Gentoo: 屏蔽Linux的启动信息

1. 屏蔽grub的信息

Gentoo上amd64 grub的版本是0.97-r12，需要修改源码来屏蔽屏幕打印。

- 创建本地overlay：/usr/local/portage/xxx-overlay，添加内容：PORTDIR_OVERLAY="/usr/local/portage/xxx-overlay"到/etc/make.conf

- 在本地overlay目录下创建：sys-boot-xxx/grub，将grub-0.97-r12.ebuild（来自gentoo官方portage树）和metadata.xml拷贝到这里

- 修改ebuild，因为我们要加入自己的patch，所以在

    EPATCH_SUFFIX="patch" epatch "${WORKDIR}"/patch

    这句的后面添加：

    epatch "${FILESDIR}/<your patch filename>.patch"

- 在本地overlay目录下创建files目录，将我们的patch文件放进去，这里我的patch文件是（消除了所有正常情况下的输出）：

diff -u -d -r grub-0.97.bak/stage1/stage1.S grub-0.97/stage1/stage1.S
--- grub-0.97.bak/stage1/stage1.S    2012-12-21 19:13:16.864283386 +0800
+++ grub-0.97/stage1/stage1.S    2012-12-21 19:41:52.792201571 +0800
@@ -151,7 +151,7 @@
     pushw    %dx
 
     /* print a notification message on the screen */
-    MSG(notification_string)
+    /* MSG(notification_string) */
 
     /* do not probe LBA if the drive is a floppy */
     testb    $STAGE1_BIOS_HD_FLAG, %dl
diff -u -d -r grub-0.97.bak/stage2/boot.c grub-0.97/stage2/boot.c
--- grub-0.97.bak/stage2/boot.c    2012-12-21 19:13:16.855282243 +0800
+++ grub-0.97/stage2/boot.c    2012-12-21 19:15:08.341435413 +0800
@@ -280,8 +280,8 @@
     errnum = ERR_WONT_FIT;
       else
     {
-      grub_printf ("   [Linux-%s, setup=0x%x, size=0x%x]\n",
-               (big_linux ? "bzImage" : "zImage"), data_len, text_len);
+      /* grub_printf ("   [Linux-%s, setup=0x%x, size=0x%x]\n",
+               (big_linux ? "bzImage" : "zImage"), data_len, text_len); */
 
       /* Video mode selection support. What a mess!  */
       /* NOTE: Even the word "mess" is not still enough to
diff -u -d -r grub-0.97.bak/stage2/cmdline.c grub-0.97/stage2/cmdline.c
--- grub-0.97.bak/stage2/cmdline.c    2012-12-21 19:13:16.861283005 +0800
+++ grub-0.97/stage2/cmdline.c    2012-12-21 19:14:47.768836881 +0800
@@ -232,12 +232,12 @@
       builtin = find_command (heap);
       if (! builtin)
     {
-      grub_printf ("%s\n", old_entry);
+      /* grub_printf ("%s\n", old_entry); */
       continue;
     }
 
-      if (! (builtin->flags & BUILTIN_NO_ECHO))
-    grub_printf ("%s\n", old_entry);
+      /* if (! (builtin->flags & BUILTIN_NO_ECHO))
+    grub_printf ("%s\n", old_entry); */
 
       /* If BUILTIN cannot be run in the command-line, skip it.  */
       if (! (builtin->flags & BUILTIN_CMDLINE))
diff -u -d -r grub-0.97.bak/stage2/disk_io.c grub-0.97/stage2/disk_io.c
--- grub-0.97.bak/stage2/disk_io.c    2012-12-21 19:13:16.858282624 +0800
+++ grub-0.97/stage2/disk_io.c    2012-12-21 19:22:50.732885018 +0800
@@ -1351,7 +1351,7 @@
 {
   if (! do_completion)
     {
-      printf (" Filesystem type ");
+      /* printf (" Filesystem type ");
       
       if (fsys_type != NUM_FSYS)
     printf ("is %s, ", fsys_table[fsys_type].name);
@@ -1361,7 +1361,8 @@
       if (current_partition == 0xFFFFFF)
     printf ("using whole disk\n");
       else
-    printf ("partition type 0x%x\n", current_slice & 0xFF);
+    printf ("partition type 0x%x\n", current_slice & 0xFF); */
+      return;
     }
 }
 #endif /* STAGE1_5 */
diff -u -d -r grub-0.97.bak/stage2/stage1_5.c grub-0.97/stage2/stage1_5.c
--- grub-0.97.bak/stage2/stage1_5.c    2012-12-21 19:13:16.862283132 +0800
+++ grub-0.97/stage2/stage1_5.c    2012-12-21 19:24:14.499534514 +0800
@@ -30,7 +30,7 @@
 void
 cmain (void)
 {
-  grub_printf ("\n\nGRUB loading, please wait...\n");
+  /* grub_printf ("\n\nGRUB loading, please wait...\n"); */
 
