// SPDX-License-Identifier: GPL-2.0 #include <linux/compiler.h>#include <linux/context_tracking.h>#include <linux/errno.h>#include <linux/nospec.h>#include <linux/ptrace.h>#include <linux/randomize_kstack.h>#include <linux/syscalls.h> #include <asm/daifflags.h>#include <asm/debug-monitors.h>#include <asm/exception.h>#include <asm/fpsimd.h>#include <asm/syscall.h>#include <asm/thread_info.h>#include <asm/unistd.h> 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; 	add_random_kstack_offset(); 	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; 	/*	 * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),	 * but not enough for arm64 stack utilization comfort. To keep	 * reasonable stack head room, reduce the maximum offset to 9 bits.	 *	 * The actual entropy will be further reduced by the compiler when	 * applying stack alignment constraints: the AAPCS mandates a	 * 16-byte (i.e. 4-bit) aligned SP at function boundaries.	 *	 * The resulting 5 bits of entropy is seen in SP[8:4].	 */	choose_random_kstack_offset(get_random_int() & 0x1FF);} 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); 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.)	 */ 	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_COMPATvoid do_el0_svc_compat(struct pt_regs *regs){	el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls,		       compat_sys_call_table);}#endif