Re: [PATCH v5] arm64: kprobe: Enable OPTPROBE for arm64

[Jianhua Liu <jianhua.ljh@gmail.com>]

On Thu, Dec 16, 2021 at 8:26 PM Jianhua Liu <jianhua.ljh@gmail.com> wrote:
>
> On Thu, Dec 16, 2021 at 7:18 PM liuqi (BA) <liuqi115@huawei.com> wrote:
> >
> >
> >
> > On 2021/12/14 23:55, Jianhua Liu wrote:
> > > 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.
> > >
> >
> > Hi Jianhua,
> >
> > Could you kindly review this patch and test it on your UNISOC s9863a
> > platform? Let's work together to make arm64 optprobe work : )
> >
> > Thanks,
> > Qi
>
> OK, I will review. I have left UNISOC, I get some help from old
> colleage to do the test.
> Only on weekend, he can do it. So the time will be longer a little.
>
> Thanks
> Jianhua
>
>
Hi Qi,
I have tested your patch on UNISOC s9863a.
Test case "kprobe_example & kretprobe_example" is OK.

Two point:
1. backtrace is not perfect.
   optprobe_common does not saved frame pointer,
   backtrace lacks two calls.
such as for dup_mm: lack copy_process-->dup_mm
dup_mm backtrace from your patch:
[  832.387066] CPU: 0 PID: 296 Comm: sh Not tainted 5.16.0-rc5+ #8
[  832.387078] Hardware name: Spreadtrum SP9863A-1H10 Board (DT)
[  832.387083] Call trace:
[  832.387086]  dump_backtrace+0x0/0x1e0
[  832.387103]  show_stack+0x24/0x30
[  832.387112]  dump_stack_lvl+0x68/0x84
[  832.387123]  dump_stack+0x18/0x34
[  832.387131]  handler_pre+0x40/0x50 [kprobe_example]
[  832.387143]  opt_pre_handler+0x84/0xc0
[  832.387154]  optprobe_optimized_callback+0xec/0x164
[  832.387164]  optprobe_common+0x70/0xc4
[  832.387173]  kernel_clone+0x98/0x440
[  832.387182]  __do_sys_clone+0x54/0x80
[  832.387191]  __arm64_sys_clone+0x2c/0x40
[  832.387199]  invoke_syscall+0x50/0x120
[  832.387208]  el0_svc_common.constprop.0+0x4c/0xf4
[  832.387217]  do_el0_svc+0x30/0x9c
[  832.387225]  el0_svc+0x20/0x60
[  832.387235]  el0t_64_sync_handler+0xe8/0xf0
[  832.387242]  el0t_64_sync+0x1a0/0x1a4


dup_mm backtrace from other:
[  173.352294] CPU: 6 PID: 309 Comm: sh Not tainted 5.16.0-rc5+ #19
[  173.352301] Hardware name: Spreadtrum SP9863A-1H10 Board (DT)
[  173.352304] Call trace:
[  173.352307]  dump_backtrace+0x0/0x1d4
[  173.352319]  show_stack+0x18/0x24
[  173.352326]  dump_stack_lvl+0x68/0x84
[  173.352333]  dump_stack+0x18/0x34
[  173.352338]  handler_pre+0x38/0x48 [kprobe_example]
[  173.352347]  opt_pre_handler+0x74/0xb0
[  173.352354]  optimized_callback+0x108/0x130
[  173.352361]  optinsn_slot+0x258/0x1000
[  173.352366]  dup_mm+0x4/0x4b0
[  173.352373]  copy_process+0x1284/0x1360
[  173.352378]  kernel_clone+0x5c/0x3c0
[  173.352384]  __do_sys_clone+0x54/0x80
[  173.352390]  __arm64_sys_clone+0x24/0x30
[  173.352396]  invoke_syscall+0x48/0x114
[  173.352402]  el0_svc_common.constprop.0+0x44/0xec
[  173.352408]  do_el0_svc+0x24/0x90
[  173.352413]  el0_svc+0x20/0x60
[  173.352420]  el0t_64_sync_handler+0xe8/0xf0
[  173.352427]  el0t_64_sync+0x1a0/0x1a4

2. The reserve memory "OPT_SLOT_SIZE - PAGE_SIZE"  is waste.
   kernel/kprobe.c used only one PAGE_SIZE slot memory.

Thanks
Jianhua

> > 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>
> > > .
> > >