Re: [PATCH V3 3/4] arch/powerpc: Implement Optprobes

From: Masami Hiramatsu
Date: Sat Dec 24 2016 - 21:54:57 EST

On Mon, 19 Dec 2016 18:48:24 +0530
Anju T Sudhakar <anju@xxxxxxxxxxxxxxxxxx> wrote:

> Detour buffer contains instructions to create an in memory pt_regs.
> 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.
>
> Instruction slot for detour buffer is allocated from the reserved area.
> For the time being, 64KB is reserved in memory for this purpose.
>
> Instructions which can be emulated using analyse_instr() are suppliants
> 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@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>

Looks good to me :)

Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

Thanks!

> ---
> .../features/debug/optprobes/arch-support.txt | 2 +-
> arch/powerpc/Kconfig | 1 +
> arch/powerpc/include/asm/kprobes.h | 24 +-
> arch/powerpc/include/asm/sstep.h | 1 +
> arch/powerpc/kernel/Makefile | 1 +
> arch/powerpc/kernel/optprobes.c | 331 +++++++++++++++++++++
> arch/powerpc/kernel/optprobes_head.S | 135 +++++++++
> arch/powerpc/lib/sstep.c | 21 ++
> 8 files changed, 514 insertions(+), 2 deletions(-)
> create mode 100644 arch/powerpc/kernel/optprobes.c
> create mode 100644 arch/powerpc/kernel/optprobes_head.S
>
> diff --git a/Documentation/features/debug/optprobes/arch-support.txt b/Documentation/features/debug/optprobes/arch-support.txt
> index b8999d8..45bc99d 100644
> --- a/Documentation/features/debug/optprobes/arch-support.txt
> +++ b/Documentation/features/debug/optprobes/arch-support.txt
> @@ -27,7 +27,7 @@
> | nios2: | TODO |
> | openrisc: | TODO |
> | parisc: | TODO |
> - | powerpc: | TODO |
> + | powerpc: | ok |
> | s390: | TODO |
> | score: | TODO |
> | sh: | TODO |
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 65fba4c..f7e9296 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -98,6 +98,7 @@ 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/kprobes.h b/arch/powerpc/include/asm/kprobes.h
> index 2c9759bd..0cf640b 100644
> --- a/arch/powerpc/include/asm/kprobes.h
> +++ b/arch/powerpc/include/asm/kprobes.h
> @@ -38,7 +38,23 @@ 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[];
> +extern kprobe_opcode_t optprobe_template_end[];
> +
> +/* 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 PPC64_ELF_ABI_v2
> /* PPC64 ABIv2 needs local entry point */
> @@ -124,6 +140,12 @@ struct kprobe_ctlblk {
> struct prev_kprobe prev_kprobe;
> };
>
> +struct arch_optimized_insn {
> + kprobe_opcode_t copied_insn[1];
> + /* detour buffer */
> + kprobe_opcode_t *insn;
> +};
> +
> 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/include/asm/sstep.h b/arch/powerpc/include/asm/sstep.h
> index d3a42cc..f7ad425 100644
> --- a/arch/powerpc/include/asm/sstep.h
> +++ b/arch/powerpc/include/asm/sstep.h
> @@ -87,3 +87,4 @@ struct instruction_op {
>
> extern int analyse_instr(struct instruction_op *op, struct pt_regs *regs,
> unsigned int instr);
> +extern bool is_conditional_branch(unsigned int instr);
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> index 1925341..54f0f47 100644
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -98,6 +98,7 @@ 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..fb5e62d
> --- /dev/null
> +++ b/arch/powerpc/kernel/optprobes.c
> @@ -0,0 +1,331 @@
> +/*
> + * Code for Kernel probes Jump optimization.
> + *
> + * Copyright 2016, 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 <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.
> + */
> + if (!is_kernel_addr((unsigned long)p->addr))
> + return 0;
> +
> + regs.nip = (unsigned long)p->addr;
> + regs.trap = 0x0;
> + regs.msr = MSR_KERNEL;
> +
> + /*
> + * Ensure that the instruction is not a conditional branch,
> + * and that can be emulated.
> + */
> + if (!is_conditional_branch(*p->ainsn.insn) &&
> + analyse_instr(&op, &regs, *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);
> +
> + 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);
> + }
> + 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..c86976b
> --- /dev/null
> +++ b/arch/powerpc/kernel/optprobes_head.S
> @@ -0,0 +1,135 @@
> +/*
> + * Code to prepare detour buffer for optprobes in Kernel.
> + *
> + * Copyright 2016, 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>
> +
> +#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 r0,GPR1(r1)
> + SAVE_10GPRS(2,r1)
> + SAVE_10GPRS(12,r1)
> + SAVE_10GPRS(22,r1)
> + /* Save SPRS */
> + 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)
> + 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)
> +
> + .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
> +
> + .global optprobe_template_call_handler
> +optprobe_template_call_handler:
> + /* 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
> +optprobe_template_insn:
> + /* 2, Pass instruction to be emulated in r4 */
> + nop
> + nop
> +
> + .global optprobe_template_call_emulate
> +optprobe_template_call_emulate:
> + /* Branch to emulate_step() */
> + nop
> +
> + /*
> + * All done.
> + * Now, restore the registers...
> + */
> + ld r5,_MSR(r1)
> + mtmsr r5
> + ld r5,_CTR(r1)
> + mtctr r5
> + ld r5,_LINK(r1)
> + 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_10GPRS(2,r1)
> + REST_10GPRS(12,r1)
> + REST_10GPRS(22,r1)
> + /* Restore the previous SP */
> + addi r1,r1,INT_FRAME_SIZE
> +
> + .global optprobe_template_ret
> +optprobe_template_ret:
> + /* ... and jump back from trampoline */
> + nop
> +
> + .global optprobe_template_end
> +optprobe_template_end:
> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> index 3362299..895dcdd 100644
> --- a/arch/powerpc/lib/sstep.c
> +++ b/arch/powerpc/lib/sstep.c
> @@ -618,6 +618,27 @@ static int __kprobes trap_compare(long v1, long v2)
> }
>
> /*
> + * 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;
> +}
> +
> +/*
> * Elements of 32-bit rotate and mask instructions.
> */
> #define MASK32(mb, me) ((0xffffffffUL >> (mb)) + \
> --
> 2.7.4
>


--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>