1// SPDX-License-Identifier: GPL-2.0
  2
  3#include <linux/compiler.h>
  4#include <linux/context_tracking.h>
  5#include <linux/errno.h>
  6#include <linux/nospec.h>
  7#include <linux/ptrace.h>
  8#include <linux/syscalls.h>
  9
 10#include <asm/daifflags.h>
 11#include <asm/debug-monitors.h>
 12#include <asm/fpsimd.h>
 13#include <asm/syscall.h>
 14#include <asm/thread_info.h>
 15#include <asm/unistd.h>
 16
 17long compat_arm_syscall(struct pt_regs *regs, int scno);
 18long sys_ni_syscall(void);
 19
 20static long do_ni_syscall(struct pt_regs *regs, int scno)
 21{
 22#ifdef CONFIG_COMPAT
 23	long ret;
 24	if (is_compat_task()) {
 25		ret = compat_arm_syscall(regs, scno);
 26		if (ret != -ENOSYS)
 27			return ret;
 28	}
 29#endif
 30
 31	return sys_ni_syscall();
 32}
 33
 34static long __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn)
 35{
 36	return syscall_fn(regs);
 37}
 38
 39static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 40			   unsigned int sc_nr,
 41			   const syscall_fn_t syscall_table[])
 42{
 43	long ret;
 44
 45	if (scno < sc_nr) {
 46		syscall_fn_t syscall_fn;
 47		syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)];
 48		ret = __invoke_syscall(regs, syscall_fn);
 49	} else {
 50		ret = do_ni_syscall(regs, scno);
 51	}
 52
 53	regs->regs[0] = ret;
 54}
 55
 56static inline bool has_syscall_work(unsigned long flags)
 57{
 58	return unlikely(flags & _TIF_SYSCALL_WORK);
 59}
 60
 61int syscall_trace_enter(struct pt_regs *regs);
 62void syscall_trace_exit(struct pt_regs *regs);
 63
 64#ifdef CONFIG_ARM64_ERRATUM_1463225
 65DECLARE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa);
 66
 67static void cortex_a76_erratum_1463225_svc_handler(void)
 68{
 69	u32 reg, val;
 70
 71	if (!unlikely(test_thread_flag(TIF_SINGLESTEP)))
 72		return;
 73
 74	if (!unlikely(this_cpu_has_cap(ARM64_WORKAROUND_1463225)))
 75		return;
 76
 77	__this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 1);
 78	reg = read_sysreg(mdscr_el1);
 79	val = reg | DBG_MDSCR_SS | DBG_MDSCR_KDE;
 80	write_sysreg(val, mdscr_el1);
 81	asm volatile("msr daifclr, #8");
 82	isb();
 83
 84	/* We will have taken a single-step exception by this point */
 85
 86	write_sysreg(reg, mdscr_el1);
 87	__this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 0);
 88}
 89#else
 90static void cortex_a76_erratum_1463225_svc_handler(void) { }
 91#endif /* CONFIG_ARM64_ERRATUM_1463225 */
 92
 93static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 94			   const syscall_fn_t syscall_table[])
 95{
 96	unsigned long flags = current_thread_info()->flags;
 97
 98	regs->orig_x0 = regs->regs[0];
 99	regs->syscallno = scno;
100
101	cortex_a76_erratum_1463225_svc_handler();
102	local_daif_restore(DAIF_PROCCTX);
103	user_exit();
104
105	if (has_syscall_work(flags)) {
106		/* set default errno for user-issued syscall(-1) */
107		if (scno == NO_SYSCALL)
108			regs->regs[0] = -ENOSYS;
109		scno = syscall_trace_enter(regs);
110		if (scno == NO_SYSCALL)
111			goto trace_exit;
112	}
113
114	invoke_syscall(regs, scno, sc_nr, syscall_table);
115
116	/*
117	 * The tracing status may have changed under our feet, so we have to
118	 * check again. However, if we were tracing entry, then we always trace
119	 * exit regardless, as the old entry assembly did.
120	 */
121	if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
122		local_daif_mask();
123		flags = current_thread_info()->flags;
124		if (!has_syscall_work(flags)) {
125			/*
126			 * We're off to userspace, where interrupts are
127			 * always enabled after we restore the flags from
128			 * the SPSR.
129			 */
130			trace_hardirqs_on();
131			return;
132		}
133		local_daif_restore(DAIF_PROCCTX);
134	}
135
136trace_exit:
137	syscall_trace_exit(regs);
138}
139
140static inline void sve_user_discard(void)
141{
142	if (!system_supports_sve())
143		return;
144
145	clear_thread_flag(TIF_SVE);
146
147	/*
148	 * task_fpsimd_load() won't be called to update CPACR_EL1 in
149	 * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only
150	 * happens if a context switch or kernel_neon_begin() or context
151	 * modification (sigreturn, ptrace) intervenes.
152	 * So, ensure that CPACR_EL1 is already correct for the fast-path case.
153	 */
154	sve_user_disable();
155}
156
157asmlinkage void el0_svc_handler(struct pt_regs *regs)
158{
159	sve_user_discard();
160	el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table);
161}
162
163#ifdef CONFIG_COMPAT
164asmlinkage void el0_svc_compat_handler(struct pt_regs *regs)
165{
166	el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls,
167		       compat_sys_call_table);
168}
169#endif