[linux-block.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/sched/task_stack.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/nospec.h>
#include <linux/uprobes.h>
#include <linux/livepatch.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>

#include <asm/desc.h>
#include <asm/traps.h>
#include <asm/vdso.h>
#include <asm/cpufeature.h>
#include <asm/fpu/api.h>
#include <asm/nospec-branch.h>

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

#ifdef CONFIG_CONTEXT_TRACKING
/* Called on entry from user mode with IRQs off. */
__visible inline 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);
	}
}

/*
 * Returns the syscall nr to run (which should match regs->orig_ax) or -1
 * to skip the syscall.
 */
static long syscall_trace_enter(struct pt_regs *regs)
{
	u32 arch = in_ia32_syscall() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;

	struct thread_info *ti = current_thread_info();
	unsigned long ret = 0;
	bool emulated = false;
	u32 work;

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

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

	if (unlikely(work & _TIF_SYSCALL_EMU))
		emulated = true;

	if ((emulated || (work & _TIF_SYSCALL_TRACE)) &&
	    tracehook_report_syscall_entry(regs))
		return -1L;

	if (emulated)
		return -1L;

#ifdef CONFIG_SECCOMP
	/*
	 * Do seccomp after ptrace, to catch any tracer changes.
	 */
	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;
		}

		ret = __secure_computing(&sd);
		if (ret == -1)
			return ret;
	}
#endif

	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;
}

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

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 EXIT_TO_USERMODE_LOOP_FLAGS set.  Several of these flags
	 * can be set at any time on preemptible 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);

		if (cached_flags & _TIF_PATCH_PENDING)
			klp_update_patch_state(current);

		/* 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);
			rseq_handle_notify_resume(NULL, regs);
		}

		if (cached_flags & _TIF_USER_RETURN_NOTIFY)
			fire_user_return_notifiers();

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

		cached_flags = READ_ONCE(current_thread_info()->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 = current_thread_info();
	u32 cached_flags;

	addr_limit_user_check();

	lockdep_assert_irqs_disabled();
	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);

	/* Reload ti->flags; we may have rescheduled above. */
	cached_flags = READ_ONCE(ti->flags);

	fpregs_assert_state_consistent();
	if (unlikely(cached_flags & _TIF_NEED_FPU_LOAD))
		switch_fpu_return();

#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.
	 *
	 * We also need to clear TS_REGS_POKED_I386: the 32-bit tracer
	 * special case only applies after poking regs and before the
	 * very next return to user mode.
	 */
	ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
#endif

	user_enter_irqoff();

	mds_user_clear_cpu_buffers();
}

#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 = current_thread_info();
	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();

	rseq_syscall(regs);

	/*
	 * 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(unsigned long nr, struct pt_regs *regs)
{
	struct thread_info *ti;

	enter_from_user_mode();
	local_irq_enable();
	ti = current_thread_info();
	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.
	 */
	nr &= __SYSCALL_MASK;
	if (likely(nr < NR_syscalls)) {
		nr = array_index_nospec(nr, NR_syscalls);
		regs->ax = sys_call_table[nr](regs);
	}

	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 = current_thread_info();
	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)) {
		nr = array_index_nospec(nr, IA32_NR_syscalls);
#ifdef CONFIG_IA32_EMULATION
		regs->ax = ia32_sys_call_table[nr](regs);
#else
		/*
		 * 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);
#endif /* CONFIG_IA32_EMULATION */
	}

