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authorThomas Gleixner <tglx@linutronix.de>2020-07-23 00:59:57 +0300
committerThomas Gleixner <tglx@linutronix.de>2020-07-24 15:59:03 +0300
commita9f3a74a29af095f3e1b89e9176f8127912ae0f0 (patch)
treeb21efe2125aaf7d3ff9c336927be6e0abd26628e /include/linux/entry-common.h
parent142781e108b13b2b0e8f035cfb5bfbbc8f14d887 (diff)
downloadlinux-a9f3a74a29af095f3e1b89e9176f8127912ae0f0.tar.xz
entry: Provide generic syscall exit function
Like syscall entry all architectures have similar and pointlessly different code to handle pending work before returning from a syscall to user space. 1) One-time syscall exit work: - rseq syscall exit - audit - syscall tracing - tracehook (single stepping) 2) Preparatory work - Exit to user mode loop (common TIF handling). - Architecture specific one time work arch_exit_to_user_mode_prepare() - Address limit and lockdep checks 3) Final transition (lockdep, tracing, context tracking, RCU). Invokes arch_exit_to_user_mode() to handle e.g. speculation mitigations Provide a generic version based on the x86 code which has all the RCU and instrumentation protections right. Provide a variant for interrupt return to user mode as well which shares the above #2 and #3 work items. After syscall_exit_to_user_mode() and irqentry_exit_to_user_mode() the architecture code just has to return to user space. The code after returning from these functions must not be instrumented. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Kees Cook <keescook@chromium.org> Link: https://lkml.kernel.org/r/20200722220519.613977173@linutronix.de
Diffstat (limited to 'include/linux/entry-common.h')
-rw-r--r--include/linux/entry-common.h189
1 files changed, 189 insertions, 0 deletions
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 42fc8e4632bb..c4a57be9cde4 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -29,6 +29,14 @@
# define _TIF_SYSCALL_AUDIT (0)
#endif
+#ifndef _TIF_PATCH_PENDING
+# define _TIF_PATCH_PENDING (0)
+#endif
+
+#ifndef _TIF_UPROBE
+# define _TIF_UPROBE (0)
+#endif
+
/*
* TIF flags handled in syscall_enter_from_usermode()
*/
@@ -41,6 +49,29 @@
_TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_EMU | \
ARCH_SYSCALL_ENTER_WORK)
+/*
+ * TIF flags handled in syscall_exit_to_user_mode()
+ */
+#ifndef ARCH_SYSCALL_EXIT_WORK
+# define ARCH_SYSCALL_EXIT_WORK (0)
+#endif
+
+#define SYSCALL_EXIT_WORK \
+ (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
+ _TIF_SYSCALL_TRACEPOINT | ARCH_SYSCALL_EXIT_WORK)
+
+/*
+ * TIF flags handled in exit_to_user_mode_loop()
+ */
+#ifndef ARCH_EXIT_TO_USER_MODE_WORK
+# define ARCH_EXIT_TO_USER_MODE_WORK (0)
+#endif
+
+#define EXIT_TO_USER_MODE_WORK \
+ (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
+ _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | \
+ ARCH_EXIT_TO_USER_MODE_WORK)
+
/**
* arch_check_user_regs - Architecture specific sanity check for user mode regs
* @regs: Pointer to currents pt_regs
@@ -106,6 +137,149 @@ static inline __must_check int arch_syscall_enter_tracehook(struct pt_regs *regs
long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall);
/**
+ * local_irq_enable_exit_to_user - Exit to user variant of local_irq_enable()
+ * @ti_work: Cached TIF flags gathered with interrupts disabled
+ *
+ * Defaults to local_irq_enable(). Can be supplied by architecture specific
+ * code.
+ */
+static inline void local_irq_enable_exit_to_user(unsigned long ti_work);
+
+#ifndef local_irq_enable_exit_to_user
+static inline void local_irq_enable_exit_to_user(unsigned long ti_work)
+{
+ local_irq_enable();
+}
+#endif
+
+/**
+ * local_irq_disable_exit_to_user - Exit to user variant of local_irq_disable()
+ *
+ * Defaults to local_irq_disable(). Can be supplied by architecture specific
+ * code.
+ */
+static inline void local_irq_disable_exit_to_user(void);
+
+#ifndef local_irq_disable_exit_to_user
+static inline void local_irq_disable_exit_to_user(void)
+{
+ local_irq_disable();
+}
+#endif
+
+/**
+ * arch_exit_to_user_mode_work - Architecture specific TIF work for exit
+ * to user mode.
