From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6835CC433EF for ; Thu, 30 Jun 2022 13:13:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235252AbiF3NN2 (ORCPT ); Thu, 30 Jun 2022 09:13:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50766 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230305AbiF3NN0 (ORCPT ); Thu, 30 Jun 2022 09:13:26 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 136E01C1 for ; Thu, 30 Jun 2022 06:13:25 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id BA2B41F8D0; Thu, 30 Jun 2022 13:13:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1656594803; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=az2PcmLsfEyzYuYIxAQ6rsUqJQi4Vdffo4HR1jW5Or8=; b=JJ4uujP9SF4zLf7LbDiy17w8clfiG1Cx9LdLEwmO+1NEjL/aSXH4bYagqTBYcCP2i0bXqg VARxnuhaJw9fuX79/pSuqsQl4pPQ4lkuKJF16KQbZdG679q06WczXdAt6X67thgnmKbAIL BnfD+sB0u7dKwDSYpYmQTjCWAt9eG4g= Received: from suse.cz (unknown [10.100.201.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 822C52C141; Thu, 30 Jun 2022 13:13:23 +0000 (UTC) Date: Thu, 30 Jun 2022 15:13:20 +0200 From: Petr Mladek To: Antonio Borneo Cc: Jan Kiszka , Kieran Bingham , John Ogness , linux-kernel@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com Subject: Re: [PATCH] scripts/gdb: fix 'lx-dmesg' on 32 bits arch Message-ID: References: <20220617143758.137307-1-antonio.borneo@foss.st.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220617143758.137307-1-antonio.borneo@foss.st.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 2022-06-17 16:37:58, Antonio Borneo wrote: > The type atomic_long_t can have size 4 or 8 bytes, depending on > CONFIG_64BIT; it's only content, the field 'counter', is either an > int or a s64 value. > > Current code incorrectly uses the fixed size utils.read_u64() to > read the field 'counter' inside atomic_long_t. > > On 32 bits architectures reading the last element 'tail_id' of the > struct prb_desc_ring: > struct prb_desc_ring { > ... > atomic_long_t tail_id; > }; > causes the utils.read_u64() to access outside the boundary of the > struct and the gdb command 'lx-dmesg' exits with error: > Python Exception : index out of range > Error occurred in Python: index out of range > > Use the existing utils.read_ulong() to read 'counter' inside the > atomic_long_t. I was about to accept this. But then I wondered if we could somehow detect the really used atomic_long_t counter type size. I have updated your patch. It works for me on x86_64. Could you please check it on 32-bit system? Here is the patch: >From bb5b6a7ad6f4339a1102585c691cb725182c0acf Mon Sep 17 00:00:00 2001 From: Antonio Borneo Date: Fri, 17 Jun 2022 16:37:58 +0200 Subject: [PATCH] scripts/gdb: fix 'lx-dmesg' on 32 bits arch The type atomic_long_t can have size 4 or 8 bytes, depending on CONFIG_64BIT; it's only content, the field 'counter', is either an int or a s64 value. Current code incorrectly uses the fixed size utils.read_u64() to read the field 'counter' inside atomic_long_t. On 32 bits architectures reading the last element 'tail_id' of the struct prb_desc_ring: struct prb_desc_ring { ... atomic_long_t tail_id; }; causes the utils.read_u64() to access outside the boundary of the struct and the gdb command 'lx-dmesg' exits with error: Python Exception : index out of range Error occurred in Python: index out of range Query the really used atomic_long_t counter type size. Fixes: e60768311af8 ("scripts/gdb: update for lockless printk ringbuffer") Signed-off-by: Antonio Borneo [pmladek@suse.com: Query the really used atomic_long_t counter type size] Link: https://lore.kernel.org/r/20220617143758.137307-1-antonio.borneo@foss.st.com --- scripts/gdb/linux/dmesg.py | 9 +++------ scripts/gdb/linux/utils.py | 14 ++++++++++++-- 2 files changed, 15 insertions(+), 8 deletions(-) diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py index d5983cf3db7d..c771831eb077 100644 --- a/scripts/gdb/linux/dmesg.py +++ b/scripts/gdb/linux/dmesg.py @@ -22,7 +22,6 @@ prb_desc_type = utils.CachedType("struct prb_desc") prb_desc_ring_type = utils.CachedType("struct prb_desc_ring") prb_data_ring_type = utils.CachedType("struct prb_data_ring") printk_ringbuffer_type = utils.CachedType("struct printk_ringbuffer") -atomic_long_type = utils.CachedType("atomic_long_t") class LxDmesg(gdb.Command): """Print Linux kernel log buffer.""" @@ -68,8 +67,6 @@ class LxDmesg(gdb.Command): off = prb_data_ring_type.get_type()['data'].bitpos // 8 text_data_addr = utils.read_ulong(text_data_ring, off) - counter_off = atomic_long_type.get_type()['counter'].bitpos // 8 - sv_off = prb_desc_type.get_type()['state_var'].bitpos // 8 off = prb_desc_type.get_type()['text_blk_lpos'].bitpos // 8 @@ -89,9 +86,9 @@ class LxDmesg(gdb.Command): # read in tail and head descriptor ids off = prb_desc_ring_type.get_type()['tail_id'].bitpos // 8 - tail_id = utils.read_u64(desc_ring, off + counter_off) + tail_id = utils.read_atomic_long(desc_ring, off) off = prb_desc_ring_type.get_type()['head_id'].bitpos // 8 - head_id = utils.read_u64(desc_ring, off + counter_off) + head_id = utils.read_atomic_long(desc_ring, off) did = tail_id while True: @@ -102,7 +99,7 @@ class LxDmesg(gdb.Command): desc = utils.read_memoryview(inf, desc_addr + desc_off, desc_sz).tobytes() # skip non-committed record - state = 3 & (utils.read_u64(desc, sv_off + counter_off) >> desc_flags_shift) + state = 3 & (utils.read_atomic_long(desc, sv_off) >> desc_flags_shift) if state != desc_committed and state != desc_finalized: if did == head_id: break diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py index ff7c1799d588..1553f68716cc 100644 --- a/scripts/gdb/linux/utils.py +++ b/scripts/gdb/linux/utils.py @@ -35,13 +35,12 @@ class CachedType: long_type = CachedType("long") - +atomic_long_type = CachedType("atomic_long_t") def get_long_type(): global long_type return long_type.get_type() - def offset_of(typeobj, field): element = gdb.Value(0).cast(typeobj) return int(str(element[field].address).split()[0], 16) @@ -129,6 +128,17 @@ def read_ulong(buffer, offset): else: return read_u32(buffer, offset) +atomic_long_counter_offset = atomic_long_type.get_type()['counter'].bitpos +atomic_long_counter_sizeof = atomic_long_type.get_type()['counter'].type.sizeof + +def read_atomic_long(buffer, offset): + global atomic_long_counter_offset + global atomic_long_counter_sizeof + + if atomic_long_counter_sizeof == 8: + return read_u64(buffer, offset + atomic_long_counter_offset) + else: + return read_u32(buffer, offset + atomic_long_counter_offset) target_arch = None -- 2.35.3