From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Fri, 24 Feb 2012 18:16:21 +0000 Subject: [PATCH] ARM: ptrace: fix ptrace_read_user for !CONFIG_MMU platforms In-Reply-To: <20120224143655.GH13504@mudshark.cambridge.arm.com> References: <1329763029-18220-1-git-send-email-will.deacon@arm.com> <20120220194634.GK26840@n2100.arm.linux.org.uk> <201202210124.23028.paul@codesourcery.com> <20120221083612.GG22562@n2100.arm.linux.org.uk> <20120221100041.GA19696@mudshark.cambridge.arm.com> <20120221101052.GH22562@n2100.arm.linux.org.uk> <20120221105250.GC19696@mudshark.cambridge.arm.com> <20120221113548.GK22562@n2100.arm.linux.org.uk> <20120221132216.GJ19696@mudshark.cambridge.arm.com> <20120224143655.GH13504@mudshark.cambridge.arm.com> Message-ID: <20120224181621.GH22562@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Feb 24, 2012 at 02:36:55PM +0000, Will Deacon wrote: > On Tue, Feb 21, 2012 at 01:22:16PM +0000, Will Deacon wrote: > > On Tue, Feb 21, 2012 at 11:35:48AM +0000, Russell King - ARM Linux wrote: > > > I don't think fixing this in mainline until we know the full story behind > > > this is the right thing to be doing. There's no point fixing a feature > > > which no one's using. > > > > Understood. Paul - would you please be able to confirm that: > > > > (a) GDB is currently broken on uclinux? (it certainly looks that way) > > (b) My proposed patch fixes the problem? > > > > If you don't have an environment set up, I wonder if there's somebody else > > we can poke who's playing with this stuff. > > Well in the meantime I had a play with the latest CodeSourcery tools: > > GNU gdbserver (Sourcery G++ Lite 2011.03-46) 7.2.50.20100908-cvs > Copyright (C) 2010 Free Software Foundation, Inc. > gdbserver is free software, covered by the GNU General Public License. > This gdbserver was configured as "arm-uclinuxeabi" > > on the target and > > GNU gdb (Sourcery G++ Lite 2011.03-46) 7.2.50.20100908-cvs > Copyright (C) 2010 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. Type "show copying" > and "show warranty" for details. > This GDB was configured as "--host=i686-pc-linux-gnu --target=arm-uclinuxeabi". > > on the host. > > It seems as though my ptrace patch makes *no difference* because these > tools don't even use the PT_ADDR_TEXT etc magic offsets! As a result, > trying to set a breakpoint by symbol fails miserably because it tries to > poke the symbol offset directly, without adding on the base address of the > text. > > Are there any tools available that use these magic numbers or are mine just > too old? Given that the whole thing dies after a while with: > > [ 909.062821] [430] gdbserver: obsolete system call 02b37558. > > I'm not entirely convinced by the stability of what I'm using (that syscall > number looks like an address to me). That suggests that this stuff definitely hasn't been tested, and there's no users of it (if there were I'm sure someone - either gdb folk or some kernel people) would've seen a bug report. Therefore, I propose that we remove this code from the kernel unless there's someone out there who can positively test this stuff as definitely working.