	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>
68db0cf1	12	#include <linux/sched/task_stack.h>
1f484aa6 AL	13	#include <linux/mm.h>
	14	#include <linux/smp.h>
	15	#include <linux/errno.h>
	16	#include <linux/ptrace.h>
	17	#include <linux/tracehook.h>
	18	#include <linux/audit.h>
	19	#include <linux/seccomp.h>
	20	#include <linux/signal.h>
	21	#include <linux/export.h>
	22	#include <linux/context_tracking.h>
	23	#include <linux/user-return-notifier.h>
2fbd7af5	24	#include <linux/nospec.h>
1f484aa6	25	#include <linux/uprobes.h>
afb94c9e	26	#include <linux/livepatch.h>
5ea0727b	27	#include <linux/syscalls.h>
5f409e20	28	#include <linux/uaccess.h>
1f484aa6 AL	29
	30	#include <asm/desc.h>
	31	#include <asm/traps.h>
710246df	32	#include <asm/vdso.h>
cd4d09ec	33	#include <asm/cpufeature.h>
5f409e20	34	#include <asm/fpu/api.h>
04dcbdb8	35	#include <asm/nospec-branch.h>
1f484aa6 AL	36
	37	#define CREATE_TRACE_POINTS
	38	#include <trace/events/syscalls.h>
	39
feed36cd AL	40	#ifdef CONFIG_CONTEXT_TRACKING
feed36cd AL	41	/* Called on entry from user mode with IRQs off. */
be8a18e2	42	__visible inline void enter_from_user_mode(void)
feed36cd AL	43	{
feed36cd AL	44	CT_WARN_ON(ct_state() != CONTEXT_USER);
2e9d1e15	45	user_exit_irqoff();
feed36cd	46	}
9999c8c0 AL	47	#else
9999c8c0 AL	48	static inline void enter_from_user_mode(void) {}
feed36cd AL	49	#endif
feed36cd AL	50
1f484aa6 AL	51	static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
	52	{
	53	#ifdef CONFIG_X86_64
	54	if (arch == AUDIT_ARCH_X86_64) {
	55	audit_syscall_entry(regs->orig_ax, regs->di,
	56	regs->si, regs->dx, regs->r10);
	57	} else
	58	#endif
	59	{
	60	audit_syscall_entry(regs->orig_ax, regs->bx,
	61	regs->cx, regs->dx, regs->si);
	62	}
	63	}
	64
	65	/*
c87a8517 AL	66	* Returns the syscall nr to run (which should match regs->orig_ax) or -1
c87a8517 AL	67	* to skip the syscall.
1f484aa6	68	*/
c87a8517	69	static long syscall_trace_enter(struct pt_regs *regs)
1f484aa6	70	{
c87a8517 AL	71	u32 arch = in_ia32_syscall() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
c87a8517 AL	72
97245d00	73	struct thread_info *ti = current_thread_info();
1f484aa6	74	unsigned long ret = 0;
93e35efb	75	bool emulated = false;
1f484aa6 AL	76	u32 work;
1f484aa6 AL	77
4aabd140 AL	78	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
4aabd140 AL	79	BUG_ON(regs != task_pt_regs(current));
1f484aa6	80
6aa7de05	81	work = READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;
1f484aa6	82
93e35efb KC	83	if (unlikely(work & _TIF_SYSCALL_EMU))
	84	emulated = true;
	85
	86	if ((emulated \|\| (work & _TIF_SYSCALL_TRACE)) &&
	87	tracehook_report_syscall_entry(regs))
	88	return -1L;
	89
	90	if (emulated)
	91	return -1L;
	92
1f484aa6 AL	93	#ifdef CONFIG_SECCOMP
1f484aa6 AL	94	/*
93e35efb	95	* Do seccomp after ptrace, to catch any tracer changes.
1f484aa6 AL	96	*/
	97	if (work & _TIF_SECCOMP) {
	98	struct seccomp_data sd;
	99
	100	sd.arch = arch;
	101	sd.nr = regs->orig_ax;
	102	sd.instruction_pointer = regs->ip;
	103	#ifdef CONFIG_X86_64
	104	if (arch == AUDIT_ARCH_X86_64) {
	105	sd.args[0] = regs->di;
	106	sd.args[1] = regs->si;
	107	sd.args[2] = regs->dx;
	108	sd.args[3] = regs->r10;
	109	sd.args[4] = regs->r8;
	110	sd.args[5] = regs->r9;
	111	} else
	112	#endif
	113	{
	114	sd.args[0] = regs->bx;
	115	sd.args[1] = regs->cx;
	116	sd.args[2] = regs->dx;
	117	sd.args[3] = regs->si;
	118	sd.args[4] = regs->di;
	119	sd.args[5] = regs->bp;
	120	}
	121
c87a8517 AL	122	ret = __secure_computing(&sd);
	123	if (ret == -1)
	124	return ret;
1f484aa6 AL	125	}
	126	#endif
	127
1f484aa6 AL	128	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
	129	trace_sys_enter(regs, regs->orig_ax);
	130
	131	do_audit_syscall_entry(regs, arch);
