user/sven/linux.git/arch/arc/kernel/process.c, branch v4.9.254

ARC: clone syscall to setp r25 as thread pointer

2018-10-13T07:18:57Z

commit c58a584f05e35d1d4342923cd7aac07d9c3d3d16 upstream. Per ARC TLS ABI, r25 is designated TP (thread pointer register). However so far kernel didn't do any special treatment, like setting up usermode r25, even for CLONE_SETTLS. We instead relied on libc runtime to do this, in say clone libc wrapper [1]. This was deliberate to keep kernel ABI agnostic (userspace could potentially change TP, specially for different ARC ISA say ARCompact vs. ARCv2 with different spare registers etc) However userspace setting up r25, after clone syscall opens a race, if child is not scheduled and gets a signal instead. It starts off in userspace not in clone but in a signal handler and anything TP sepcific there such as pthread_self() fails which showed up with uClibc testsuite nptl/tst-kill6 [2] Fix this by having kernel populate r25 to TP value. So this locks in ABI, but it was not going to change anyways, and fwiw is same for both ARCompact (arc700 core) and ARCvs (HS3x cores) [1] https://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/tree/libc/sysdeps/linux/arc/clone.S [2] https://github.com/wbx-github/uclibc-ng-test/blob/master/test/nptl/tst-kill6.c Fixes: ARC STAR 9001378481 Cc: stable@vger.kernel.org Reported-by: Nikita Sobolev Signed-off-by: Vineet Gupta Signed-off-by: Greg Kroah-Hartman

ARC: Improve cmpxchg syscall implementation

2018-08-24T11:12:37Z

[ Upstream commit e8708786d4fe21c043d38d760f768949a3d71185 ] This is used in configs lacking hardware atomics to emulate atomic r-m-w for user space, implemented by disabling preemption in kernel. However there are issues in current implementation: 1. Process not terminated if invalid user pointer passed: i.e. __get_user() failed. 2. The reason for this patch was __put_user() failure not being handled either, specifically for the COW break scenario. The zero page is initially wired up and read from __get_user() succeeds. A subsequent write by __put_user() induces a Protection Violation, but COW can't finish as Linux page fault handler is disabled due to preempt disable. And what's worse is we silently return the stale value to user space. Fix this specific case by re-enabling preemption and explicitly fixing up the fault and retrying the whole sequence over. Cc: Max Filippov Cc: linux-arch@vger.kernel.org Signed-off-by: Alexey Brodkin Signed-off-by: Peter Zijlstra Signed-off-by: Vineet Gupta [vgupta: rewrote the changelog] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

ARC: change return value of userspace cmpxchg assist syscall

2016-11-07T19:01:12Z

The original syscall only used to return errno to indicate if cmpxchg succeeded. It was not returning the "previous" value which typical cmpxchg callers are interested in to build their slowpaths or retry loops. Given user preemption in syscall return path etc, it is not wise to check this in userspace afterwards, but should be what kernel actually observed in the syscall. So change the syscall interface to always return the previous value and additionally set Z flag to indicate whether operation succeeded or not (just like ARM implementation when they used to have this syscall) The flag approach avoids having to put_user errno which is nice given the use case for this syscall cares mostly about the "previous" value. Signed-off-by: Vineet Gupta

ARC: syscall for userspace cmpxchg assist

2016-10-24T16:24:26Z

Older ARC700 cores (ARC750 specifically) lack instructions to implement atomic r-w-w. This is problematic for userspace libraries such as NPTL which need atomic primitives. So enable them by providing kernel assist. This is costly but really the only sane soluton (othern than tight spinning using the otherwise availiable atomic exchange EX instruciton). Good thing is there are only a few of these cores running Linux out in the wild. This only works on UP systems. Reviewed-by: Colin Ian King Signed-off-by: Vineet Gupta

ARC: Support syscall ABI v4

2016-08-19T17:44:34Z

The syscall ABI includes the gcc functional calling ABI since a syscall implies userland caller and kernel callee. The current gcc ABI (v3) for ARCv2 ISA required 64-bit data be passed in even-odd register pairs, (potentially punching reg holes when passing such values as args). This was partly driven by the fact that the double-word LDD/STD instructions in ARCv2 expect the register alignment and thus gcc forcing this avoids extra MOV at the cost of a few unused register (which we have plenty anyways). This however was rejected as part of upstreaming gcc port to HS. So the new ABI v4 doesn't enforce the even-odd reg restriction. Do note that for ARCompact ISA builds v3 and v4 are practically the same in terms of gcc code generation. In terms of change management, we infer the new ABI if gcc 6.x onwards is used for building the kernel. This also needs a stable backport to enable older kernels to work with new tools/user-space Cc: Signed-off-by: Vineet Gupta

exit_thread: remove empty bodies

2016-05-21T00:58:30Z

Define HAVE_EXIT_THREAD for archs which want to do something in exit_thread. For others, let's define exit_thread as an empty inline. This is a cleanup before we change the prototype of exit_thread to accept a task parameter. [akpm@linux-foundation.org: fix mips] Signed-off-by: Jiri Slaby Cc: "David S. Miller" Cc: "H. Peter Anvin" Cc: "James E.J. Bottomley" Cc: Aurelien Jacquiot Cc: Benjamin Herrenschmidt Cc: Catalin Marinas Cc: Chen Liqin Cc: Chris Metcalf Cc: Chris Zankel Cc: David Howells Cc: Fenghua Yu Cc: Geert Uytterhoeven Cc: Guan Xuetao Cc: Haavard Skinnemoen Cc: Hans-Christian Egtvedt Cc: Heiko Carstens Cc: Helge Deller Cc: Ingo Molnar Cc: Ivan Kokshaysky Cc: James Hogan Cc: Jeff Dike Cc: Jesper Nilsson Cc: Jiri Slaby Cc: Jonas Bonn Cc: Koichi Yasutake Cc: Lennox Wu Cc: Ley Foon Tan Cc: Mark Salter Cc: Martin Schwidefsky Cc: Matt Turner Cc: Max Filippov Cc: Michael Ellerman Cc: Michal Simek Cc: Mikael Starvik Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Ralf Baechle Cc: Rich Felker Cc: Richard Henderson Cc: Richard Kuo Cc: Richard Weinberger Cc: Russell King Cc: Steven Miao Cc: Thomas Gleixner Cc: Tony Luck Cc: Vineet Gupta Cc: Will Deacon Cc: Yoshinori Sato Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ARC: Abstract out ISA specific SLEEP args

2015-11-16T08:47:02Z

No semantical changes, prepares for ARCv2 specific change in next commit Signed-off-by: Vineet Gupta

ARC: add/fix some comments in code - no functional change

2015-08-20T13:35:49Z

Signed-off-by: Vineet Gupta

ARC: Fix build failures for ARCompact in linux-next after ARCv2 support

2015-06-28T15:00:13Z

Reported-by: Guenter Roeck Signed-off-by: Vineet Gupta

ARCv2: Support for ARCv2 ISA and HS38x cores

2015-06-22T08:36:55Z

The notable features are: - SMP configurations of upto 4 cores with coherency - Optional L2 Cache and IO-Coherency - Revised Interrupt Architecture (multiple priorites, reg banks, auto stack switch, auto regfile save/restore) - MMUv4 (PIPT dcache, Huge Pages) - Instructions for * 64bit load/store: LDD, STD * Hardware assisted divide/remainder: DIV, REM * Function prologue/epilogue: ENTER_S, LEAVE_S * IRQ enable/disable: CLRI, SETI * pop count: FFS, FLS * SETcc, BMSKN, XBFU... Signed-off-by: Vineet Gupta