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BUGFIX: jfbterm (1)

08-11-15@GMT-6 原紀錄 BUGFIX: jfbterm (1)

[DRBL] jfbterm Bug

https://bugs.launchpad.net/ubuntu/+source/jfbterm/+bug/253163
http://launchpadlibrarian.net/16414131/jfbterm-segfault.txt
http://launchpadlibrarian.net/16414135/jfbterm-segfault-strace.txt

[測試]

安裝 Ubuntu 8.10 Server AMD64

用 Ubuntu 8.10 的測試步驟:

root@intrepid:~# apt-get update
root@intrepid:~# apt-get upgrade
root@intrepid:~# reboot
root@intrepid:~# uname -a
Linux intrepid 2.6.27-7-server #1 SMP Tue Nov 4 20:16:57 UTC 2008 x86_64 GNU/Linux
root@intrepid:~# apt-get install jfbterm v86d
root@intrepid:~# reboot
root@intrepid:~# dpkg -S chvt
kbd: /usr/share/man/man1/chvt.1.gz
kbd: /bin/chvt
root@intrepid:~# chvt 1
root@intrepid:~# rmmod uvesafb
ERROR: Module uvesafb does not exist in /proc/modules
root@intrepid:~# modprobe uvesafb mode_option=1024x768
root@intrepid:~# screen
root@intrepid:~# jfbterm -e ls
... 略 ...
color 15 : ffff, ffff
cannot mmap(mmio) : Invalid argument
Segmentation fault

[備註] 如果沒有 modprobe uvesafb 的話，會缺少 /dev/fb0，因此當執行 jfbterm 時就會出現以下錯誤訊息

ENCODING: locale = UTF-8
FONT : (4) [iso10646.1]/pcf/U:///usr/share/fonts/X11/misc/unifont.pcf.gz/
encoding : UTF-8,iso10646.1
exec : ls open /dev/fb0: No such file or directory

[備註] 如果沒有裝 v86d 的話，當執行 modprobe uvesafb 時會在 dmesg 看到以下資訊

[  703.839376] uvesafb: failed to execute /sbin/v86d
[  703.840224] uvesafb: make sure that the v86d helper is installed and executable
[  703.841494] uvesafb: Getting VBE info block failed (eax=0x4f00, err=-2)
[  703.842307] uvesafb: vbe_init() failed with -22
[  703.843019] uvesafb: probe of uvesafb.0 failed with error -22

[備註] 如果有裝 v86d 的話，當執行 modprobe uvesafb 時會在 dmesg 看到以下資訊

[  268.848377] uvesafb: VMware, IncVMware virtual machine2.0, VMware virtual machine2.0, 2.0, OEM: V M ware, Inc. VBE support 2.0VMware, IncVMware virtual machine2.0, VBE v2.0
[  268.884099] uvesafb: no monitor limits have been set, default refresh rate will be used
[  268.885202] uvesafb: VBE state buffer size cannot be determined (eax=0x0, err=0)
[  268.885265] uvesafb: scrolling: redraw
[  268.896617] mtrr: your processor doesn't support write-combining
[  268.909303] Console: switching to colour frame buffer device 128x48
[  269.938085] uvesafb: framebuffer at 0xf0000000, mapped to 0xffffc20000180000, using 16384k, total 16384k
[  269.938101] fb0: VESA VGA frame buffer device

編輯 GRUB 的 menu.lst 就可以不用每次都跑 modprobe

menu.lst

-                      old
+                      new
 title          Ubuntu 8.10, kernel 2.6.27-7-server
 uuid           574912ac-8bd6-4cc7-90c6-8c5362033fec
 kernel         /boot/vmlinuz-2.6.27-7-server root=UUID=574912ac-8bd6-4cc7-90c6-8c5362033fec ro quiet splash
+kernel         /boot/vmlinuz-2.6.27-7-server root=UUID=574912ac-8bd6-4cc7-90c6-8c5362033fec ro quiet splash vga=0x305
 initrd         /boot/initrd.img-2.6.27-7-server
 quiet

