// SPDX-License-Identifier: GPL-2.0 #include #include #include #include #include #include #include #include #include #include #include #include #include long compat_arm_syscall(struct pt_regs *regs, int scno); long sys_ni_syscall(void); static long do_ni_syscall(struct pt_regs *regs, int scno) { #ifdef CONFIG_COMPAT long ret; if (is_compat_task()) { ret = compat_arm_syscall(regs, scno); if (ret != -ENOSYS) return ret; } #endif return sys_ni_syscall(); } static long __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn) { return syscall_fn(regs); } static void invoke_syscall(struct pt_regs *regs, unsigned int scno, unsigned int sc_nr, const syscall_fn_t syscall_table[]) { long ret; if (scno < sc_nr) { syscall_fn_t syscall_fn; syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)]; ret = __invoke_syscall(regs, syscall_fn); } else { ret = do_ni_syscall(regs, scno); } if (is_compat_task()) ret = lower_32_bits(ret); regs->regs[0] = ret; } static inline bool has_syscall_work(unsigned long flags) { return unlikely(flags & _TIF_SYSCALL_WORK); } int syscall_trace_enter(struct pt_regs *regs); void syscall_trace_exit(struct pt_regs *regs); #ifdef CONFIG_ARM64_ERRATUM_1463225 DECLARE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa); static void cortex_a76_erratum_1463225_svc_handler(void) { u32 reg, val; if (!unlikely(test_thread_flag(TIF_SINGLESTEP))) return; if (!unlikely(this_cpu_has_cap(ARM64_WORKAROUND_1463225))) return; __this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 1); reg = read_sysreg(mdscr_el1); val = reg | DBG_MDSCR_SS | DBG_MDSCR_KDE; write_sysreg(val, mdscr_el1); asm volatile("msr daifclr, #8"); isb(); /* We will have taken a single-step exception by this point */ write_sysreg(reg, mdscr_el1); __this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 0); } #else static void cortex_a76_erratum_1463225_svc_handler(void) { } #endif /* CONFIG_ARM64_ERRATUM_1463225 */ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, const syscall_fn_t syscall_table[]) { unsigned long flags = current_thread_info()->flags; regs->orig_x0 = regs->regs[0]; regs->syscallno = scno; /* * BTI note: * The architecture does not guarantee that SPSR.BTYPE is zero * on taking an SVC, so we could return to userspace with a * non-zero BTYPE after the syscall. * * This shouldn't matter except when userspace is explicitly * doing something stupid, such as setting PROT_BTI on a page * that lacks conforming BTI/PACIxSP instructions, falling * through from one executable page to another with differing * PROT_BTI, or messing with BTYPE via ptrace: in such cases, * userspace should not be surprised if a SIGILL occurs on * syscall return. * * So, don't touch regs->pstate & PSR_BTYPE_MASK here. * (Similarly for HVC and SMC elsewhere.) */ cortex_a76_erratum_1463225_svc_handler(); local_daif_restore(DAIF_PROCCTX); if (flags & _TIF_MTE_ASYNC_FAULT) { /* * Process the asynchronous tag check fault before the actual * syscall. do_notify_resume() will send a signal to userspace * before the syscall is restarted. */ regs->regs[0] = -ERESTARTNOINTR; return; } if (has_syscall_work(flags)) { /* * The de-facto standard way to skip a system call using ptrace * is to set the system call to -1 (NO_SYSCALL) and set x0 to a * suitable error code for consumption by userspace. However, * this cannot be distinguished from a user-issued syscall(-1) * and so we must set x0 to -ENOSYS here in case the tracer doesn't * issue the skip and we fall into trace_exit with x0 preserved. * * This is slightly odd because it also means that if a tracer * sets the system call number to -1 but does not initialise x0, * then x0 will be preserved for all system calls apart from a * user-issued syscall(-1). However, requesting a skip and not * setting the return value is unlikely to do anything sensible * anyway. */ if (scno == NO_SYSCALL) regs->regs[0] = -ENOSYS; scno = syscall_trace_enter(regs); if (scno == NO_SYSCALL) goto trace_exit; } invoke_syscall(regs, scno, sc_nr, syscall_table); /* * The tracing status may have changed under our feet, so we have to * check again. However, if we were tracing entry, then we always trace * exit regardless, as the old entry assembly did. */ if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) { local_daif_mask(); flags = current_thread_info()->flags; if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP)) return; local_daif_restore(DAIF_PROCCTX); } trace_exit: syscall_trace_exit(regs); } static inline void sve_user_discard(void) { if (!system_supports_sve()) return; clear_thread_flag(TIF_SVE); /* * task_fpsimd_load() won't be called to update CPACR_EL1 in * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only * happens if a context switch or kernel_neon_begin() or context * modification (sigreturn, ptrace) intervenes. * So, ensure that CPACR_EL1 is already correct for the fast-path case. */ sve_user_disable(); } void do_el0_svc(struct pt_regs *regs) { sve_user_discard(); el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table); } #ifdef CONFIG_COMPAT void do_el0_svc_compat(struct pt_regs *regs) { el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls, compat_sys_call_table); } #endif