Messages in this thread | | | From | Jianhua Liu <> | Date | Tue, 14 Dec 2021 23:55:58 +0800 | Subject | Re: [PATCH v5] arm64: kprobe: Enable OPTPROBE for arm64 |
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On Tue, Dec 14, 2021 at 8:27 AM Masami Hiramatsu <mhiramat@kernel.org> wrote: > > On Mon, 13 Dec 2021 18:38:52 +0000 > Will Deacon <will@kernel.org> wrote: > > > Hi, > > > > [+Janet Liu] > > > > On Tue, Dec 07, 2021 at 08:40:02PM +0800, Qi Liu wrote: > > > This patch introduce optprobe for ARM64. In optprobe, probed > > > instruction is replaced by a branch instruction to trampoline. > > > > > > Performance of optprobe on Hip08 platform is test using kprobe > > > example module[1] to analyze the latency of a kernel function, > > > and here is the result: > > > > > > common kprobe: > > > [280709.846380] do_empty returned 0 and took 1530 ns to execute > > > [280709.852057] do_empty returned 0 and took 550 ns to execute > > > [280709.857631] do_empty returned 0 and took 440 ns to execute > > > [280709.863215] do_empty returned 0 and took 380 ns to execute > > > [280709.868787] do_empty returned 0 and took 360 ns to execute > > > [280709.874362] do_empty returned 0 and took 340 ns to execute > > > [280709.879936] do_empty returned 0 and took 320 ns to execute > > > [280709.885505] do_empty returned 0 and took 300 ns to execute > > > [280709.891075] do_empty returned 0 and took 280 ns to execute > > > [280709.896646] do_empty returned 0 and took 290 ns to execute > > > > > > optprobe: > > > [ 2965.964572] do_empty returned 0 and took 90 ns to execute > > > [ 2965.969952] do_empty returned 0 and took 80 ns to execute > > > [ 2965.975332] do_empty returned 0 and took 70 ns to execute > > > [ 2965.980714] do_empty returned 0 and took 60 ns to execute > > > [ 2965.986128] do_empty returned 0 and took 80 ns to execute > > > [ 2965.991507] do_empty returned 0 and took 70 ns to execute > > > [ 2965.996884] do_empty returned 0 and took 70 ns to execute > > > [ 2966.002262] do_empty returned 0 and took 80 ns to execute > > > [ 2966.007642] do_empty returned 0 and took 70 ns to execute > > > [ 2966.013020] do_empty returned 0 and took 70 ns to execute > > > [ 2966.018400] do_empty returned 0 and took 70 ns to execute > > > > > > As the result shows, optprobe can greatly reduce the latency. Big > > > latency of common kprobe will significantly impact the real result > > > while doing performance analysis or debugging performance issues > > > in lab, so optprobe is useful in this scenario. > > > > > > Acked-by: Masami Hiramatsu <mhiramat@kernel.org> > > > Signed-off-by: Qi Liu <liuqi115@huawei.com> > > > > > > Note: > > > As branch instruction in Arm64 has a 128M range limitation, optprobe > > > could only used when offset between probe point and trampoline > > > is less than 128M, otherwise kernel will choose common kprobe > > > automaticly. > > > > > > Limitation caused by branch isn't unique to Arm64, but also to > > > x86/arm/powerpc. > > > > > > In fact, Module PLT has been tried to get rid of limiation, but > > > destination of PLT must be a fixed value, and we need to modify > > > the destination (as each optprobe