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authorThomas Gleixner <tglx@linutronix.de>2020-07-22 23:59:56 +0200
committerThomas Gleixner <tglx@linutronix.de>2020-07-24 14:59:03 +0200
commit142781e108b13b2b0e8f035cfb5bfbbc8f14d887 (patch)
treee11ce626a38bf77bd2ec08499f2199534e2a9a15 /kernel/entry
parent6823ecabf03031d610a6c5afe7ed4b4fd659a99f (diff)
entry: Provide generic syscall entry functionality
On syscall entry certain work needs to be done: - Establish state (lockdep, context tracking, tracing) - Conditional work (ptrace, seccomp, audit...) This code is needlessly duplicated and different in all architectures. Provide a generic version based on the x86 implementation which has all the RCU and instrumentation bits right. As interrupt/exception entry from user space needs parts of the same functionality, provide a function for this as well. syscall_enter_from_user_mode() and irqentry_enter_from_user_mode() must be called right after the low level ASM entry. The calling code must be non-instrumentable. After the functions returns state is correct and the subsequent functions can be instrumented. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Kees Cook <keescook@chromium.org> Link: https://lkml.kernel.org/r/20200722220519.513463269@linutronix.de
Diffstat (limited to 'kernel/entry')
-rw-r--r--kernel/entry/Makefile12
-rw-r--r--kernel/entry/common.c88
2 files changed, 100 insertions, 0 deletions
diff --git a/kernel/entry/Makefile b/kernel/entry/Makefile
new file mode 100644
index 000000000000..c207d202bf3a
--- /dev/null
+++ b/kernel/entry/Makefile
@@ -0,0 +1,12 @@
+# 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
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
new file mode 100644
index 000000000000..1d636dee2fec
--- /dev/null
+++ b/kernel/entry/common.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/context_tracking.h>
+#include <linux/entry-common.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/syscalls.h>
+
+/**
+ * enter_from_user_mode - Establish state when coming from user mode
+ *
+ * Syscall/interrupt entry disables interrupts, but user mode is traced as
+ * interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
+ *
+ * 1) Tell lockdep that interrupts are disabled
+ * 2) Invoke context tracking if enabled to reactivate RCU
+ * 3) Trace interrupts off state
+ */
+static __always_inline void enter_from_user_mode(struct pt_regs *regs)
+{
+ arch_check_user_regs(regs);
+ lockdep_hardirqs_off(CALLER_ADDR0);
+
+ CT_WARN_ON(ct_state() != CONTEXT_USER);
+ user_exit_irqoff();
+
+ instrumentation_begin();
+ trace_hardirqs_off_finish();
+ instrumentation_end();
+}
+
+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 ti_work)
+{
+ long ret = 0;
+
+ /* Handle ptrace */
+ if (ti_work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
+ ret = arch_syscall_enter_tracehook(regs);
+ if (ret || (ti_work & _TIF_SYSCALL_EMU))
+ return -1L;
+ }
+
+ /* Do seccomp after ptrace, to catch any tracer changes. */
+ if (ti_work & _TIF_SECCOMP) {
+ ret = __secure_computing(NULL);
+ if (ret == -1L)
+ return ret;
+ }
+
+ if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT))
+ trace_sys_enter(regs, syscall);
+
+ syscall_enter_audit(regs, syscall);
+
+ return ret ? : syscall;
+}
+
+noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
+{
+ unsigned long ti_work;
+
+ enter_from_user_mode(regs);
+ instrumentation_begin();
+
+ local_irq_enable();
+ ti_work = READ_ONCE(current_thread_info()->flags);
+ if (ti_work & SYSCALL_ENTER_WORK)
+ syscall = syscall_trace_enter(regs, syscall, ti_work);
+ instrumentation_end();
+
+ return syscall;
+}
+
+noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
+{
+ enter_from_user_mode(regs);
+}