- linaro-toolchain - lists.linaro.org

by Ulrich Weigand

== GDB == * Worked with Will Deacon and the Linaro kernel team to make sure HW watchpoint and Versatile Express errata fixes are included in the upcoming Linaro kernel release. * Committed GDB HW watchpoint patches to mainline, and backport to Linaro GDB. This completes work on the HW watchpoint blueprint. * Worked on fixing the GDB part of #620611 (Unable to backtrace out of vector page 0xffff0000). Posted (two versions of) mainline patch for discussion. * Worked on kernel patch for #615974 (Interrupted system call handling). Mit freundlichen Gruessen / Best Regards Ulrich Weigand -- Dr. Ulrich Weigand | Phone: +49-7031/16-3727 STSM, GNU compiler and toolchain for Linux on System z and Cell/B.E. IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Martin Jetter | Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen | Registergericht: Amtsgericht Stuttgart, HRB 243294

14 years, 10 months

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[ACTIVITY] Weekly status

by Richard Sandiford

== This week == * Looked at the poor code generated for Neon load/store intrinsics. Looked into the history behind the treatment of VFP registers by CANNOT_CHANGE_MODE_CLASS. Peter confirmed that the restrictions apply only to VFPv1. Wrote a patch to improve the code, which partly overlapped with Julian's. * Looked at how the operations should be represented at the tree level. Experimented with various combinations of tree codes and types to see which felt right. Wrote this up in the message I sent today. == Next week == * More vectorisation. * Submit some queued patches. * Maybe some bug fixing. (I see there's a reload bug just waiting to be claimed by a lucky developer.) On holiday the following week. Richard

14 years, 10 months

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Re: Unavailable for a bit

by Michael Hope

Services at ex.seabright.co.nz are back up. On Tue, Feb 22, 2011 at 10:06 PM, Michael Hope <michael.hope(a)linaro.org> wrote: > Hi there. We've had an earthquake. Family and friends are fine but i'll be > unavailable for a few days. Services on ex.seabright.co.nz are down. I'll > cancel Wednesdays standup call. > > See you soon, > > -- Michael

14 years, 10 months

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[ACTIVITY] February 20-24

by Revital1 Eres

Hello, Implemented a patch for SMS to support targets that their doloop part is not decoupled from the rest of the loop's instructions (which is the current assumption of SMS). ARM is an example of such target, where the loop's instructions might use CC reg which is used in the doloop part. Now testing the patch on ARM and other targets that have do-loop. Thanks, Revital

14 years, 10 months

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[ACTIVITY] February 20-24

by Ira Rosen

Hi, * vectorizer cost model - implemented builtin_vectorization_cost for NEON - added register spilling considerations to the cost model - started testing/tuning on EEMBC Telecom and DenBench (for now I have only two examples for spilling: fdct_int32 mp4encode that shouldn't get vectorized and viterbi that should) * measured vectorization impact on Telecom autcor - it's about 5x (initially I got run time segfault, but the bug is already fixed on GCC trunk, I'll have to check gcc-linaro-4.5 as well) * NEON-vs.non-NEON degradation - started to look at aes. There are 6 loops that get vectorized with 4.6 (due to this patch http://gcc.gnu.org/ml/gcc-patches/2010-05/msg01927.html that allows cond_expr in number of loop iterations expressions) and vzip/vuzp patch, but not with gcc-linaro-4.5. But it doesn't explain the degradation of course. - I don't understand mp4decodepsnr improvement, since I don't see any loops or basic blocks vectorized. Ira

14 years, 10 months

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Weekly Activity report

by Mounir Bsaibes

Please find the compilation of the weekly activity reports at the following link, if I have missed anyone let me know. https://wiki.linaro.org/WorkingGroups/ToolChain/ActivityReports/2011-02-18 In your report please try to stick to the following format, to help make the report consistant: == Topic == * item 1 * items 2 See https://wiki.linaro.org/Process/Reporting Thanks & Regards, Mounir