   /*
    *  Here load the true second-stage boot-loader.
diff -u -d -r grub-0.97.bak/stage2/stage2.c grub-0.97/stage2/stage2.c
--- grub-0.97.bak/stage2/stage2.c    2012-12-21 19:13:16.857282497 +0800
+++ grub-0.97/stage2/stage2.c    2012-12-21 20:02:25.576707562 +0800
@@ -288,8 +288,8 @@
           grub_timeout--;
           
           /* Print a message.  */
-          grub_printf ("\rPress `ESC' to enter the menu... %d   ",
-               grub_timeout);
+          /* grub_printf ("\rPress `ESC' to enter the menu... %d   ",
+               grub_timeout); */
         }
     }
     }
@@ -730,11 +730,11 @@
   
   while (1)
     {
-      if (config_entries)
+      /* if (config_entries)
     printf ("  Booting \'%s\'\n\n",
         get_entry (menu_entries, first_entry + entryno, 0));
       else
-    printf ("  Booting command-list\n\n");
+    printf ("  Booting command-list\n\n"); */
 
       if (! cur_entry)
     cur_entry = get_entry (config_entries, first_entry + entryno, 1);
diff -u -d -r grub-0.97.bak/stage2/start.S grub-0.97/stage2/start.S
--- grub-0.97.bak/stage2/start.S    2012-12-21 19:13:16.857282497 +0800
+++ grub-0.97/stage2/start.S    2012-12-21 20:18:41.119650361 +0800
@@ -67,7 +67,7 @@
 
     /* print a notification message on the screen */
     pushw    %si
-    MSG(notification_string)
+    /* MSG(notification_string) */
     popw    %si
     
     /* this sets up for the first run through "bootloop" */
@@ -293,7 +293,7 @@
     /* restore addressing regs and print a dot with correct DS 
        (MSG modifies SI, which is saved, and unused AX and BX) */
     popw    %ds
-    MSG(notification_step)
+    /* MSG(notification_step) */
     popa
 
     /* check if finished with this dataset */
@@ -310,7 +310,7 @@
 
 bootit:
     /* print a newline */
-    MSG(notification_done)
+    /* MSG(notification_done) */
     popw    %dx    /* this makes sure %dl is our "boot" drive */
 #ifdef STAGE1_5
     ljmp    $0, $0x2200

- ebuild grub-0.97-r12.ebuild manifest

- 前面我们创建的grub包所属的category是sys-boot-xxx，这是为了区别系统的sys-boot/grub，方便emerge我们自己的grub。为了让这个category能被emerge认识，为此，在我们的overlay根目录（/usr/local/portage/xxx-overlay）下创建目录profiles，然后继续在profiles下新建文件categories，在其中输入内容：sys-boot-xxx

- emerge -C sys-boot/grub

- emerge -avt sys-boot-xxx/grub，这里注意观察我们的patch是否被apply了（官方grub本身就有很多patch会打，所以注意观察我们的，是最后一个打的。我们制作这个patch时，其实也是在官方grub+官方patch的基础上制作出来的，否则patch是打不上的）。

- grub编译安装完成了，运行：grub --no-floppy，然后：root (hd0,0) -> setup (hd0) -> quit

- 编辑/boot/grub/grub.conf，加入一行：hiddenmenu，这样grub的menu就不会出现了。如果只是将timeout设成0的话，还是有一个闪动的画面，所以这里禁止了menu。

- Done. 可以重启试一下。

2. 屏蔽kernel和Linux启动信息（init开始执行之后产生的信息）

这相对就简单很多了。网上有说添加kernel command option：console=/dev/null或者console=/dev/ttyS0，但是这样还有一小部分信息无法屏蔽，比如一开始的Uncompressing kernel...。所以我的做法是直接关掉所有的console，也就是VGA console（x86架构）和framebuffer console，make menuconfig轻松搞定。需要注意首先要enable CONFIG_EXPERT，否则VGA console是默认enable并且无法更改的。

Done. 现在除了BIOS信息，其他就什么信息都没有了。