x86/entry: Move C entry and exit code to arch/x86/entry/common.c

The entry and exit C helpers were confusingly scattered between
ptrace.c and signal.c, even though they aren't specific to
ptrace or signal handling.  Move them together in a new file.

This change just moves code around.  It doesn't change anything.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/324d686821266544d8572423cc281f961da445f4.1435952415.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/entry/Makefile b/arch/x86/entry/Makefile
index 7a14497..bd55ded 100644 (file)
--- a/arch/x86/entry/Makefile
+++ b/arch/x86/entry/Makefile
@@ -2,6 +2,7 @@
 # Makefile for the x86 low level entry code
 #
 obj-y                          := entry_$(BITS).o thunk_$(BITS).o syscall_$(BITS).o
+obj-y                          += common.o
 
 obj-y                          += vdso/
 obj-y                          += vsyscall/

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
new file mode 100644 (file)
index 0000000..917d0c3
--- /dev/null
+++ b/arch/x86/entry/common.c
@@ -0,0 +1,253 @@
+/*
+ * common.c - C code for kernel entry and exit
+ * Copyright (c) 2015 Andrew Lutomirski
+ * GPL v2
+ *
+ * Based on asm and ptrace code by many authors.  The code here originated
+ * in ptrace.c and signal.c.
+ */
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/errno.h>
+#include <linux/ptrace.h>
+#include <linux/tracehook.h>
+#include <linux/audit.h>
+#include <linux/seccomp.h>
+#include <linux/signal.h>
+#include <linux/export.h>
+#include <linux/context_tracking.h>
+#include <linux/user-return-notifier.h>
+#include <linux/uprobes.h>
+
+#include <asm/desc.h>
+#include <asm/traps.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/syscalls.h>
+
+static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
+{
+#ifdef CONFIG_X86_64
+       if (arch == AUDIT_ARCH_X86_64) {
+               audit_syscall_entry(regs->orig_ax, regs->di,
+                                   regs->si, regs->dx, regs->r10);
+       } else
+#endif
+       {
+               audit_syscall_entry(regs->orig_ax, regs->bx,
+                                   regs->cx, regs->dx, regs->si);
+       }
+}
+
+/*
+ * We can return 0 to resume the syscall or anything else to go to phase
+ * 2.  If we resume the syscall, we need to put something appropriate in
+ * regs->orig_ax.
+ *
+ * NB: We don't have full pt_regs here, but regs->orig_ax and regs->ax
+ * are fully functional.
+ *
+ * For phase 2's benefit, our return value is:
+ * 0:                  resume the syscall
+ * 1:                  go to phase 2; no seccomp phase 2 needed
+ * anything else:      go to phase 2; pass return value to seccomp
+ */
+unsigned long syscall_trace_enter_phase1(struct pt_regs *regs, u32 arch)
+{
+       unsigned long ret = 0;
+       u32 work;
+
+       BUG_ON(regs != task_pt_regs(current));
+
+       work = ACCESS_ONCE(current_thread_info()->flags) &
+               _TIF_WORK_SYSCALL_ENTRY;
+
+       /*
+        * If TIF_NOHZ is set, we are required to call user_exit() before
+        * doing anything that could touch RCU.
+        */
+       if (work & _TIF_NOHZ) {
+               user_exit();
+               work &= ~_TIF_NOHZ;
+       }
+
+#ifdef CONFIG_SECCOMP
+       /*
+        * Do seccomp first -- it should minimize exposure of other
+        * code, and keeping seccomp fast is probably more valuable
+        * than the rest of this.
+        */
+       if (work & _TIF_SECCOMP) {
+               struct seccomp_data sd;
+
+               sd.arch = arch;
+               sd.nr = regs->orig_ax;
+               sd.instruction_pointer = regs->ip;
+#ifdef CONFIG_X86_64
+               if (arch == AUDIT_ARCH_X86_64) {
+                       sd.args[0] = regs->di;
+                       sd.args[1] = regs->si;
+                       sd.args[2] = regs->dx;
+                       sd.args[3] = regs->r10;
+                       sd.args[4] = regs->r8;
+                       sd.args[5] = regs->r9;
+               } else
+#endif
+               {
+                       sd.args[0] = regs->bx;
+                       sd.args[1] = regs->cx;
+                       sd.args[2] = regs->dx;
+                       sd.args[3] = regs->si;
+                       sd.args[4] = regs->di;
+                       sd.args[5] = regs->bp;
+               }
+
+               BUILD_BUG_ON(SECCOMP_PHASE1_OK != 0);
+               BUILD_BUG_ON(SECCOMP_PHASE1_SKIP != 1);
+
+               ret = seccomp_phase1(&sd);
+               if (ret == SECCOMP_PHASE1_SKIP) {
+                       regs->orig_ax = -1;
+                       ret = 0;
+               } else if (ret != SECCOMP_PHASE1_OK) {
