On Wednesday 09 February 2011 20:25:32 Will Deacon wrote:
> > - Why is architecture 0x4 not supported? This seems to be the variant of
> > the v7 debug architecture with memory-mapped registers. Apparently the
> > IGEP only supports this version ... Do you know what the
> > Beagle-/Pandaboard and other clones do? What would it take to support this
> > architecture variant? Given the widespread use of those boards, it would
> > be really nice if we could support hardware debugging on them ...
>
> The memory-mapped interface is hugely unreliable in real hardware because
> you have to calculate the address of the memory-mapped debug registers by
> using a base and offset, which are hardcoded in some information registers.
> Unfortunately, I've never found a board where these registers have been
> programmed correctly so (a) I had nothing to test my code with (b) few people
> would be able to use it and (c) there's not really a safe way to go around
> poking random areas of memory.
So the only problem is that it's board specific? That's something we
know how to deal with -- all I/O components have some random board
specific address, and we put them in a platform device that is
listed in the board file. This should be easy enough to do for another
register area, though it means we have to do it separately for each board.
> > - Which hardware is supported? Can you recommend a board I should be
> > using to verify GDB support is working?
>
> The simple rule is Cortex-A8 is unsupported and Cortex-A9 is supported.
> The A5 should work (untested) and the A15 will need a bit of hacking to
> get it supported.
Is that because A8 is memory mapped and A9 uses CP14, or is there another
problem with A8?
Arnd
Hello Will,
I've been trying to get GDB support for hardware watchpoints/breakpoints
going. I've ported Matthew's GDB patch to current mainline, and am running
this under a 2.6.37-1002-linaro-omap kernel on an IGEPv2 board.
However, something seems to be not quite working: I'm seeing this kernel
message on boot:
hw-breakpoint: debug architecture 0x4 unsupported.
and then at runtime, the result of a PTRACE_GETHBPREGS call for register 0
is 0x04000106:
debug architecture: 4
watchpoint size: 0
nr. watchpoints: 1
nr. breakpoints: 6
This leads me to a couple of questions:
- It seems odd that the kernel says it doesn't support the debug
architecture, but then reports to user space that 1 watchpoint and 6
breakpoints are supported ... GDB will never use the watchpoint, because
the maximum watchpoint size is reported as zero, but GDB will attempt to
use the breakpoints. Setting a breakpoint will appear to succeed, but then
the breakpoint just never triggers. The kernel should IMO be more
consistent in how unsupported configurations are handled ...
- Why is architecture 0x4 not supported? This seems to be the variant of
the v7 debug architecture with memory-mapped registers. Apparently the
IGEP only supports this version ... Do you know what the
Beagle-/Pandaboard and other clones do? What would it take to support this
architecture variant? Given the widespread use of those boards, it would
be really nice if we could support hardware debugging on them ...
- Which hardware *is* supported? Can you recommend a board I should be
using to verify GDB support is working?
Thanks for your help in getting this working!
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
Hi,
I'm working in the Linaro toolchain team on adding ARM support for GNU
indirect functions (STT_GNU_IFUNCs). The indirect function feature
requires a new relocation type, which is typically called R_FOO_IRELATIVE.
I'd therefore like to propose a new R_ARM_IRELATIVE relocation type for
the ARM EABI.
This relocation is only used in ET_EXEC and ET_DYN objects. If the
object has a PT_DYNAMIC tag, then the relocation may only appear in
the DT_REL(A) table; it cannot appear in the DT_JMPREL table.
(Note that this is a deliberate divergence from the x86 and x86_64
behaviour, which does allow the IRELATIVE relocation to be used in
DT_JMPREL table, but which requires it to be applied at load time,
regardless of bind-now vs. lazy semantics. However, the proposed
ARM behaviour matches that of other targets like PowerPC.)
Static ET_EXEC objects may have R_ARM_IRELATIVE relocations. In this
case, the relocations are stored in a relocation table that contains no
other type of relocation (not even R_ARM_NONE). The static linker
defines two symbols:
__rel_iplt_start, which the linker points to the start of this table
__rel_iplt_end, which the linker points to the last byte of this table
plus one.
The two symbols are equal if the executable has no R_ARM_IRELATIVE
relocations. It is the executable's responsibility to apply these
relocations as appropriate. If the static linker emits a symbol table,
then it is not defined whether the linker includes __rel_iplt_start and
__rel_iplt_end in that symbol table.
The static linker may (or may not) define __rel_iplt_start and
__rel_iplt_end in dynamic objects. However, if it does define them,
the symbols must refer to part of the DT_REL(A) table, and it is still
the dynamic linker's responsibility to apply the relocations.
An R_ARM_IRELATIVE relocation applies to all bits of a 4-byte field.
There are no alignment restrictions on the field. The relocation
value is:
call(B(S) + A)
where call(X) represents the value of r0 after performing an indirect
branch-with-link-and-exchange (BLX) to address X.
The dynamic linker must have applied all earlier DT_REL(A) relocations
before calling X. It is undefined whether later DT_REL(A) relocations
have been applied or not, and X must not make any assumptions about the
status of those relocations.
If there is an R_ARM_IRELATIVE relocation with symbol S and addend A,
then the relocation value:
call(B(S) + A)
is considered to be a load-time constant. It is possible for an object
to have more than one R_ARM_IRELATIVE relocation with the same value
of B(S) + A, and in such a case, it is not defined whether the dynamic
linker invokes the target function each time, or whether it caches the
results of earlier calls.
I realise this isn't the cleanest extension in the world. As Alan Modra
noted on the binutils list, the choice of __rel_iplt_start and __rel_iplt_end
is particularly unfortunate, since the relocations are not specific to
"PLTs". However, the GNU extension has been defined this way,
so unfortunately there isn't much room for target-specific variation.
