/powerpc/include/asm/code-patching.h
++++ b/arch/powerpc/include/asm/code-patching.h
+@@ -35,6 +35,7 @@ int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr);
+ unsigned long branch_target(const unsigned int *instr);
+ unsigned int translate_branch(const unsigned int *dest,
+ const unsigned int *src);
++extern bool is_conditional_branch(unsigned int instr);
+ #ifdef CONFIG_PPC_BOOK3E_64
+ void __patch_exception(int exc, unsigned long addr);
+ #define patch_exception(exc, name) do { \
diff --git a/arch/powerpc/include/asm/kprobes.h b/arch/powerpc/include/asm/kprobes.h
-index 039b583..3e4c998 100644
+index 77885d8..d821835 100644
--- a/arch/powerpc/include/asm/kprobes.h
+++ b/arch/powerpc/include/asm/kprobes.h
-@@ -38,7 +38,25 @@ struct pt_regs;
+@@ -40,7 +40,23 @@ struct pt_regs;
struct kprobe;
typedef ppc_opcode_t kprobe_opcode_t;
+-#define MAX_INSN_SIZE 1
+
+extern kprobe_opcode_t optinsn_slot;
++
+/* Optinsn template address */
+extern kprobe_opcode_t optprobe_template_entry[];
++extern kprobe_opcode_t optprobe_template_op_address[];
+extern kprobe_opcode_t optprobe_template_call_handler[];
++extern kprobe_opcode_t optprobe_template_insn[];
+extern kprobe_opcode_t optprobe_template_call_emulate[];
-+extern kprobe_opcode_t optprobe_template_ret_branch[];
+extern kprobe_opcode_t optprobe_template_ret[];
-+extern kprobe_opcode_t optprobe_template_insn[];
-+extern kprobe_opcode_t optprobe_template_op_address1[];
-+extern kprobe_opcode_t optprobe_template_op_address2[];
+extern kprobe_opcode_t optprobe_template_end[];
+
- #define MAX_INSN_SIZE 1
-+#define MAX_OPTIMIZED_LENGTH 4
-+#define MAX_OPTINSN_SIZE \
-+ ((unsigned long)&optprobe_template_end - \
-+ (unsigned long)&optprobe_template_entry)
-+#define RELATIVEJUMP_SIZE 4
++/* Fixed instruction size for powerpc */
++#define MAX_INSN_SIZE 1
++#define MAX_OPTIMIZED_LENGTH sizeof(kprobe_opcode_t) /* 4 bytes */
++#define MAX_OPTINSN_SIZE (optprobe_template_end - optprobe_template_entry)
++#define RELATIVEJUMP_SIZE sizeof(kprobe_opcode_t) /* 4 bytes */
- #ifdef CONFIG_PPC64
- #if defined(_CALL_ELF) && _CALL_ELF == 2
-@@ -129,5 +147,12 @@ struct kprobe_ctlblk {
- extern int kprobe_exceptions_notify(struct notifier_block *self,
- unsigned long val, void *data);
- extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
-+
+ #ifdef PPC64_ELF_ABI_v2
+ /* PPC64 ABIv2 needs local entry point */
+@@ -126,6 +142,12 @@ struct kprobe_ctlblk {
+ struct prev_kprobe prev_kprobe;
+ };
+
+struct arch_optimized_insn {
+ kprobe_opcode_t copied_insn[1];
+ /* detour buffer */
+ kprobe_opcode_t *insn;
+};
+
- #endif /* __KERNEL__ */
- #endif /* _ASM_POWERPC_KPROBES_H */
-diff --git a/arch/powerpc/kernel/optprobes_head.S b/arch/powerpc/kernel/optprobes_head.S
+ extern int kprobe_exceptions_notify(struct notifier_block *self,
+ unsigned long val, void *data);
+ extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
+diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
+index 23f8082..ff0eef5 100644
+--- a/arch/powerpc/kernel/Makefile
++++ b/arch/powerpc/kernel/Makefile
+@@ -100,6 +100,7 @@ obj-$(CONFIG_KGDB) += kgdb.o
+ obj-$(CONFIG_BOOTX_TEXT) += btext.o
+ obj-$(CONFIG_SMP) += smp.o
+ obj-$(CONFIG_KPROBES) += kprobes.o
++obj-$(CONFIG_OPTPROBES) += optprobes.o optprobes_head.o
+ obj-$(CONFIG_UPROBES) += uprobes.o
+ obj-$(CONFIG_PPC_UDBG_16550) += legacy_serial.o udbg_16550.o
+ obj-$(CONFIG_STACKTRACE) += stacktrace.o
+diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
new file mode 100644
-index 0000000..025bab7
+index 0000000..b569e08
--- /dev/null
-+++ b/arch/powerpc/kernel/optprobes_head.S
-@@ -0,0 +1,104 @@
++++ b/arch/powerpc/kernel/optprobes.c
+@@ -0,0 +1,348 @@
+/*
-+ * Code to prepare detour buffer for optprobes in kernel.
