From patchwork Tue Oct 31 15:50:53 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Dave Martin X-Patchwork-Id: 832569 Return-Path: X-Original-To: incoming-imx@patchwork.ozlabs.org Delivered-To: patchwork-incoming-imx@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=lists.infradead.org (client-ip=65.50.211.133; helo=bombadil.infradead.org; envelope-from=linux-arm-kernel-bounces+incoming-imx=patchwork.ozlabs.org@lists.infradead.org; receiver=) Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="j9K7Kb5V"; dkim-atps=neutral Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3yRG80290pz9sRg for ; Wed, 1 Nov 2017 02:52:32 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=VQkiUn18ZPYwMjdWW5skqM4s+eyWx3NdjX0kqn3PE9U=; b=j9K7Kb5VUE6WiC sx1xbBSkQi+TkddrYKWNMwbunUZsMmtLS6Y7sY0JXunzqu0Iv5ZhcBaCgJrMxu08K27eSAh93I5x+ Cp87RUZ43n22lx+kVflHATrbvLixQR/O2lGUzj/EER2TxW98JCenUrVTlZf5Jhu+qeqL3BAbEtigN avx/il+pUtPynWjgBDkbCtcfP7ckH7NwNin2D3r4NG1ZHf0fWKCgtJ+SQZxAmVgOBd3kAqYYTU5mB Clue0tbi0+oT0PUegdQLXQznV7d26dbdwCPtgS1oc2NqdUmDEFLU0myAELMLZRNy3wx+LBaNWHG32 t+88OwnOJhqfHzAWLhRw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1e9Yq1-0004Lz-DL; Tue, 31 Oct 2017 15:52:25 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1e9YpS-0003xy-Ov for linux-arm-kernel@lists.infradead.org; Tue, 31 Oct 2017 15:51:54 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 568151596; Tue, 31 Oct 2017 08:51:33 -0700 (PDT) Received: from e103592.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id A89803F24A; Tue, 31 Oct 2017 08:51:30 -0700 (PDT) From: Dave Martin To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 01/30] regset: Add support for dynamically sized regsets Date: Tue, 31 Oct 2017 15:50:53 +0000 Message-Id: <1509465082-30427-2-git-send-email-Dave.Martin@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1509465082-30427-1-git-send-email-Dave.Martin@arm.com> References: <1509465082-30427-1-git-send-email-Dave.Martin@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20171031_085150_832884_B16D8F49 X-CRM114-Status: GOOD ( 21.41 ) X-Spam-Score: -6.9 (------) X-Spam-Report: SpamAssassin version 3.4.1 on bombadil.infradead.org summary: Content analysis details: (-6.9 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at http://www.dnswl.org/, high trust [217.140.101.70 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -0.0 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, "H. J. Lu" , Okamoto Takayuki , libc-alpha@sourceware.org, Ard Biesheuvel , Szabolcs Nagy , Catalin Marinas , Will Deacon , Oleg Nesterov , Dmitry Safonov , Ingo Molnar , Alexander Viro , "H. Peter Anvin" , Thomas Gleixner , =?utf-8?q?Alex?= =?utf-8?q?_Benn=C3=A9e?= , kvmarm@lists.cs.columbia.edu Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+incoming-imx=patchwork.ozlabs.org@lists.infradead.org List-Id: linux-imx-kernel.lists.patchwork.ozlabs.org Currently the regset API doesn't allow for the possibility that regsets (or at least, the amount of meaningful data in a regset) may change in size. In particular, this results in useless padding being added to coredumps if a regset's current size is smaller than its theoretical maximum size. This patch adds a get_size() function to struct user_regset. Individual regset implementations can implement this function to return the current size of the regset data. A regset_size() function is added to provide callers with an abstract interface for determining the size of a regset without needing to know whether the regset is dynamically sized or not. The only affected user of this interface is the ELF coredump code: This patch ports ELF coredump to dump regsets with their actual size in the coredump. This has no effect except for new regsets that are dynamically sized and provide a get_size() implementation. Signed-off-by: Dave Martin Reviewed-by: Alex Bennée Reviewed-by: Catalin Marinas Cc: Oleg Nesterov Cc: Alexander Viro Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Dmitry Safonov Cc: H. J. Lu Reviewed-by: Catalin Marinas Reviewed-by: Alex Bennée --- **Dropped** Reviewed-by: Alex Bennée **Dropped** Reviewed-by: Catalin Marinas (due to bug fix applied against v4 of this patch.) Changes since v4 ---------------- * [bugfix] Due to some mis-renaming, the previous version of this patch changed NT_PRFPREG dumping behaviour in some situations on x86. To reduce the scope for confusion, the local variable previously named regset_size that was renamed (ambiguously) to size, is renamed again, to regset0_size. This makes it clear exactly what this variable is referring to. The reference to this variable from inside the regset loop is fixed to point back to it. --- fs/binfmt_elf.c | 10 ++++---- include/linux/regset.h | 67 ++++++++++++++++++++++++++++++++++++++++++++------ 2 files changed, 65 insertions(+), 12 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 73b01e4..c697882 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1699,7 +1699,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t, long signr, size_t *total) { unsigned int i; - unsigned int regset_size = view->regsets[0].n * view->regsets[0].size; + unsigned int regset0_size = regset_size(t->task, &view->regsets[0]); /* * NT_PRSTATUS is the one special case, because the regset data @@ -1708,11 +1708,11 @@ static int fill_thread_core_info(struct elf_thread_core_info *t, * We assume that regset 0 is NT_PRSTATUS. */ fill_prstatus(&t->prstatus, t->task, signr); - (void) view->regsets[0].get(t->task, &view->regsets[0], 