summaryrefslogtreecommitdiffstats
path: root/kernel/entry
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/entry')
-rw-r--r--kernel/entry/Makefile13
-rw-r--r--kernel/entry/common.c483
-rw-r--r--kernel/entry/common.h7
-rw-r--r--kernel/entry/kvm.c49
-rw-r--r--kernel/entry/syscall_user_dispatch.c108
5 files changed, 660 insertions, 0 deletions
diff --git a/kernel/entry/Makefile b/kernel/entry/Makefile
new file mode 100644
index 000000000..095c775e0
--- /dev/null
+++ b/kernel/entry/Makefile
@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# Prevent the noinstr section from being pestered by sanitizer and other goodies
+# as long as these things cannot be disabled per function.
+KASAN_SANITIZE := n
+UBSAN_SANITIZE := n
+KCOV_INSTRUMENT := n
+
+CFLAGS_REMOVE_common.o = -fstack-protector -fstack-protector-strong
+CFLAGS_common.o += -fno-stack-protector
+
+obj-$(CONFIG_GENERIC_ENTRY) += common.o syscall_user_dispatch.o
+obj-$(CONFIG_KVM_XFER_TO_GUEST_WORK) += kvm.o
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
new file mode 100644
index 000000000..be61332c6
--- /dev/null
+++ b/kernel/entry/common.c
@@ -0,0 +1,483 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/context_tracking.h>
+#include <linux/entry-common.h>
+#include <linux/resume_user_mode.h>
+#include <linux/highmem.h>
+#include <linux/jump_label.h>
+#include <linux/kmsan.h>
+#include <linux/livepatch.h>
+#include <linux/audit.h>
+#include <linux/tick.h>
+
+#include "common.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/syscalls.h>
+
+/* See comment for enter_from_user_mode() in entry-common.h */
+static __always_inline void __enter_from_user_mode(struct pt_regs *regs)
+{
+ arch_enter_from_user_mode(regs);
+ lockdep_hardirqs_off(CALLER_ADDR0);
+
+ CT_WARN_ON(__ct_state() != CONTEXT_USER);
+ user_exit_irqoff();
+
+ instrumentation_begin();
+ kmsan_unpoison_entry_regs(regs);
+ trace_hardirqs_off_finish();
+ instrumentation_end();
+}
+
+void noinstr enter_from_user_mode(struct pt_regs *regs)
+{
+ __enter_from_user_mode(regs);
+}
+
+static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
+{
+ if (unlikely(audit_context())) {
+ unsigned long args[6];
+
+ syscall_get_arguments(current, regs, args);
+ audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
+ }
+}
+
+static long syscall_trace_enter(struct pt_regs *regs, long syscall,
+ unsigned long work)
+{
+ long ret = 0;
+
+ /*
+ * Handle Syscall User Dispatch. This must comes first, since
+ * the ABI here can be something that doesn't make sense for
+ * other syscall_work features.