++ * Code for Kernel probes Jump optimization.
+ *
-+ * Copyright 2016, Anju T, IBM Corp.
++ * Copyright 2017, Anju T, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
@@ -70,74 +127,456 @@
+ * 2 of the License, or (at your option) any later version.
+ */
+
++#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>
++
++#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)
++
++DEFINE_INSN_CACHE_OPS(ppc_optinsn);
++
++static bool insn_page_in_use;
++
++static void *__ppc_alloc_insn_page(void)
++{
++ if (insn_page_in_use)
++ return NULL;
++ insn_page_in_use = true;
++ return &optinsn_slot;
++}
++
++static void __ppc_free_insn_page(void *page __maybe_unused)
++{
++ insn_page_in_use = false;
++}
++
++struct kprobe_insn_cache kprobe_ppc_optinsn_slots = {
++ .mutex = __MUTEX_INITIALIZER(kprobe_ppc_optinsn_slots.mutex),
++ .pages = LIST_HEAD_INIT(kprobe_ppc_optinsn_slots.pages),
++ /* insn_size initialized later */
++ .alloc = __ppc_alloc_insn_page,
++ .free = __ppc_free_insn_page,
++ .nr_garbage = 0,
++};
++
++/*
++ * 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;
++
++ /*
++ * kprobe placed for kretprobe during boot time
++ * is not optimizing now.
++ *
++ * TODO: Optimize kprobe in kretprobe_trampoline
++ */
++ if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
++ return 0;
++
++ /*
++ * We only support optimizing kernel addresses, but not
++ * module addresses.
++ *
++ * FIXME: Optimize kprobes placed in module addresses.
++ */
++ if (!is_kernel_addr((unsigned long)p->addr))
++ return 0;
++
++ memset(®s, 0, sizeof(struct pt_regs));
++ regs.nip = (unsigned long)p->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(*p->ainsn.insn) &&
++ analyse_instr(&op, ®s, *p->ainsn.insn))
++ nip = regs.nip;
++
++ return nip;
++}
++
++static void optimized_callback(struct optimized_kprobe *op,
++ struct pt_regs *regs)
++{
++ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
++ unsigned long flags;
++
++ /* This is possible if op is under delayed unoptimizing */
++ if (kprobe_disabled(&op->kp))
++ return;
++
++ local_irq_save(flags);
++ hard_irq_disable();
++
++ if (kprobe_running()) {
++ kprobes_inc_nmissed_count(&op->kp);
++ } else {
++ __this_cpu_write(current_kprobe, &op->kp);
++ regs->nip = (unsigned long)op->kp.addr;
++ kcb->kprobe_status = KPROBE_HIT_ACTIVE;
++ opt_pre_handler(&op->kp, regs);
++ __this_cpu_write(current_kprobe, NULL);
++ }
++
++ /*
++ * No need for an explicit __hard_irq_enable() here.
++ * local_irq_restore() will re-enable interrupts,
++ * if they were hard disabled.
