Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753474AbcD0SyE (ORCPT ); Wed, 27 Apr 2016 14:54:04 -0400 Received: from mail-qk0-f172.google.com ([209.85.220.172]:32938 "EHLO mail-qk0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753338AbcD0Sxa (ORCPT ); Wed, 27 Apr 2016 14:53:30 -0400 From: David Long To: Catalin Marinas , Will Deacon , Sandeepa Prabhu , William Cohen , Pratyush Anand , Steve Capper , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Marc Zyngier Cc: Dave P Martin , Mark Rutland , Robin Murphy , Ard Biesheuvel , Jens Wiklander , Christoffer Dall , =?UTF-8?q?Alex=20Benn=C3=A9e?= , Yang Shi , Greg Kroah-Hartman , Viresh Kumar , "Suzuki K. Poulose" , Kees Cook , Zi Shen Lim , John Blackwood , Feng Kan , Balamurugan Shanmugam , James Morse , Vladimir Murzin , Mark Salyzyn , Petr Mladek , Andrew Morton , Mark Brown Subject: [PATCH v12 09/10] arm64: Add kernel return probes support (kretprobes) Date: Wed, 27 Apr 2016 14:53:04 -0400 Message-Id: <1461783185-9056-10-git-send-email-dave.long@linaro.org> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1461783185-9056-1-git-send-email-dave.long@linaro.org> References: <1461783185-9056-1-git-send-email-dave.long@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3689 Lines: 114 From: Sandeepa Prabhu The pre-handler of this special 'trampoline' kprobe executes the return probe handler functions and restores original return address in ELR_EL1. This way the saved pt_regs still hold the original register context to be carried back to the probed kernel function. Signed-off-by: Sandeepa Prabhu Signed-off-by: David A. Long --- arch/arm64/Kconfig | 1 + arch/arm64/kernel/kprobes.c | 75 ++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 75 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 222bfb9..39bea20 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -84,6 +84,7 @@ config ARM64 select HAVE_RCU_TABLE_FREE select HAVE_SYSCALL_TRACEPOINTS select HAVE_KPROBES + select HAVE_KRETPROBES if HAVE_KPROBES select IOMMU_DMA if IOMMU_SUPPORT select IRQ_DOMAIN select IRQ_FORCED_THREADING diff --git a/arch/arm64/kernel/kprobes.c b/arch/arm64/kernel/kprobes.c index 0a2e00e..1c881cd 100644 --- a/arch/arm64/kernel/kprobes.c +++ b/arch/arm64/kernel/kprobes.c @@ -552,7 +552,80 @@ bool arch_within_kprobe_blacklist(unsigned long addr) void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs) { - return NULL; + 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) { + __this_cpu_write(current_kprobe, &ri->rp->kp); + get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; + ri->rp->handler(ri, regs); + __this_cpu_write(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); + + 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 (void *) orig_ret_addr; +} + +void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, + struct pt_regs *regs) +{ + ri->ret_addr = (kprobe_opcode_t *)regs->regs[30]; + + /* replace return addr (x30) with trampoline */ + regs->regs[30] = (long)&kretprobe_trampoline; +} + +int __kprobes arch_trampoline_kprobe(struct kprobe *p) +{ + return 0; } int __init arch_init_kprobes(void) -- 2.5.0