[deliverable/linux.git] / arch / x86 / entry / common.c

/*
 * 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>
#include <asm/vdso.h>
#include <asm/uaccess.h>
#include <asm/cpufeature.h>

#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>

static struct thread_info *pt_regs_to_thread_info(struct pt_regs *regs)
{
	unsigned long top_of_stack =
		(unsigned long)(regs + 1) + TOP_OF_KERNEL_STACK_PADDING;
	return (struct thread_info *)(top_of_stack - THREAD_SIZE);
}

#ifdef CONFIG_CONTEXT_TRACKING
/* Called on entry from user mode with IRQs off. */
__visible void enter_from_user_mode(void)
{
	CT_WARN_ON(ct_state() != CONTEXT_USER);
	user_exit_irqoff();
}
#else
static inline void enter_from_user_mode(void) {}
#endif

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)
{
	struct thread_info *ti = pt_regs_to_thread_info(regs);
	unsigned long ret = 0;
	u32 work;

	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
		BUG_ON(regs != task_pt_regs(current));

	work = ACCESS_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;

#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)
{
	struct thread_info *ti = pt_regs_to_thread_info(regs);
	long ret = 0;
	u32 work = ACCESS_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;

	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
		BUG_ON(regs != task_pt_regs(current));

#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 = in_ia32_syscall() ? 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);
}

#define EXIT_TO_USERMODE_LOOP_FLAGS				\
	(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE |	\
	 _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY)

static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
{
	/*
	 * In order to return to user mode, we need to have IRQs off with
	 * none of _TIF_SIGPENDING, _TIF_NOTIFY_RESUME, _TIF_USER_RETURN_NOTIFY,
	 * _TIF_UPROBE, or _TIF_NEED_RESCHED set.  Several of these flags
	 * can be set at any time on preemptable kernels if we have IRQs on,
	 * so we need to loop.  Disabling preemption wouldn't help: doing the
	 * work to clear some of the flags can sleep.
	 */
	while (true) {
		/* We have work to do. */
		local_irq_enable();

		if (cached_flags & _TIF_NEED_RESCHED)
			schedule();

		if (cached_flags & _TIF_UPROBE)
			uprobe_notify_resume(regs);

		/* deal with pending signal delivery */
		if (cached_flags & _TIF_SIGPENDING)
			do_signal(regs);

		if (cached_flags & _TIF_NOTIFY_RESUME) {
			clear_thread_flag(TIF_NOTIFY_RESUME);
			tracehook_notify_resume(regs);
		}

		if (cached_flags & _TIF_USER_RETURN_NOTIFY)
			fire_user_return_notifiers();

		/* Disable IRQs and retry */
		local_irq_disable();

		cached_flags = READ_ONCE(pt_regs_to_thread_info(regs)->flags);

		if (!(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
			break;

	}
}

/* Called with IRQs disabled. */
__visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
{
	struct thread_info *ti = pt_regs_to_thread_info(regs);
	u32 cached_flags;

	if (IS_ENABLED(CONFIG_PROVE_LOCKING) && WARN_ON(!irqs_disabled()))
		local_irq_disable();

	lockdep_sys_exit();

	cached_flags = READ_ONCE(ti->flags);

	if (unlikely(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
		exit_to_usermode_loop(regs, cached_flags);

#ifdef CONFIG_COMPAT
	/*
	 * Compat syscalls set TS_COMPAT.  Make sure we clear it before
	 * returning to user mode.  We need to clear it *after* signal
	 * handling, because syscall restart has a fixup for compat
	 * syscalls.  The fixup is exercised by the ptrace_syscall_32
	 * selftest.
	 */
	ti->status &= ~TS_COMPAT;
#endif

	user_enter_irqoff();
}

#define SYSCALL_EXIT_WORK_FLAGS				\
	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT |	\
	 _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT)

static void syscall_slow_exit_work(struct pt_regs *regs, u32 cached_flags)
{
	bool step;

	audit_syscall_exit(regs);

	if (cached_flags & _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(
		(cached_flags & (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU))
		== _TIF_SINGLESTEP);
	if (step || cached_flags & _TIF_SYSCALL_TRACE)
		tracehook_report_syscall_exit(regs, step);
}