++ */
++ local_irq_restore(flags);
++}
++NOKPROBE_SYMBOL(optimized_callback);
++
++void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
++{
++ if (op->optinsn.insn) {
++ free_ppc_optinsn_slot(op->optinsn.insn, 1);
++ op->optinsn.insn = NULL;
++ }
++}
++
++/*
++ * emulate_step() requires insn to be emulated as
++ * second parameter. Load register 'r4' with the
++ * instruction.
++ */
++void patch_imm32_load_insns(unsigned int val, kprobe_opcode_t *addr)
++{
++ /* addis r4,0,(insn)@h */
++ *addr++ = PPC_INST_ADDIS | ___PPC_RT(4) |
++ ((val >> 16) & 0xffff);
++
++ /* ori r4,r4,(insn)@l */
++ *addr = PPC_INST_ORI | ___PPC_RA(4) | ___PPC_RS(4) |
++ (val & 0xffff);
++}
++
++/*
++ * Generate instructions to load provided immediate 64-bit value
++ * to register 'r3' and patch these instructions at 'addr'.
++ */
++void patch_imm64_load_insns(unsigned long val, kprobe_opcode_t *addr)
++{
++ /* lis r3,(op)@highest */
++ *addr++ = PPC_INST_ADDIS | ___PPC_RT(3) |
++ ((val >> 48) & 0xffff);
++
++ /* ori r3,r3,(op)@higher */
++ *addr++ = PPC_INST_ORI | ___PPC_RA(3) | ___PPC_RS(3) |
++ ((val >> 32) & 0xffff);
++
++ /* rldicr r3,r3,32,31 */
++ *addr++ = PPC_INST_RLDICR | ___PPC_RA(3) | ___PPC_RS(3) |
++ __PPC_SH64(32) | __PPC_ME64(31);
++
++ /* oris r3,r3,(op)@h */
++ *addr++ = PPC_INST_ORIS | ___PPC_RA(3) | ___PPC_RS(3) |
++ ((val >> 16) & 0xffff);
++
++ /* ori r3,r3,(op)@l */
++ *addr = PPC_INST_ORI | ___PPC_RA(3) | ___PPC_RS(3) |
++ (val & 0xffff);
++}
++
++int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
++{
++ kprobe_opcode_t *buff, branch_op_callback, branch_emulate_step;
++ kprobe_opcode_t *op_callback_addr, *emulate_step_addr;
++ long b_offset;
++ unsigned long nip;
++
++ kprobe_ppc_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
++
++ nip = can_optimize(p);
++ if (!nip)
++ return -EILSEQ;
++
++ /* Allocate instruction slot for detour buffer */
++ buff = get_ppc_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) -
++ (unsigned long)nip;
++ if (!is_offset_in_branch_range(b_offset))
++ goto error;
++
++ /* Setup template */
++ memcpy(buff, optprobe_template_entry,
++ TMPL_END_IDX * sizeof(kprobe_opcode_t));
++
++ /*
++ * Fixup the template with instructions to:
++ * 1. load the address of the actual probepoint
++ */
++ patch_imm64_load_insns((unsigned long)op, buff + TMPL_OP_IDX);
++
++ /*
++ * 2. branch to optimized_callback() and emulate_step()
++ */
++ kprobe_lookup_name("optimized_callback", op_callback_addr);
++ kprobe_lookup_name("emulate_step", emulate_step_addr);
++ if (!op_callback_addr || !emulate_step_addr) {
++ WARN(1, "kprobe_lookup_name() failed\n");
++ goto error;
++ }
++
++ branch_op_callback = create_branch((unsigned int *)buff + TMPL_CALL_HDLR_IDX,
++ (unsigned long)op_callback_addr,
++ BRANCH_SET_LINK);
++
++ branch_emulate_step = create_branch((unsigned int *)buff + TMPL_EMULATE_IDX,
++ (unsigned long)emulate_step_addr,
++ BRANCH_SET_LINK);
++
++ if (!branch_op_callback || !branch_emulate_step)
++ goto error;
++
++ buff[TMPL_CALL_HDLR_IDX] = branch_op_callback;
++ buff[TMPL_EMULATE_IDX] = branch_emulate_step;
++
++ /*
++ * 3. load instruction to be emulated into relevant register, and
++ */
++ patch_imm32_load_insns(*p->ainsn.insn, buff + TMPL_INSN_IDX);
++
++ /*
++ * 4. branch back from trampoline
++ */
++ buff[TMPL_RET_IDX] = create_branch((unsigned int *)buff + TMPL_RET_IDX,