用 modinfo 觀看 Ubuntu 8.10 Kernel 2.6.27-7-server 的 uvesafb 模組參數，發現包括 scroll、vgapal、pmipal、mtrr、blank、nocrtc、noedid、vram_remap、vram_total、maxclk、maxhf、maxvf、mode_option、vbemode、v86d。並沒有 mode 這個參數。

root@intrepid:~# modinfo uvesafb
filename:       /lib/modules/2.6.27-7-server/kernel/drivers/video/uvesafb.ko
description:    Framebuffer driver for VBE2.0+ compliant graphics boards
author:         Michal Januszewski <spock@gentoo.org>
license:        GPL
srcversion:     21EDEFDED06E0673208A0D5
depends:
vermagic:       2.6.27-7-server SMP mod_unload modversions
parm:           scroll:Scrolling mode, set to 'redraw', 'ypan', or 'ywrap' (scroll)
parm:           vgapal:Set palette using VGA registers (invbool)
parm:           pmipal:Set palette using PMI calls (bool)
parm:           mtrr:Memory Type Range Registers setting. Use 0 to disable. (uint)
parm:           blank:Enable hardware blanking (bool)
parm:           nocrtc:Ignore CRTC timings when setting modes (bool)
parm:           noedid:Ignore EDID-provided monitor limits when setting modes (bool)
parm:           vram_remap:Set amount of video memory to be used [MiB] (uint)
parm:           vram_total:Set total amount of video memoery [MiB] (uint)
parm:           maxclk:Maximum pixelclock [MHz], overrides EDID data (ushort)
parm:           maxhf:Maximum horizontal frequency [kHz], overrides EDID data (ushort)
parm:           maxvf:Maximum vertical frequency [Hz], overrides EDID data (ushort)
parm:           mode_option:Specify initial video mode as "<xres>x<yres>[-<bpp>][@<refresh>]" (charp)
parm:           vbemode:VBE mode number to set, overrides the 'mode' option (ushort)
parm:           v86d:Path to the v86d userspace helper. (string)

root@intrepid:~# LANG=C apt-cache policy v86d
v86d:
  Installed: 0.1.5-1ubuntu2
  Candidate: 0.1.5-1ubuntu2
  Version table:
 *** 0.1.5-1ubuntu2 0
        500 http://tw.archive.ubuntu.com intrepid/universe Packages
        100 /var/lib/dpkg/status

root@intrepid:~# LANG=C apt-cache policy jfbterm
jfbterm:
  Installed: 0.4.7-7.2
  Candidate: 0.4.7-7.2
  Version table:
 *** 0.4.7-7.2 0
        500 http://tw.archive.ubuntu.com intrepid/universe Packages
        100 /var/lib/dpkg/status

追蹤 jfbterm 的 deb package 原始碼

root@intrepid:~# apt-get build-dep jfbterm
root@intrepid:~# apt-get install dpkg-dev
root@intrepid:~# apt-get source jfbterm

uvesafb 作者的推測:

As to why the console becomes unresponsive after exiting jfbterm --
jfbterm sets KD_GRAPHICS mode on the console on which it is started,
and apparently fails to set it back to KD_TEXT before segfaulting.  This
leaves the console in the broken state.

尋找合理懷疑對象(1):

root@intrepid:~/jfbterm-0.4.7# grep "KD_GRAPHICS" *
vterm.c:        ioctl(0, KDSETMODE, KD_GRAPHICS);

root@intrepid:~/jfbterm-0.4.7# grep "KD_TEXT" *
main.c:        if (mode == KD_TEXT) {
vterm.c:        ioctl(0, KDSETMODE, KD_TEXT);

BUGFIX: jfbterm (2)

08-11-16@GMT-6 原紀錄 BUGFIX: jfbterm (2)

尋找合理懷疑對象(2):

root@intrepid:~/jfbterm-0.4.7# grep "cannot mmap" *
fbcommon.c:             die("cannot mmap(smem)");
fbcommon.c:             die("cannot mmap(mmio)");
fbcommon.c:             print_message("cannot mmap(mmio) : %s\n", strerror(errno));

啟用 DEBUG 旗標，編譯 jfbterm，使用 gdb 追蹤

root@intrepid:~/jfbterm-0.4.7# ./configure --enable-debug
root@intrepid:~/jfbterm-0.4.7# make
root@intrepid:~/jfbterm-0.4.7# gdb ./jfbterm
(gdb) run

縱使用 gdb 還是無法正常跳回文字模式，因此直接追原始碼。
- [後記] uvesafb 作者的猜測確實合理，因為已經進入圖形模式，除非跳回文字模式，否則所有輸入輸出都不會正常顯示在畫面上。

根據錯誤訊息,應該是錯在 fbcommon.c 的第 572 行，往前追造成錯誤的原因是 566 行的 mmap()，歸屬在 tfbm_open() 函數

< fbcommon.c >

482 void tfbm_open(TFrameBufferMemory* p)

566         p->mmio = (u_char*)mmap(NULL, p->mlen, PROT_READ|PROT_WRITE,
567                                 MAP_SHARED, p->fh, p->slen);
568         if ((long)p->mmio == -1) {
569 #ifdef JFB_MMIO_CHECK
570                 die("cannot mmap(mmio)");
571 #else
572                 print_message("cannot mmap(mmio) : %s\n", strerror(errno));
573 #endif

< main.c >

368 int main(int argc, char *argv[])
431         tfbm_open(&gFramebuffer);

安裝 manpages-dev 套件，查 mmap 、 strerror 跟 errno 的 manpage。從 cannot mmap(mmio) : Invalid argument 這個錯誤訊息可以判斷 errno 等於 EINVAL。而 mmap 發生 EINVAL 的情形有三種，最可能的原因是第一個：We don't like addr, length, or offset (e.g., they are too large, or not aligned on a page boundary).