has its own trampoline). > > > > > > As discussed with Masami[2], we can start with core-kernel point > > > (within 128M) as the first step, like other architectures. > > > > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/samples/kprobes/kretprobe_example.c > > > [2] https://lore.kernel.org/lkml/20211201105001.5164f98ba783e7207df1229c@kernel.org/ > > > --- > > > arch/arm64/Kconfig | 1 + > > > arch/arm64/include/asm/kprobes.h | 21 ++ > > > arch/arm64/kernel/probes/Makefile | 2 + > > > arch/arm64/kernel/probes/opt_arm64.c | 199 ++++++++++++++++++ > > > .../arm64/kernel/probes/optprobe_trampoline.S | 97 +++++++++ > > > include/linux/kprobes.h | 2 + > > > kernel/kprobes.c | 22 ++ > > > 7 files changed, 344 insertions(+) > > > create mode 100644 arch/arm64/kernel/probes/opt_arm64.c > > > create mode 100644 arch/arm64/kernel/probes/optprobe_trampoline.S > > > > I've not looked at these changes in detail, but it looks like there is an > > independent patch from Janet Liu trying to do the same thing: > > > > https://lore.kernel.org/r/1635858706-27320-1-git-send-email-jianhua.ljh@gmail.com > > > > Thanks for noticing. I missed it. > > > The patch here from Qi Liu looks like it's a bit further along, but it > > would be good for Janet to at least test it out and confirm that it works > > for them. > > Yeah, it's now v5. > But it seems Janet's one also has good points. I would like Janet's sharing > save_all_base_regs macro and the comment about the branch instruction. > > > > > Cheers, > > > > Will > > > > [Kept diff inline for Janet] > > Janet, please feel free to review and test it. It is important that you confirm > this can work with your envionment too. > I will review your KPROBE_ON_FTRACE patch. > I have tested these patch on UNISOC s9863a platform before sending.
The test case from: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/samples/kprobes/
And I do the following change for kprobe_example.c before testing: 1. delete function handler_post, kprobe_init does "kp.post_handler = handler_post; ---> p.post_handler = NULL;" 2. handler_pre calls dump_stack.
Thanks for the review.
> Thank you, > > > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > > index c4207cf9bb17..6b68ec498e67 100644 > > > --- a/arch/arm64/Kconfig > > > +++ b/arch/arm64/Kconfig > > > @@ -200,6 +200,7 @@ config ARM64 > > > select HAVE_STACKPROTECTOR > > > select HAVE_SYSCALL_TRACEPOINTS > > > select HAVE_KPROBES > > > + select HAVE_OPTPROBES > > > select HAVE_KRETPROBES > > > select HAVE_GENERIC_VDSO > > > select IOMMU_DMA if IOMMU_SUPPORT > > > diff --git a/arch/arm64/include/asm/kprobes.h b/arch/arm64/include/asm/kprobes.h > > > index 05cd82eeca13..3838e4317877 100644 > > > --- a/arch/arm64/include/asm/kprobes.h > > > +++ b/arch/arm64/include/asm/kprobes.h > > > @@ -39,6 +39,27 @@ void arch_remove_kprobe(struct kprobe *); > > > int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr); > > > int kprobe_exceptions_notify(struct notifier_block *self, > > > unsigned long val, void *data); > > > + > > > +struct arch_optimized_insn { > > > + kprobe_opcode_t orig_insn[1]; > > > + kprobe_opcode_t *trampoline; > > > +}; > > > + > > > +#define