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Commit 1f484aa6 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
Browse files

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: default avatarAndy 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: default avatarIngo Molnar <mingo@kernel.org>
parent e727c7d7

arch/x86/entry/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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/

arch/x86/entry/common.c

0 → 100644
+253 −0
Original line number Diff line number Diff line 
/*

 * 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();

}

arch/x86/include/asm/signal.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/ptrace.c

+1 −201
Original line number Diff line number Diff line
@@ -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,
@@ -1444,201 +1442,3 @@ 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();

}

arch/x86/kernel/signal.c

+1 −27
Original line number Diff line number Diff line
@@ -700,7 +700,7 @@ 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;
@@ -735,32 +735,6 @@ 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;