/*
 * Called with IRQs on and fully valid regs.  Returns with IRQs off in a
 * state such that we can immediately switch to user mode.
 */
__visible inline void syscall_return_slowpath(struct pt_regs *regs)
{
	struct thread_info *ti = pt_regs_to_thread_info(regs);
	u32 cached_flags = READ_ONCE(ti->flags);

	CT_WARN_ON(ct_state() != CONTEXT_KERNEL);

	if (IS_ENABLED(CONFIG_PROVE_LOCKING) &&
	    WARN(irqs_disabled(), "syscall %ld left IRQs disabled", regs->orig_ax))
		local_irq_enable();

	/*
	 * First do one-time work.  If these work items are enabled, we
	 * want to run them exactly once per syscall exit with IRQs on.
	 */
	if (unlikely(cached_flags & SYSCALL_EXIT_WORK_FLAGS))
		syscall_slow_exit_work(regs, cached_flags);

	local_irq_disable();
	prepare_exit_to_usermode(regs);
}

#ifdef CONFIG_X86_64
__visible void do_syscall_64(struct pt_regs *regs)
{
	struct thread_info *ti = pt_regs_to_thread_info(regs);
	unsigned long nr = regs->orig_ax;

	enter_from_user_mode();
	local_irq_enable();

	if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY)
		nr = syscall_trace_enter(regs);

	/*
	 * NB: Native and x32 syscalls are dispatched from the same
	 * table.  The only functional difference is the x32 bit in
	 * regs->orig_ax, which changes the behavior of some syscalls.
	 */
	if (likely((nr & __SYSCALL_MASK) < NR_syscalls)) {
		regs->ax = sys_call_table[nr & __SYSCALL_MASK](
			regs->di, regs->si, regs->dx,
			regs->r10, regs->r8, regs->r9);
	}

	syscall_return_slowpath(regs);
}
#endif

#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
/*
 * Does a 32-bit syscall.  Called with IRQs on in CONTEXT_KERNEL.  Does
 * all entry and exit work and returns with IRQs off.  This function is
 * extremely hot in workloads that use it, and it's usually called from
 * do_fast_syscall_32, so forcibly inline it to improve performance.
 */
static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
{
	struct thread_info *ti = pt_regs_to_thread_info(regs);
	unsigned int nr = (unsigned int)regs->orig_ax;

#ifdef CONFIG_IA32_EMULATION
	ti->status |= TS_COMPAT;
#endif

	if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) {
		/*
		 * Subtlety here: if ptrace pokes something larger than
		 * 2^32-1 into orig_ax, this truncates it.  This may or
		 * may not be necessary, but it matches the old asm
		 * behavior.
		 */
		nr = syscall_trace_enter(regs);
	}

	if (likely(nr < IA32_NR_syscalls)) {
		/*
		 * It's possible that a 32-bit syscall implementation
		 * takes a 64-bit parameter but nonetheless assumes that
		 * the high bits are zero.  Make sure we zero-extend all
		 * of the args.
		 */
		regs->ax = ia32_sys_call_table[nr](
			(unsigned int)regs->bx, (unsigned int)regs->cx,
			(unsigned int)regs->dx, (unsigned int)regs->si,
			(unsigned int)regs->di, (unsigned int)regs->bp);
	}

	syscall_return_slowpath(regs);
}

/* Handles int $0x80 */
__visible void do_int80_syscall_32(struct pt_regs *regs)
{
	enter_from_user_mode();
	local_irq_enable();
	do_syscall_32_irqs_on(regs);
}