+ */
+ if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
+ if (syscall_user_dispatch(regs))
+ return -1L;
+ }
+
+ /* Handle ptrace */
+ if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
+ ret = ptrace_report_syscall_entry(regs);
+ if (ret || (work & SYSCALL_WORK_SYSCALL_EMU))
+ return -1L;
+ }
+
+ /* Do seccomp after ptrace, to catch any tracer changes. */
+ if (work & SYSCALL_WORK_SECCOMP) {
+ ret = __secure_computing(NULL);
+ if (ret == -1L)
+ return ret;
+ }
+
+ /* Either of the above might have changed the syscall number */
+ syscall = syscall_get_nr(current, regs);
+
+ if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))
+ trace_sys_enter(regs, syscall);
+
+ syscall_enter_audit(regs, syscall);
+
+ return ret ? : syscall;
+}
+
+static __always_inline long
+__syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
+{
+ unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
+
+ if (work & SYSCALL_WORK_ENTER)
+ syscall = syscall_trace_enter(regs, syscall, work);
+
+ return syscall;
+}
+
+long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
+{
+ return __syscall_enter_from_user_work(regs, syscall);
+}
+
+noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
+{
+ long ret;
+
+ __enter_from_user_mode(regs);
+
+ instrumentation_begin();
+ local_irq_enable();
+ ret = __syscall_enter_from_user_work(regs, syscall);
+ instrumentation_end();
+
+ return ret;
+}
+
+noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
+{
+ __enter_from_user_mode(regs);
+ instrumentation_begin();
+ local_irq_enable();
+ instrumentation_end();
+}
+
+/* See comment for exit_to_user_mode() in entry-common.h */
+static __always_inline void __exit_to_user_mode(void)
+{
+ instrumentation_begin();
+ trace_hardirqs_on_prepare();
+ lockdep_hardirqs_on_prepare();
+ instrumentation_end();
+
+ user_enter_irqoff();
+ arch_exit_to_user_mode();
+ lockdep_hardirqs_on(CALLER_ADDR0);
+}
+
+void noinstr exit_to_user_mode(void)
+{
+ __exit_to_user_mode();
+}
+
+/* Workaround to allow gradual conversion of architecture code */
+void __weak arch_do_signal_or_restart(struct pt_regs *regs) { }
+
+static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
+ unsigned long ti_work)
+{
+ /*
+ * Before returning to user space ensure that all pending work
+ * items have been completed.
+ */
+ while (ti_work & EXIT_TO_USER_MODE_WORK) {
+
+ local_irq_enable_exit_to_user(ti_work);
+
+ if (ti_work & _TIF_NEED_RESCHED)
+ schedule();
+
+ if (ti_work & _TIF_UPROBE)
+ uprobe_notify_resume(regs);
+
+ if (ti_work & _TIF_PATCH_PENDING)
+ klp_update_patch_state(current);
+
+ if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
+ arch_do_signal_or_restart(regs);
+
+ if (ti_work & _TIF_NOTIFY_RESUME)
+ resume_user_mode_work(regs);
+
+ /* Architecture specific TIF work */
+ arch_exit_to_user_mode_work(regs, ti_work);
+
+ /*
+ * Disable interrupts and reevaluate the work flags as they
+ * might have changed while interrupts and preemption was
+ * enabled above.
+ */
+ local_irq_disable_exit_to_user();
+
+ /* Check if any of the above work has queued a deferred wakeup */
+ tick_nohz_user_enter_prepare();
+
+ ti_work = read_thread_flags();
+ }
+
+ /* Return the latest work state for arch_exit_to_user_mode() */
+ return ti_work;
+}
+
+static void exit_to_user_mode_prepare(struct pt_regs *regs)
+{
+ unsigned long ti_work;
+
+ lockdep_assert_irqs_disabled();
+
+ /* Flush pending rcuog wakeup before the last need_resched() check */
+ tick_nohz_user_enter_prepare();
+
+ ti_work = read_thread_flags();
+ if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
+ ti_work = exit_to_user_mode_loop(regs, ti_work);
+
+ arch_exit_to_user_mode_prepare(regs, ti_work);
+
+ /* Ensure that the address limit is intact and no locks are held */
+ addr_limit_user_check();
+ kmap_assert_nomap();
+ lockdep_assert_irqs_disabled();
+ lockdep_sys_exit();
+}
+
+/*
+ * If SYSCALL_EMU is set, then the only reason to report is when
+ * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
+ * instruction has been already reported in syscall_enter_from_user_mode().
+ */
+static inline bool report_single_step(unsigned long work)
+{
+ if (work & SYSCALL_WORK_SYSCALL_EMU)
+ return false;
+
+ return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
+}
+
+static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
+{
+ bool step;
+
+ /*
+ * If the syscall was rolled back due to syscall user dispatching,
+ * then the tracers below are not invoked for the same reason as
+ * the entry side was not invoked in syscall_trace_enter(): The ABI
+ * of these syscalls is unknown.