++ (unsigned long)nip, 0);
++
++ flush_icache_range((unsigned long)buff,
++ (unsigned long)(&buff[TMPL_END_IDX]));
++
++ op->optinsn.insn = buff;
++
++ return 0;
++
++ error:
++ free_ppc_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)
++{
++ 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);
++ patch_instruction(op->kp.addr,
++ create_branch((unsigned int *)op->kp.addr,
++ (unsigned long)op->optinsn.insn, 0));
++ 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,
++ unsigned long addr)
++{
++ return ((unsigned long)op->kp.addr <= addr &&
++ (unsigned long)op->kp.addr + RELATIVEJUMP_SIZE > addr);
++}
+diff --git a/arch/powerpc/kernel/optprobes_head.S b/arch/powerpc/kernel/optprobes_head.S
+new file mode 100644
+index 0000000..53e429b
+--- /dev/null
++++ b/arch/powerpc/kernel/optprobes_head.S
+@@ -0,0 +1,135 @@
++/*
++ * Code to prepare detour buffer for optprobes in Kernel.
++ *
++ * Copyright 2017, Anju T, IBM Corp.
++ *
++ * This program is free software; you can redistribute it and/or
++ * modify it under the terms of the GNU General Public License
++ * as published by the Free Software Foundation; either version
++ * 2 of the License, or (at your option) any later version.
++ */
++
+#include <asm/ppc_asm.h>
+#include <asm/ptrace.h>
+#include <asm/asm-offsets.h>
+
-+.global optprobe_template_entry
++#define OPT_SLOT_SIZE 65536
++
++ .balign 4
++
++ /*
++ * Reserve an area to allocate slots for detour buffer.
++ * This is part of .text section (rather than vmalloc area)
++ * as this needs to be within 32MB of the probed address.
++ */
++ .global optinsn_slot
++optinsn_slot:
++ .space OPT_SLOT_SIZE
++
++ /*
++ * Optprobe template:
++ * This template gets copied into one of the slots in optinsn_slot
++ * and gets fixed up with real optprobe structures et al.
++ */
++ .global optprobe_template_entry
+optprobe_template_entry:
++ /* Create an in-memory pt_regs */
+ stdu r1,-INT_FRAME_SIZE(r1)
+ SAVE_GPR(0,r1)
+ /* Save the previous SP into stack */
+ addi r0,r1,INT_FRAME_SIZE
-+ std 0,GPR1(r1)
-+ SAVE_2GPRS(2,r1)
-+ SAVE_8GPRS(4,r1)
++ std r0,GPR1(r1)
++ SAVE_10GPRS(2,r1)
+ SAVE_10GPRS(12,r1)
+ SAVE_10GPRS(22,r1)
+ /* Save SPRS */
-+ mfcfar r5
-+ std r5,_NIP(r1)
+ mfmsr r5
+ std r5,_MSR(r1)
++ li r5,0x700
++ std r5,_TRAP(r1)
++ li r5,0
++ std r5,ORIG_GPR3(r1)
++ std r5,RESULT(r1)
+ mfctr r5
+ std r5,_CTR(r1)
+ mflr r5
+ std r5,_LINK(r1)
+ mfspr r5,SPRN_XER
+ std r5,_XER(r1)
-+ li r5,0
-+ std r5,_TRAP(r1)
++ mfcr r5
++ std r5,_CCR(r1)
++ lbz r5,PACASOFTIRQEN(r13)
++ std r5,SOFTE(r1)
+ mfdar r5
+ std r5,_DAR(r1)
+ mfdsisr r5
+ std r5,_DSISR(r1)
-+ /* Pass parameters for optimized_callback */
-+.global optprobe_template_op_address1
-+optprobe_template_op_address1:
-+ nop
-+ nop
-+ nop
-+ nop
-+ nop
++
++ .global optprobe_template_op_address
++optprobe_template_op_address:
++ /*
++ * Parameters to optimized_callback():
++ * 1. optimized_kprobe structure in r3
++ */
++ nop
++ nop
++ nop
++ nop
++ nop
++ /* 2. pt_regs pointer in r4 */
+ addi r4,r1,STACK_FRAME_OVERHEAD
-+ /* Branch to the prehandler */
-+.global optprobe_template_call_handler
++
++ .global optprobe_template_call_handler
+optprobe_template_call_handler:
-+ nop
-+ /* Pass parameters for instruction emulation */
++ /* Branch to optimized_callback() */
++ nop
++
++ /*
++ * Parameters for instruction emulation:
++ * 1. Pass SP in register r3.