/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
__visible long do_fast_syscall_32(struct pt_regs *regs)
{
	/*
	 * Called using the internal vDSO SYSENTER/SYSCALL32 calling
	 * convention.  Adjust regs so it looks like we entered using int80.
	 */

	unsigned long landing_pad = (unsigned long)current->mm->context.vdso +
		vdso_image_32.sym_int80_landing_pad;

	/*
	 * SYSENTER loses EIP, and even SYSCALL32 needs us to skip forward
	 * so that 'regs->ip -= 2' lands back on an int $0x80 instruction.
	 * Fix it up.
	 */
	regs->ip = landing_pad;

	enter_from_user_mode();

	local_irq_enable();

	/* Fetch EBP from where the vDSO stashed it. */
	if (
#ifdef CONFIG_X86_64
		/*
		 * Micro-optimization: the pointer we're following is explicitly
		 * 32 bits, so it can't be out of range.
		 */
		__get_user(*(u32 *)&regs->bp,
			    (u32 __user __force *)(unsigned long)(u32)regs->sp)
#else
		get_user(*(u32 *)&regs->bp,
			 (u32 __user __force *)(unsigned long)(u32)regs->sp)
#endif
		) {

		/* User code screwed up. */
		local_irq_disable();
		regs->ax = -EFAULT;
		prepare_exit_to_usermode(regs);
		return 0;	/* Keep it simple: use IRET. */
	}

	/* Now this is just like a normal syscall. */
	do_syscall_32_irqs_on(regs);