+ */
+ if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
+ if (unlikely(current->syscall_dispatch.on_dispatch)) {
+ current->syscall_dispatch.on_dispatch = false;
+ return;
+ }
+ }
+
+ audit_syscall_exit(regs);
+
+ if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
+ trace_sys_exit(regs, syscall_get_return_value(current, regs));
+
+ step = report_single_step(work);
+ if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
+ ptrace_report_syscall_exit(regs, step);
+}
+
+/*
+ * Syscall specific exit to user mode preparation. Runs with interrupts
+ * enabled.
+ */
+static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
+{
+ unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
+ unsigned long nr = syscall_get_nr(current, regs);
+
+ CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
+
+ if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
+ if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
+ local_irq_enable();
+ }
+
+ rseq_syscall(regs);
+
+ /*
+ * Do one-time syscall specific work. If these work items are
+ * enabled, we want to run them exactly once per syscall exit with
+ * interrupts enabled.
+ */
+ if (unlikely(work & SYSCALL_WORK_EXIT))
+ syscall_exit_work(regs, work);
+}
+
+static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs)
+{
+ syscall_exit_to_user_mode_prepare(regs);
+ local_irq_disable_exit_to_user();
+ exit_to_user_mode_prepare(regs);
+}
+
+void syscall_exit_to_user_mode_work(struct pt_regs *regs)
+{
+ __syscall_exit_to_user_mode_work(regs);
+}
+
+__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
+{
+ instrumentation_begin();
+ __syscall_exit_to_user_mode_work(regs);
+ instrumentation_end();
+ __exit_to_user_mode();
+}
+
+noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
+{
+ __enter_from_user_mode(regs);
+}
+
+noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
+{
+ instrumentation_begin();
+ exit_to_user_mode_prepare(regs);
+ instrumentation_end();
+ __exit_to_user_mode();
+}
+
+noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
+{
+ irqentry_state_t ret = {
+ .exit_rcu = false,
+ };
+
+ if (user_mode(regs)) {
+ irqentry_enter_from_user_mode(regs);
+ return ret;
+ }
+
+ /*
+ * If this entry hit the idle task invoke ct_irq_enter() whether
+ * RCU is watching or not.
+ *
+ * Interrupts can nest when the first interrupt invokes softirq
+ * processing on return which enables interrupts.
+ *
+ * Scheduler ticks in the idle task can mark quiescent state and
+ * terminate a grace period, if and only if the timer interrupt is
+ * not nested into another interrupt.
+ *
+ * Checking for rcu_is_watching() here would prevent the nesting
+ * interrupt to invoke ct_irq_enter(). If that nested interrupt is
+ * the tick then rcu_flavor_sched_clock_irq() would wrongfully
+ * assume that it is the first interrupt and eventually claim
+ * quiescent state and end grace periods prematurely.
+ *
+ * Unconditionally invoke ct_irq_enter() so RCU state stays
+ * consistent.
+ *
+ * TINY_RCU does not support EQS, so let the compiler eliminate
+ * this part when enabled.
+ */
+ if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
+ /*
+ * If RCU is not watching then the same careful
+ * sequence vs. lockdep and tracing is required
+ * as in irqentry_enter_from_user_mode().
+ */
+ lockdep_hardirqs_off(CALLER_ADDR0);
+ ct_irq_enter();
+ instrumentation_begin();
+ kmsan_unpoison_entry_regs(regs);
+ trace_hardirqs_off_finish();
+ instrumentation_end();
+
+ ret.exit_rcu = true;
+ return ret;
+ }
+
+ /*
+ * If RCU is watching then RCU only wants to check whether it needs
+ * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
+ * already contains a warning when RCU is not watching, so no point
+ * in having another one here.
