Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753757Ab3I0PmJ (ORCPT ); Fri, 27 Sep 2013 11:42:09 -0400 Received: from mail-pd0-f174.google.com ([209.85.192.174]:46231 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752219Ab3I0PmH (ORCPT ); Fri, 27 Sep 2013 11:42:07 -0400 Message-ID: <5245A73F.9030207@gmail.com> Date: Fri, 27 Sep 2013 23:41:51 +0800 From: Jiang Liu User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: Sandeepa Prabhu CC: Steven Rostedt , Catalin Marinas , Will Deacon , Jiang Liu , "linux-arm-kernel@lists.infradead.org" , linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 2/7] arm64: introduce interfaces to hotpatch kernel and module code References: <1380105868-31985-1-git-send-email-liuj97@gmail.com> <1380105868-31985-3-git-send-email-liuj97@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6347 Lines: 171 On 09/25/2013 10:35 PM, Sandeepa Prabhu wrote: > On 25 September 2013 16:14, Jiang Liu wrote: >> From: Jiang Liu >> >> Introduce aarch64_insn_patch_text() and __aarch64_insn_patch_text() >> to patch kernel and module code. >> >> Function aarch64_insn_patch_text() is a heavy version which may use >> stop_machine() to serialize all online CPUs, and function >> __aarch64_insn_patch_text() is light version without explicitly >> serialization. > Hi Jiang, > > I have written kprobes support for aarch64, and need both the > functionality (lightweight and stop_machine() versions). > I would like to rebase these API in kprobes, however slight changes > would require in case of stop_machine version, which I explained > below. > [Though kprobes cannot share Instruction encode support of jump labels > as, decoding & simulation quite different for kprobes/uprobes and > based around single stepping] > >> >> Signed-off-by: Jiang Liu >> Cc: Jiang Liu >> --- >> arch/arm64/include/asm/insn.h | 2 ++ >> arch/arm64/kernel/insn.c | 64 +++++++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 66 insertions(+) >> >> diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h >> index e7d1bc8..0ea7193 100644 >> --- a/arch/arm64/include/asm/insn.h >> +++ b/arch/arm64/include/asm/insn.h >> @@ -49,5 +49,7 @@ __AARCH64_INSN_FUNCS(nop, 0xFFFFFFFF, 0xD503201F) >> enum aarch64_insn_class aarch64_get_insn_class(u32 insn); >> >> bool aarch64_insn_hotpatch_safe(u32 old_insn, u32 new_insn); >> +int aarch64_insn_patch_text(void *addr, u32 *insns, int cnt); >> +int __aarch64_insn_patch_text(void *addr, u32 *insns, int cnt); >> >> #endif /* _ASM_ARM64_INSN_H */ >> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c >> index 8541c3a..50facfc 100644 >> --- a/arch/arm64/kernel/insn.c >> +++ b/arch/arm64/kernel/insn.c >> @@ -15,6 +15,8 @@ >> * along with this program. If not, see . >> */ >> #include >> +#include >> +#include >> #include >> >> static int aarch64_insn_cls[] = { >> @@ -69,3 +71,65 @@ bool __kprobes aarch64_insn_hotpatch_safe(u32 old_insn, u32 new_insn) >> return __aarch64_insn_hotpatch_safe(old_insn) && >> __aarch64_insn_hotpatch_safe(new_insn); >> } >> + >> +struct aarch64_insn_patch { >> + void *text_addr; >> + u32 *new_insns; >> + int insn_cnt; >> +}; >> + >> +int __kprobes __aarch64_insn_patch_text(void *addr, u32 *insns, int cnt) >> +{ >> + int i; >> + u32 *tp = addr; >> + >> + /* instructions must be word aligned */ >> + if (cnt <= 0 || ((uintptr_t)addr & 0x3)) >> + return -EINVAL; >> + >> + for (i = 0; i < cnt; i++) >> + tp[i] = insns[i]; >> + >> + flush_icache_range((uintptr_t)tp, (uintptr_t)tp + cnt * sizeof(u32)); >> + >> + return 0; >> +} > Looks fine, but do you need to check for CPU big endian mode here? (I > think swab32() needed if EL1 is in big-endian mode) Hi Sandeepa, Thanks for reminder, we do need to take care of data access endian issue here, will fix it in next version. > >> + >> +static int __kprobes aarch64_insn_patch_text_cb(void *arg) >> +{ >> + struct aarch64_insn_patch *pp = arg; >> + >> + return __aarch64_insn_patch_text(pp->text_addr, pp->new_insns, >> + pp->insn_cnt); >> +} >> + >> +int __kprobes aarch64_insn_patch_text(void *addr, u32 *insns, int cnt) >> +{ >> + int ret; >> + bool safe = false; >> + >> + /* instructions must be word aligned */ >> + if (cnt <= 0 || ((uintptr_t)addr & 0x3)) >> + return -EINVAL; >> + >> + if (cnt == 1) >> + safe = aarch64_insn_hotpatch_safe(*(u32 *)addr, insns[0]); >> + >> + if (safe) { >> + ret = __aarch64_insn_patch_text(addr, insns, cnt); >> + } else { > > Can you move the code below this into separate API that just apply > patch with stop_machine? And then a wrapper function for jump label > specific handling that checks for aarch64_insn_hotpatch_safe() ? > Also, it will be good to move the patching code out of insn.c to > patch.c (refer to arch/arm/kernel/patch.c). > > Please refer to attached file (my current implementation) to make > sense of exactly what kprobes would need (ignore the big-endian part > for now). I think splitting the code should be straight-forward and we > can avoid two different implementations. Please let me know if this > can be done, I will rebase my patches above your next version. After reading the attached file, I feel current implementation of aarch64_insn_patch_text() should satisfy kprobe's requirements too. The extra optimization of aarch64_insn_hotpatch_safe() should work for kprobe too. For example, if we install a kprobe on a function call instruction(BL), we need to replace "BL offset1" with "BRK" or "BL offset2". In such cases, we could directly patch the code without stop_machine(). Is there any special requirement that we must use stop_machine() for kprobe here? Thanks! Gerry > > Thanks, > Sandeepa >> + struct aarch64_insn_patch patch = { >> + .text_addr = addr, >> + .new_insns = insns, >> + .insn_cnt = cnt, >> + }; >> + >> + /* >> + * Execute __aarch64_insn_patch_text() on every online CPU, >> + * which ensure serialization among all online CPUs. >> + */ >> + ret = stop_machine(aarch64_insn_patch_text_cb, &patch, NULL); >> + } >> + >> + return ret; >> +} >> -- >> 1.8.1.2 >> >> -- >> 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/ -- 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/