#ifdef CONFIG_X86_64
	/*
	 * Opportunistic SYSRETL: if possible, try to return using SYSRETL.
	 * SYSRETL is available on all 64-bit CPUs, so we don't need to
	 * bother with SYSEXIT.
	 *
	 * Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
	 * because the ECX fixup above will ensure that this is essentially
	 * never the case.
	 */
	return regs->cs == __USER32_CS && regs->ss == __USER_DS &&
		regs->ip == landing_pad &&
		(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF)) == 0;
#else
	/*
	 * Opportunistic SYSEXIT: if possible, try to return using SYSEXIT.
	 *
	 * Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
	 * because the ECX fixup above will ensure that this is essentially
	 * never the case.
	 *
	 * We don't allow syscalls at all from VM86 mode, but we still
	 * need to check VM, because we might be returning from sys_vm86.
	 */
	return static_cpu_has(X86_FEATURE_SEP) &&
		regs->cs == __USER_CS && regs->ss == __USER_DS &&
		regs->ip == landing_pad &&
		(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF | X86_EFLAGS_VM)) == 0;
#endif
}
#endif
Commit	Line	Data
1f484aa6 AL	1	/*
	2	* common.c - C code for kernel entry and exit
	3	* Copyright (c) 2015 Andrew Lutomirski
	4	* GPL v2
	5	*
	6	* Based on asm and ptrace code by many authors. The code here originated
	7	* in ptrace.c and signal.c.
	8	*/
	9
	10	#include <linux/kernel.h>
	11	#include <linux/sched.h>
	12	#include <linux/mm.h>
	13	#include <linux/smp.h>
	14	#include <linux/errno.h>
	15	#include <linux/ptrace.h>
	16	#include <linux/tracehook.h>
	17	#include <linux/audit.h>
	18	#include <linux/seccomp.h>
	19	#include <linux/signal.h>
	20	#include <linux/export.h>
	21	#include <linux/context_tracking.h>
	22	#include <linux/user-return-notifier.h>
	23	#include <linux/uprobes.h>
	24
	25	#include <asm/desc.h>
	26	#include <asm/traps.h>
710246df AL	27	#include <asm/vdso.h>
710246df AL	28	#include <asm/uaccess.h>
cd4d09ec	29	#include <asm/cpufeature.h>
1f484aa6 AL	30
	31	#define CREATE_TRACE_POINTS
	32	#include <trace/events/syscalls.h>
	33
dd636071 AL	34	static struct thread_info pt_regs_to_thread_info(struct pt_regs regs)
	35	{
	36	unsigned long top_of_stack =
	37	(unsigned long)(regs + 1) + TOP_OF_KERNEL_STACK_PADDING;
	38	return (struct thread_info *)(top_of_stack - THREAD_SIZE);
	39	}
	40
feed36cd AL	41	#ifdef CONFIG_CONTEXT_TRACKING
	42	/* Called on entry from user mode with IRQs off. */
	43	__visible void enter_from_user_mode(void)
	44	{
	45	CT_WARN_ON(ct_state() != CONTEXT_USER);
2e9d1e15	46	user_exit_irqoff();
feed36cd	47	}
9999c8c0 AL	48	#else
9999c8c0 AL	49	static inline void enter_from_user_mode(void) {}
feed36cd AL	50	#endif
feed36cd AL	51
1f484aa6 AL	52	static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
	53	{
	54	#ifdef CONFIG_X86_64
	55	if (arch == AUDIT_ARCH_X86_64) {
	56	audit_syscall_entry(regs->orig_ax, regs->di,
	57	regs->si, regs->dx, regs->r10);
	58	} else
	59	#endif
	60	{
	61	audit_syscall_entry(regs->orig_ax, regs->bx,
	62	regs->cx, regs->dx, regs->si);
	63	}
	64	}
	65
	66	/*
	67	* We can return 0 to resume the syscall or anything else to go to phase
	68	* 2. If we resume the syscall, we need to put something appropriate in
	69	* regs->orig_ax.
	70	*
	71	* NB: We don't have full pt_regs here, but regs->orig_ax and regs->ax
	72	* are fully functional.
	73	*
	74	* For phase 2's benefit, our return value is:
	75	* 0: resume the syscall
	76	* 1: go to phase 2; no seccomp phase 2 needed