這裡注意到 mmap 的 offset 參數必須是 sysconf 中定義 _SC_PAGE_SIZE 的倍數。(offset must be a multiple of the page size as returned by sysconf(_SC_PAGE_SIZE).)

root@intrepid:~/jfbterm-0.4.7# apt-get install manpages-dev

root@intrepid:~/jfbterm-0.4.7# man errno

       EINVAL          Invalid argument (POSIX.1)

void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset);

offset must be a multiple of the page size as returned by sysconf(_SC_PAGE_SIZE).

ERRORS
       EINVAL We don't like addr, length, or offset (e.g., they are too large, or not aligned on a page boundary).
       EINVAL (since Linux 2.6.12) length was 0.
       EINVAL flags contained neither MAP_PRIVATE or MAP_SHARED, or contained both of these values.

使用 gdb 設定中斷點在 fbcomm.c 第 566 行並觀察變數狀態

root@intrepid:~/jfbterm-0.4.7# gdb
(gdb) file jfbterm
Reading symbols from /root/jfbterm-0.4.7/jfbterm...done.
(gdb) set args -e ls
(gdb) show args
Argument list to give program being debugged when it is started is "-e ls".
(gdb) break fbcommon.c:566
Breakpoint 1 at 0x4034ba: file fbcommon.c, line 566.
(gdb) run
... 略 ...
Breakpoint 1, tfbm_open (p=0x6146e0) at fbcommon.c:566
566             p->mmio = (u_char*)mmap(NULL, p->mlen, PROT_READ|PROT_WRITE,
(gdb) l
561             }
562             p->smem = (char *)p->smem + p->soff;
563
564             p->moff = (u_long)(fb_fix.mmio_start) & (~PAGE_MASK);
565             p->mlen = (fb_fix.mmio_len + p->moff + ~PAGE_MASK) & PAGE_MASK;
566             p->mmio = (u_char*)mmap(NULL, p->mlen, PROT_READ|PROT_WRITE,
567                                     MAP_SHARED, p->fh, p->slen);
568             if ((long)p->mmio == -1) {
569     #ifdef JFB_MMIO_CHECK
570                     die("cannot mmap(mmio)");
(gdb) p fb_fix.mmio_len
$1 = 0
(gdb) p p->moff
$2 = 0
(gdb) p p->mlen
$3 = 0
(gdb) p p->fh
$4 = 6
(gdb) p p->slen
$5 = 1572864
(gdb) p fb_fix.smem_len
$6 = 1572864

BUGFIX: jfbterm (3)

08-11-17@GMT-6 原紀錄 BUGFIX: jfbterm (3)

mmap 的 offset 參數必須是 sysconf 中定義 _SC_PAGE_SIZE 的倍數。(offset must be a multiple of the page size as returned by sysconf(_SC_PAGE_SIZE).)
使用 gdb 設定中斷點在 fbcomm.c 第 566 行並觀察變數狀態，可以知道送到 mmap 函數的 offset 參數內容為 1572864 。
```
(gdb) p p->slen
$5 = 1572864
```

為了確認 offset 參數是否為 _SC_PAGESIZE 的整數倍，先撰寫測試程式，用 sysconf 取得目前系統的 _SC_PAGESIZE 屬性。

root@intrepid:~# cat > get_sc_pagesize.c << EOF
#include <unistd.h>
#include <stdio.h>

int main()
{
  printf("_SC_PAGESIZE = %ld\n",sysconf(_SC_PAGESIZE));
}
EOF
root@intrepid:~# gcc get_sc_pagesize.c -o get_sc_pagesize
root@intrepid:~# ./get_sc_pagesize
_SC_PAGESIZE = 4096

根據 mmap 的 manpages，產生 EINVAL 錯誤的另一個原因是 length 等於零(從 Linux 2.6.12 以後)，確認主因為 length 參數 = p->mlen = 0

MMAP(2): void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset);
MMAP(2): EINVAL (since Linux 2.6.12) length was 0.

