arch/um/sys-i386/bugs.c

   1 /*
   2  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <errno.h>
   7 #include <signal.h>
   8 #include <string.h>
   9 #include "kern_constants.h"
  10 #include "os.h"
  11 #include "task.h"
  12 #include "user.h"
  13
  14 #define MAXTOKEN 64
  15
  16 /* Set during early boot */
  17 int host_has_cmov = 1;
  18 int host_has_xmm = 0;
  19
  20 static char token(int fd, char *buf, int len, char stop)
  21 {
  22         int n;
  23         char *ptr, *end, c;
  24
  25         ptr = buf;
  26         end = &buf[len];
  27         do {
  28                 n = os_read_file(fd, ptr, sizeof(*ptr));
  29                 c = *ptr++;
  30                 if (n != sizeof(*ptr)) {
  31                         if (n == 0)
  32                                 return 0;
  33                         printk(UM_KERN_ERR "Reading /proc/cpuinfo failed, "
  34                                "err = %d\n", -n);
  35                         if (n < 0)
  36                                 return n;
  37                         else return -EIO;
  38                 }
  39         } while ((c != '\n') && (c != stop) && (ptr < end));
  40
  41         if (ptr == end) {
  42                 printk(UM_KERN_ERR "Failed to find '%c' in /proc/cpuinfo\n",
  43                        stop);
  44                 return -1;
  45         }
  46         *(ptr - 1) = '\0';
  47         return c;
  48 }
  49
  50 static int find_cpuinfo_line(int fd, char *key, char *scratch, int len)
  51 {
  52         int n;
  53         char c;
  54
  55         scratch[len - 1] = '\0';
  56         while (1) {
  57                 c = token(fd, scratch, len - 1, ':');
  58                 if (c <= 0)
  59                         return 0;
  60                 else if (c != ':') {
  61                         printk(UM_KERN_ERR "Failed to find ':' in "
  62                                "/proc/cpuinfo\n");
  63                         return 0;
  64                 }
  65
  66                 if (!strncmp(scratch, key, strlen(key)))
  67                         return 1;
  68
  69                 do {
  70                         n = os_read_file(fd, &c, sizeof(c));
  71                         if (n != sizeof(c)) {
  72                                 printk(UM_KERN_ERR "Failed to find newline in "
  73                                        "/proc/cpuinfo, err = %d\n", -n);
  74                                 return 0;
  75                         }
  76                 } while (c != '\n');
  77         }
  78         return 0;
  79 }
  80
  81 static int check_cpu_flag(char *feature, int *have_it)
  82 {
  83         char buf[MAXTOKEN], c;
  84         int fd, len = ARRAY_SIZE(buf);
  85
  86         printk(UM_KERN_INFO "Checking for host processor %s support...",
  87                feature);
  88         fd = os_open_file("/proc/cpuinfo", of_read(OPENFLAGS()), 0);
  89         if (fd < 0) {
  90                 printk(UM_KERN_ERR "Couldn't open /proc/cpuinfo, err = %d\n",
  91                        -fd);
  92                 return 0;
  93         }
  94
  95         *have_it = 0;
  96         if (!find_cpuinfo_line(fd, "flags", buf, ARRAY_SIZE(buf)))
  97                 goto out;
  98
  99         c = token(fd, buf, len - 1, ' ');
 100         if (c < 0)
 101                 goto out;
 102         else if (c != ' ') {
 103                 printk(UM_KERN_ERR "Failed to find ' ' in /proc/cpuinfo\n");
 104                 goto out;
 105         }
 106
 107         while (1) {
 108                 c = token(fd, buf, len - 1, ' ');
 109                 if (c < 0)
 110                         goto out;
 111                 else if (c == '\n')
 112                         break;
 113
 114                 if (!strcmp(buf, feature)) {
 115                         *have_it = 1;
 116                         goto out;
 117                 }
 118         }
 119  out:
 120         if (*have_it == 0)
 121                 printk("No\n");
 122         else if (*have_it == 1)
 123                 printk("Yes\n");
 124         os_close_file(fd);
 125         return 1;
 126 }
 127
 128 #if 0 /*
 129        * This doesn't work in tt mode, plus it's causing compilation problems
 130        * for some people.
 131        */
 132 static void disable_lcall(void)
 133 {
 134         struct modify_ldt_ldt_s ldt;
 135         int err;
 136
 137         bzero(&ldt, sizeof(ldt));
 138         ldt.entry_number = 7;
 139         ldt.base_addr = 0;
 140         ldt.limit = 0;
 141         err = modify_ldt(1, &ldt, sizeof(ldt));
 142         if (err)
 143                 printk(UM_KERN_ERR "Failed to disable lcall7 - errno = %d\n",
 144                        errno);
 145 }
 146 #endif
 147
 148 void arch_init_thread(void)
 149 {
 150 #if 0
 151         disable_lcall();
 152 #endif
 153 }
 154
 155 void arch_check_bugs(void)
 156 {
 157         int have_it;
 158
 159         if (os_access("/proc/cpuinfo", OS_ACC_R_OK) < 0) {
 160                 printk(UM_KERN_ERR "/proc/cpuinfo not available - skipping CPU "
 161                        "capability checks\n");
 162                 return;
 163         }
 164         if (check_cpu_flag("cmov", &have_it))
 165                 host_has_cmov = have_it;
 166         if (check_cpu_flag("xmm", &have_it))
 167                 host_has_xmm = have_it;
 168 }
 169
 170 int arch_handle_signal(int sig, struct uml_pt_regs *regs)
 171 {
 172         unsigned char tmp[2];
 173
 174         /*
 175          * This is testing for a cmov (0x0f 0x4x) instruction causing a
 176          * SIGILL in init.
 177          */
 178         if ((sig != SIGILL) || (TASK_PID(get_current()) != 1))
 179                 return 0;
 180
 181         if (copy_from_user_proc(tmp, (void *) UPT_IP(regs), 2))
 182                 panic("SIGILL in init, could not read instructions!\n");
 183         if ((tmp[0] != 0x0f) || ((tmp[1] & 0xf0) != 0x40))
 184                 return 0;
 185
 186         if (host_has_cmov == 0)
 187                 panic("SIGILL caused by cmov, which this processor doesn't "
 188                       "implement, boot a filesystem compiled for older "
 189                       "processors");
 190         else if (host_has_cmov == 1)
 191                 panic("SIGILL caused by cmov, which this processor claims to "
 192                       "implement");
 193         else if (host_has_cmov == -1)
 194                 panic("SIGILL caused by cmov, couldn't tell if this processor "
 195                       "implements it, boot a filesystem compiled for older "
 196                       "processors");
 197         else panic("Bad value for host_has_cmov (%d)", host_has_cmov);
 198         return 0;
 199 }