	77	* anything else: go to phase 2; pass return value to seccomp
	78	*/
	79	unsigned long syscall_trace_enter_phase1(struct pt_regs *regs, u32 arch)
	80	{
dd636071	81	struct thread_info *ti = pt_regs_to_thread_info(regs);
1f484aa6 AL	82	unsigned long ret = 0;
	83	u32 work;
	84
4aabd140 AL	85	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
4aabd140 AL	86	BUG_ON(regs != task_pt_regs(current));
1f484aa6	87
dd636071	88	work = ACCESS_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;
1f484aa6	89
1f484aa6 AL	90	#ifdef CONFIG_SECCOMP
	91	/*
	92	* Do seccomp first -- it should minimize exposure of other
	93	* code, and keeping seccomp fast is probably more valuable
	94	* than the rest of this.
	95	*/
	96	if (work & _TIF_SECCOMP) {
	97	struct seccomp_data sd;
	98
	99	sd.arch = arch;
	100	sd.nr = regs->orig_ax;
	101	sd.instruction_pointer = regs->ip;
	102	#ifdef CONFIG_X86_64
	103	if (arch == AUDIT_ARCH_X86_64) {
	104	sd.args[0] = regs->di;
	105	sd.args[1] = regs->si;
	106	sd.args[2] = regs->dx;
	107	sd.args[3] = regs->r10;
	108	sd.args[4] = regs->r8;
	109	sd.args[5] = regs->r9;
	110	} else
	111	#endif
	112	{
	113	sd.args[0] = regs->bx;
	114	sd.args[1] = regs->cx;
	115	sd.args[2] = regs->dx;
	116	sd.args[3] = regs->si;
	117	sd.args[4] = regs->di;
	118	sd.args[5] = regs->bp;
	119	}
	120
	121	BUILD_BUG_ON(SECCOMP_PHASE1_OK != 0);
	122	BUILD_BUG_ON(SECCOMP_PHASE1_SKIP != 1);
	123
	124	ret = seccomp_phase1(&sd);
	125	if (ret == SECCOMP_PHASE1_SKIP) {
	126	regs->orig_ax = -1;
	127	ret = 0;
	128	} else if (ret != SECCOMP_PHASE1_OK) {
	129	return ret; /* Go directly to phase 2 */
	130	}
	131
	132	work &= ~_TIF_SECCOMP;
	133	}
	134	#endif
	135
	136	/* Do our best to finish without phase 2. */
	137	if (work == 0)
	138	return ret; /* seccomp and/or nohz only (ret == 0 here) */
	139
	140	#ifdef CONFIG_AUDITSYSCALL
	141	if (work == _TIF_SYSCALL_AUDIT) {
	142	/*
	143	* If there is no more work to be done except auditing,
	144	* then audit in phase 1. Phase 2 always audits, so, if
	145	* we audit here, then we can't go on to phase 2.
	146	*/
	147	do_audit_syscall_entry(regs, arch);
	148	return 0;
	149	}
	150	#endif
	151
	152	return 1; /* Something is enabled that we can't handle in phase 1 */
	153	}
154
155	/* Returns the syscall nr to run (which should match regs->orig_ax). */
156	long syscall_trace_enter_phase2(struct pt_regs *regs, u32 arch,
157	unsigned long phase1_result)
158	{
dd636071	159	struct thread_info *ti = pt_regs_to_thread_info(regs);
1f484aa6	160	long ret = 0;
dd636071	161	u32 work = ACCESS_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;
1f484aa6	162
4aabd140 AL	163	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
4aabd140 AL	164	BUG_ON(regs != task_pt_regs(current));
1f484aa6	165
1f484aa6 AL	166	#ifdef CONFIG_SECCOMP
	167	/*
	168	* Call seccomp_phase2 before running the other hooks so that
	169	* they can see any changes made by a seccomp tracer.
	170	*/
	171	if (phase1_result > 1 && seccomp_phase2(phase1_result)) {
	172	/* seccomp failures shouldn't expose any additional code. */
	173	return -1;
	174	}
	175	#endif
	176
	177	if (unlikely(work & _TIF_SYSCALL_EMU))
	178	ret = -1L;
	179
	180	if ((ret \|\| test_thread_flag(TIF_SYSCALL_TRACE)) &&
	181	tracehook_report_syscall_entry(regs))
	182	ret = -1L;
	183
	184	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
	185	trace_sys_enter(regs, regs->orig_ax);
	186
	187	do_audit_syscall_entry(regs, arch);
	188
