Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755588AbbFQShJ (ORCPT ); Wed, 17 Jun 2015 14:37:09 -0400 Received: from mail-qk0-f169.google.com ([209.85.220.169]:36690 "EHLO mail-qk0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754447AbbFQShD (ORCPT ); Wed, 17 Jun 2015 14:37:03 -0400 Message-ID: <5581BE4C.8070604@linaro.org> Date: Wed, 17 Jun 2015 14:37:00 -0400 From: David Long User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: William Cohen , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, Russell King CC: sandeepa.s.prabhu@gmail.com, Steve Capper , "Jon Medhurst (Tixy)" , Masami Hiramatsu , Ananth N Mavinakayanahalli , Anil S Keshavamurthy , davem@davemloft.net, Mark Brown , linux-kernel@vger.kernel.org Subject: Re: [PATCH v7 5/7] arm64: Add trampoline code for kretprobes References: <1434395229-6654-1-git-send-email-dave.long@linaro.org> <1434395229-6654-6-git-send-email-dave.long@linaro.org> <55803C47.6030000@redhat.com> In-Reply-To: <55803C47.6030000@redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5082 Lines: 134 On 06/16/15 11:09, William Cohen wrote: > On 06/15/2015 03:07 PM, David Long wrote: >> From: William Cohen >> >> The trampoline code is used by kretprobes to capture a return from a probed >> function. This is done by saving the registers, calling the handler, and >> restoring the registers. The code then returns to the roginal saved caller > > s/roginal/original > Hopefully no one wants a v8 if it turns out only to be to fix this typo in the commit description. I'll keep this in mind if a respin is needed for other reasons. >> return address. It is necessary to do this directly instead of using a >> software breakpoint because the code used in processing that breakpoint >> could itself be kprobe'd and cause a problematic reentry into the debug >> exception handler. >> >> Signed-off-by: William Cohen >> Signed-off-by: David A. Long >> --- >> arch/arm64/include/asm/kprobes.h | 1 + >> arch/arm64/kernel/kprobes-arm64.h | 41 +++++++++++++++++++++++++++++++++++++++ >> arch/arm64/kernel/kprobes.c | 26 +++++++++++++++++++++++++ >> 3 files changed, 68 insertions(+) >> >> diff --git a/arch/arm64/include/asm/kprobes.h b/arch/arm64/include/asm/kprobes.h >> index af31c4d..d081f49 100644 >> --- a/arch/arm64/include/asm/kprobes.h >> +++ b/arch/arm64/include/asm/kprobes.h >> @@ -58,5 +58,6 @@ int kprobe_exceptions_notify(struct notifier_block *self, >> unsigned long val, void *data); >> int kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr); >> int kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr); >> +void kretprobe_trampoline(void); >> >> #endif /* _ARM_KPROBES_H */ >> diff --git a/arch/arm64/kernel/kprobes-arm64.h b/arch/arm64/kernel/kprobes-arm64.h >> index ff8a55f..bdcfa62 100644 >> --- a/arch/arm64/kernel/kprobes-arm64.h >> +++ b/arch/arm64/kernel/kprobes-arm64.h >> @@ -27,4 +27,45 @@ extern kprobes_pstate_check_t * const kprobe_condition_checks[16]; >> enum kprobe_insn __kprobes >> arm_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi); >> >> +#define SAVE_REGS_STRING\ >> + " stp x0, x1, [sp, #16 * 0]\n" \ >> + " stp x2, x3, [sp, #16 * 1]\n" \ >> + " stp x4, x5, [sp, #16 * 2]\n" \ >> + " stp x6, x7, [sp, #16 * 3]\n" \ >> + " stp x8, x9, [sp, #16 * 4]\n" \ >> + " stp x10, x11, [sp, #16 * 5]\n" \ >> + " stp x12, x13, [sp, #16 * 6]\n" \ >> + " stp x14, x15, [sp, #16 * 7]\n" \ >> + " stp x16, x17, [sp, #16 * 8]\n" \ >> + " stp x18, x19, [sp, #16 * 9]\n" \ >> + " stp x20, x21, [sp, #16 * 10]\n" \ >> + " stp x22, x23, [sp, #16 * 11]\n" \ >> + " stp x24, x25, [sp, #16 * 12]\n" \ >> + " stp x26, x27, [sp, #16 * 13]\n" \ >> + " stp x28, x29, [sp, #16 * 14]\n" \ >> + " str x30, [sp, #16 * 15]\n" \ >> + " mrs x0, nzcv\n" \ >> + " str x0, [sp, #8 * 33]\n" >> + >> + >> +#define RESTORE_REGS_STRING\ >> + " ldr x0, [sp, #8 * 33]\n" \ >> + " msr nzcv, x0\n" \ >> + " ldp x0, x1, [sp, #16 * 0]\n" \ >> + " ldp x2, x3, [sp, #16 * 1]\n" \ >> + " ldp x4, x5, [sp, #16 * 2]\n" \ >> + " ldp x6, x7, [sp, #16 * 3]\n" \ >> + " ldp x8, x9, [sp, #16 * 4]\n" \ >> + " ldp x10, x11, [sp, #16 * 5]\n" \ >> + " ldp x12, x13, [sp, #16 * 6]\n" \ >> + " ldp x14, x15, [sp, #16 * 7]\n" \ >> + " ldp x16, x17, [sp, #16 * 8]\n" \ >> + " ldp x18, x19, [sp, #16 * 9]\n" \ >> + " ldp x20, x21, [sp, #16 * 10]\n" \ >> + " ldp x22, x23, [sp, #16 * 11]\n" \ >> + " ldp x24, x25, [sp, #16 * 12]\n" \ >> + " ldp x26, x27, [sp, #16 * 13]\n" \ >> + " ldp x28, x29, [sp, #16 * 14]\n" \ >> + " ldr x30, [sp, #16 * 15]\n" >> + >> #endif /* _ARM_KERNEL_KPROBES_ARM64_H */ >> diff --git a/arch/arm64/kernel/kprobes.c b/arch/arm64/kernel/kprobes.c >> index 6255814..570218c 100644 >> --- a/arch/arm64/kernel/kprobes.c >> +++ b/arch/arm64/kernel/kprobes.c >> @@ -560,6 +560,32 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) >> return 0; >> } >> >> +/* >> + * When a retprobed function returns, this code saves registers and >> + * calls trampoline_handler() runs, which calls the kretprobe's handler. >> + */ >> +static void __used __kprobes kretprobe_trampoline_holder(void) >> +{ >> + asm volatile (".global kretprobe_trampoline\n" >> + "kretprobe_trampoline:\n" >> + "sub sp, sp, %0\n" >> + SAVE_REGS_STRING >> + "mov x0, sp\n" >> + "bl trampoline_probe_handler\n" >> + /* Replace trampoline address in lr with actual >> + orig_ret_addr return address. */ >> + "str x0, [sp, #16 * 15]\n" >> + RESTORE_REGS_STRING >> + "add sp, sp, %0\n" >> + "ret\n" >> + : : "I"(sizeof(struct pt_regs)) : "memory"); >> +} >> + >> +static void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs) >> +{ >> + return (void *) 0; >> +} >> + >> int __init arch_init_kprobes(void) >> { >> return 0; >> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/