From 2f24ef7413a4d91657ef04e77c27ce0b313e6c95 Mon Sep 17 00:00:00 2001 From: Alexey Brodkin Date: Wed, 29 Nov 2017 11:21:45 +0300 Subject: ARC: Enable machine_desc->init_per_cpu for !CONFIG_SMP machine_desc->init_per_cpu() hook is supposed to be per cpu initialization and would seem to apply equally to UP and/or SMP. Infact the comment in header file seems to suggest it works for UP too, which was not the case and this patch. This enables !CONFIG_SMP build for platforms such as hsdk. Signed-off-by: Alexey Brodkin Signed-off-by: Vineet Gupta [vgupta: trimmeed changelog] --- arch/arc/kernel/irq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/arc/kernel') diff --git a/arch/arc/kernel/irq.c b/arch/arc/kernel/irq.c index 538b36afe89e..62b185057c04 100644 --- a/arch/arc/kernel/irq.c +++ b/arch/arc/kernel/irq.c @@ -31,10 +31,10 @@ void __init init_IRQ(void) /* a SMP H/w block could do IPI IRQ request here */ if (plat_smp_ops.init_per_cpu) plat_smp_ops.init_per_cpu(smp_processor_id()); +#endif if (machine_desc->init_per_cpu) machine_desc->init_per_cpu(smp_processor_id()); -#endif } /* -- cgit v1.2.3 From e8708786d4fe21c043d38d760f768949a3d71185 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 19 Jun 2018 17:22:05 +0300 Subject: ARC: Improve cmpxchg syscall implementation 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] --- arch/arc/kernel/process.c | 47 ++++++++++++++++++++++++++++++++++++----------- 1 file changed, 36 insertions(+), 11 deletions(-) (limited to 'arch/arc/kernel') diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c index 5ac3b547453f..4674541eba3f 100644 --- a/arch/arc/kernel/process.c +++ b/arch/arc/kernel/process.c @@ -47,7 +47,8 @@ SYSCALL_DEFINE0(arc_gettls) SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new) { struct pt_regs *regs = current_pt_regs(); - int uval = -EFAULT; + u32 uval; + int ret; /* * This is only for old cores lacking LLOCK/SCOND, which by defintion @@ -60,23 +61,47 @@ SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new) /* Z indicates to userspace if operation succeded */ regs->status32 &= ~STATUS_Z_MASK; - if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int))) - return -EFAULT; + ret = access_ok(VERIFY_WRITE, uaddr, sizeof(*uaddr)); + if (!ret) + goto fail; +again: preempt_disable(); - if (__get_user(uval, uaddr)) - goto done; + ret = __get_user(uval, uaddr); + if (ret) + goto fault; - if (uval == expected) { - if (!__put_user(new, uaddr)) - regs->status32 |= STATUS_Z_MASK; - } + if (uval != expected) + goto out; -done: - preempt_enable(); + ret = __put_user(new, uaddr); + if (ret) + goto fault; + + regs->status32 |= STATUS_Z_MASK; +out: + preempt_enable(); return uval; + +fault: + preempt_enable(); + + if (unlikely(ret != -EFAULT)) + goto fail; + + down_read(¤t->mm->mmap_sem); + ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr, + FAULT_FLAG_WRITE, NULL); + up_read(¤t->mm->mmap_sem); + + if (likely(!ret)) + goto again; + +fail: + force_sig(SIGSEGV, current); + return ret; } #ifdef CONFIG_ISA_ARCV2 -- cgit v1.2.3