0, regset_size, + (void) view->regsets[0].get(t->task, &view->regsets[0], 0, regset0_size, &t->prstatus.pr_reg, NULL); fill_note(&t->notes[0], "CORE", NT_PRSTATUS, - PRSTATUS_SIZE(t->prstatus, regset_size), &t->prstatus); + PRSTATUS_SIZE(t->prstatus, regset0_size), &t->prstatus); *total += notesize(&t->notes[0]); do_thread_regset_writeback(t->task, &view->regsets[0]); @@ -1728,7 +1728,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t, if (regset->core_note_type && regset->get && (!regset->active || regset->active(t->task, regset))) { int ret; - size_t size = regset->n * regset->size; + size_t size = regset_size(t->task, regset); void *data = kmalloc(size, GFP_KERNEL); if (unlikely(!data)) return 0; @@ -1743,7 +1743,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t, size, data); else { SET_PR_FPVALID(&t->prstatus, - 1, regset_size); + 1, regset0_size); fill_note(&t->notes[i], "CORE", NT_PRFPREG, size, data); } diff --git a/include/linux/regset.h b/include/linux/regset.h index 8e0c9fe..494ceda 100644 --- a/include/linux/regset.h +++ b/include/linux/regset.h @@ -107,6 +107,28 @@ typedef int user_regset_writeback_fn(struct task_struct *target, int immediate); /** + * user_regset_get_size_fn - type of @get_size function in &struct user_regset + * @target: thread being examined + * @regset: regset being examined + * + * This call is optional; usually the pointer is %NULL. + * + * When provided, this function must return the current size of regset + * data, as observed by the @get function in &struct user_regset. The + * value returned must be a multiple of @size. The returned size is + * required to be valid only until the next time (if any) @regset is + * modified for @target. + * + * This function is intended for dynamically sized regsets. A regset + * that is statically sized does not need to implement it. + * + * This function should not be called directly: instead, callers should + * call regset_size() to determine the current size of a regset. + */ +typedef unsigned int user_regset_get_size_fn(struct task_struct *target, + const struct user_regset *regset); + +/** * struct user_regset - accessible thread CPU state * @n: Number of slots (registers). * @size: Size in bytes of a slot (register). @@ -117,19 +139,33 @@ typedef int user_regset_writeback_fn(struct task_struct *target, * @set: Function to store values. * @active: Function to report if regset is active, or %NULL. * @writeback: Function to write data back to user memory, or %NULL. + * @get_size: Function to return the regset's size, or %NULL. * * This data structure describes a machine resource we call a register set. * This is part of the state of an individual thread, not necessarily * actual CPU registers per se. A register set consists of a number of * similar slots, given by @n. Each slot is @size bytes, and aligned to - * @align bytes (which is at least @size). + * @align bytes (which is at least @size). For dynamically-sized + * regsets, @n must contain the maximum possible number of slots for the + * regset, and @get_size must point to a function that returns the + * current regset size. * - * These functions must be called only on the current thread or on a - * thread that is in %TASK_STOPPED or %TASK_TRACED state, that we are - * guaranteed will not be woken up and return to user mode, and that we - * have called wait_task_inactive() on. (The target thread always might - * wake up for SIGKILL while these functions are working, in which case - * that thread's user_regset state might be scrambled.) + * Callers that need to know only the current size of the regset and do + * not care about its internal structure should call regset_size() + * instead of inspecting @n or calling @get_size. + * + * For backward compatibility, the @get and @set methods must pad to, or + * accept, @n * @size bytes, even if the current regset size is smaller. + * The precise semantics of these operations depend on the regset being + * accessed. + * + * The functions to which &struct user_regset members point must be + * called only on the current thread or on a thread that is in + * %TASK_STOPPED or %TASK_TRACED state, that we are guaranteed will not + * be woken up and return to user mode, and that we have called + * wait_task_inactive() on. (The target thread always might wake up for + * SIGKILL while these functions are working, in which case that + * thread's user_regset state might be scrambled.) * * The @pos argument must be aligned according to @align; the @count * argument must be a multiple of @size. These functions are not @@ -156,6 +192,7 @@ struct user_regset { user_regset_set_fn *set; user_regset_active_fn *active; user_regset_writeback_fn *writeback; + user_regset_get_size_fn *get_size; unsigned int n; unsigned int size; unsigned int align; @@ -371,5 +408,21 @@ static inline int copy_regset_from_user(struct task_struct *target, return regset->set(target, regset, offset, size, NULL, data); } +/** + * regset_size - determine the current size of a regset + * @target: thread to be examined + * @regset: regset to be examined + * + * Note that the returned size is valid only until the next time + * (if any) @regset is modified for @target. + */ +static inline unsigned int regset_size(struct task_struct *target, + const struct user_regset *regset) +{ + if (!regset->get_size) + return regset->n * regset->size; + else + return regset->get_size(target, regset); +} #endif /* */