++ */
+ addi r3,r1,STACK_FRAME_OVERHEAD
-+.global optprobe_template_insn
++
++ .global optprobe_template_insn
+optprobe_template_insn:
-+ nop
-+ nop
-+ /* Branch to instruction emulation */
-+.global optprobe_template_call_emulate
++ /* 2, Pass instruction to be emulated in r4 */
++ nop
++ nop
++
++ .global optprobe_template_call_emulate
+optprobe_template_call_emulate:
-+ nop
-+.global optprobe_template_op_address2
-+optprobe_template_op_address2:
-+ nop
-+ nop
-+ nop
-+ nop
-+ nop
-+ addi r4,r1,STACK_FRAME_OVERHEAD
-+ /* Branch to create_return_branch() function */
-+.global optprobe_template_ret_branch
-+optprobe_template_ret_branch:
-+ nop
-+ /* Restore the registers */
++ /* Branch to emulate_step() */
++ nop
++
++ /*
++ * All done.
++ * Now, restore the registers...
++ */
+ ld r5,_MSR(r1)
+ mtmsr r5
+ ld r5,_CTR(r1)
@@ -146,22 +585,57 @@
+ mtlr r5
+ ld r5,_XER(r1)
+ mtxer r5
++ ld r5,_CCR(r1)
++ mtcr r5
+ ld r5,_DAR(r1)
+ mtdar r5
+ ld r5,_DSISR(r1)
+ mtdsisr r5
+ REST_GPR(0,r1)
-+ REST_2GPRS(2,r1)
-+ REST_8GPRS(4,r1)
++ REST_10GPRS(2,r1)
+ REST_10GPRS(12,r1)
+ REST_10GPRS(22,r1)
+ /* Restore the previous SP */
+ addi r1,r1,INT_FRAME_SIZE
-+ /* Jump back to the normal workflow from trampoline */
-+.global optprobe_template_ret
++
++ .global optprobe_template_ret
+optprobe_template_ret:
-+ nop
-+.global optprobe_template_end
++ /* ... and jump back from trampoline */
++ nop
++
++ .global optprobe_template_end
+optprobe_template_end:
+diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
+index 4ccf16a..0899315 100644
+--- a/arch/powerpc/lib/code-patching.c
++++ b/arch/powerpc/lib/code-patching.c
+@@ -54,6 +54,27 @@ bool is_offset_in_branch_range(long offset)
+ return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
+ }
+
++/*
++ * Helper to check if a given instruction is a conditional branch
++ * Derived from the conditional checks in analyse_instr()
++ */
++bool __kprobes is_conditional_branch(unsigned int instr)
++{
++ unsigned int opcode = instr >> 26;
++
++ if (opcode == 16) /* bc, bca, bcl, bcla */
++ return true;
++ if (opcode == 19) {
++ switch ((instr >> 1) & 0x3ff) {
++ case 16: /* bclr, bclrl */
++ case 528: /* bcctr, bcctrl */
++ case 560: /* bctar, bctarl */
++ return true;
++ }
++ }
++ return false;
++}
++
+ unsigned int create_branch(const unsigned int *addr,
+ unsigned long target, int flags)
+ {
--
-2.1.0
+2.7.4