566             p->mmio = (u_char*)mmap(NULL, p->mlen, PROT_READ|PROT_WRITE,
567                                     MAP_SHARED, p->fh, p->slen);
(gdb) p p->mlen
$3 = 0

避開 mmap 回傳零的修正

jfbterm-0.4.

diff -Naur jfbterm-0.4.7/fbcommon.c jfbterm-0.4.7-dev/fbcommon.c

-                      old
+                      new
        p->moff = (u_long)(fb_fix.mmio_start) & (~PAGE_MASK);
        p->mlen = (fb_fix.mmio_len + p->moff + ~PAGE_MASK) & PAGE_MASK;
+       p->mmio = (u_char*)mmap(NULL, p->mlen, PROT_READ|PROT_WRITE,
+       if(p->mlen == 0)
+       {
+         p->mmio = 0;
+       } else {
+         p->mmio = (u_char*)mmap(NULL, p->mlen, PROT_READ|PROT_WRITE,
                                MAP_SHARED, p->fh, p->slen);
+       }
        if ((long)p->mmio == -1) {
 #ifdef JFB_MMIO_CHECK
                die("cannot mmap(mmio)");

BUGFIX: jfbterm (4)

09-01-14@GMT+8 原紀錄 BUGFIX: jfbterm (4)

在看 fbcommon.c 時，發現在這組出現錯誤的 mmap 前曾跑過另一組 mmap, 因此把參數印出來對照看看。

gdb debug 程序

file jfbterm
set args -e ls
show args
break fbcommon.c:500
break fbcommon.c:557
break fbcommon.c:566
run
p fb_fix
c
p fb_fix
c
p fb_fix.smem_len
p p->soff
p p->slen
p fb_fix.mmio_len
p p->moff
p p->mlen

root@intrepid:~/jfbterm-0.4.7-dev# gdb
GNU gdb 6.8-debian
Copyright (C) 2008 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
(gdb) file jfbterm
Reading symbols from /root/jfbterm-0.4.7-dev/jfbterm...done.
(gdb) set args -e ls
(gdb) show args
Argument list to give program being debugged when it is started is "-e ls".
(gdb) break fbcommon.c:500
Breakpoint 1 at 0x40303d: file fbcommon.c, line 500.
(gdb) break fbcommon.c:557
Breakpoint 2 at 0x40327e: file fbcommon.c, line 557.
(gdb) break fbcommon.c:566
Breakpoint 3 at 0x403301: file fbcommon.c, line 566.
(gdb) run
Starting program: /root/jfbterm-0.4.7-dev/jfbterm -e ls
...略...
Breakpoint 1, tfbm_open (p=0x6146e0) at fbcommon.c:501
501             if (fb_var.yres_virtual != fb_var.yres) {
(gdb) p fb_fix
$1 = {id = "▒\204▒▒Q\177\000\000\006\000\000\000\000\000\000", smem_start = 21037808, 
  smem_len = 4269392626, type = 32593, type_aux = 0, visual = 0,
  xpanstep = 65535, ypanstep = 65535, ywrapstep = 65535, line_length = 1, mmio_start = 15, 
  mmio_len = 21076240, accel = 0, reserved = {53071, 64, 0}}
(gdb) c
Continuing.
...略...
Breakpoint 2, tfbm_open (p=0x6146e0) at fbcommon.c:557
557             p->smem = (u_char*)mmap(NULL, p->slen, PROT_READ|PROT_WRITE,
(gdb) p fb_fix
$2 = {id = "VESA VGA\000\000\000\000\000\000\000", smem_start = 4026531840, 
  smem_len = 1572864, type = 0, type_aux = 0, visual = 3, xpanstep = 0,
  ypanstep = 0, ywrapstep = 0, line_length = 1024, mmio_start = 0, 
  mmio_len = 0, accel = 0, reserved = {0, 0, 0}}
(gdb) c
Continuing.

Breakpoint 3, tfbm_open (p=0x6146e0) at fbcommon.c:566
566             if(p->mlen == 0)
(gdb) p fb_fix.smem_len
$3 = 1572864
(gdb) p p->soff
$4 = 0
(gdb) p p->slen
$5 = 1572864
(gdb) p fb_fix.mmio_len
$6 = 0
(gdb) p p->moff
$7 = 0
(gdb) p p->mlen
$8 = 0

fb_fix.smem_len = 1572864	p->soff = 0	p->slen = 1572864	mmap 成功
fb_fix.mmio_len = 0	p->moff = 0	p->mlen = 0	mmap 失敗 (因為 length = 0)

從數據看起來，無論是從 SSH 登入，或在本機 tty 使用，所得到的 fb_fix.mmio_len = 0 是主要原因。只是 mmio 所代表的意涵，fbcommon.h 程式碼並無註解。