+ */
+ lockdep_hardirqs_off(CALLER_ADDR0);
+ instrumentation_begin();
+ kmsan_unpoison_entry_regs(regs);
+ rcu_irq_enter_check_tick();
+ trace_hardirqs_off_finish();
+ instrumentation_end();
+
+ return ret;
+}
+
+void raw_irqentry_exit_cond_resched(void)
+{
+ if (!preempt_count()) {
+ /* Sanity check RCU and thread stack */
+ rcu_irq_exit_check_preempt();
+ if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
+ WARN_ON_ONCE(!on_thread_stack());
+ if (need_resched())
+ preempt_schedule_irq();
+ }
+}
+#ifdef CONFIG_PREEMPT_DYNAMIC
+#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
+DEFINE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
+#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
+DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
+void dynamic_irqentry_exit_cond_resched(void)
+{
+ if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
+ return;
+ raw_irqentry_exit_cond_resched();
+}
+#endif
+#endif
+
+noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
+{
+ lockdep_assert_irqs_disabled();
+
+ /* Check whether this returns to user mode */
+ if (user_mode(regs)) {
+ irqentry_exit_to_user_mode(regs);
+ } else if (!regs_irqs_disabled(regs)) {
+ /*
+ * If RCU was not watching on entry this needs to be done
+ * carefully and needs the same ordering of lockdep/tracing
+ * and RCU as the return to user mode path.
+ */
+ if (state.exit_rcu) {
+ instrumentation_begin();
+ /* Tell the tracer that IRET will enable interrupts */
+ trace_hardirqs_on_prepare();
+ lockdep_hardirqs_on_prepare();
+ instrumentation_end();
+ ct_irq_exit();
+ lockdep_hardirqs_on(CALLER_ADDR0);
+ return;
+ }
+
+ instrumentation_begin();
+ if (IS_ENABLED(CONFIG_PREEMPTION))
+ irqentry_exit_cond_resched();
+
+ /* Covers both tracing and lockdep */
+ trace_hardirqs_on();
+ instrumentation_end();
+ } else {
+ /*
+ * IRQ flags state is correct already. Just tell RCU if it
+ * was not watching on entry.
+ */
+ if (state.exit_rcu)
+ ct_irq_exit();
+ }
+}
+
+irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
+{
+ irqentry_state_t irq_state;
+
+ irq_state.lockdep = lockdep_hardirqs_enabled();
+
+ __nmi_enter();
+ lockdep_hardirqs_off(CALLER_ADDR0);
+ lockdep_hardirq_enter();
+ ct_nmi_enter();
+
+ instrumentation_begin();
+ kmsan_unpoison_entry_regs(regs);
+ trace_hardirqs_off_finish();
+ ftrace_nmi_enter();
+ instrumentation_end();
+
+ return irq_state;
+}
+
+void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
+{
+ instrumentation_begin();
+ ftrace_nmi_exit();
+ if (irq_state.lockdep) {
+ trace_hardirqs_on_prepare();
+ lockdep_hardirqs_on_prepare();
+ }
+ instrumentation_end();
+
+ ct_nmi_exit();
+ lockdep_hardirq_exit();
+ if (irq_state.lockdep)
+ lockdep_hardirqs_on(CALLER_ADDR0);
+ __nmi_exit();
+}
diff --git a/kernel/entry/common.h b/kernel/entry/common.h
new file mode 100644
index 000000000..f6e6d02f0
--- /dev/null
+++ b/kernel/entry/common.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _COMMON_H
+#define _COMMON_H
+
+bool syscall_user_dispatch(struct pt_regs *regs);
+
+#endif
diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c
new file mode 100644
index 000000000..2e0f75bcb
--- /dev/null
+++ b/kernel/entry/kvm.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/entry-kvm.h>
+#include <linux/kvm_host.h>
+
+static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
+{
+ do {
+ int ret;
+
+ if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
+ kvm_handle_signal_exit(vcpu);
+ return -EINTR;
+ }
+
+ if (ti_work & _TIF_NEED_RESCHED)
+ schedule();
+
+ if (ti_work & _TIF_NOTIFY_RESUME)
+ resume_user_mode_work(NULL);
+
+ ret = arch_xfer_to_guest_mode_handle_work(vcpu, ti_work);
+ if (ret)
+ return ret;
+
+ ti_work = read_thread_flags();
+ } while (ti_work & XFER_TO_GUEST_MODE_WORK || need_resched());
+ return 0;
+}
+
+int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu)
+{
+ unsigned long ti_work;
+
+ /*
+ * This is invoked from the outer guest loop with interrupts and
+ * preemption enabled.
