Date: Fri, 18 Sep 2015 17:10:00 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r287961 - head/sys/arm64/arm64 Message-ID: <201509181710.t8IHA0np065993@repo.freebsd.org>
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Author: kib Date: Fri Sep 18 17:09:59 2015 New Revision: 287961 URL: https://svnweb.freebsd.org/changeset/base/287961 Log: Do not execute exception handlers with disabled interrupts. We should not call vm_fault(), or send a signal, with interrupts disabled. MI kernel code is not prepared for such environment, not to mention that this increases system latency, since code appears to be executing as being under spinlock. The FAR register for data aborts is read before the interrupts are enabled, to avoid its corruption due to nested exception or context switch. Add asserts, similar to the checks done by other architectures, about not taking page faults in non-sleepable contexts, rather than die with late and somewhat confusing witness diagnostic. Reviewed by: andrew Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D3669 Modified: head/sys/arm64/arm64/trap.c Modified: head/sys/arm64/arm64/trap.c ============================================================================== --- head/sys/arm64/arm64/trap.c Fri Sep 18 16:52:18 2015 (r287960) +++ head/sys/arm64/arm64/trap.c Fri Sep 18 17:09:59 2015 (r287961) @@ -76,6 +76,7 @@ extern register_t fsu_intr_fault; void do_el1h_sync(struct trapframe *); void do_el0_sync(struct trapframe *); void do_el0_error(struct trapframe *); +static void print_registers(struct trapframe *frame); int (*dtrace_invop_jump_addr)(struct trapframe *); @@ -144,7 +145,7 @@ svc_handler(struct trapframe *frame) } static void -data_abort(struct trapframe *frame, uint64_t esr, int lower) +data_abort(struct trapframe *frame, uint64_t esr, uint64_t far, int lower) { struct vm_map *map; struct thread *td; @@ -152,7 +153,6 @@ data_abort(struct trapframe *frame, uint struct pcb *pcb; vm_prot_t ftype; vm_offset_t va; - uint64_t far; int error, sig, ucode; /* @@ -181,17 +181,23 @@ data_abort(struct trapframe *frame, uint return; } - far = READ_SPECIALREG(far_el1); - p = td->td_proc; + KASSERT(td->td_md.md_spinlock_count == 0, + ("data abort with spinlock held")); + if (td->td_critnest != 0 || WITNESS_CHECK(WARN_SLEEPOK | + WARN_GIANTOK, NULL, "Kernel page fault") != 0) { + print_registers(frame); + panic("data abort in critical section or under mutex"); + } + p = td->td_proc; if (lower) - map = &td->td_proc->p_vmspace->vm_map; + map = &p->p_vmspace->vm_map; else { /* The top bit tells us which range to use */ if ((far >> 63) == 1) map = kernel_map; else - map = &td->td_proc->p_vmspace->vm_map; + map = &p->p_vmspace->vm_map; } va = trunc_page(far); @@ -246,7 +252,7 @@ void do_el1h_sync(struct trapframe *frame) { uint32_t exception; - uint64_t esr; + uint64_t esr, far; /* Read the esr register to get the exception details */ esr = READ_SPECIALREG(esr_el1); @@ -281,7 +287,9 @@ do_el1h_sync(struct trapframe *frame) print_registers(frame); panic("VFP exception in the kernel"); case EXCP_DATA_ABORT: - data_abort(frame, esr, 0); + far = READ_SPECIALREG(far_el1); + intr_enable(); + data_abort(frame, esr, far, 0); break; case EXCP_BRK: #ifdef KDTRACE_HOOKS @@ -328,7 +336,7 @@ do_el0_sync(struct trapframe *frame) { struct thread *td; uint32_t exception; - uint64_t esr; + uint64_t esr, far; /* Check we have a sane environment when entering from userland */ KASSERT((uintptr_t)get_pcpu() >= VM_MIN_KERNEL_ADDRESS, @@ -337,6 +345,13 @@ do_el0_sync(struct trapframe *frame) esr = READ_SPECIALREG(esr_el1); exception = ESR_ELx_EXCEPTION(esr); + switch (exception) { + case EXCP_INSN_ABORT_L: + case EXCP_DATA_ABORT_L: + case EXCP_DATA_ABORT: + far = READ_SPECIALREG(far_el1); + } + intr_enable(); CTR4(KTR_TRAP, "do_el0_sync: curthread: %p, esr %lx, elr: %lx, frame: %p", @@ -352,18 +367,12 @@ do_el0_sync(struct trapframe *frame) #endif break; case EXCP_SVC: - /* - * Ensure the svc_handler is being run with interrupts enabled. - * They will be automatically restored when returning from - * exception handler. - */ - intr_enable(); svc_handler(frame); break; case EXCP_INSN_ABORT_L: case EXCP_DATA_ABORT_L: case EXCP_DATA_ABORT: - data_abort(frame, esr, 1); + data_abort(frame, esr, far, 1); break; case EXCP_UNKNOWN: el0_excp_unknown(frame);
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