kernel.git/arch/mips/kernel, branch linux-4.11.y

MIPS: Fix IRQ tracing & lockdep when rescheduling

2017-07-05T12:41:38Z

commit d8550860d910c6b7b70f830f59003b33daaa52c9 upstream. When the scheduler sets TIF_NEED_RESCHED & we call into the scheduler from arch/mips/kernel/entry.S we disable interrupts. This is true regardless of whether we reach work_resched from syscall_exit_work, resume_userspace or by looping after calling schedule(). Although we disable interrupts in these paths we don't call trace_hardirqs_off() before calling into C code which may acquire locks, and we therefore leave lockdep with an inconsistent view of whether interrupts are disabled or not when CONFIG_PROVE_LOCKING & CONFIG_DEBUG_LOCKDEP are both enabled. Without tracing this interrupt state lockdep will print warnings such as the following once a task returns from a syscall via syscall_exit_partial with TIF_NEED_RESCHED set: [ 49.927678] ------------[ cut here ]------------ [ 49.934445] WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:3687 check_flags.part.41+0x1dc/0x1e8 [ 49.946031] DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled) [ 49.946355] CPU: 0 PID: 1 Comm: init Not tainted 4.10.0-00439-gc9fd5d362289-dirty #197 [ 49.963505] Stack : 0000000000000000 ffffffff81bb5d6a 0000000000000006 ffffffff801ce9c4 [ 49.974431] 0000000000000000 0000000000000000 0000000000000000 000000000000004a [ 49.985300] ffffffff80b7e487 ffffffff80a24498 a8000000ff160000 ffffffff80ede8b8 [ 49.996194] 0000000000000001 0000000000000000 0000000000000000 0000000077c8030c [ 50.007063] 000000007fd8a510 ffffffff801cd45c 0000000000000000 a8000000ff127c88 [ 50.017945] 0000000000000000 ffffffff801cf928 0000000000000001 ffffffff80a24498 [ 50.028827] 0000000000000000 0000000000000001 0000000000000000 0000000000000000 [ 50.039688] 0000000000000000 a8000000ff127bd0 0000000000000000 ffffffff805509bc [ 50.050575] 00000000140084e0 0000000000000000 0000000000000000 0000000000040a00 [ 50.061448] 0000000000000000 ffffffff8010e1b0 0000000000000000 ffffffff805509bc [ 50.072327] ... [ 50.076087] Call Trace: [ 50.079869] [] show_stack+0x80/0xa8 [ 50.086577] [] dump_stack+0x10c/0x190 [ 50.093498] [] __warn+0xf0/0x108 [ 50.099889] [] warn_slowpath_fmt+0x3c/0x48 [ 50.107241] [] check_flags.part.41+0x1dc/0x1e8 [ 50.114961] [] lock_is_held_type+0x8c/0xb0 [ 50.122291] [] __schedule+0x8c0/0x10f8 [ 50.129221] [] schedule+0x30/0x98 [ 50.135659] [] work_resched+0x8/0x34 [ 50.142397] ---[ end trace 0cb4f6ef5b99fe21 ]--- [ 50.148405] possible reason: unannotated irqs-off. [ 50.154600] irq event stamp: 400463 [ 50.159566] hardirqs last enabled at (400463): [] _raw_spin_unlock_irqrestore+0x40/0xa8 [ 50.171981] hardirqs last disabled at (400462): [] _raw_spin_lock_irqsave+0x30/0xb0 [ 50.183897] softirqs last enabled at (400450): [] __do_softirq+0x4ac/0x6a8 [ 50.195015] softirqs last disabled at (400425): [] irq_exit+0x110/0x128 Fix this by using the TRACE_IRQS_OFF macro to call trace_hardirqs_off() when CONFIG_TRACE_IRQFLAGS is enabled. This is done before invoking schedule() following the work_resched label because: 1) Interrupts are disabled regardless of the path we take to reach work_resched() & schedule(). 2) Performing the tracing here avoids the need to do it in paths which disable interrupts but don't call out to C code before hitting a path which uses the RESTORE_SOME macro that will call trace_hardirqs_on() or trace_hardirqs_off() as appropriate. We call trace_hardirqs_on() using the TRACE_IRQS_ON macro before calling syscall_trace_leave() for similar reasons, ensuring that lockdep has a consistent view of state after we re-enable interrupts. Signed-off-by: Paul Burton Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/15385/ Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman

MIPS: pm-cps: Drop manual cache-line alignment of ready_count

2017-07-05T12:41:38Z

commit 161c51ccb7a6faf45ffe09aa5cf1ad85ccdad503 upstream. We allocate memory for a ready_count variable per-CPU, which is accessed via a cached non-coherent TLB mapping to perform synchronisation between threads within the core using LL/SC instructions. In order to ensure that the variable is contained within its own data cache line we allocate 2 lines worth of memory & align the resulting pointer to a line boundary. This is however unnecessary, since kmalloc is guaranteed to return memory which is at least cache-line aligned (see ARCH_DMA_MINALIGN). Stop the redundant manual alignment. Besides cleaning up the code & avoiding needless work, this has the side effect of avoiding an arithmetic error found by Bryan on 64 bit systems due to the 32 bit size of the former dlinesz. This led the ready_count variable to have its upper 32b cleared erroneously for MIPS64 kernels, causing problems when ready_count was later used on MIPS64 via cpuidle. Signed-off-by: Paul Burton Fixes: 3179d37ee1ed ("MIPS: pm-cps: add PM state entry code for CPS systems") Reported-by: Bryan O'Donoghue Reviewed-by: Bryan O'Donoghue Tested-by: Bryan O'Donoghue Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/15383/ Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman

MIPS: Avoid accidental raw backtrace

2017-07-05T12:41:38Z

commit 854236363370995a609a10b03e35fd3dc5e9e4a1 upstream. Since commit 81a76d7119f6 ("MIPS: Avoid using unwind_stack() with usermode") show_backtrace() invokes the raw backtracer when cp0_status & ST0_KSU indicates user mode to fix issues on EVA kernels where user and kernel address spaces overlap. However this is used by show_stack() which creates its own pt_regs on the stack and leaves cp0_status uninitialised in most of the code paths. This results in the non deterministic use of the raw back tracer depending on the previous stack content. show_stack() deals exclusively with kernel mode stacks anyway, so explicitly initialise regs.cp0_status to KSU_KERNEL (i.e. 0) to ensure we get a useful backtrace. Fixes: 81a76d7119f6 ("MIPS: Avoid using unwind_stack() with usermode") Signed-off-by: James Hogan Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/16656/ Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman

MIPS: head: Reorder instructions missing a delay slot

2017-07-05T12:41:38Z

commit 25d8b92e0af75d72ce8b99e63e5a449cc0888efa upstream. In this sequence the 'move' is assumed in the delay slot of the 'beq', but head.S is in reorder mode and the former gets pushed one 'nop' farther by the assembler. The corrected behavior made booting with an UHI supplied dtb erratic. Fixes: 15f37e158892 ("MIPS: store the appended dtb address in a variable") Signed-off-by: Karl Beldan Reviewed-by: James Hogan Cc: Jonas Gorski Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/16614/ Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman

MIPS: Fix bnezc/jialc return address calculation

2017-06-24T05:06:21Z

commit 1a73d9310e093fc3adffba4d0a67b9fab2ee3f63 upstream. The code handling the pop76 opcode (ie. bnezc & jialc instructions) in __compute_return_epc_for_insn() needs to set the value of $31 in the jialc case, which is encoded with rs = 0. However its check to differentiate bnezc (rs != 0) from jialc (rs = 0) was unfortunately backwards, meaning that if we emulate a bnezc instruction we clobber $31 & if we emulate a jialc instruction it actually behaves like a jic instruction. Fix this by inverting the check of rs to match the way the instructions are actually encoded. Signed-off-by: Paul Burton Fixes: 28d6f93d201d ("MIPS: Emulate the new MIPS R6 BNEZC and JIALC instructions") Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/16178/ Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman

kthread: fix boot hang (regression) on MIPS/OpenRISC

2017-06-14T13:07:51Z

commit b0f5a8f32e8bbdaae1abb8abe2d3cbafaba57e08 upstream. This fixes a regression in commit 4d6501dce079 where I didn't notice that MIPS and OpenRISC were reinitialising p->{set,clear}_child_tid to NULL after our initialisation in copy_process(). We can simply get rid of the arch-specific initialisation here since it is now always done in copy_process() before hitting copy_thread{,_tls}(). Review notes: - As far as I can tell, copy_process() is the only user of copy_thread_tls(), which is the only caller of copy_thread() for architectures that don't implement copy_thread_tls(). - After this patch, there is no arch-specific code touching p->set_child_tid or p->clear_child_tid whatsoever. - It may look like MIPS/OpenRISC wanted to always have these fields be NULL, but that's not true, as copy_process() would unconditionally set them again _after_ calling copy_thread_tls() before commit 4d6501dce079. Fixes: 4d6501dce079c1eb6bf0b1d8f528a5e81770109e ("kthread: Fix use-after-free if kthread fork fails") Reported-by: Guenter Roeck Tested-by: Guenter Roeck # MIPS only Acked-by: Stafford Horne Acked-by: Oleg Nesterov Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: Jonas Bonn Cc: Stefan Kristiansson Cc: openrisc@lists.librecores.org Cc: Jamie Iles Cc: Thomas Gleixner Signed-off-by: Vegard Nossum Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

