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);
54 ret = lower_32_bits(ret);
59 static inline bool has_syscall_work(unsigned long flags)
61 return unlikely(flags & _TIF_SYSCALL_WORK);
64 int syscall_trace_enter(struct pt_regs *regs);
65 void syscall_trace_exit(struct pt_regs *regs);
67 #ifdef CONFIG_ARM64_ERRATUM_1463225
68 DECLARE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa);
70 static void cortex_a76_erratum_1463225_svc_handler(void)
74 if (!unlikely(test_thread_flag(TIF_SINGLESTEP)))
77 if (!unlikely(this_cpu_has_cap(ARM64_WORKAROUND_1463225)))
80 __this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 1);
81 reg = read_sysreg(mdscr_el1);
82 val = reg | DBG_MDSCR_SS | DBG_MDSCR_KDE;
83 write_sysreg(val, mdscr_el1);
84 asm volatile("msr daifclr, #8");
87 /* We will have taken a single-step exception by this point */
89 write_sysreg(reg, mdscr_el1);
90 __this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 0);
93 static void cortex_a76_erratum_1463225_svc_handler(void) { }
94 #endif /* CONFIG_ARM64_ERRATUM_1463225 */
96 static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
97 const syscall_fn_t syscall_table[])
99 unsigned long flags = current_thread_info()->flags;
101 regs->orig_x0 = regs->regs[0];
102 regs->syscallno = scno;
106 * The architecture does not guarantee that SPSR.BTYPE is zero
107 * on taking an SVC, so we could return to userspace with a
108 * non-zero BTYPE after the syscall.
110 * This shouldn't matter except when userspace is explicitly
111 * doing something stupid, such as setting PROT_BTI on a page
112 * that lacks conforming BTI/PACIxSP instructions, falling
113 * through from one executable page to another with differing
114 * PROT_BTI, or messing with BTYPE via ptrace: in such cases,
115 * userspace should not be surprised if a SIGILL occurs on
118 * So, don't touch regs->pstate & PSR_BTYPE_MASK here.
119 * (Similarly for HVC and SMC elsewhere.)
122 cortex_a76_erratum_1463225_svc_handler();
123 local_daif_restore(DAIF_PROCCTX);
126 if (system_supports_mte() && (flags & _TIF_MTE_ASYNC_FAULT)) {
128 * Process the asynchronous tag check fault before the actual
129 * syscall. do_notify_resume() will send a signal to userspace
130 * before the syscall is restarted.
132 regs->regs[0] = -ERESTARTNOINTR;
136 if (has_syscall_work(flags)) {
138 * The de-facto standard way to skip a system call using ptrace
139 * is to set the system call to -1 (NO_SYSCALL) and set x0 to a
140 * suitable error code for consumption by userspace. However,
141 * this cannot be distinguished from a user-issued syscall(-1)
142 * and so we must set x0 to -ENOSYS here in case the tracer doesn't
143 * issue the skip and we fall into trace_exit with x0 preserved.
145 * This is slightly odd because it also means that if a tracer
146 * sets the system call number to -1 but does not initialise x0,
147 * then x0 will be preserved for all system calls apart from a
148 * user-issued syscall(-1). However, requesting a skip and not
149 * setting the return value is unlikely to do anything sensible
152 if (scno == NO_SYSCALL)
153 regs->regs[0] = -ENOSYS;
154 scno = syscall_trace_enter(regs);
155 if (scno == NO_SYSCALL)
159 invoke_syscall(regs, scno, sc_nr, syscall_table);
162 * The tracing status may have changed under our feet, so we have to
163 * check again. However, if we were tracing entry, then we always trace
164 * exit regardless, as the old entry assembly did.
166 if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
168 flags = current_thread_info()->flags;
169 if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP)) {
171 * We're off to userspace, where interrupts are
172 * always enabled after we restore the flags from
178 local_daif_restore(DAIF_PROCCTX);
182 syscall_trace_exit(regs);
185 static inline void sve_user_discard(void)
187 if (!system_supports_sve())
190 clear_thread_flag(TIF_SVE);
193 * task_fpsimd_load() won't be called to update CPACR_EL1 in
194 * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only
195 * happens if a context switch or kernel_neon_begin() or context
196 * modification (sigreturn, ptrace) intervenes.
197 * So, ensure that CPACR_EL1 is already correct for the fast-path case.
202 void do_el0_svc(struct pt_regs *regs)
205 el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table);
209 void do_el0_svc_compat(struct pt_regs *regs)
211 el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls,
212 compat_sys_call_table);