1 // SPDX-License-Identifier: GPL-2.0-only
3  * single_step_syscall.c - single-steps various x86 syscalls
4  * Copyright (c) 2014-2015 Andrew Lutomirski
6  * This is a very simple series of tests that makes system calls with
7  * the TF flag set.  This exercises some nasty kernel code in the
8  * SYSENTER case: SYSENTER does not clear TF, so SYSENTER with TF set
78 		printf("[WARN]\tSIGTRAP handler had TF set\n");  in sigtrap()
87 		       (unsigned long)info->si_addr,  in sigtrap()
88 		       (unsigned long)ctx->uc_mcontext.gregs[REG_IP]);  in sigtrap()
103 	printf("\tGot %s with RIP=%lx, TF=%ld\n", signames[sig],  in print_and_longjmp()
104 	       (unsigned long)ctx->uc_mcontext.gregs[REG_IP],  in print_and_longjmp()
105 	       (unsigned long)ctx->uc_mcontext.gregs[REG_EFL] & X86_EFLAGS_TF);  in print_and_longjmp()
107 	sig_eflags = (unsigned long)ctx->uc_mcontext.gregs[REG_EFL];  in print_and_longjmp()
126 	printf("[OK]\tSurvived with TF set and %d traps\n", (int)sig_traps);  in check_result()
133 	printf("[RUN]\tFast syscall with TF cleared\n");  in fast_syscall_no_tf()
134 	fflush(stdout);  /* Force a syscall */  in fast_syscall_no_tf()
154 	printf("[RUN]\tSet TF and check nop\n");  in main()
160 	printf("[RUN]\tSet TF and check syscall-less opportunistic sysret\n");  in main()
171 	printf("[RUN]\tSet TF and check int80\n");  in main()
173 	asm volatile ("int $0x80" : "=a" (tmp) : "a" (SYS_getpid)  in main()
180 	 * SYSENTER: it triggers a nasty design flaw in SYSENTER.  in main()
181 	 * Specifically, SYSENTER does not clear TF, so either SYSENTER  in main()
184 	 * get a CPL0 fault with usergs (on 64-bit kernels) and possibly  in main()
186 	 * it is to clear TF on return from the #DB handler, but this  in main()
187 	 * happens way too early to set TF in the saved pt_regs, so the  in main()
189 	 * the TF bit.  in main()
193 	syscall(SYS_getpid);  /* Force symbol binding without TF set. */  in main()
194 	printf("[RUN]\tSet TF and check a fast syscall\n");  in main()
199 	/* Now make sure that another fast syscall doesn't set TF again. */  in main()
203 	 * And do a forced SYSENTER to make sure that this works even if  in main()
211 		printf("[RUN]\tSet TF and check SYSENTER\n");  in main()
223 		asm volatile ("xorl %%ebp, %%ebp; SYSENTER" : "+a" (nr) :: "flags", "rcx"  in main()
238 	/* Now make sure that another fast syscall doesn't set TF again. */  in main()