繼續往 fb_fix.mmio_len 的源頭追，是 tfbm_get_fix_screen_info 函式去更新 fb_fix 這個結構。資料是透過 ioctl 去詢問核心中對應的 FBIOGET_FSCREENINFO。

<fbcommon.c>

509         tfbm_get_fix_screen_info(p->fh, &fb_fix);

244 static void tfbm_get_fix_screen_info(int fh, struct fb_fix_screeninfo *fix)
245 {
246         if (ioctl(fh, FBIOGET_FSCREENINFO, fix)) {
247                 print_strerror_and_exit("ioctl FBIOGET_FSCREENINFO");
248         }
249 }

定義在 Kernel 2.6.11/drivers/video/fbmem.c 中 FBIOGET_FSCREENINFO 的 ioctl handler

 804        case FBIOGET_FSCREENINFO:
 805                return copy_to_user(argp, &info->fix,
 806                                    sizeof(fix)) ? -EFAULT : 0;

定義在 Kernel 2.6.27/drivers/video/fbmem.c 中 FBIOGET_FSCREENINFO 的 ioctl handler

1247        case FBIOGET_FSCREENINFO:
1248                ret = fb_get_fscreeninfo(inode, file, cmd, arg);
1249                break;

fb_get_fscreeninfo 會呼叫 fb_ioctl 並以 cmd = FBIOGET_FSCREENINFO 去處理，看起來最後執行的程式碼是跟 2.6.11 一樣。

1013 static int 
1014 fb_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
1015          unsigned long arg)

1018        struct fb_info *info = registered_fb[fbidx];

1046        case FBIOGET_FSCREENINFO:
1047                return copy_to_user(argp, &info->fix,
1048                                    sizeof(fix)) ? -EFAULT : 0;

從 fb.h 的定義，我們可以確定 mmio_len 是從 info (型態為 fb_info) 結構中抓出 fb_fix_screeninfo 型態的 fix 回傳給使用者。

<linux-2.6.27.7/include/linux/fb.h>

 152 struct fb_fix_screeninfo {

 156        __u32 smem_len;                 /* Length of frame buffer mem */

 164        unsigned long mmio_start;       /* Start of Memory Mapped I/O   */
 165                                        /* (physical address) */
 166        __u32 mmio_len;                 /* Length of Memory Mapped I/O  */

 808 struct fb_info {

 811        struct fb_var_screeninfo var;   /* Current var */
 812        struct fb_fix_screeninfo fix;   /* Current fix */

目前懷疑是 uvesafb 攔截了 FBIOGET_FSCREENINFO 的 ioctl 並回傳了不正確的 fb_fix_screeninfo 內容。因此先來寫一個測試程式，透過 FBIOGET_FSCREENINFO 的 ioctl 把 fb_fix_screeninfo 內容取出來。
- [參考] http://www.harlan.idv.tw/Computer/EmbeddedLinux/Chapter4.htm

BUGFIX: jfbterm (5)

09-02-01@GMT+8 原紀錄 BUGFIX: jfbterm (5)

#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>       // include frame buffer header files
#include <sys/ioctl.h>

int main(void)
{
  int fbfd = 0 ;            // frame buffer file description

  /* Get device independent unchangeable information about a frame buffer
   * device and a specific video mode by FBIOGET_FSCREENINFO ioctl. */
  struct  fb_fix_screeninfo finfo;

  fbfd = open( "/dev/fb0" , O_RDWR );
  if ( !fbfd )
  {
    printf( "Error: cannot open framebuffer device.\n" );
    exit(1);
  }
  printf("The framebuffer device was opened successfully.\n");

  /* Get fixed screen information */
  if ( ioctl ( fbfd ,  FBIOGET_FSCREENINFO , &finfo )  )
  {
    printf("Error reading fixed screen information.\n");
    exit(2);
  } else {
    printf("Succesfully Read the Fixed Screen Information\n");
  }

  printf("fb_fix_screeninfo.smem_len = %d\n", finfo.smem_len);
  printf("fb_fix_screeninfo.mmio_len = %d\n", finfo.mmio_len);
}

在 Ubuntu Intrepid 上執行結果

root@intrepid:~# uname -a
Linux intrepid 2.6.27-7-server #1 SMP Tue Nov 4 20:16:57 UTC 2008 x86_64 GNU/Linux
root@intrepid:~# ./fbinfo
The framebuffer device was opened successfully.
Succesfully Read the Fixed Screen Information
fb_fix_screeninfo.smem_len = 16777216
fb_fix_screeninfo.mmio_len = 0