	189	return ret ?: regs->orig_ax;
	190	}
	191
	192	long syscall_trace_enter(struct pt_regs *regs)
	193	{
abfb9498	194	u32 arch = in_ia32_syscall() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
1f484aa6 AL	195	unsigned long phase1_result = syscall_trace_enter_phase1(regs, arch);
	196
	197	if (phase1_result == 0)
	198	return regs->orig_ax;
	199	else
	200	return syscall_trace_enter_phase2(regs, arch, phase1_result);
	201	}
	202
39b48e57 AL	203	#define EXIT_TO_USERMODE_LOOP_FLAGS \
	204	(_TIF_SIGPENDING \| _TIF_NOTIFY_RESUME \| _TIF_UPROBE \| \
	205	_TIF_NEED_RESCHED \| _TIF_USER_RETURN_NOTIFY)
72f92478	206
39b48e57 AL	207	static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
39b48e57 AL	208	{
c5c46f59 AL	209	/*
	210	* In order to return to user mode, we need to have IRQs off with
	211	* none of _TIF_SIGPENDING, _TIF_NOTIFY_RESUME, _TIF_USER_RETURN_NOTIFY,
	212	* _TIF_UPROBE, or _TIF_NEED_RESCHED set. Several of these flags
	213	* can be set at any time on preemptable kernels if we have IRQs on,
	214	* so we need to loop. Disabling preemption wouldn't help: doing the
	215	* work to clear some of the flags can sleep.
	216	*/
	217	while (true) {
c5c46f59 AL	218	/* We have work to do. */
	219	local_irq_enable();
	220
	221	if (cached_flags & _TIF_NEED_RESCHED)
	222	schedule();
	223
	224	if (cached_flags & _TIF_UPROBE)
	225	uprobe_notify_resume(regs);
	226
	227	/* deal with pending signal delivery */
	228	if (cached_flags & _TIF_SIGPENDING)
	229	do_signal(regs);
	230
	231	if (cached_flags & _TIF_NOTIFY_RESUME) {
	232	clear_thread_flag(TIF_NOTIFY_RESUME);
	233	tracehook_notify_resume(regs);
	234	}
	235
	236	if (cached_flags & _TIF_USER_RETURN_NOTIFY)
	237	fire_user_return_notifiers();
	238
	239	/* Disable IRQs and retry */
	240	local_irq_disable();
39b48e57 AL	241
	242	cached_flags = READ_ONCE(pt_regs_to_thread_info(regs)->flags);
	243
	244	if (!(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
	245	break;
	246
c5c46f59	247	}
39b48e57 AL	248	}
	249
	250	/* Called with IRQs disabled. */
	251	__visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
	252	{
4e79e182	253	struct thread_info *ti = pt_regs_to_thread_info(regs);
39b48e57 AL	254	u32 cached_flags;
	255
	256	if (IS_ENABLED(CONFIG_PROVE_LOCKING) && WARN_ON(!irqs_disabled()))
	257	local_irq_disable();
	258
	259	lockdep_sys_exit();
	260
4e79e182	261	cached_flags = READ_ONCE(ti->flags);
39b48e57 AL	262
	263	if (unlikely(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
	264	exit_to_usermode_loop(regs, cached_flags);
c5c46f59	265
4e79e182 AL	266	#ifdef CONFIG_COMPAT
	267	/*
	268	* Compat syscalls set TS_COMPAT. Make sure we clear it before
	269	* returning to user mode. We need to clear it after signal
	270	* handling, because syscall restart has a fixup for compat
	271	* syscalls. The fixup is exercised by the ptrace_syscall_32
	272	* selftest.
	273	*/
	274	ti->status &= ~TS_COMPAT;
	275	#endif
	276
2e9d1e15	277	user_enter_irqoff();
c5c46f59 AL	278	}
c5c46f59 AL	279
f5e6a975 AL	280	#define SYSCALL_EXIT_WORK_FLAGS \
	281	(_TIF_SYSCALL_TRACE \| _TIF_SYSCALL_AUDIT \| \
	282	_TIF_SINGLESTEP \| _TIF_SYSCALL_TRACEPOINT)
	283
	284	static void syscall_slow_exit_work(struct pt_regs *regs, u32 cached_flags)
	285	{
	286	bool step;
	287
	288	audit_syscall_exit(regs);
	289
	290	if (cached_flags & _TIF_SYSCALL_TRACEPOINT)
	291	trace_sys_exit(regs, regs->ax);
	292
	293	/*
	294	* If TIF_SYSCALL_EMU is set, we only get here because of
