[PATCH v2 04/14] x86: Move C entry and exit code to arch/x86/entry/common.c

From: Andy Lutomirski
Date: Thu Jun 18 2015 - 15:09:40 EST

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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@xxxxxxxxxx>
---
arch/x86/entry/Makefile | 1 +
arch/x86/entry/common.c | 253 ++++++++++++++++++++++++++++++++++++++++++
arch/x86/include/asm/signal.h | 1 +
arch/x86/kernel/ptrace.c | 202 +--------------------------------
arch/x86/kernel/signal.c | 28 +----
5 files changed, 257 insertions(+), 228 deletions(-)
create mode 100644 arch/x86/entry/common.c

diff --git a/arch/x86/entry/Makefile b/arch/x86/entry/Makefile
index 7a144971db79..bd55dedd7614 100644
--- 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
index 000000000000..348465473e55
--- /dev/null
+++ b/arch/x86/entry/common.c
@@ -0,0 +1,253 @@
+/*
+ * entry.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 --git a/arch/x86/include/asm/signal.h b/arch/x86/include/asm/signal.h
index 31eab867e6d3..b42408bcf6b5 100644
--- a/arch/x86/include/asm/signal.h
+++ b/arch/x86/include/asm/signal.h
@@ -30,6 +30,7 @@ typedef sigset_t compat_sigset_t;
#endif /* __ASSEMBLY__ */
#include <uapi/asm/signal.h>
#ifndef __ASSEMBLY__
+extern void do_signal(struct pt_regs *regs);
extern void do_notify_resume(struct pt_regs *, void *, __u32);

#define __ARCH_HAS_SA_RESTORER
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index a7bc79480719..d9417430a4b0 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -37,12 +37,10 @@
#include <asm/proto.h>
#include <asm/hw_breakpoint.h>
#include <asm/traps.h>
+#include <asm/syscall.h>

#include "tls.h"

-#define CREATE_TRACE_POINTS
-#include <trace/events/syscalls.h>
-
enum x86_regset {
REGSET_GENERAL,
REGSET_FP,
@@ -1434,201 +1432,3 @@ void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
/* Send us the fake SIGTRAP */
force_sig_info(SIGTRAP, &info, tsk);
}
-
-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();
-}
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 1ea14fd53933..c0ad42a640b9 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -683,7 +683,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
* want to handle. Thus you cannot kill init even with a SIGKILL even by
* mistake.
*/
-static void do_signal(struct pt_regs *regs)
+void do_signal(struct pt_regs *regs)
{
struct ksignal ksig;

@@ -718,32 +718,6 @@ static void do_signal(struct pt_regs *regs)
restore_saved_sigmask();
}

-/*
- * 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();
-}
-
void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
{
struct task_struct *me = current;
--
2.4.3

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Next message: Andy Lutomirski: "[PATCH v2 13/14] x86/entry: Remove exception_enter from trap handlers"
Previous message: Andy Lutomirski: "[PATCH v2 05/14] x86/traps: Assert that we're in CONTEXT_KERNEL in exception entries"
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