以下是在 Debian Sarge 上執行結果，值得一提的是 jfbterm 在 2.6.8 核心上可以正常執行。(不過還有字型問題需要調整)

root@wsu-admin:~# uname -a
Linux wsu-admin 2.6.8-2-386 #1 Tue Aug 16 12:46:35 UTC 2005 i686 GNU/Linux
root@wsu-admin:~# ./fbinfo
The framebuffer device was opened successfully.
Succesfully Read the Fixed Screen Information
fb_fix_screeninfo.smem_len = 65536
fb_fix_screeninfo.mmio_len = 0

root@wsu-admin:~# jfbterm
jfbterm - Kanji on framebuffer console Version 0.4.7
       Copyright (C) 2003 Fumitoshi UKAI
        Copyright (C) 1999-2000 Noritoshi Masuichi
This program is based on KON2
        Copyright (C) 1992-1996 Takashi MANABE

(**) : Configuration file `/etc/jfbterm.conf'
.... 略 ....
exec : /bin/bash ioctl FBIOGET_CON2FBMAP: Invalid argument
color 0 : 0, 0
color 1 : 2a, 2a
color 2 : 2a, 2a
color 3 : 2a, 2a
color 4 : 2a, 2a
color 5 : 2a, 2a
color 6 : 2a, 2a
color 7 : 2a, 2a
color 8 : 15, 15
color 9 : 3f, 3f
color 10 : 3f, 3f
color 11 : 3f, 3f
color 12 : 3f, 3f
color 13 : 3f, 3f
color 14 : 3f, 3f
color 15 : 3f, 3f

以下是在 Debian Etch 上執行結果，有趣的是 jfbterm 0.4.7-7 在 2.6.18-4 上執行，縱使有 cannot mmap(mmio) : Invalid argument 的錯誤訊息，但仍舊可以正常進入 jfbterm 的環境。

root@etch:~# uname -a
Linux etch 2.6.18-4-686 #1 SMP Wed May 9 23:03:12 UTC 2007 i686 GNU/Linux
root@etch:~# ./fbinfo
The framebuffer device was opened successfully.
Succesfully Read the Fixed Screen Information
fb_fix_screeninfo.smem_len = 1920000
fb_fix_screeninfo.mmio_len = 0

root@etch:~# jfbterm
jfbterm - Kanji on framebuffer console Version 0.4.7
       Copyright (C) 2003 Fumitoshi UKAI
        Copyright (C) 1999-2000 Noritoshi Masuichi
This program is based on KON2
        Copyright (C) 1992-1996 Takashi MANABE

(**) : Configuration file `/etc/jfbterm.conf'
... 略 ...
exec : /bin/bash color 0 : 0, 0
color 1 : 15, 15
color 2 : 540, 540
color 3 : 555, 555
color 4 : a800, a800
color 5 : a815, a815
color 6 : ad40, ad40
color 7 : ad55, ad55
color 8 : 52aa, 52aa
color 9 : 52bf, 52bf
color 10 : 57ea, 57ea
color 11 : 57ff, 57ff
color 12 : faaa, faaa
color 13 : fabf, fabf
color 14 : ffea, ffea
color 15 : ffff, ffff
cannot mmap(mmio) : Invalid argument

為了測試 jfbterm 的中文相容性，我們寫了一隻簡單的 script

#!/bin/bash
echo " TEST 中文測試 "
echo "Press Any Key to continue!"
read

在 Ubutnu intriped 的 tty1 上執行 jfbterm -f /etc/jfbterm.conf -e /root/test.sh 可以正常看到" TEST 中文測試 "字樣，但卻無法正常跳出，因此我們再來 DEBUG 一下。

file jfbterm
set args -f /etc/jfbterm.conf -e /root/test.sh
show args
break fbcommon.c:500
break fbcommon.c:557
break fbcommon.c:566
break term.c:103
break term.c:284
r
c
c
c
bt
c
bt
p utp->ut_time
p utp->ut_tv

Breakpoint 4, tterm_final (p=0x6147c0) at term.c:103
(gdb) bt
#0  tterm_final (p=0x6147c0) at term.c:103
#1  0x0000000000408adf in sigchld (sig=<value optimized out>) at term.c:82
#2  <signal handler called>
#3  0x00007f5dfc00f433 in select () from /lib/libc.so.6
#4  0x0000000000408873 in tterm_start (p=0x6147c0, tn=<value optimized out>, en=<value optimized out>) at term.c:192
#5  0x0000000000402cf2 in main (argc=<value optimized out>, argv=0x7fff049477f8) at main.c:438
(gdb) c
Continuing.