	295	* TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
	296	* We already reported this syscall instruction in
	297	* syscall_trace_enter().
	298	*/
	299	step = unlikely(
	300	(cached_flags & (_TIF_SINGLESTEP \| _TIF_SYSCALL_EMU))
	301	== _TIF_SINGLESTEP);
	302	if (step \|\| cached_flags & _TIF_SYSCALL_TRACE)
	303	tracehook_report_syscall_exit(regs, step);
	304	}
	305
c5c46f59 AL	306	/*
	307	* Called with IRQs on and fully valid regs. Returns with IRQs off in a
	308	* state such that we can immediately switch to user mode.
	309	*/
f5e6a975	310	__visible inline void syscall_return_slowpath(struct pt_regs *regs)
c5c46f59 AL	311	{
	312	struct thread_info *ti = pt_regs_to_thread_info(regs);
	313	u32 cached_flags = READ_ONCE(ti->flags);
c5c46f59 AL	314
	315	CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
	316
460d1245 AL	317	if (IS_ENABLED(CONFIG_PROVE_LOCKING) &&
460d1245 AL	318	WARN(irqs_disabled(), "syscall %ld left IRQs disabled", regs->orig_ax))
c5c46f59 AL	319	local_irq_enable();
	320
	321	/*
	322	* First do one-time work. If these work items are enabled, we
	323	* want to run them exactly once per syscall exit with IRQs on.
	324	*/
f5e6a975 AL	325	if (unlikely(cached_flags & SYSCALL_EXIT_WORK_FLAGS))
f5e6a975 AL	326	syscall_slow_exit_work(regs, cached_flags);
c5c46f59	327
c5c46f59 AL	328	local_irq_disable();
	329	prepare_exit_to_usermode(regs);
	330	}
bd2d3a3b	331
1e423bff AL	332	#ifdef CONFIG_X86_64
	333	__visible void do_syscall_64(struct pt_regs *regs)
	334	{
	335	struct thread_info *ti = pt_regs_to_thread_info(regs);
	336	unsigned long nr = regs->orig_ax;
	337
9999c8c0	338	enter_from_user_mode();
1e423bff AL	339	local_irq_enable();
	340
	341	if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY)
	342	nr = syscall_trace_enter(regs);
	343
	344	/*
	345	* NB: Native and x32 syscalls are dispatched from the same
	346	* table. The only functional difference is the x32 bit in
	347	* regs->orig_ax, which changes the behavior of some syscalls.
	348	*/
	349	if (likely((nr & __SYSCALL_MASK) < NR_syscalls)) {
	350	regs->ax = sys_call_table[nr & __SYSCALL_MASK](
	351	regs->di, regs->si, regs->dx,
	352	regs->r10, regs->r8, regs->r9);
	353	}
	354
	355	syscall_return_slowpath(regs);
	356	}
	357	#endif
	358
bd2d3a3b AL	359	#if defined(CONFIG_X86_32) \|\| defined(CONFIG_IA32_EMULATION)
bd2d3a3b AL	360	/*
9999c8c0 AL	361	* Does a 32-bit syscall. Called with IRQs on in CONTEXT_KERNEL. Does
	362	* all entry and exit work and returns with IRQs off. This function is
	363	* extremely hot in workloads that use it, and it's usually called from
33c52129	364	* do_fast_syscall_32, so forcibly inline it to improve performance.
bd2d3a3b	365	*/
a798f091	366	static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
bd2d3a3b AL	367	{
	368	struct thread_info *ti = pt_regs_to_thread_info(regs);
	369	unsigned int nr = (unsigned int)regs->orig_ax;
	370
	371	#ifdef CONFIG_IA32_EMULATION
	372	ti->status \|= TS_COMPAT;
	373	#endif
	374
bd2d3a3b AL	375	if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) {
	376	/*
	377	* Subtlety here: if ptrace pokes something larger than
	378	* 2^32-1 into orig_ax, this truncates it. This may or
	379	* may not be necessary, but it matches the old asm
	380	* behavior.
	381	*/
	382	nr = syscall_trace_enter(regs);
	383	}
	384
33c52129	385	if (likely(nr < IA32_NR_syscalls)) {
bd2d3a3b AL	386	/*
	387	* It's possible that a 32-bit syscall implementation