14 years, 10 months

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Improving the code generated for vld and vst intrinsics

by Richard Sandiford

One of the vectorisation discussions from last year was about the poor code GCC generates for vld{2,3,4}_*() and vst{2,3,4}_*(). It forces the result of the loads onto the stack, then loads the individual pieces from there. It does the same thing in reverse for stores. I think there are two major problems here: 1. The result of the vld*() is a record type such as: typedef struct int16x4x3_t { int16x4_t val[3]; } int16x4x3_t; Ideally, we'd like one of these structures to be stored in a pseudo register. However, the ARM port currently limits in-register record types to 64 bits, so something this big is always given BLKmode and stored on the stack. A simple "fix" for this is to increase MAX_FIXED_MODE_SIZE. That would do the right thing for the structures in arm_neon.h, but wouldn't be safe in general. 2. The vld*() returns values as a single integer (such as EI mode), while uses of the value will typically be in a vector mode such as V4SI. CANNOT_CHANGE_MODE_CLASS doesn't allow direct "mode-punning" between the two in VFP_REGS, so this again forces the punning to be done on the stack. The code in question is: /* FPA registers can't do subreg as all values are reformatted to internal precision. VFP registers may only be accessed in the mode they were set. */ #define CANNOT_CHANGE_MODE_CLASS(FROM, TO, CLASS) \ (GET_MODE_SIZE (FROM) != GET_MODE_SIZE (TO) \ ? reg_classes_intersect_p (FPA_REGS, (CLASS)) \ || reg_classes_intersect_p (VFP_REGS, (CLASS)) \ However, the VFP restriction appears to be specific to VFPv1 -- thanks to Peter for the archaeology -- and isn't a problem for v6+. In that case, removing this restriction is an important optimisation. I tried the patch below on the following simple testcase: #include "arm_neon.h" void foo (uint16_t *a) { uint16x4x3_t x, y; x = vld3_u16 (a); y = vld3_u16 (a + 12); x.val[0] = vadd_u16 (x.val[0], y.val[0]); x.val[1] = vadd_u16 (x.val[1], y.val[1]); x.val[2] = vadd_u16 (x.val[2], y.val[2]); vst3_u16 (a, x); } (not necessarily sensible!). Before the patch, -O2 produced: sub sp, sp, #48 add r3, r0, #24 vld3.16 {d16-d18}, [r3] vld3.16 {d20-d22}, [r0] add r3, sp, #24 vstmia sp, {d20-d22} vstmia r3, {d16-d18} fldd d19, [sp, #8] fldd d16, [sp, #0] fldd d17, [sp, #24] fldd d20, [sp, #32] vadd.i16 d18, d16, d17 vadd.i16 d17, d19, d20 fldd d19, [sp, #16] fldd d20, [sp, #40] vadd.i16 d16, d19, d20 fstd d18, [sp, #0] fstd d17, [sp, #8] fstd d16, [sp, #16] vldmia sp, {d16-d18} vst3.16 {d16-d18}, [r0] add sp, sp, #48 bx lr After the patch we get: vld3.16 {d24-d26}, [r0] add r3, r0, #24 vld3.16 {d20-d22}, [r3] vmov q8, q12 @ ti vadd.i16 d17, d17, d21 vadd.i16 d16, d24, d20 vadd.i16 d18, d26, d22 vst3.16 {d16-d18}, [r0] bx lr The VMOV is a bit disappointing, and needs further investigation. The first hunk fixes (2), and I think is correct. The second hunk hacks (1), and isn't suitable in itself. I'll next try to make arm_neon.h use built-in record types that are explicitly EImode, which should remove the need to change MAX_FIXED_MODE_SIZE. Richard Index: gcc/gcc/config/arm/arm.h =================================================================== --- gcc.orig/gcc/config/arm/arm.h +++ gcc/gcc/config/arm/arm.h @@ -1171,10 +1171,12 @@ enum reg_class /* FPA registers can't do subreg as all values are reformatted to internal precision. VFP registers may only be accessed in the mode they were set. */ -#define CANNOT_CHANGE_MODE_CLASS(FROM, TO, CLASS) \ - (GET_MODE_SIZE (FROM) != GET_MODE_SIZE (TO) \ - ? reg_classes_intersect_p (FPA_REGS, (CLASS)) \ - || reg_classes_intersect_p (VFP_REGS, (CLASS)) \ 2+#define CANNOT_CHANGE_MODE_CLASS(FROM, TO, CLASS) \ + (GET_MODE_SIZE (FROM) != GET_MODE_SIZE (TO) \ + ? (reg_classes_intersect_p (FPA_REGS, (CLASS)) \ + || (TARGET_VFP \ + && reg_classes_intersect_p (VFP_REGS, (CLASS)) \ + && arm_fpu_desc->rev == 1)) \ : 0) /* The class value for index registers, and the one for base regs. */ @@ -2458,4 +2460,6 @@ enum arm_builtins instruction. */ #define MAX_LDM_STM_OPS 4 +#define MAX_FIXED_MODE_SIZE GET_MODE_BITSIZE (XImode) + #endif /* ! GCC_ARM_H */

