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/exception.h>
13 #include <asm/fpsimd.h>
14 #include <asm/syscall.h>
15 #include <asm/thread_info.h>
16 #include <asm/unistd.h>
18 long compat_arm_syscall(struct pt_regs *regs, int scno);
19 long sys_ni_syscall(void);
21 static long do_ni_syscall(struct pt_regs *regs, int scno)
25 if (is_compat_task()) {
26 ret = compat_arm_syscall(regs, scno);
32 return sys_ni_syscall();
35 static long __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn)
37 return syscall_fn(regs);
40 static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
42 const syscall_fn_t syscall_table[])
47 syscall_fn_t syscall_fn;
48 syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)];
49 ret = __invoke_syscall(regs, syscall_fn);
51 ret = do_ni_syscall(regs, scno);
55 ret = lower_32_bits(ret);
60 static inline bool has_syscall_work(unsigned long flags)
62 return unlikely(flags & _TIF_SYSCALL_WORK);
65 int syscall_trace_enter(struct pt_regs *regs);
66 void syscall_trace_exit(struct pt_regs *regs);
68 static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
69 const syscall_fn_t syscall_table[])
71 unsigned long flags = current_thread_info()->flags;
73 regs->orig_x0 = regs->regs[0];
74 regs->syscallno = scno;
78 * The architecture does not guarantee that SPSR.BTYPE is zero
79 * on taking an SVC, so we could return to userspace with a
80 * non-zero BTYPE after the syscall.
82 * This shouldn't matter except when userspace is explicitly
83 * doing something stupid, such as setting PROT_BTI on a page
84 * that lacks conforming BTI/PACIxSP instructions, falling
85 * through from one executable page to another with differing
86 * PROT_BTI, or messing with BTYPE via ptrace: in such cases,
87 * userspace should not be surprised if a SIGILL occurs on
90 * So, don't touch regs->pstate & PSR_BTYPE_MASK here.
91 * (Similarly for HVC and SMC elsewhere.)
94 local_daif_restore(DAIF_PROCCTX);
96 if (flags & _TIF_MTE_ASYNC_FAULT) {
98 * Process the asynchronous tag check fault before the actual
99 * syscall. do_notify_resume() will send a signal to userspace
100 * before the syscall is restarted.
102 regs->regs[0] = -ERESTARTNOINTR;
106 if (has_syscall_work(flags)) {
108 * The de-facto standard way to skip a system call using ptrace
109 * is to set the system call to -1 (NO_SYSCALL) and set x0 to a
110 * suitable error code for consumption by userspace. However,
111 * this cannot be distinguished from a user-issued syscall(-1)
112 * and so we must set x0 to -ENOSYS here in case the tracer doesn't
113 * issue the skip and we fall into trace_exit with x0 preserved.
115 * This is slightly odd because it also means that if a tracer
116 * sets the system call number to -1 but does not initialise x0,
117 * then x0 will be preserved for all system calls apart from a
118 * user-issued syscall(-1). However, requesting a skip and not
119 * setting the return value is unlikely to do anything sensible
122 if (scno == NO_SYSCALL)
123 regs->regs[0] = -ENOSYS;
124 scno = syscall_trace_enter(regs);
125 if (scno == NO_SYSCALL)
129 invoke_syscall(regs, scno, sc_nr, syscall_table);
132 * The tracing status may have changed under our feet, so we have to
133 * check again. However, if we were tracing entry, then we always trace
134 * exit regardless, as the old entry assembly did.
136 if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
138 flags = current_thread_info()->flags;
139 if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP))
141 local_daif_restore(DAIF_PROCCTX);
145 syscall_trace_exit(regs);
148 static inline void sve_user_discard(void)
150 if (!system_supports_sve())
153 clear_thread_flag(TIF_SVE);
156 * task_fpsimd_load() won't be called to update CPACR_EL1 in
157 * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only
158 * happens if a context switch or kernel_neon_begin() or context
159 * modification (sigreturn, ptrace) intervenes.
160 * So, ensure that CPACR_EL1 is already correct for the fast-path case.
165 void do_el0_svc(struct pt_regs *regs)
168 el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table);
172 void do_el0_svc_compat(struct pt_regs *regs)
174 el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls,
175 compat_sys_call_table);