MAX_OPTIMIZED_LENGTH sizeof(kprobe_opcode_t) > > > +#define MAX_OPTINSN_SIZE \ > > > + ((unsigned long)optprobe_template_restore_end - (unsigned long)optprobe_template_entry) > > > + > > > +extern __visible kprobe_opcode_t optprobe_template_entry[]; > > > +extern __visible kprobe_opcode_t optprobe_template_val[]; > > > +extern __visible kprobe_opcode_t optprobe_template_common[]; > > > +extern __visible kprobe_opcode_t optprobe_template_end[]; > > > +extern __visible kprobe_opcode_t optprobe_template_restore_begin[]; > > > +extern __visible kprobe_opcode_t optprobe_template_restore_orig_insn[]; > > > +extern __visible kprobe_opcode_t optprobe_template_restore_end[]; > > > +extern __visible kprobe_opcode_t optinsn_slot[]; > > > + > > > +void optprobe_common(void); > > > + > > > void __kretprobe_trampoline(void); > > > void __kprobes *trampoline_probe_handler(struct pt_regs *regs); > > > > > > diff --git a/arch/arm64/kernel/probes/Makefile b/arch/arm64/kernel/probes/Makefile > > > index 8e4be92e25b1..07105fd3261d 100644 > > > --- a/arch/arm64/kernel/probes/Makefile > > > +++ b/arch/arm64/kernel/probes/Makefile > > > @@ -4,3 +4,5 @@ obj-$(CONFIG_KPROBES) += kprobes.o decode-insn.o \ > > > simulate-insn.o > > > obj-$(CONFIG_UPROBES) += uprobes.o decode-insn.o \ > > > simulate-insn.o > > > +obj-$(CONFIG_OPTPROBES) += opt_arm64.o \ > > > + optprobe_trampoline.o > > > diff --git a/arch/arm64/kernel/probes/opt_arm64.c b/arch/arm64/kernel/probes/opt_arm64.c > > > new file mode 100644 > > > index 000000000000..1bad5cddcdf2 > > > --- /dev/null > > > +++ b/arch/arm64/kernel/probes/opt_arm64.c > > > @@ -0,0 +1,199 @@ > > > +// SPDX-License-Identifier: GPL-2.0-only > > > +/* > > > + * Code for Kernel probes Jump optimization. > > > + * > > > + * Copyright (C) 2021 Hisilicon Limited > > > + */ > > > + > > > +#include <linux/jump_label.h> > > > +#include <linux/kprobes.h> > > > + > > > +#include <asm/cacheflush.h> > > > +#include <asm/compiler.h> > > > +#include <asm/insn.h> > > > +#include <asm/kprobes.h> > > > +#include <asm/patching.h> > > > + > > > +#define OPTPROBE_BATCH_SIZE 64 > > > +#define GET_LO_VAL(val) FIELD_GET(GENMASK(31, 0), val) > > > +#define GET_HI_VAL(val) FIELD_GET(GENMASK(63, 32), val) > > > + > > > +#define TMPL_VAL_IDX \ > > > + (optprobe_template_val - optprobe_template_entry) > > > +#define TMPL_CALL_COMMON \ > > > + (optprobe_template_common - optprobe_template_entry) > > > +#define TMPL_RESTORE_ORIGN_INSN \ > > > + (optprobe_template_restore_orig_insn - optprobe_template_entry) > > > +#define TMPL_RESTORE_END \ > > > + (optprobe_template_restore_end - 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; > > > +} > > > + > > > +int arch_check_optimized_kprobe(struct optimized_kprobe *op) > > > +{ > > > + return 0; > > > +} > > > + > > > +int arch_prepared_optinsn(struct arch_optimized_insn *optinsn) > > > +{ > > > + return optinsn->trampoline != NULL; > > > +} > > > + > > > +int arch_within_optimized_kprobe(struct optimized_kprobe *op, kprobe_opcode_t *addr) > > > +{ > > > + return op->kp.addr == addr; > > > +} > > > + > > > +static void optprobe_set_pc_value(struct optimized_kprobe *op, struct