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Unavailable for a bit

by Michael Hope

Hi there. We've had an earthquake. Family and friends are fine but i'll be unavailable for a few days. Services on ex.seabright.co.nz are down. I'll cancel Wednesdays standup call. See you soon, -- Michael

14 years, 10 months

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[ACTIVITY] Feb 14 - Feb 17

by Ulrich Weigand

== GDB == * Working with Will Deacon, identified root cause of GDB problems running on Versatile Express in SMP mode, and verified that Errata workaround fixes the problem * Finished testing GDB HW watchpoints patch on vexpress, submitted complete patch set for mainline inclusion * Reviewed Yao's mainline patch to enable displaced stepping in Thumb mode Mit freundlichen Gruessen / Best Regards Ulrich Weigand -- Dr. Ulrich Weigand | Phone: +49-7031/16-3727 STSM, GNU compiler and toolchain for Linux on System z and Cell/B.E. IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Martin Jetter | Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen | Registergericht: Amtsgericht Stuttgart, HRB 243294

14 years, 10 months

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[ACTIVITY] Feb 14 -- Feb 20

by Chung-Lin Tang

== Last week == * PR46178, PR46002: both upstream issues related to the priority coloring mode of IRA. Both patches submitted, the first already approved and committed. Vladimir M. did mention that the priority algorithm would be removed once his newer "cover class-less" patches goes in during stage1. Anyways, I got more familiar with IRA during the process, and the patches will still be applicable to 4.5/4.6. * PR43872: incorrectly aligned VLAs under ARM. This turned out to be a one-liner fix. Submitted upstream awaiting approval. * Discussed on email/IRC with Revital Eres on SMS and ARM doloop pattern issues. * Launchpad #721021: Linaro GCC ICE under -mtune=xscale. Investigated a bit; did not see ICE immediately, but GCC went into infinite loop (Khem Raj, the reporter, says it runs for a while then ICEs). * Coremark ARMv5TE vs ARMv7-A performance regression: reproduced consistently using our own Tegra boards. Investigated and seem to have found something, will post more detailed findings later. == This week == * Coremark investigation. * More GCC issues.

14 years, 10 months

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Continuous build results

by Michael Hope

Hi there. I've created a new mailing list for the automated build results of Linaro GCC, Linaro GDB, and (once-weekly) FSF 4.5 and 4.6. You can subscribe by going to: https://launchpad.net/~linaro-toolchain-builds I've subscribed everyone in the toolchain working group. If you'd like to get these emails, go to: https://launchpad.net/people/+me/+editemails and set 'Linaro Toolchain Builds' to 'Preferred address'. Any build failures will also go to linaro-toolchain(a)l.linaro.org. The archive is here: https://lists.launchpad.net/linaro-toolchain-builds/ You can also track the crude state of the build hosts here: http://ex.seabright.co.nz/helpers/scheduler and see things status scroll by on #linaro-cbuild on Freenode. This was kicked off due to the problems with the 2011.01 release. The follow-up is tracked here: https://blueprints.launchpad.net/gcc-linaro/+spec/incident-followup-1 -- Michael