Breakpoint 5, tterm_reset_utmp (p=<value optimized out>) at term.c:284
(gdb) bt
#0  tterm_reset_utmp (p=<value optimized out>) at term.c:284
#1  0x0000000000408a50 in tterm_final (p=0xe) at term.c:103
#2  0x0000000000408adf in sigchld (sig=<value optimized out>) at term.c:82
#3  <signal handler called>
#4  0x00007fa268131433 in select () from /lib/libc.so.6
#5  0x0000000000408873 in tterm_start (p=0x6147c0, tn=<value optimized out>, en=<value optimized out>) at term.c:192
#6  0x0000000000402cf2 in main (argc=<value optimized out>, argv=0x7fff70a69328) at main.c:438
(gdb) p utp->ut_time
There is no member named ut_time.

[註] utp->ut_time = utp->ut_tv.tv_sec

< /usr/include/bits/utmp.h >

 59 /* The structure describing an entry in the user accounting database.  */
 60 struct utmp
 61 {
 62   short int ut_type;            /* Type of login.  */
 63   pid_t ut_pid;                 /* Process ID of login process.  */
 64   char ut_line[UT_LINESIZE];    /* Devicename.  */
 65   char ut_id[4];                /* Inittab ID.  */
 66   char ut_user[UT_NAMESIZE];    /* Username.  */
 67   char ut_host[UT_HOSTSIZE];    /* Hostname for remote login.  */
 68   struct exit_status ut_exit;   /* Exit status of a process marked
 69                                    as DEAD_PROCESS.  */
 70 /* The ut_session and ut_tv fields must be the same size when compiled
 71    32- and 64-bit.  This allows data files and shared memory to be
 72    shared between 32- and 64-bit applications.  */
 73 #if __WORDSIZE == 64 && defined __WORDSIZE_COMPAT32
 74   int32_t ut_session;           /* Session ID, used for windowing.  */
 75   struct
 76   {
 77     int32_t tv_sec;             /* Seconds.  */
 78     int32_t tv_usec;            /* Microseconds.  */
 79   } ut_tv;                      /* Time entry was made.  */
 80 #else
 81   long int ut_session;          /* Session ID, used for windowing.  */
 82   struct timeval ut_tv;         /* Time entry was made.  */
 83 #endif
 84
 85   int32_t ut_addr_v6[4];        /* Internet address of remote host.  */
 86   char __unused[20];            /* Reserved for future use.  */
 87 };

 94 # define ut_time        ut_tv.tv_sec

GDB 線上除錯練習

[tty1]

root@etch:~# apt-get build-dep jfbterm
root@etch:~# apt-get source jfbterm
root@etch:~# apt-get install jfbterm
root@etch:~# cd jfbterm-0.4.7
root@etch:~/jfbterm-0.4.7# ./configure --enable-debug
root@etch:~/jfbterm-0.4.7# make
root@etch:~/jfbterm-0.4.7# ./jfbterm -f /etc/jfbterm.conf -e /root/test.sh

[tty2]

root@etch:~# gdb /root/jfbterm-0.4.7/jfbterm `pidof jfbterm`
GNU gdb 6.4.90-debian
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i486-linux-gnu"...Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".

Attaching to program: /root/jfbterm-0.4.7/jfbterm, process 7480
Reading symbols from /lib/tls/i686/cmov/libutil.so.1...done.
Loaded symbols for /lib/tls/i686/cmov/libutil.so.1
Reading symbols from /lib/tls/i686/cmov/libm.so.6...done.
Loaded symbols for /lib/tls/i686/cmov/libm.so.6
Reading symbols from /lib/tls/i686/cmov/libc.so.6...done.
Loaded symbols for /lib/tls/i686/cmov/libc.so.6
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
Reading symbols from /lib/tls/i686/cmov/libnss_compat.so.2...done.
Loaded symbols for /lib/tls/i686/cmov/libnss_compat.so.2
Reading symbols from /lib/tls/i686/cmov/libnsl.so.1...done.
Loaded symbols for /lib/tls/i686/cmov/libnsl.so.1
Reading symbols from /lib/tls/i686/cmov/libnss_nis.so.2...done.
Loaded symbols for /lib/tls/i686/cmov/libnss_nis.so.2
Reading symbols from /lib/tls/i686/cmov/libnss_files.so.2...done.
Loaded symbols for /lib/tls/i686/cmov/libnss_files.so.2
Failed to read a valid object file image from memory.
0xb7fea410 in ?? ()
(gdb) break term.c:284
Breakpoint 1 at 0x804f552: file term.c, line 284.
(gdb) c
Continuing.

Breakpoint 1, tterm_final (p=0x8058be0) at term.c:284
284             time(&(utp->ut_time));
(gdb) c
Continuing.

Breakpoint 1, tterm_final (p=0x8058be0) at term.c:284
284             time(&(utp->ut_time));
(gdb) c
Continuing.

