From patchwork Tue Oct 1 15:58:00 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sandeepa Prabhu X-Patchwork-Id: 2970851 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id D460F9F245 for ; Tue, 1 Oct 2013 16:02:26 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 0641E2041C for ; Tue, 1 Oct 2013 16:02:22 +0000 (UTC) Received: from casper.infradead.org (casper.infradead.org [85.118.1.10]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7569820417 for ; Tue, 1 Oct 2013 16:02:12 +0000 (UTC) Received: from merlin.infradead.org ([2001:4978:20e::2]) by casper.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1VR2Nn-00054U-QJ; Tue, 01 Oct 2013 16:01:08 +0000 Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1VR2NT-0005pK-CV; Tue, 01 Oct 2013 16:00:47 +0000 Received: from mail-pd0-f174.google.com ([209.85.192.174]) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1VR2Mw-0005dR-27 for linux-arm-kernel@lists.infradead.org; Tue, 01 Oct 2013 16:00:19 +0000 Received: by mail-pd0-f174.google.com with SMTP id y13so7398264pdi.5 for ; Tue, 01 Oct 2013 08:59:51 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=e1hvJAiC0T6sjOwm0tyKC1ODxS8KYVpfaqXmdl2jCsY=; b=QM+UIJ/zwrE79CYWClBaHwPQaBwIWaDEB4WFE2Cjx5u8xrInSQurM2xBp4ZnxVqEXG ckDoN4KSOyhij2C/44G+cRzCEfuox0jc5uOsfTNvBfoSDbW19+k0KjXHJAUBP3yomxKD 934h7whNA7R0SJKvKAfEf+69et/bj3w20T3fXTVIjRWCOQR+Zz8AHvTS0WrMK9YbqCFT FhclcnJdSp/ZsydHRknd31Nvtihhj2jQ8bX+L8ZBMQWoKGdfK2lnt7lPG3KylSmUQkot KXjHcXxX6yZdRxf8MvWP4H9T3Ri9mNXH1eriAfhnmJPkTj550y3x5yyiPIwwdvHis1Oe GVDg== X-Gm-Message-State: ALoCoQm1b7ThsvAxGtq6u8znvwY4tJNUjy8a4zjUQRjetZThc7rcE21yWSrrusji82Tzm4ylBJJT X-Received: by 10.68.252.33 with SMTP id zp1mr30448436pbc.95.1380643191888; Tue, 01 Oct 2013 08:59:51 -0700 (PDT) Received: from linaro-workstation.ban.broadcom.com ([202.122.18.226]) by mx.google.com with ESMTPSA id nj9sm7593660pbc.13.1969.12.31.16.00.00 (version=TLSv1.1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 01 Oct 2013 08:59:51 -0700 (PDT) From: Sandeepa Prabhu To: linux-arm-kernel@lists.infradead.org Subject: [PATCH RFC v1 5/5] AArch64: Support kretprobe support for ARM v8 Date: Tue, 1 Oct 2013 21:28:00 +0530 Message-Id: <1380643080-8984-6-git-send-email-sandeepa.prabhu@linaro.org> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1380643080-8984-1-git-send-email-sandeepa.prabhu@linaro.org> References: <1380643080-8984-1-git-send-email-sandeepa.prabhu@linaro.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20131001_120014_307323_37EE5660 X-CRM114-Status: GOOD ( 19.75 ) X-Spam-Score: -1.9 (-) Cc: tixy@linaro.org, deepak.saxena@linaro.org, linaro-kernel@lists.linaro.org, patches@linaro.org, Sandeepa Prabhu , catalin.marinas@arm.com, will.deacon@arm.com X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Unlike ARM v7(ldmia {.., pc} ) ARM v8 ISA does not support popping the PC value from stack or absolute addr without using one of the general purpose registers. This means return probes cannot return to the original return address directly without modifying register context, without trapping into debug exception. So like many other architectures, we prepare a global routine with NOPs, which serve as trampoline that hacks away the function return address, by placing an extra kprobe on the trampoline entry. The pre-handler of this special trampoline' kprobe execute return probe handlers and restore original return address in ELR_EL1, this way, saved pt_regs still hold the original register values to be carried back to the caller. Signed-off-by: Sandeepa Prabhu --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/kprobes.h | 1 + arch/arm64/kernel/kprobes.c | 115 ++++++++++++++++++++++++++++++++++++++- 3 files changed, 116 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 8cf5cde..9ca71b0 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -25,6 +25,7 @@ config ARM64 select HAVE_GENERIC_DMA_COHERENT select HAVE_HW_BREAKPOINT if PERF_EVENTS select HAVE_KPROBES if !XIP_KERNEL + select HAVE_KRETPROBES if (HAVE_KPROBES) select HAVE_MEMBLOCK select HAVE_PERF_EVENTS select IRQ_DOMAIN diff --git a/arch/arm64/include/asm/kprobes.h b/arch/arm64/include/asm/kprobes.h index a43f74f..c2a1ff1 100644 --- a/arch/arm64/include/asm/kprobes.h +++ b/arch/arm64/include/asm/kprobes.h @@ -53,5 +53,6 @@ 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); +void kretprobe_trampoline(void); #endif /* _ARM_KPROBES_H */ diff --git a/arch/arm64/kernel/kprobes.c b/arch/arm64/kernel/kprobes.c index 4840433..8c0f32d 100644 --- a/arch/arm64/kernel/kprobes.c +++ b/arch/arm64/kernel/kprobes.c @@ -508,6 +508,118 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) return 0; } +/* + * Kretprobes: kernel return probes handling + * + * ARM v8 ISA does not support popping the PC value from the + * stack like on v7(ldmia {..,pc}), so atleast one register need + * to be used for achieving branch. It means return probes cannot + * return back to the original return address directly without + * modifying the register context. + * + * So like many other architectures, we prepare a global routine + * with NOPs, which serve as trampoline address that hack away the + * function return, with the exact register context. + * + * We place a kprobe on trampoline routine entry to trap again and + * execute return probe handlers and restore original return address + * in ELR_EL1, this way saved pt_regs still hold the original + * register values to be carried back to the caller. + */ +static void __used kretprobe_trampoline_holder(void) +{ + asm volatile (".global kretprobe_trampoline\n" + "kretprobe_trampoline:\n" + "NOP\n\t" + "NOP\n\t"); +} + +static int __kprobes +trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) +{ + struct kretprobe_instance *ri = NULL; + struct hlist_head *head, empty_rp; + struct hlist_node *tmp; + unsigned long flags, orig_ret_addr = 0; + unsigned long trampoline_address = + (unsigned long)&kretprobe_trampoline; + + INIT_HLIST_HEAD(&empty_rp); + kretprobe_hash_lock(current, &head, &flags); + + /* + * It is possible to have multiple instances associated with a given + * task either because multiple functions in the call path have + * a return probe installed on them, and/or more than one return + * probe was registered for a target function. + * + * We can handle this because: + * - instances are always inserted at the head of the list + * - when multiple return probes are registered for the same + * function, the first instance's ret_addr will point to the + * real return address, and all the rest will point to + * kretprobe_trampoline + */ + hlist_for_each_entry_safe(ri, tmp, head, hlist) { + if (ri->task != current) + /* another task is sharing our hash bucket */ + continue; + + if (ri->rp && ri->rp->handler) { + __get_cpu_var(current_kprobe) = &ri->rp->kp; + get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; + ri->rp->handler(ri, regs); + __get_cpu_var(current_kprobe) = NULL; + } + + orig_ret_addr = (unsigned long)ri->ret_addr; + recycle_rp_inst(ri, &empty_rp); + + if (orig_ret_addr != trampoline_address) + /* + * This is the real return address. Any other + * instances associated with this task are for + * other calls deeper on the call stack + */ + break; + } + + kretprobe_assert(ri, orig_ret_addr, trampoline_address); + /* restore the original return address */ + instruction_pointer(regs) = orig_ret_addr; + reset_current_kprobe(); + kretprobe_hash_unlock(current, &flags); + preempt_enable_no_resched(); + + hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) { + hlist_del(&ri->hlist); + kfree(ri); + } + + /* return 1 so that post handlers not called */ + return 1; +} + +void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, + struct pt_regs *regs) +{ + ri->ret_addr = (kprobe_opcode_t *) + (instruction_pointer(regs) + sizeof(kprobe_opcode_t)); + + /* Replace the return addr with trampoline addr */ + instruction_pointer(regs) = (unsigned long)&kretprobe_trampoline; +} + +static struct kprobe trampoline = { + .addr = (kprobe_opcode_t *) &kretprobe_trampoline, + .pre_handler = trampoline_probe_handler +}; + +int __kprobes arch_trampoline_kprobe(struct kprobe *p) +{ + return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline; +} + /* Break Handler hook */ static struct break_hook kprobes_break_hook = { .esr_mask = BRK64_ESR_MASK, @@ -525,5 +637,6 @@ int __init arch_init_kprobes() register_break_hook(&kprobes_break_hook); register_step_hook(&kprobes_step_hook); - return 0; + /* register trampoline for kret probe */ + return register_kprobe(&trampoline); }