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[ACTIVITY] 14th - 19th February

by Andrew Stubbs

== GCC == Posted 2 of our 4.5 patches upstream. My latest 4.6 build and test completed, so I've pushed an update to the bzr branch. The branch is now up to mainline state as of the 12th. Merged 3 4.5 patches into Linaro GCC 4.6. Upstream review isn't happening, so I've decided to commit them anyway. The last upload (FSF mainline as of 12th Feb) will therefore become the baseline I'm going to use for Linaro GCC 4.6. Begun benchmarking the questionable patches before forward porting them, using EEMBC. Michael Hope has given me access to one of his A9 Panda boards in New Zealand. This ought to have been straight-forward, but of course it wasn't. It took me a while to convince myself I was getting meaningful results and testing the right thing. Also the A9 seemed to be able to complete the configured iterations in 'zero' time, which fooled me for a while. I think I now have a set up that works. It seems to run very slowly sometimes though - something to do with SSH? ---- Upstream patched requiring review: * Thumb2 constants: http://gcc.gnu.org/ml/gcc-patches/2010-12/msg00652.html * Kazu's VFP testcases: http://gcc.gnu.org/ml/gcc-patches/2011-02/msg00128.html * Jie's thumb2 testcase fix: http://gcc.gnu.org/ml/gcc-patches/2011-02/msg00670.html * ARM EABI half-precision functions http://gcc.gnu.org/ml/gcc-patches/2011-02/msg00874.html * ARM Thumb2 Spill Likely tweak http://gcc.gnu.org/ml/gcc-patches/2011-02/msg00880.html

14 years, 10 months

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[ACTIVITY] report week 07

by Peter Maydell

RAG: Red: Amber: Green: DATE/QEMU conference place confirmed, travel booked Current Milestones: | Planned | Estimate | Actual | qemu-linaro 2011-03 | 2011-03-08 | 2011-03-08 | | Historical Milestones: finish virtio-system | 2010-08-27 | postponed | | finish testing PCI patches | 2010-10-01 | 2010-10-22 | 2010-10-18 | successful ARM qemu pull req | 2010-12-16 | 2010-12-16 | 2010-12-16 | finish qemu-cont-integration | 2011-01-25 | 2011-01-25 | handed off | first qemu-linaro release | 2011-02-08 | 2011-02-08 | 2011-02-08 | * maintain-beagle-models: + implemented missing epoll syscalls for qemu usermode, submitted upstream https://bugs.launchpad.net/qemu-linaro/+bug/644961 + tracked down the problem causing serial console to break: the new Linux driver uses some extra features of the UART which we weren't modelling https://bugs.launchpad.net/qemu-linaro/+bug/714600 * merge-correctness-fixes: + reworked VZIP/VUZP patch as per review comments, resubmitted + reviewed CL's latest shift patches, added fixes of my own for large shift counts and overlapping src/dest regs, submitted a 10 patch rolled up series + reviewed a patch for adding cp15 VA-PA translation ops + reviewed various versions of vrecpe/vsqrte patches from CL * versatile-express model: B Labs kindly made available their Versatile Express board model: https://github.com/bbalban/qemu/commits/universal-branch and I've spent a few days getting it to boot a Linaro kernel, fixing a few bugs and cleaning up the patchset in preparation for upstreaming it. This included discovering a bug in qemu's SD card model which was causing Linux not to be able to detect cards on PL181, and resulting in spurious qemu warnings on omap3: https://bugs.launchpad.net/qemu-linaro/+bug/714606 * other: + ARM architecture Q&A for modelling engineers + booked travel/hotel for QEMU conference * meetings: toolchain, PDSW-tools, PD comms, Linaro-in-ARM network infrastructure, pdsw-doughnuts and 1st birthday celebration, Current qemu patch status is tracked here: https://wiki.linaro.org/PeterMaydell/QemuPatchStatus Absences: 17/18 March: QEMU Users Forum, Grenoble Holiday: 22 Apr - 2 May 9-13 May: UDS, Budapest (maybe) ~17-19 August: QEMU/KVM strand at LinuxCon NA, Vancouver