+                       return ret;  /* Go directly to phase 2 */
+               }
+
+               work &= ~_TIF_SECCOMP;
+       }
+#endif
+
+       /* Do our best to finish without phase 2. */
+       if (work == 0)
+               return ret;  /* seccomp and/or nohz only (ret == 0 here) */
+
+#ifdef CONFIG_AUDITSYSCALL
+       if (work == _TIF_SYSCALL_AUDIT) {
+               /*
+                * If there is no more work to be done except auditing,
+                * then audit in phase 1.  Phase 2 always audits, so, if
+                * we audit here, then we can't go on to phase 2.
+                */
+               do_audit_syscall_entry(regs, arch);
+               return 0;
+       }
+#endif
+
+       return 1;  /* Something is enabled that we can't handle in phase 1 */
+}
+
+/* Returns the syscall nr to run (which should match regs->orig_ax). */
+long syscall_trace_enter_phase2(struct pt_regs *regs, u32 arch,
+                               unsigned long phase1_result)
+{
+       long ret = 0;
+       u32 work = ACCESS_ONCE(current_thread_info()->flags) &
+               _TIF_WORK_SYSCALL_ENTRY;
+
+       BUG_ON(regs != task_pt_regs(current));
+
+       /*
+        * If we stepped into a sysenter/syscall insn, it trapped in
+        * kernel mode; do_debug() cleared TF and set TIF_SINGLESTEP.
+        * If user-mode had set TF itself, then it's still clear from
+        * do_debug() and we need to set it again to restore the user
+        * state.  If we entered on the slow path, TF was already set.
+        */
+       if (work & _TIF_SINGLESTEP)
+               regs->flags |= X86_EFLAGS_TF;
+
+#ifdef CONFIG_SECCOMP
+       /*
+        * Call seccomp_phase2 before running the other hooks so that
+        * they can see any changes made by a seccomp tracer.
+        */
+       if (phase1_result > 1 && seccomp_phase2(phase1_result)) {
+               /* seccomp failures shouldn't expose any additional code. */
+               return -1;
+       }
+#endif
+
+       if (unlikely(work & _TIF_SYSCALL_EMU))
+               ret = -1L;
+
+       if ((ret || test_thread_flag(TIF_SYSCALL_TRACE)) &&
+           tracehook_report_syscall_entry(regs))
+               ret = -1L;
+
+       if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
+               trace_sys_enter(regs, regs->orig_ax);
+
+       do_audit_syscall_entry(regs, arch);
+
+       return ret ?: regs->orig_ax;
+}
+
+long syscall_trace_enter(struct pt_regs *regs)
+{
+       u32 arch = is_ia32_task() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
+       unsigned long phase1_result = syscall_trace_enter_phase1(regs, arch);
+
+       if (phase1_result == 0)
+               return regs->orig_ax;
+       else
+               return syscall_trace_enter_phase2(regs, arch, phase1_result);
+}
+
+void syscall_trace_leave(struct pt_regs *regs)
+{
+       bool step;
+
+       /*
+        * We may come here right after calling schedule_user()
+        * or do_notify_resume(), in which case we can be in RCU
+        * user mode.
+        */
+       user_exit();
+
+       audit_syscall_exit(regs);
+
+       if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
+               trace_sys_exit(regs, regs->ax);
+
+       /*
+        * If TIF_SYSCALL_EMU is set, we only get here because of
+        * TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
+        * We already reported this syscall instruction in
+        * syscall_trace_enter().
+        */
+       step = unlikely(test_thread_flag(TIF_SINGLESTEP)) &&
+                       !test_thread_flag(TIF_SYSCALL_EMU);
+       if (step || test_thread_flag(TIF_SYSCALL_TRACE))
+               tracehook_report_syscall_exit(regs, step);
+
+       user_enter();
+}
+
+/*
+ * notification of userspace execution resumption
+ * - triggered by the TIF_WORK_MASK flags
+ */
+__visible void
+do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
+{
+       user_exit();
+
+       if (thread_info_flags & _TIF_UPROBE)
+               uprobe_notify_resume(regs);
+
+       /* deal with pending signal delivery */
+       if (thread_info_flags & _TIF_SIGPENDING)
+               do_signal(regs);
+
+       if (thread_info_flags & _TIF_NOTIFY_RESUME) {
+               clear_thread_flag(TIF_NOTIFY_RESUME);
+               tracehook_notify_resume(regs);
+       }
+       if (thread_info_flags & _TIF_USER_RETURN_NOTIFY)
+               fire_user_return_notifiers();
+
+       user_enter();
+}

diff --cc arch/x86/include/asm/signal.h
Simple merge

diff --cc arch/x86/kernel/ptrace.c
Simple merge

diff --cc arch/x86/kernel/signal.c
Simple merge