+ * @regs: Pointer to currents pt_regs
+ * @ti_work: Cached TIF flags gathered with interrupts disabled
+ *
+ * Invoked from exit_to_user_mode_loop() with interrupt enabled
+ *
+ * Defaults to NOOP. Can be supplied by architecture specific code.
+ */
+static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
+ unsigned long ti_work);
+
+#ifndef arch_exit_to_user_mode_work
+static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
+ unsigned long ti_work)
+{
+}
+#endif
+
+/**
+ * arch_exit_to_user_mode_prepare - Architecture specific preparation for
+ * exit to user mode.
+ * @regs: Pointer to currents pt_regs
+ * @ti_work: Cached TIF flags gathered with interrupts disabled
+ *
+ * Invoked from exit_to_user_mode_prepare() with interrupt disabled as the last
+ * function before return. Defaults to NOOP.
+ */
+static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
+ unsigned long ti_work);
+
+#ifndef arch_exit_to_user_mode_prepare
+static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
+ unsigned long ti_work)
+{
+}
+#endif
+
+/**
+ * arch_exit_to_user_mode - Architecture specific final work before
+ * exit to user mode.
+ *
+ * Invoked from exit_to_user_mode() with interrupt disabled as the last
+ * function before return. Defaults to NOOP.
+ *
+ * This needs to be __always_inline because it is non-instrumentable code
+ * invoked after context tracking switched to user mode.
+ *
+ * An architecture implementation must not do anything complex, no locking
+ * etc. The main purpose is for speculation mitigations.
+ */
+static __always_inline void arch_exit_to_user_mode(void);
+
+#ifndef arch_exit_to_user_mode
+static __always_inline void arch_exit_to_user_mode(void) { }
+#endif
+
+/**
+ * arch_do_signal - Architecture specific signal delivery function
+ * @regs: Pointer to currents pt_regs
+ *
+ * Invoked from exit_to_user_mode_loop().
+ */
+void arch_do_signal(struct pt_regs *regs);
+
+/**
+ * arch_syscall_exit_tracehook - Wrapper around tracehook_report_syscall_exit()
+ * @regs: Pointer to currents pt_regs
+ * @step: Indicator for single step
+ *
+ * Defaults to tracehook_report_syscall_exit(). Can be replaced by
+ * architecture specific code.
+ *
+ * Invoked from syscall_exit_to_user_mode()
+ */
+static inline void arch_syscall_exit_tracehook(struct pt_regs *regs, bool step);
+
+#ifndef arch_syscall_exit_tracehook
+static inline void arch_syscall_exit_tracehook(struct pt_regs *regs, bool step)
+{
+ tracehook_report_syscall_exit(regs, step);
+}
+#endif
+
+/**
+ * syscall_exit_to_user_mode - Handle work before returning to user mode
+ * @regs: Pointer to currents pt_regs
+ *
+ * Invoked with interrupts enabled and fully valid regs. Returns with all
+ * work handled, interrupts disabled such that the caller can immediately
+ * switch to user mode. Called from architecture specific syscall and ret
+ * from fork code.
+ *
+ * The call order is:
+ * 1) One-time syscall exit work:
+ * - rseq syscall exit
+ * - audit
+ * - syscall tracing
+ * - tracehook (single stepping)
+ *
+ * 2) Preparatory work
+ * - Exit to user mode loop (common TIF handling). Invokes
+ * arch_exit_to_user_mode_work() for architecture specific TIF work
+ * - Architecture specific one time work arch_exit_to_user_mode_prepare()
+ * - Address limit and lockdep checks
+ *
+ * 3) Final transition (lockdep, tracing, context tracking, RCU). Invokes
+ * arch_exit_to_user_mode() to handle e.g. speculation mitigations
+ */
+void syscall_exit_to_user_mode(struct pt_regs *regs);
+
+/**
* irqentry_enter_from_user_mode - Establish state before invoking the irq handler
* @regs: Pointer to currents pt_regs
*
@@ -118,4 +292,19 @@ long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall);
*/
void irqentry_enter_from_user_mode(struct pt_regs *regs);
+/**
+ * irqentry_exit_to_user_mode - Interrupt exit work
+ * @regs: Pointer to current's pt_regs
+ *
+ * Invoked with interrupts disbled and fully valid regs. Returns with all
+ * work handled, interrupts disabled such that the caller can immediately
+ * switch to user mode. Called from architecture specific interrupt
+ * handling code.
+ *
+ * The call order is #2 and #3 as described in syscall_exit_to_user_mode().
+ * Interrupt exit is not invoking #1 which is the syscall specific one time
+ * work.
+ */
+void irqentry_exit_to_user_mode(struct pt_regs *regs);
+
#endif