14 years, 10 months

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[ACTIVITY] weekly status

by Ken Werner

Hi, * continued to look into latrace and found an issue in case a dynamic library gets unloaded. Otherwise latrace looks quite good on ARM. https://wiki.linaro.org/KenWerner/Sandbox/latrace * chasing bugs: - After a lot of testing Andy Green has made a big step forward in finding the root cause for the shut-down issue of my PandaBoard. The PMIC is seeing an overcurrent and issues an interrupt that gets ignored by current kernels. Then the PMIC shuts the board down for safety reasons. As a workaround Andy has made a kernel patch for the twl6030 driver that enables all interrupt sources. The kernel will acknowledge the overcurrent reported by the PMIC and the board survives. A patched kernel binary can be found at: https://wiki.linaro.org/KenWerner/Sandbox/708883 - While testing Andys patches on the linaro natty kernels I ran into https://bugs.launchpad.net/bugs/720055 - The flash-kernel utility doesn't work on the PandaBoard because the subarch check expects omap4 instead of omap: https://bugs.launchpad.net/bugs/721147 - Looked into the apr fail (process shared mutex's fail on armel v7). Their mutex functionality can be mappped to various methods, but only pthread is of interest here. The code relies on pthread_mutex_lock and pthread_mutex_trylock which is implemented by the (e)glibc. The c library uses GCCs __sync primitives if eglibc >= 2.12.1-0ubuntu11 and GCC >=4.5. The testprocmutex testcase passes now. https://bugs.launchpad.net/bugs/604753 Regards Ken

14 years, 10 months

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RE: Problems with kernel support for hardware watchpoints

by Ulrich Weigand

"Will Deacon" <will.deacon(a)arm.com> wrote on 02/16/2011 01:07:09 PM: > > I've now built a kernel with CONFIG_ARM_ERRATA_720789 enabled, and the > > symptoms indeed seem to have disappeared completely ... > > Yup - that's because without it, invalidating a TLB entry for a particular > process isn't broadcast correctly, so you can end up using the old (pre-COW) > mappings if you're running on a different core. OK. So I guess the only remaining questions is: if this hardware needs the errata fix to work properly, shouldn't it be automatically selected by the kernel configure logic? Note that this appears to happen for certain OMAP boards, see arch/arm/mach-omap2/Kconfig: config ARCH_OMAP4 bool "TI OMAP4" default y depends on ARCH_OMAP2PLUS select CPU_V7 select ARM_GIC select PL310_ERRATA_588369 select ARM_ERRATA_720789 <<===== select USB_ARCH_HAS_EHCI But this does not happen for the vexpress; arch/arm/mach-vexpress/Kconfig has only: config ARCH_VEXPRESS_CA9X4 bool "Versatile Express Cortex-A9x4 tile" select CPU_V7 select ARM_GIC Mit freundlichen Gruessen / Best Regards Ulrich Weigand -- Dr. Ulrich Weigand | Phone: +49-7031/16-3727 STSM, GNU compiler and toolchain for Linux on System z and Cell/B.E. IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Martin Jetter | Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen | Registergericht: Amtsgericht Stuttgart, HRB 243294

14 years, 10 months

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[ACTIVITY] February 13-17

by Revital1 Eres

Hello, * Continue looking into DENbench benchmarks. * While testing SMS I realized that my current implementation of doloop pattern for ARM does not follow SMS's requirement to have the doloop instructions be decoupled from the other loop's instructions. This happens because doloop uses CC register which might be used elsewhere in the loop. I am looking into a solution for that. Thanks, Revital

14 years, 10 months

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[ACTIVITY] February 13-17

by Ira Rosen

Hi, This week I looked into DENBench: * sad8_c (hot function from mp4encode) needs SLP reduction, but it also contains cond_expr which cannot be vectorized as reduction, so I don't think there is anything I can do here * fdct_int32 (another hot function from mp4encode) now gets vectorized with vzip/vuzp patch, but the vectorization causes performance degradation here because of multiple register spills. I also noticed that vectorizer costs are not set for NEON, i.e., it uses default costs. So, I am now working on costs for NEON and adding registers consideration into vectorizer's cost model. I also did some general vectorization research, checking opportunities of collaboration with GRAPHITE pass and auto-parallelization. Ira

