Improve error reporting on file access

By making the error reporting include strerror(errno), it gives the user
a bit more indication as to why qemu failed.  This is particularly
important for people running qemu as a non root user.
Signed-off-by: NJustin M. Forbes <jforbes@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/pc.c

@@ -844,8 +844,8 @@ static void load_linux(void *fw_cfg,
     if (!f || !(kernel_size = get_file_size(f)) ||
 	fread(header, 1, MIN(ARRAY_SIZE(header), kernel_size), f) !=
 	MIN(ARRAY_SIZE(header), kernel_size)) {
-	fprintf(stderr, "qemu: could not load kernel '%s'\n",
-		kernel_filename);
+	fprintf(stderr, "qemu: could not load kernel '%s': %s\n",
+		kernel_filename, strerror(errno));
 	exit(1);
     }
 
@@ -950,8 +950,8 @@ static void load_linux(void *fw_cfg,
 
 	fi = fopen(initrd_filename, "rb");
 	if (!fi) {
-	    fprintf(stderr, "qemu: could not load initial ram disk '%s'\n",
-		    initrd_filename);
+	    fprintf(stderr, "qemu: could not load initial ram disk '%s': %s\n",
+		    initrd_filename, strerror(errno));
 	    exit(1);
 	}
 
@@ -959,8 +959,8 @@ static void load_linux(void *fw_cfg,
 	initrd_addr = (initrd_max-initrd_size) & ~4095;
 
 	if (!fread_targphys_ok(initrd_addr, initrd_size, fi)) {
-	    fprintf(stderr, "qemu: read error on initial ram disk '%s'\n",
-		    initrd_filename);
+	    fprintf(stderr, "qemu: read error on initial ram disk '%s': %s\n",
+		    initrd_filename, strerror(errno));
 	    exit(1);
 	}
 	fclose(fi);

vl.c

@@ -2328,8 +2328,8 @@ DriveInfo *drive_init(QemuOpts *opts, void *opaque,
     }
 
     if (bdrv_open2(dinfo->bdrv, file, bdrv_flags, drv) < 0) {
-        fprintf(stderr, "qemu: could not open disk image %s\n",
-                        file);
+        fprintf(stderr, "qemu: could not open disk image %s: %s\n",
+                        file, strerror(errno));
         return NULL;
     }
 
@@ -5566,7 +5566,7 @@ int main(int argc, char **argv, char **envp)
             if (len != 1)
                 exit(1);
             else if (status == 1) {
-                fprintf(stderr, "Could not acquire pidfile\n");
+                fprintf(stderr, "Could not acquire pidfile: %s\n", strerror(errno));
                 exit(1);
             } else
                 exit(0);
@@ -5593,7 +5593,7 @@ int main(int argc, char **argv, char **envp)
             uint8_t status = 1;
             write(fds[1], &status, 1);
         } else
-            fprintf(stderr, "Could not acquire pid file\n");
+            fprintf(stderr, "Could not acquire pid file: %s\n", strerror(errno));
         exit(1);
     }
 #endif
@@ -5777,8 +5777,8 @@ int main(int argc, char **argv, char **envp)
             snprintf(label, sizeof(label), "serial%d", i);
             serial_hds[i] = qemu_chr_open(label, devname, NULL);
             if (!serial_hds[i]) {
-                fprintf(stderr, "qemu: could not open serial device '%s'\n",
-                        devname);
+                fprintf(stderr, "qemu: could not open serial device '%s': %s\n",
+                        devname, strerror(errno));
                 exit(1);
             }
         }
@@ -5791,8 +5791,8 @@ int main(int argc, char **argv, char **envp)
             snprintf(label, sizeof(label), "parallel%d", i);
             parallel_hds[i] = qemu_chr_open(label, devname, NULL);
             if (!parallel_hds[i]) {
-                fprintf(stderr, "qemu: could not open parallel device '%s'\n",
-                        devname);
+                fprintf(stderr, "qemu: could not open parallel device '%s': %s\n",
+                        devname, strerror(errno));
                 exit(1);
             }
         }
@@ -5805,8 +5805,8 @@ int main(int argc, char **argv, char **envp)
             snprintf(label, sizeof(label), "virtcon%d", i);
             virtcon_hds[i] = qemu_chr_open(label, devname, NULL);
             if (!virtcon_hds[i]) {
-                fprintf(stderr, "qemu: could not open virtio console '%s'\n",
-                        devname);
+                fprintf(stderr, "qemu: could not open virtio console '%s': %s\n",
+                        devname, strerror(errno));
                 exit(1);
             }
         }