pt_regs *regs) > > > +{ > > > + regs->pc = (unsigned long)op->kp.addr; > > > +} > > > + > > > +static int optprobe_check_branch_limit(unsigned long pc, unsigned long addr) > > > +{ > > > + long offset; > > > + > > > + if ((pc & 0x3) || (addr & 0x3)) > > > + return -ERANGE; > > > + > > > + offset = (long)addr - (long)pc; > > > + if (offset < -SZ_128M || offset >= SZ_128M) > > > + return -ERANGE; > > > + > > > + return 0; > > > +} > > > + > > > +int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *orig) > > > +{ > > > + kprobe_opcode_t *code, *buf; > > > + u32 insn; > > > + int ret = -ENOMEM; > > > + int i; > > > + > > > + buf = kcalloc(MAX_OPTINSN_SIZE, sizeof(kprobe_opcode_t), GFP_KERNEL); > > > + if (!buf) > > > + return ret; > > > + > > > + code = get_optinsn_slot(); > > > + if (!code) > > > + goto out; > > > + > > > + if (optprobe_check_branch_limit((unsigned long)code, (unsigned long)orig->addr + 8)) { > > > + ret = -ERANGE; > > > + goto error; > > > + } > > > + > > > + op->set_pc = optprobe_set_pc_value; > > > + memcpy(buf, optprobe_template_entry, MAX_OPTINSN_SIZE * sizeof(kprobe_opcode_t)); > > > + > > > + insn = aarch64_insn_gen_branch_imm((unsigned long)&code[TMPL_CALL_COMMON], > > > + (unsigned long)&optprobe_common, > > > + AARCH64_INSN_BRANCH_LINK); > > > + buf[TMPL_CALL_COMMON] = insn; > > > + > > > + insn = aarch64_insn_gen_branch_imm((unsigned long)&code[TMPL_RESTORE_END], > > > + (unsigned long)op->kp.addr + 4, > > > + AARCH64_INSN_BRANCH_NOLINK); > > > + buf[TMPL_RESTORE_END] = insn; > > > + > > > + buf[TMPL_VAL_IDX] = cpu_to_le32(GET_LO_VAL((unsigned long)op)); > > > + buf[TMPL_VAL_IDX + 1] = cpu_to_le32(GET_HI_VAL((unsigned long)op)); > > > + buf[TMPL_RESTORE_ORIGN_INSN] = orig->opcode; > > > + > > > + /* Setup template */ > > > + for (i = 0; i < MAX_OPTINSN_SIZE; i++) > > > + aarch64_insn_patch_text_nosync(code + i, buf[i]); > > > + > > > + flush_icache_range((unsigned long)code, (unsigned long)(&code[TMPL_VAL_IDX])); > > > + /* Set op->optinsn.trampoline means prepared. */ > > > + op->optinsn.trampoline = code; > > > + > > > +out: > > > + kfree(buf); > > > + return ret; > > > + > > > +error: > > > + free_optinsn_slot(code, 0); > > > + goto out; > > > +} > > > + > > > +void arch_optimize_kprobes(struct list_head *oplist) > > > +{ > > > + struct optimized_kprobe *op, *tmp; > > > + kprobe_opcode_t insns[OPTPROBE_BATCH_SIZE]; > > > + void *addrs[OPTPROBE_BATCH_SIZE]; > > > + int i = 0; > > > + > > > + list_for_each_entry_safe(op, tmp, oplist, list) { > > > + WARN_ON(kprobe_disabled(&op->kp)); > > > + > > > + /* > > > + * Backup instructions which will be replaced > > > + * by jump address > > > + */ > > > + memcpy(op->optinsn.orig_insn, op->kp.addr, AARCH64_INSN_SIZE); > > > + > > > + addrs[i] = (void *)op->kp.addr; > > > + insns[i] = aarch64_insn_gen_branch_imm((unsigned long)op->kp.addr, > > > + (unsigned long)op->optinsn.trampoline, > > > + AARCH64_INSN_BRANCH_NOLINK); > > > + > > > + list_del_init(&op->list); > > > + if (++i == OPTPROBE_BATCH_SIZE) > > > + break; > > > + } > > > + > > > + aarch64_insn_patch_text(addrs, insns, i); > > > +} > > > + > > > +void arch_unoptimize_kprobe(struct