14 years, 10 months

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Summary of required work for a Versatile Express QEMU model

by Peter Maydell

I mentioned in the toolchain standup call that I'd done a quick estimate of the work required to support vexpress, so I thought I might as well clean it up a little and post it. This is a quick summary and time estimate for adding Versatile Express support to qemu. The general idea is that most of the components on this board already have QEMU implementations (since they're standard ARM primecells used in versatile/realview), and we can live without the few major components that aren't implemented (maybe we'd need dummy implementations if the kernel prods them on startup.) Components already supported by QEMU: ------------------------------------- A9MPx4 PL050 keyboard, mouse SMCS LAN9118 ethernet PL011 UARTs SP804 timers Components with a near match in QEMU: ------------------------------------- PL111 CLCD -- qemu has a PL110 PL180 MMC card -- qemu has a PL181 -- both cases should either just work or be fairly trivial tweaks Components not supported by QEMU: --------------------------------- PL041 audio compact flash two-wire serial bus (for PCI-express switch config and DVI-I displays) ISP1761 Philips USB controller User switches and LEDs -- vexpress specific, but trivial to do Components where a dummy implementation should be sufficient: ------------------------------------------------------------- PL310 L2 cache controller PL341 dynamic memory controller PL354 static memory bus controller trustzone controllers Other required work: -------------------- The usual knitting for interrupts, clocks, reset etc etc. Summary ------- Assuming we're happy not to worry about support for audio, USB, two-wire serial bus or compact flash, this is about two weeks work to put together, test and get a more-or-less upstreamable patchset from. This would produce a platform hopefully at least as usable as versatile, but with an A9 and 1GB RAM. -- PMM

14 years, 10 months

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RE: Problems with kernel support for hardware watchpoints

by Ulrich Weigand

"Will Deacon" <will.deacon(a)arm.com> wrote on 02/14/2011 11:30:45 AM: > > - In testing on Versatile Express, I noticed what appears to be SMP > > related bugs in handling regular software breakpoints: occasionally, > > software breakpoints simply are not hit and execution continues as if > > the underlying code had not been changed at all. This symptom > > completely goes away if GDB and the debugged process are forced to > > the same CPU using the affinity feature (e.g. with schedtool). > > I've seen this issue in the past but I thought I'd fixed it. What kernel are > you using and do you have CONFIG_ARM_ERRATA_720789 enabled? I'm using the 2.6.37-1002-linaro-vexpress kernel from the Linaro package of the same name. This does *not* have CONFIG_ARM_ERRATA_720789 enabled (presumably because the mach-vexpress/Kconfig file does not add it?) ... > > My guess, just from seeing those symptoms, would be that when inserting > > a software breakpoint via ptrace, not all i-caches on all CPUs are > > reliably flushed ... Any thoughts on this? > > There was an I-cache aliasing problem in the kernel coupled with a TLB > invalidation hardware bug on the versatile express. I fixed these though > and haven't seen any problems since. Hmm, a TLB flush problem could also explain the symptom (because the write of the breakpoint to the text section causes a copy-on-write operation which installs a new page ...) I'll try rebuilding the kernel with the above config option enabled. > Hmmm, I'll need to have a think about this. What does GDB do if it receives > a SIGTRAP with si_addr set to (potentially) complete nonsense? As an aside, > Cortex-A15 reports the faulting address for a watchpoint correctly, so we > will be able to use multiple watchpoints there. The GDB common core can handle either of the following two indications: A) The (read/write/access) watchpoint at address XXX triggered. B) A write watchpoint may have triggered at some address. In the case of B, GDB will scan all the write breakpoints it is currently tracking and compare the current value at that address with the last value it remembers being present there. Any changes GDB sees will cause it to report the corresponding watchpoint as triggered. As far as the kernel interface is concerned, the important issue that the ARM native target in GDB is able to understand what the kernel reports, so it can in turn report either case A or B to the common core. This means as long as there is some way for GDB to understand the kernel is reporting a write watchpoint hit at an unknown address, everything is fine. This could be done e.g. be reporting a "slot" zero in si_errno to indicate the slot (and then also the address) triggering the watchpoint is unknown ... > > - Finally, I noticed when reading kernel code that under some > > circumstances, the kernel will automatically do a single step to > > get off a watchpoint that was just hit. However, this does not > > happen for user-space watchpoints installed via ptrace, right? > > (Just wanting to confirm; since GDB currently does that single > > step itself -- we don't want *both* kernel and GDB to issue a > > single step each ...) > > If the {break,watch}point has been inserted via ptrace, the kernel will > send a SIGTRAP instead of stepping the instruction. OK, thanks for the confirmation! > > I haven't gotten to looking further into other hardware (IGEP, > > Panda) -- that's next on the list. > > Good stuff, keep me posted if you see any further problems! Sure, will do! Mit freundlichen Gruessen / Best Regards Ulrich Weigand -- Dr. Ulrich Weigand | Phone: +49-7031/16-3727 STSM, GNU compiler and toolchain for Linux on System z and Cell/B.E. IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Martin Jetter | Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen | Registergericht: Amtsgericht Stuttgart, HRB 243294

