1 // SPDX-License-Identifier: GPL-2.0
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>
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>
17 long compat_arm_syscall(struct pt_regs *regs, int scno);
18 long sys_ni_syscall(void);
20 static long do_ni_syscall(struct pt_regs *regs, int scno)
24 if (is_compat_task()) {
25 ret = compat_arm_syscall(regs, scno);
31 return sys_ni_syscall();
34 static long __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn)
36 return syscall_fn(regs);
39 static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
41 const syscall_fn_t syscall_table[])
46 syscall_fn_t syscall_fn;
47 syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)];
48 ret = __invoke_syscall(regs, syscall_fn);
50 ret = do_ni_syscall(regs, scno);
56 static inline bool has_syscall_work(unsigned long flags)
58 return unlikely(flags & _TIF_SYSCALL_WORK);
61 int syscall_trace_enter(struct pt_regs *regs);
62 void syscall_trace_exit(struct pt_regs *regs);
64 #ifdef CONFIG_ARM64_ERRATUM_1463225
65 DECLARE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa);
67 static void cortex_a76_erratum_1463225_svc_handler(void)
71 if (!unlikely(test_thread_flag(TIF_SINGLESTEP)))
74 if (!unlikely(this_cpu_has_cap(ARM64_WORKAROUND_1463225)))
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");
84 /* We will have taken a single-step exception by this point */
86 write_sysreg(reg, mdscr_el1);
87 __this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 0);
90 static void cortex_a76_erratum_1463225_svc_handler(void) { }
91 #endif /* CONFIG_ARM64_ERRATUM_1463225 */
93 static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
94 const syscall_fn_t syscall_table[])
96 unsigned long flags = current_thread_info()->flags;
98 regs->orig_x0 = regs->regs[0];
99 regs->syscallno = scno;
103 * The architecture does not guarantee that SPSR.BTYPE is zero
104 * on taking an SVC, so we could return to userspace with a
105 * non-zero BTYPE after the syscall.
107 * This shouldn't matter except when userspace is explicitly
108 * doing something stupid, such as setting PROT_BTI on a page
109 * that lacks conforming BTI/PACIxSP instructions, falling
110 * through from one executable page to another with differing
111 * PROT_BTI, or messing with BTYPE via ptrace: in such cases,
112 * userspace should not be surprised if a SIGILL occurs on
115 * So, don't touch regs->pstate & PSR_BTYPE_MASK here.
116 * (Similarly for HVC and SMC elsewhere.)
119 cortex_a76_erratum_1463225_svc_handler();
120 local_daif_restore(DAIF_PROCCTX);
123 if (has_syscall_work(flags)) {
124 /* set default errno for user-issued syscall(-1) */
125 if (scno == NO_SYSCALL)
126 regs->regs[0] = -ENOSYS;
127 scno = syscall_trace_enter(regs);
128 if (scno == NO_SYSCALL)
132 invoke_syscall(regs, scno, sc_nr, syscall_table);
135 * The tracing status may have changed under our feet, so we have to
136 * check again. However, if we were tracing entry, then we always trace
137 * exit regardless, as the old entry assembly did.
139 if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
141 flags = current_thread_info()->flags;
142 if (!has_syscall_work(flags)) {
144 * We're off to userspace, where interrupts are
145 * always enabled after we restore the flags from
151 local_daif_restore(DAIF_PROCCTX);
155 syscall_trace_exit(regs);
158 static inline void sve_user_discard(void)
160 if (!system_supports_sve())
163 clear_thread_flag(TIF_SVE);
166 * task_fpsimd_load() won't be called to update CPACR_EL1 in
167 * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only
168 * happens if a context switch or kernel_neon_begin() or context
169 * modification (sigreturn, ptrace) intervenes.
170 * So, ensure that CPACR_EL1 is already correct for the fast-path case.
175 void do_el0_svc(struct pt_regs *regs)
178 el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table);
182 void do_el0_svc_compat(struct pt_regs *regs)
184 el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls,
185 compat_sys_call_table);