MIPS: KGDB: Use kernel context for sleeping threads

2017-04-12T20:29:22Z

KGDB is a kernel debug stub and it can't be used to debug userland as it can only safely access kernel memory. On MIPS however KGDB has always got the register state of sleeping processes from the userland register context at the beginning of the kernel stack. This is meaningless for kernel threads (which never enter userland), and for user threads it prevents the user seeing what it is doing while in the kernel: (gdb) info threads Id Target Id Frame ... 3 Thread 2 (kthreadd) 0x0000000000000000 in ?? () 2 Thread 1 (init) 0x000000007705c4b4 in ?? () 1 Thread -2 (shadowCPU0) 0xffffffff8012524c in arch_kgdb_breakpoint () at arch/mips/kernel/kgdb.c:201 Get the register state instead from the (partial) kernel register context stored in the task's thread_struct for resume() to restore. All threads now correctly appear to be in context_switch(): (gdb) info threads Id Target Id Frame ... 3 Thread 2 (kthreadd) context_switch (rq=, cookie=..., next=, prev=0x0) at kernel/sched/core.c:2903 2 Thread 1 (init) context_switch (rq=, cookie=..., next=, prev=0x0) at kernel/sched/core.c:2903 1 Thread -2 (shadowCPU0) 0xffffffff8012524c in arch_kgdb_breakpoint () at arch/mips/kernel/kgdb.c:201 Call clobbered registers which aren't saved and exception registers (BadVAddr & Cause) which can't be easily determined without stack unwinding are reported as 0. The PC is taken from the return address, such that the state presented matches that found immediately after returning from resume(). Fixes: 8854700115ec ("[MIPS] kgdb: add arch support for the kernel's kgdb core") Signed-off-by: James Hogan Cc: Jason Wessel Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/15829/ Signed-off-by: Ralf Baechle

MIPS: smp-cps: Fix potentially uninitialised value of core

2017-04-12T19:34:30Z

Turning on DEBUG in smp-cps.c, or compiling the kernel with CONFIG_DYNAMIC_DEBUG enabled results the build error: arch/mips/kernel/smp-cps.c: In function 'play_dead': ./include/linux/dynamic_debug.h:126:3: error: 'core' may be used uninitialized in this function [-Werror=maybe-uninitialized] Fix this by always initialising the variable. Fixes: 0d2808f338c7 ("MIPS: smp-cps: Add support for CPU hotplug of MIPSr6 processors") Signed-off-by: Matt Redfearn Cc: James Hogan Cc: Masahiro Yamada Cc: Paul Burton Cc: Ingo Molnar Cc: Andrew Morton Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/15848/ Signed-off-by: Ralf Baechle

MIPS: KASLR: Add missing header files

2017-04-12T15:02:04Z

After the split of linux/sched.h, KASLR stopped building. Fix this by including the correct header file for init_thread_union Signed-off-by: Matt Redfearn Cc: James Hogan Cc: Marcin Nowakowski Cc: Steven J. Hill Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/15849/ Signed-off-by: Ralf Baechle

MIPS: Avoid BUG warning in arch_check_elf

2017-04-12T13:22:13Z

arch_check_elf contains a usage of current_cpu_data that will call smp_processor_id() with preemption enabled and therefore triggers a "BUG: using smp_processor_id() in preemptible" warning when an fpxx executable is loaded. As a follow-up to commit b244614a60ab ("MIPS: Avoid a BUG warning during prctl(PR_SET_FP_MODE, ...)"), apply the same fix to arch_check_elf by using raw_current_cpu_data instead. The rationale quoted from the previous commit: "It is assumed throughout the kernel that if any CPU has an FPU, then all CPUs would have an FPU as well, so it is safe to perform the check with preemption enabled - change the code to use raw_ variant of the check to avoid the warning." Fixes: 46490b572544 ("MIPS: kernel: elf: Improve the overall ABI and FPU mode checks") Signed-off-by: James Cowgill CC: # 4.0+ Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/15951/ Signed-off-by: Ralf Baechle