14 years, 10 months

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Announcing the Linaro porting jam

by Steve Langasek

Hello, my fellow ARM aficionados! The Linaro Developer Platform Team is pleased to announce a new initiative to help improve the state of software on ARM: the ARM porting jam. Starting today, February 16th, we will be running a weekly IRC jam on Wednesdays from 1400-1800 UTC to bring developers together to work on all manner of userspace porting bugs, with the aim of fixing portability issues and getting the fixes delivered to our upstreams. An initial porting queue of known issues can be found here: https://bugs.launchpad.net/ubuntu/+bugs?field.tag=arm-porting-queue Interested in making the software in Ubuntu run better on ARM? Stop on by the #linaro channel on irc.linaro.org today! -- Steve Langasek Give me a lever long enough and a Free OS Debian Developer to set it on, and I can move the world. Ubuntu Developer http://www.debian.org/ slangasek(a)ubuntu.com vorlon(a)debian.org

14 years, 10 months

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RE: Problems with kernel support for hardware watchpoints

by Ulrich Weigand

"Will Deacon" <will.deacon(a)arm.com> wrote on 02/11/2011 10:13:01 AM: > I don't have a pandaboard, so I'd be interested to see if the code > works there. I developed it using ARM boards, so the versatile express > is a known good target. I've now got it working reliably on on Versatile Express, after fixing a couple of bugs on the GDB side (both in the HW-watchpoint patch, and in common GDB code). The testsuite now passes with no regressions when enabling HW watchpoints, except for two tests that require more than one single watchpoint to be supported. This raises another couple of issues/questions, however: - In testing on Versatile Express, I noticed what appears to be SMP related bugs in handling regular software breakpoints: occasionally, software breakpoints simply are not hit and execution continues as if the underlying code had not been changed at all. This symptom completely goes away if GDB and the debugged process are forced to the same CPU using the affinity feature (e.g. with schedtool). My guess, just from seeing those symptoms, would be that when inserting a software breakpoint via ptrace, not all i-caches on all CPUs are reliably flushed ... Any thoughts on this? - As mentioned above, the kernel currently only supports one single watchpoint to be active at a time, even though hardware might support multiple ones. The reason seems to be that when a watchpoint triggers, the kernel cannot figure out which one it was (if there's more than one choice). This is a bit unfortunate, given that GDB will attempt to insert two or more watchpoints in many interesting cases (e.g. a "watch *p" command will insert *two* low-level watchpoints, one at the address of p, and one at the address where p (currently) points to). In addition, for regular (write) watchpoints, GDB does not actually *require* the underlying hardware/kernel to specify which watchpoint was hit; GDB is able to find out by itself by checking whether the values at any of the currently active locations actually changed. (For read/access type watchpoints, GDB does require that underlying support -- but those are much more rarely used anyway.) Do you see any chance of improving upon the current behaviour? - Finally, I noticed when reading kernel code that under some circumstances, the kernel will automatically do a single step to get off a watchpoint that was just hit. However, this does not happen for user-space watchpoints installed via ptrace, right? (Just wanting to confirm; since GDB currently does that single step itself -- we don't want *both* kernel and GDB to issue a single step each ...) I haven't gotten to looking further into other hardware (IGEP, Panda) -- that's next on the list. Mit freundlichen Gruessen / Best Regards Ulrich Weigand -- Dr. Ulrich Weigand | Phone: +49-7031/16-3727 STSM, GNU compiler and toolchain for Linux on System z and Cell/B.E. IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Martin Jetter | Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen | Registergericht: Amtsgericht Stuttgart, HRB 243294