optimized_kprobe *op) > > > +{ > > > + arch_arm_kprobe(&op->kp); > > > +} > > > + > > > +/* > > > + * Recover original instructions and breakpoints from relative jumps. > > > + * Caller must call with locking kprobe_mutex. > > > + */ > > > +void arch_unoptimize_kprobes(struct list_head *oplist, > > > + struct list_head *done_list) > > > +{ > > > + struct optimized_kprobe *op, *tmp; > > > + kprobe_opcode_t insns[OPTPROBE_BATCH_SIZE]; > > > + void *addrs[OPTPROBE_BATCH_SIZE]; > > > + int i = 0; > > > + > > > + list_for_each_entry_safe(op, tmp, oplist, list) { > > > + addrs[i] = (void *)op->kp.addr; > > > + insns[i] = BRK64_OPCODE_KPROBES; > > > + list_move(&op->list, done_list); > > > + > > > + if (++i == OPTPROBE_BATCH_SIZE) > > > + break; > > > + } > > > + > > > + aarch64_insn_patch_text(addrs, insns, i); > > > +} > > > + > > > +void arch_remove_optimized_kprobe(struct optimized_kprobe *op) > > > +{ > > > + if (op->optinsn.trampoline) { > > > + free_optinsn_slot(op->optinsn.trampoline, 1); > > > + op->optinsn.trampoline = NULL; > > > + } > > > +} > > > diff --git a/arch/arm64/kernel/probes/optprobe_trampoline.S b/arch/arm64/kernel/probes/optprobe_trampoline.S > > > new file mode 100644 > > > index 000000000000..1376daeae844 > > > --- /dev/null > > > +++ b/arch/arm64/kernel/probes/optprobe_trampoline.S > > > @@ -0,0 +1,97 @@ > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > +/* > > > + * trampoline entry and return code for optprobes. > > > + */ > > > + > > > +#include <linux/linkage.h> > > > +#include <asm/asm-offsets.h> > > > +#include <asm/assembler.h> > > > + > > > +#define OPT_SLOT_SIZE 65536 > > > + > > > + .global optinsn_slot > > > +optinsn_slot: > > > + .space OPT_SLOT_SIZE > > > + > > > +SYM_CODE_START(optprobe_common) > > > + stp x2, x3, [sp, #S_X2] > > > + stp x4, x5, [sp, #S_X4] > > > + stp x6, x7, [sp, #S_X6] > > > + stp x8, x9, [sp, #S_X8] > > > + stp x10, x11, [sp, #S_X10] > > > + stp x12, x13, [sp, #S_X12] > > > + stp x14, x15, [sp, #S_X14] > > > + stp x16, x17, [sp, #S_X16] > > > + stp x18, x19, [sp, #S_X18] > > > + stp x20, x21, [sp, #S_X20] > > > + stp x22, x23, [sp, #S_X22] > > > + stp x24, x25, [sp, #S_X24] > > > + stp x26, x27, [sp, #S_X26] > > > + stp x28, x29, [sp, #S_X28] > > > + add x2, sp, #PT_REGS_SIZE > > > + str x2, [sp, #S_SP] > > > + /* Construct a useful saved PSTATE */ > > > + mrs x2, nzcv > > > + mrs x3, daif > > > + orr x2, x2, x3 > > > + mrs x3, CurrentEL > > > + orr x2, x2, x3 > > > + mrs x3, SPSel > > > + orr x2, x2, x3 > > > + stp xzr, x2, [sp, #S_PC] > > > + > > > + /* set the pt_regs address to x1 */ > > > + mov x1, sp > > > + /* store lr of optprobe_common temporary */ > > > + sub sp, sp, #0x10 > > > + str lr, [sp, #0x8] > > > + > > > + bl optprobe_optimized_callback > > > + > > > + ldr lr, [sp, #0x8] > > > + add sp, sp, #0x10 > > > + ldr x0, [sp, #S_PSTATE] > > > + and x0, x0, #(PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT) > > > + msr nzcv, x0 > > > + ldp x0, x1, [sp, #S_X0] > > > + ldp x2, x3, [sp, #S_X2] > > > + ldp x4, x5, [sp, #S_X4] > > > + ldp x6, x7, [sp, #S_X6] > > > + ldp x8, x9, [sp, #S_X8] > > > + ldp x10, x11, [sp, #S_X10] > > > + ldp