	132
	133	return ret ?: regs->orig_ax;
	134	}
	135
39b48e57 AL	136	#define EXIT_TO_USERMODE_LOOP_FLAGS \
39b48e57 AL	137	(_TIF_SIGPENDING \| _TIF_NOTIFY_RESUME \| _TIF_UPROBE \| \
afb94c9e	138	_TIF_NEED_RESCHED \| _TIF_USER_RETURN_NOTIFY \| _TIF_PATCH_PENDING)
72f92478	139
39b48e57 AL	140	static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
39b48e57 AL	141	{
c5c46f59 AL	142	/*
c5c46f59 AL	143	* In order to return to user mode, we need to have IRQs off with
afb94c9e	144	* none of EXIT_TO_USERMODE_LOOP_FLAGS set. Several of these flags
a97673a1	145	* can be set at any time on preemptible kernels if we have IRQs on,
c5c46f59 AL	146	* so we need to loop. Disabling preemption wouldn't help: doing the
	147	* work to clear some of the flags can sleep.
	148	*/
	149	while (true) {
c5c46f59 AL	150	/* We have work to do. */
	151	local_irq_enable();
	152
	153	if (cached_flags & _TIF_NEED_RESCHED)
	154	schedule();
	155
	156	if (cached_flags & _TIF_UPROBE)
	157	uprobe_notify_resume(regs);
	158
43347d56 MB	159	if (cached_flags & _TIF_PATCH_PENDING)
	160	klp_update_patch_state(current);
	161
c5c46f59 AL	162	/* deal with pending signal delivery */
	163	if (cached_flags & _TIF_SIGPENDING)
	164	do_signal(regs);
	165
	166	if (cached_flags & _TIF_NOTIFY_RESUME) {
	167	clear_thread_flag(TIF_NOTIFY_RESUME);
	168	tracehook_notify_resume(regs);
784e0300	169	rseq_handle_notify_resume(NULL, regs);
c5c46f59 AL	170	}
	171
	172	if (cached_flags & _TIF_USER_RETURN_NOTIFY)
	173	fire_user_return_notifiers();
	174
	175	/* Disable IRQs and retry */
	176	local_irq_disable();
39b48e57	177
97245d00	178	cached_flags = READ_ONCE(current_thread_info()->flags);
39b48e57 AL	179
	180	if (!(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
	181	break;
c5c46f59	182	}
39b48e57 AL	183	}
	184
	185	/* Called with IRQs disabled. */
	186	__visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
	187	{
97245d00	188	struct thread_info *ti = current_thread_info();
39b48e57 AL	189	u32 cached_flags;
39b48e57 AL	190
5ea0727b TG	191	addr_limit_user_check();
5ea0727b TG	192
7a10e2a9	193	lockdep_assert_irqs_disabled();
39b48e57 AL	194	lockdep_sys_exit();
39b48e57 AL	195
4e79e182	196	cached_flags = READ_ONCE(ti->flags);
39b48e57 AL	197
	198	if (unlikely(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
	199	exit_to_usermode_loop(regs, cached_flags);
c5c46f59	200
5f409e20 RR	201	/* Reload ti->flags; we may have rescheduled above. */
	202	cached_flags = READ_ONCE(ti->flags);
	203
	204	fpregs_assert_state_consistent();
	205	if (unlikely(cached_flags & _TIF_NEED_FPU_LOAD))
	206	switch_fpu_return();
	207
4e79e182 AL	208	#ifdef CONFIG_COMPAT
	209	/*
	210	* Compat syscalls set TS_COMPAT. Make sure we clear it before
	211	* returning to user mode. We need to clear it after signal
	212	* handling, because syscall restart has a fixup for compat
	213	* syscalls. The fixup is exercised by the ptrace_syscall_32
	214	* selftest.
609c19a3 AL	215	*
	216	* We also need to clear TS_REGS_POKED_I386: the 32-bit tracer
	217	* special case only applies after poking regs and before the
	218	* very next return to user mode.
4e79e182	219	*/
37a8f7c3	220	ti->status &= ~(TS_COMPAT\|TS_I386_REGS_POKED);
4e79e182 AL	221	#endif
4e79e182 AL	222
2e9d1e15	223	user_enter_irqoff();
04dcbdb8 TG	224
04dcbdb8 TG	225	mds_user_clear_cpu_buffers();
c5c46f59 AL	226	}
c5c46f59 AL	227
f5e6a975 AL	228	#define SYSCALL_EXIT_WORK_FLAGS \
	229	(_TIF_SYSCALL_TRACE \| _TIF_SYSCALL_AUDIT \| \
	230	_TIF_SINGLESTEP \| _TIF_SYSCALL_TRACEPOINT)
	231
	232	static void syscall_slow_exit_work(struct pt_regs *regs, u32 cached_flags)
	233	{
	234	bool step;
	235
	236	audit_syscall_exit(regs);
	237
	238	if (cached_flags & _TIF_SYSCALL_TRACEPOINT)