	388	* takes a 64-bit parameter but nonetheless assumes that
	389	* the high bits are zero. Make sure we zero-extend all
	390	* of the args.
	391	*/
	392	regs->ax = ia32_sys_call_table[nr](
	393	(unsigned int)regs->bx, (unsigned int)regs->cx,
	394	(unsigned int)regs->dx, (unsigned int)regs->si,
	395	(unsigned int)regs->di, (unsigned int)regs->bp);
	396	}
	397
	398	syscall_return_slowpath(regs);
	399	}
710246df	400
a798f091 AL	401	/* Handles int $0x80 */
a798f091 AL	402	__visible void do_int80_syscall_32(struct pt_regs *regs)
8b13c255	403	{
9999c8c0	404	enter_from_user_mode();
8b13c255 AL	405	local_irq_enable();
	406	do_syscall_32_irqs_on(regs);
	407	}
	408
5f310f73	409	/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
7841b408	410	__visible long do_fast_syscall_32(struct pt_regs *regs)
710246df AL	411	{
	412	/*
	413	* Called using the internal vDSO SYSENTER/SYSCALL32 calling
	414	* convention. Adjust regs so it looks like we entered using int80.
	415	*/
	416
	417	unsigned long landing_pad = (unsigned long)current->mm->context.vdso +
	418	vdso_image_32.sym_int80_landing_pad;
	419
	420	/*
	421	* SYSENTER loses EIP, and even SYSCALL32 needs us to skip forward
	422	* so that 'regs->ip -= 2' lands back on an int $0x80 instruction.
	423	* Fix it up.
	424	*/
	425	regs->ip = landing_pad;
	426
9999c8c0 AL	427	enter_from_user_mode();
9999c8c0 AL	428
710246df	429	local_irq_enable();
9999c8c0 AL	430
9999c8c0 AL	431	/* Fetch EBP from where the vDSO stashed it. */
c68ca678 AL	432	if (
	433	#ifdef CONFIG_X86_64
	434	/*
	435	* Micro-optimization: the pointer we're following is explicitly
	436	* 32 bits, so it can't be out of range.
	437	*/
30bfa7b3	438	__get_user((u32 )&regs->bp,
c68ca678 AL	439	(u32 __user __force *)(unsigned long)(u32)regs->sp)
c68ca678 AL	440	#else
30bfa7b3	441	get_user((u32 )&regs->bp,
c68ca678 AL	442	(u32 __user __force *)(unsigned long)(u32)regs->sp)
	443	#endif
	444	) {
	445
710246df AL	446	/* User code screwed up. */
	447	local_irq_disable();
	448	regs->ax = -EFAULT;
710246df	449	prepare_exit_to_usermode(regs);
7841b408	450	return 0; /* Keep it simple: use IRET. */
710246df	451	}
710246df AL	452
710246df AL	453	/* Now this is just like a normal syscall. */
8b13c255	454	do_syscall_32_irqs_on(regs);
7841b408 AL	455
	456	#ifdef CONFIG_X86_64
	457	/*
	458	* Opportunistic SYSRETL: if possible, try to return using SYSRETL.
	459	* SYSRETL is available on all 64-bit CPUs, so we don't need to
	460	* bother with SYSEXIT.
	461	*
	462	* Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
	463	* because the ECX fixup above will ensure that this is essentially
	464	* never the case.
	465	*/
	466	return regs->cs == __USER32_CS && regs->ss == __USER_DS &&
	467	regs->ip == landing_pad &&
	468	(regs->flags & (X86_EFLAGS_RF \| X86_EFLAGS_TF)) == 0;
	469	#else
5f310f73 AL	470	/*
	471	* Opportunistic SYSEXIT: if possible, try to return using SYSEXIT.
	472	*
	473	* Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
	474	* because the ECX fixup above will ensure that this is essentially
	475	* never the case.
	476	*
	477	* We don't allow syscalls at all from VM86 mode, but we still
	478	* need to check VM, because we might be returning from sys_vm86.
	479	*/
	480	return static_cpu_has(X86_FEATURE_SEP) &&
	481	regs->cs == __USER_CS && regs->ss == __USER_DS &&
	482	regs->ip == landing_pad &&
	483	(regs->flags & (X86_EFLAGS_RF \| X86_EFLAGS_TF \| X86_EFLAGS_VM)) == 0;
7841b408	484	#endif
710246df	485	}
bd2d3a3b	486	#endif