+ *
+ * KVM invokes xfer_to_guest_mode_work_pending() with interrupts
+ * disabled in the inner loop before going into guest mode. No need
+ * to disable interrupts here.
+ */
+ ti_work = read_thread_flags();
+ if (!(ti_work & XFER_TO_GUEST_MODE_WORK))
+ return 0;
+
+ return xfer_to_guest_mode_work(vcpu, ti_work);
+}
+EXPORT_SYMBOL_GPL(xfer_to_guest_mode_handle_work);
diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
new file mode 100644
index 000000000..0b6379adf
--- /dev/null
+++ b/kernel/entry/syscall_user_dispatch.c
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Collabora Ltd.
+ */
+#include <linux/sched.h>
+#include <linux/prctl.h>
+#include <linux/syscall_user_dispatch.h>
+#include <linux/uaccess.h>
+#include <linux/signal.h>
+#include <linux/elf.h>
+
+#include <linux/sched/signal.h>
+#include <linux/sched/task_stack.h>
+
+#include <asm/syscall.h>
+
+#include "common.h"
+
+static void trigger_sigsys(struct pt_regs *regs)
+{
+ struct kernel_siginfo info;
+
+ clear_siginfo(&info);
+ info.si_signo = SIGSYS;
+ info.si_code = SYS_USER_DISPATCH;
+ info.si_call_addr = (void __user *)KSTK_EIP(current);
+ info.si_errno = 0;
+ info.si_arch = syscall_get_arch(current);
+ info.si_syscall = syscall_get_nr(current, regs);
+
+ force_sig_info(&info);
+}
+
+bool syscall_user_dispatch(struct pt_regs *regs)
+{
+ struct syscall_user_dispatch *sd = &current->syscall_dispatch;
+ char state;
+
+ if (likely(instruction_pointer(regs) - sd->offset < sd->len))
+ return false;
+
+ if (unlikely(arch_syscall_is_vdso_sigreturn(regs)))
+ return false;
+
+ if (likely(sd->selector)) {
+ /*
+ * access_ok() is performed once, at prctl time, when
+ * the selector is loaded by userspace.
+ */
+ if (unlikely(__get_user(state, sd->selector))) {
+ force_exit_sig(SIGSEGV);
+ return true;
+ }
+
+ if (likely(state == SYSCALL_DISPATCH_FILTER_ALLOW))
+ return false;
+
+ if (state != SYSCALL_DISPATCH_FILTER_BLOCK) {
+ force_exit_sig(SIGSYS);
+ return true;
+ }
+ }
+
+ sd->on_dispatch = true;
+ syscall_rollback(current, regs);
+ trigger_sigsys(regs);
+
+ return true;
+}
+
+int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
+ unsigned long len, char __user *selector)
+{
+ switch (mode) {
+ case PR_SYS_DISPATCH_OFF:
+ if (offset || len || selector)
+ return -EINVAL;
+ break;
+ case PR_SYS_DISPATCH_ON:
+ /*
+ * Validate the direct dispatcher region just for basic
+ * sanity against overflow and a 0-sized dispatcher
+ * region. If the user is able to submit a syscall from
+ * an address, that address is obviously valid.
+ */
+ if (offset && offset + len <= offset)
+ return -EINVAL;
+
+ if (selector && !access_ok(selector, sizeof(*selector)))
+ return -EFAULT;
+
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ current->syscall_dispatch.selector = selector;
+ current->syscall_dispatch.offset = offset;
+ current->syscall_dispatch.len = len;
+ current->syscall_dispatch.on_dispatch = false;
+
+ if (mode == PR_SYS_DISPATCH_ON)
+ set_syscall_work(SYSCALL_USER_DISPATCH);
+ else
+ clear_syscall_work(SYSCALL_USER_DISPATCH);
+
+ return 0;
+}