1 /* 2 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) 3 * Licensed under the GPL 4 */ 5 6 #include <arch.h> 7 #include <signal.h> 8 #include <kern_util.h> 9 #include <longjmp.h> 10 #include <sysdep/ptrace.h> 11 #include <generated/asm-offsets.h> 12 13 /* Set during early boot */ 14 static int host_has_cmov = 1; 15 static jmp_buf cmov_test_return; 16 17 static void cmov_sigill_test_handler(int sig) 18 { 19 host_has_cmov = 0; 20 longjmp(cmov_test_return, 1); 21 } 22 23 void arch_check_bugs(void) 24 { 25 struct sigaction old, new; 26 27 printk(UM_KERN_INFO "Checking for host processor cmov support..."); 28 new.sa_handler = cmov_sigill_test_handler; 29 30 /* Make sure that SIGILL is enabled after the handler longjmps back */ 31 new.sa_flags = SA_NODEFER; 32 sigemptyset(&new.sa_mask); 33 sigaction(SIGILL, &new, &old); 34 35 if (setjmp(cmov_test_return) == 0) { 36 unsigned long foo = 0; 37 __asm__ __volatile__("cmovz %0, %1" : "=r" (foo) : "0" (foo)); 38 printk(UM_KERN_CONT "Yes\n"); 39 } else 40 printk(UM_KERN_CONT "No\n"); 41 42 sigaction(SIGILL, &old, &new); 43 } 44 45 void arch_examine_signal(int sig, struct uml_pt_regs *regs) 46 { 47 unsigned char tmp[2]; 48 49 /* 50 * This is testing for a cmov (0x0f 0x4x) instruction causing a 51 * SIGILL in init. 52 */ 53 if ((sig != SIGILL) || (get_current_pid() != 1)) 54 return; 55 56 if (copy_from_user_proc(tmp, (void *) UPT_IP(regs), 2)) { 57 printk(UM_KERN_ERR "SIGILL in init, could not read " 58 "instructions!\n"); 59 return; 60 } 61 62 if ((tmp[0] != 0x0f) || ((tmp[1] & 0xf0) != 0x40)) 63 return; 64 65 if (host_has_cmov == 0) 66 printk(UM_KERN_ERR "SIGILL caused by cmov, which this " 67 "processor doesn't implement. Boot a filesystem " 68 "compiled for older processors"); 69 else if (host_has_cmov == 1) 70 printk(UM_KERN_ERR "SIGILL caused by cmov, which this " 71 "processor claims to implement"); 72 else 73 printk(UM_KERN_ERR "Bad value for host_has_cmov (%d)", 74 host_has_cmov); 75 } 76