	239	trace_sys_exit(regs, regs->ax);
	240
	241	/*
	242	* If TIF_SYSCALL_EMU is set, we only get here because of
	243	* TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
	244	* We already reported this syscall instruction in
	245	* syscall_trace_enter().
	246	*/
	247	step = unlikely(
	248	(cached_flags & (_TIF_SINGLESTEP \| _TIF_SYSCALL_EMU))
	249	== _TIF_SINGLESTEP);
	250	if (step \|\| cached_flags & _TIF_SYSCALL_TRACE)
	251	tracehook_report_syscall_exit(regs, step);
	252	}
	253
c5c46f59 AL	254	/*
	255	* Called with IRQs on and fully valid regs. Returns with IRQs off in a
	256	* state such that we can immediately switch to user mode.
	257	*/
f5e6a975	258	__visible inline void syscall_return_slowpath(struct pt_regs *regs)
c5c46f59	259	{
97245d00	260	struct thread_info *ti = current_thread_info();
c5c46f59	261	u32 cached_flags = READ_ONCE(ti->flags);
c5c46f59 AL	262
	263	CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
	264
460d1245 AL	265	if (IS_ENABLED(CONFIG_PROVE_LOCKING) &&
460d1245 AL	266	WARN(irqs_disabled(), "syscall %ld left IRQs disabled", regs->orig_ax))
c5c46f59 AL	267	local_irq_enable();
c5c46f59 AL	268
d6761b8f MD	269	rseq_syscall(regs);
d6761b8f MD	270
c5c46f59 AL	271	/*
	272	* First do one-time work. If these work items are enabled, we
	273	* want to run them exactly once per syscall exit with IRQs on.
	274	*/
f5e6a975 AL	275	if (unlikely(cached_flags & SYSCALL_EXIT_WORK_FLAGS))
f5e6a975 AL	276	syscall_slow_exit_work(regs, cached_flags);
c5c46f59	277
c5c46f59 AL	278	local_irq_disable();
	279	prepare_exit_to_usermode(regs);
	280	}
bd2d3a3b	281
1e423bff	282	#ifdef CONFIG_X86_64
dfe64506	283	__visible void do_syscall_64(unsigned long nr, struct pt_regs *regs)
1e423bff	284	{
dfe64506	285	struct thread_info *ti;
1e423bff	286
9999c8c0	287	enter_from_user_mode();
1e423bff	288	local_irq_enable();
dfe64506	289	ti = current_thread_info();
1e423bff AL	290	if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY)
	291	nr = syscall_trace_enter(regs);
	292
	293	/*
	294	* NB: Native and x32 syscalls are dispatched from the same
	295	* table. The only functional difference is the x32 bit in
	296	* regs->orig_ax, which changes the behavior of some syscalls.
	297	*/
dfe64506 LT	298	nr &= __SYSCALL_MASK;
	299	if (likely(nr < NR_syscalls)) {
	300	nr = array_index_nospec(nr, NR_syscalls);
fa697140	301	regs->ax = sys_call_table[nr](regs);
1e423bff AL	302	}
	303
	304	syscall_return_slowpath(regs);
	305	}
	306	#endif
	307
bd2d3a3b AL	308	#if defined(CONFIG_X86_32) \|\| defined(CONFIG_IA32_EMULATION)
bd2d3a3b AL	309	/*
9999c8c0 AL	310	* Does a 32-bit syscall. Called with IRQs on in CONTEXT_KERNEL. Does
	311	* all entry and exit work and returns with IRQs off. This function is
	312	* extremely hot in workloads that use it, and it's usually called from
33c52129	313	* do_fast_syscall_32, so forcibly inline it to improve performance.
bd2d3a3b	314	*/
a798f091	315	static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
bd2d3a3b	316	{
97245d00	317	struct thread_info *ti = current_thread_info();
bd2d3a3b AL	318	unsigned int nr = (unsigned int)regs->orig_ax;
	319
	320	#ifdef CONFIG_IA32_EMULATION
37a8f7c3	321	ti->status \|= TS_COMPAT;
bd2d3a3b AL	322	#endif
bd2d3a3b AL	323
bd2d3a3b AL	324	if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) {
	325	/*
	326	* Subtlety here: if ptrace pokes something larger than
	327	* 2^32-1 into orig_ax, this truncates it. This may or
	328	* may not be necessary, but it matches the old asm
	329	* behavior.
	330	*/
	331	nr = syscall_trace_enter(regs);
	332	}
	333
33c52129	334	if (likely(nr < IA32_NR_syscalls)) {
2fbd7af5	335	nr = array_index_nospec(nr, IA32_NR_syscalls);
f8781c4a	336	#ifdef CONFIG_IA32_EMULATION