x12, x13, [sp, #S_X12] > > > + ldp x14, x15, [sp, #S_X14] > > > + ldp x16, x17, [sp, #S_X16] > > > + ldp x18, x19, [sp, #S_X18] > > > + ldp x20, x21, [sp, #S_X20] > > > + ldp x22, x23, [sp, #S_X22] > > > + ldp x24, x25, [sp, #S_X24] > > > + ldp x26, x27, [sp, #S_X26] > > > + ldp x28, x29, [sp, #S_X28] > > > + ret > > > +SYM_CODE_END(optprobe_common) > > > + > > > + .global optprobe_template_entry > > > +optprobe_template_entry: > > > + sub sp, sp, #PT_REGS_SIZE > > > + str lr, [sp, #S_LR] > > > + stp x0, x1, [sp, #S_X0] > > > + /* Get parameters to optimized_callback() */ > > > + ldr x0, 1f > > > + .global optprobe_template_common > > > +optprobe_template_common: > > > + nop > > > + ldr lr, [sp, #S_LR] > > > + add sp, sp, #PT_REGS_SIZE > > > + .global optprobe_template_restore_orig_insn > > > +optprobe_template_restore_orig_insn: > > > + nop > > > + .global optprobe_template_restore_end > > > +optprobe_template_restore_end: > > > + nop > > > + .global optprobe_template_val > > > +optprobe_template_val: > > > + 1: .long 0 > > > + .long 0 > > > + .global optprobe_template_end > > > +optprobe_template_end: > > > diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h > > > index 8c8f7a4d93af..7be680155df7 100644 > > > --- a/include/linux/kprobes.h > > > +++ b/include/linux/kprobes.h > > > @@ -329,6 +329,7 @@ struct optimized_kprobe { > > > struct kprobe kp; > > > struct list_head list; /* list for optimizing queue */ > > > struct arch_optimized_insn optinsn; > > > + void (*set_pc)(struct optimized_kprobe *op, struct pt_regs *regs); > > > }; > > > > > > /* Architecture dependent functions for direct jump optimization */ > > > @@ -345,6 +346,7 @@ extern int arch_within_optimized_kprobe(struct optimized_kprobe *op, > > > kprobe_opcode_t *addr); > > > > > > extern void opt_pre_handler(struct kprobe *p, struct pt_regs *regs); > > > +extern void optprobe_optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs); > > > > > > DEFINE_INSN_CACHE_OPS(optinsn); > > > > > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > > index 21eccc961bba..d799e562a39a 100644 > > > --- a/kernel/kprobes.c > > > +++ b/kernel/kprobes.c > > > @@ -430,6 +430,28 @@ void opt_pre_handler(struct kprobe *p, struct pt_regs *regs) > > > } > > > NOKPROBE_SYMBOL(opt_pre_handler); > > > > > > +void optprobe_optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) > > > +{ > > > + if (kprobe_disabled(&op->kp)) > > > + return; > > > + > > > + preempt_disable(); > > > + > > > + if (kprobe_running()) { > > > + kprobes_inc_nmissed_count(&op->kp); > > > + } else { > > > + op->set_pc(op, regs); > > > + __this_cpu_write(current_kprobe, &op->kp); > > > + get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; > > > + opt_pre_handler(&op->kp, regs); > > > + __this_cpu_write(current_kprobe, NULL); > > > + } > > > + > > > + preempt_enable(); > > > +} > > > +NOKPROBE_SYMBOL(optprobe_optimized_callback) > > > + > > > + > > > /* Free optimized instructions and optimized_kprobe */ > > > static void free_aggr_kprobe(struct kprobe *p) > > > { > > > -- > > > 2.33.0 > > > > > > -- > Masami Hiramatsu <mhiramat@kernel.org>
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