Thanks,
Richard
Hi,
I'd like to check vzip/vuzp patch in big endian mode. But when I try
to compile with -mbig-endian flag, I get
> ~/mainline/bin/bin/gcc -O3 -mfloat-abi=softfp -mfpu=neon neon-vtrnu8.c -mbig-endian
/home/irar/mainline/bin/lib/gcc/armv7l-unknown-linux-gnueabi/4.6.0/../../../libgcc_s.so.1:
could not read symbols: File in wrong format
collect2: ld returned 1 exit status
What am I missing?
Thanks,
Ira
The Linaro Toolchain Working Group is pleased to announce the release
of Linaro GDB 7.2.
Linaro GDB 7.2 2011.02-0 is the third release in the 7.2 series. Based
off the latest GDB 7.2, it includes a number of ARM-focused bug fixes
and enhancements.
Interesting changes include:
* Backtracing is more reliable through using the ARM specific
exception tables for unwinding
* Better supports debugging functions compiled with GCC's -fstack-protector
* Multiple testsuite related fixes
The source tarball is available at:
https://launchpad.net/gdb-linaro/+milestone/7.2-2011.02-0
More information on Linaro GDB is available at:
https://launchpad.net/gdb-linaro
-- Michael
The Linaro Toolchain Working Group is pleased to announce the release
of both Linaro GCC 4.4 and Linaro GCC 4.5.
Linaro GCC 4.5 is the seventh release in the 4.5 series. Based off the
latest GCC 4.5.2, it includes many ARM-focused performance
improvements and bug fixes.
Interesting changes include:
* Improved code generation in the __sync primitives
* Better modelling of the Cortex-A9 NEON pipeline
* Added a performance improvement that converts a tree of ifs into a switchs
* Many bug fixes
Linaro GCC 4.4 is the seventh release in the 4.4 series. Based off the
latest GCC 4.4.5, it is a maintenance release that fixes one fault
found with offsets on NEON loads.
The source tarballs are available from:
https://launchpad.net/gcc-linaro/+milestone/4.5-2011.02-0https://launchpad.net/gcc-linaro/+milestone/4.4-2011.02-0
Downloads are available from the Linaro GCC page on Launchpad:
https://launchpad.net/gcc-linaro
-- Michael
The Linaro Toolchain Working Group is pleased to announce the release
of Linaro QEMU 2011.02-0.
Linaro QEMU 2011.02-0 is the first official release of qemu-linaro. Based
off upstream qemu, it includes a number of ARM-focused bug fixes and
enhancements.
- This initial qemu-linaro release includes all the ARM code generation
fixes from the qemu-meego tree; these are mainly Neon related
- The OMAP3 support from qemu-meego is also included
- Various bugs which prevented newer Linaro snapshots from booting
on the beagle model have been fixed
- Bugs causing linaro-media-create to print warnings about unimplemented
syscalls and ioctls have been fixed
Known issues:
- There is no support for USB keyboard or mouse, so only a serial console
is usable (#708703)
- Images built with linaro-media-create's --swap_file option will not
boot (#713101)
The source tarball is available at:
https://launchpad.net/qemu-linaro/+milestone/2011.02
Binary builds of this qemu-linaro release are available for users of
Ubuntu. Natty users can find qemu-linaro 2011.02-0 in the Ubuntu archive.
Users of Ubuntu 10.04 LTS and Ubuntu 10.10 can find packages in the
linaro-maintainers tools ppa:
https://launchpad.net/~linaro-maintainers/+archive/tools/
More information on Linaro QEMU is available at:
https://launchpad.net/qemu-linaro
== Linaro GCC 4.5 ==
Reviewed, tested and merged all the outstanding patches waiting to go
into Linaro GCC 4.5. Michael reported that there was a build failure on
i686 and amd64. I attempted to reproduce this but my builds completed
successfully - very strange. Eventually I found that I had a corrupted
checkout and managed to reproduce the problem - thanks bzr! The problem
is in Tom's recent changes to stmt.c, so I informed him and backed out
the patches, temporarily.
Spun the Linaro GCC 4.4 and 4.5 release tarballs and passed them to
Michael Hope for final testing.
== GCC 4.6 ==
Tested a more recent version of GCC 4.6 and pushed it to the bazaar
repository. Already out of date by the time testing finished of course,
but never mind. The number of test failures is greatly reduced. Started
another build/test with an even more up-to-date check-out.
Begun work merging the 4.5 patches into 4.6. Pushed 1 patch upstream.
Got another ready to go, once I've tested it.
== Android ==
Tried to unpick a large patch I was sent that supposedly added Android
support to Linaro GCC 4.5. The patch was suspicious from the start
because it had large changes to gcc/ChangeLog that clearly backed out
the 4.5.2 release. After comparing it against various sources I
concluded that it was a 4.6 snapshot from last May with (at least some
of) the Linaro patches forward ported, and the release numbers fudged to
look like it was 4.5.2 based. This was not terribly helpful - I can't
very well backport that into our 4.5 branch!
== Upstream GCC ==
Upstream patches 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
== Last week ==
* Backported the fixes for lp693502, lp710623 and lp710652 to linaro 4.6
and linaro 4.5. Tested and sent merge requests.
* Wrote several more ifunc tests, and fixed the bugs they showed up.
Found that ARM generates unnecessary dynamic relocs against GOT entries,
so fixed that as a prerequisite. Improved the tracking of STB_LOCAL
ifuncs, so that they're treated more like STB_GLOBAL.
* Submitted a request for R_ARM_IRELATIVE to be added to the ARM EABI.
== This week ==
* More ifunc.
I'm away next week (14th-18th)
Richard