ebeb8c82 DB	337	regs->ax = ia32_sys_call_table[nr](regs);
ebeb8c82 DB	338	#else
bd2d3a3b AL	339	/*
	340	* It's possible that a 32-bit syscall implementation
	341	* takes a 64-bit parameter but nonetheless assumes that
	342	* the high bits are zero. Make sure we zero-extend all
	343	* of the args.
	344	*/
	345	regs->ax = ia32_sys_call_table[nr](
	346	(unsigned int)regs->bx, (unsigned int)regs->cx,
	347	(unsigned int)regs->dx, (unsigned int)regs->si,
	348	(unsigned int)regs->di, (unsigned int)regs->bp);
f8781c4a	349	#endif /* CONFIG_IA32_EMULATION */
bd2d3a3b AL	350	}
	351
	352	syscall_return_slowpath(regs);
	353	}
710246df	354
a798f091 AL	355	/* Handles int $0x80 */
a798f091 AL	356	__visible void do_int80_syscall_32(struct pt_regs *regs)
8b13c255	357	{
9999c8c0	358	enter_from_user_mode();
8b13c255 AL	359	local_irq_enable();
	360	do_syscall_32_irqs_on(regs);
	361	}
	362
5f310f73	363	/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
7841b408	364	__visible long do_fast_syscall_32(struct pt_regs *regs)
710246df AL	365	{
	366	/*
	367	* Called using the internal vDSO SYSENTER/SYSCALL32 calling
	368	* convention. Adjust regs so it looks like we entered using int80.
	369	*/
	370
	371	unsigned long landing_pad = (unsigned long)current->mm->context.vdso +
	372	vdso_image_32.sym_int80_landing_pad;
	373
	374	/*
	375	* SYSENTER loses EIP, and even SYSCALL32 needs us to skip forward
	376	* so that 'regs->ip -= 2' lands back on an int $0x80 instruction.
	377	* Fix it up.
	378	*/
	379	regs->ip = landing_pad;
	380
9999c8c0 AL	381	enter_from_user_mode();
9999c8c0 AL	382
710246df	383	local_irq_enable();
9999c8c0 AL	384
9999c8c0 AL	385	/* Fetch EBP from where the vDSO stashed it. */
c68ca678 AL	386	if (
	387	#ifdef CONFIG_X86_64
	388	/*
	389	* Micro-optimization: the pointer we're following is explicitly
	390	* 32 bits, so it can't be out of range.
	391	*/
30bfa7b3	392	__get_user((u32 )&regs->bp,
c68ca678 AL	393	(u32 __user __force *)(unsigned long)(u32)regs->sp)
c68ca678 AL	394	#else
30bfa7b3	395	get_user((u32 )&regs->bp,
c68ca678 AL	396	(u32 __user __force *)(unsigned long)(u32)regs->sp)
	397	#endif
	398	) {
	399
710246df AL	400	/* User code screwed up. */
	401	local_irq_disable();
	402	regs->ax = -EFAULT;
710246df	403	prepare_exit_to_usermode(regs);
7841b408	404	return 0; /* Keep it simple: use IRET. */
710246df	405	}
710246df AL	406
710246df AL	407	/* Now this is just like a normal syscall. */
8b13c255	408	do_syscall_32_irqs_on(regs);
7841b408 AL	409
	410	#ifdef CONFIG_X86_64
	411	/*
	412	* Opportunistic SYSRETL: if possible, try to return using SYSRETL.
	413	* SYSRETL is available on all 64-bit CPUs, so we don't need to
	414	* bother with SYSEXIT.
	415	*
	416	* Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
	417	* because the ECX fixup above will ensure that this is essentially
	418	* never the case.
	419	*/
	420	return regs->cs == __USER32_CS && regs->ss == __USER_DS &&
	421	regs->ip == landing_pad &&
	422	(regs->flags & (X86_EFLAGS_RF \| X86_EFLAGS_TF)) == 0;
	423	#else
5f310f73 AL	424	/*
	425	* Opportunistic SYSEXIT: if possible, try to return using SYSEXIT.
	426	*
	427	* Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
	428	* because the ECX fixup above will ensure that this is essentially
	429	* never the case.
	430	*
	431	* We don't allow syscalls at all from VM86 mode, but we still
	432	* need to check VM, because we might be returning from sys_vm86.
	433	*/
	434	return static_cpu_has(X86_FEATURE_SEP) &&
	435	regs->cs == __USER_CS && regs->ss == __USER_DS &&
	436	regs->ip == landing_pad &&
	437	(regs->flags & (X86_EFLAGS_RF \| X86_EFLAGS_TF \| X86_EFLAGS_VM)) == 0;
7841b408	438	#endif
710246df	439	}
bd2d3a3b	440	#endif