14 years, 10 months

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[ACTIVITY] 7th - 12th February 2011

by Andrew Stubbs

== Linaro GCC 4.5 == Re merged all the patches I've had to back out of Linaro GCC due to various test failures. I've now found all the extra fixes/patches necessary to make them go ... I think. Tested the build and test on ARM and x86_64. == Linaro GCC 4.6 == Continued getting the 4.5 patches forward ported to 4.6. I now have about 4 patches waiting for review upatream, or ready to be posted. Upstream review isn't happening though. This partly due to GCC being in stage 4, but mostly due to Richard Earshaw being on sabatical, and the other maintainers being inactive. I can see that I'm going to have to abandon my hopes of only merging to Linaro GCC once it's been approved upstream, and be content with merging to Linaro once it's posted upstream. Started another test to rebase the Linaro 4.6 branch with the latest from upstream. Once that's done, I think I'll start merging my changes in, and call that our baseline. (There'll still be merges from upstream, but the history will diverge.) ---- Upstream patched requiring review: * Thumb2 constants: http://gcc.gnu.org/ml/gcc-patches/2010-12/msg00652.html * Kazu's VFP testcases: http://gcc.gnu.org/ml/gcc-patches/2011-02/msg00128.html * Jie's thumb2 testcase fix: http://gcc.gnu.org/ml/gcc-patches/2011-02/msg00670.html

14 years, 10 months

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[ACTIVITY] Jan 31 -- Feb 13

by Chung-Lin Tang

== Week of Jan.31st--Feb.6th == * Vacation, Chinese New Year Holiday. == Last week == * Monday (Feb.7th), last day of vacation. * LP #711819, ICE in push_minipool_fix: this turned out to be a simple case where a memory load alternative was not tagged with the minipool range attributes. Patch sent upstream, awaiting approval. * LP #709453, wrong code generated for NEON. Tracked this down and mostly know how to fix this, but discussion with Ramana brought the issue up that the entire idea of using NEON vmov.i32 for loading VFP constants may not be good for A9, and unclear for A8. We probably should just revert the patch from the Linaro tree for now. * PR46002, IRA internal compiler error with -fira-algorithm=priority. Been looking at this as a part of my background IRA studies. Have a possible patch for this, plus found another assert fail ICE under ARM. Will see if can post upstream this week. == This week == * Continue to look at above unfinished issues, as well as other new ones.

14 years, 10 months

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[ACTIVITY] Jan 07 - Feb 11

by Ulrich Weigand

== GDB == * Installed 2.6.37 Linaro kernel on IGEP and Versatile Express in order to verify support for HW breakpoints/watchpoints * Tested GDB HW watchpoints patch, fixed several bugs in the patch and core GDB, and got it working reliably on vexpress * Started discussion with Will Deacon (ARM) regarding possible further enhancements to related kernel support Mit freundlichen Gruessen / Best Regards Ulrich Weigand -- Dr. Ulrich Weigand | Phone: +49-7031/16-3727 STSM, GNU compiler and toolchain for Linux on System z and Cell/B.E. IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Martin Jetter | Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen | Registergericht: Amtsgericht Stuttgart, HRB 243294

14 years, 11 months

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[ACTIVITY] 2011-02-11

by David Gilbert

== String routines == * Copied an improvement I'd previously made to memchr (removing a branch using a big IT block) to strlen * Modified benchmark setup to build everything as a library to fairly give everything a PLT overhead. * Pushed optimised memchr and strlen and simple strchr into cortex-strings bzr repo * Patched eglibc to use memchr and strchr code - although currently fighting to get appropriate .changes file == ffi == * Kicked off TSC request for license permissions == bugs == * Built and recreated the qt4-x11 bug, produced all the dumps and boiled it down to a few lines of suspicious RTL for Richard. ** Away next week.

14 years, 11 months

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