Program exited normally.

GDB 遠端除錯練習

[tty1]
gdbserver 127.0.0.1:1234 /root/jfbterm-0.4.7/jfbterm
[pts1]
(gdb) target remote 127.0.0.1:1234

在 DEBUG 的時候偶爾會看到 <value optimized out>，但是該怎麼去掉呢??
- [參考] http://www.cs.utk.edu/~vose/c-stuff/onlinedocs/gdb_7.html - 不要最佳化 ( 查 gcc manpage 得知 -O0 可以取消最佳化 )
```
The values of arguments that were not saved in their stack frames are shown as `<value optimized out>'.

If you need to display the values of such optimized-out arguments, either deduce that from other variables whose values depend on the one you are interested in, or recompile without optimizations.
```
- [作法] 在 configure 的時候加上 CFLAGS
  - 註: 因為如果有設定 CFLAGS 的話，在 configure 裡是會直接採用我們提供的 CFLAGS。因此縱使加上 --enable-debug 也沒有用，configure 不會幫你加 -g 進去。
```
root@intrepid:~/jfbterm-0.4.7-dev# CFLAGS="-g -O0" ./configure
```

繼續追為何結束時會收到 SIGSEGV 的主因

< 直接在 tty1 或在 screen 中執行 >
root@intrepid:~/jfbterm-0.4.7-dev# ./jfbterm -f /etc/jfbterm.conf -e /root/test.sh

root@intrepid:~/jfbterm-0.4.7-dev# gdb ./jfbterm `pidof jfbterm`
break term.c:103
break term.c:284
c
#### 直接在 tty1 不透過 screen 執行 的結果 #####
Breakpoint 1, tterm_final (p=0x617a00) at term.c:103
103             tterm_reset_utmp(p);
(gdb) s
tterm_reset_utmp (p=0x617a00) at term.c:271
271     {
(gdb) s
275             tn = rindex(p->name, '/') + 4;
(gdb) p p->name
$1 = "/dev/pts/0", '\0' <repeats 53 times>
#### 直接在 tty1 有透過 screen 執行 的結果 #####

Breakpoint 1, tterm_final (p=0x617a00) at term.c:103
103             tterm_reset_utmp(p);
(gdb) s
tterm_reset_utmp (p=0x617a00) at term.c:271
271     {
(gdb) s
275             tn = rindex(p->name, '/') + 4;
(gdb) p p->name
$1 = "/dev/pts/1", '\0' <repeats 53 times>

manpage of getutid(3)

SYNOPSIS

       struct utmp *getutid(struct utmp *ut);

DESCRIPTION

       getutid() searches forward from the current file position in  the  utmp
       file  based  upon  ut.   If  ut->ut_type  is one of RUN_LVL, BOOT_TIME,
       NEW_TIME, or OLD_TIME,  getutid()  will  find  the  first  entry  whose
       ut_type  field matches ut->ut_type.  If ut->ut_type is one of INIT_PRO-
       CESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS, getutid() will find
       the first entry whose ut_id field matches ut->ut_id.

RETURN VALUE
       getutent(), getutid(), getutline() and pututline() return a pointer  to
       a  struct  utmp  on  success, and NULL on failure.  This struct utmp is
       allocated in static storage,  and  may  be  overwritten  by  subsequent
       calls.

FILES
       /var/run/utmp  database of currently logged-in users
       /var/log/wtmp  database of past user logins

NOTES
   Glibc Notes
       The above functions are not thread-safe.  Glibc adds reentrant versions

       #define _GNU_SOURCE    /* or _SVID_SOURCE or _BSD_SOURCE */
       #include <utmp.h>

       int getutent_r(struct utmp *ubuf, struct utmp **ubufp);

       int getutid_r(struct utmp *ut,
                     struct utmp *ubuf, struct utmp **ubufp);

       int getutline_r(struct utmp *ut,
                       struct utmp *ubuf, struct utmp **ubufp);

       These  functions  are  GNU  extensions, analogs of the functions of the
       same name without the _r suffix.  The ubuf parameter gives these  func-
       tions  a  place to store their result.  On success they return 0, and a
       pointer to the result is written in *ubufp.  On error  these  functions
       return -1.

root@intrepid:~# w
 02:02:14 up 6 min,  5 users,  load average: 0.35, 0.78, 0.39
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT
root     pts/0    :tty1:S.0        01:58    1:46m  0.24s  0.21s ./jfbterm -f /etc/jfbterm.conf -e /root/test.sh ### screen 0
root     pts/1    :tty1:S.1        01:58    3:55m  0.01s  0.01s /bin/bash                                       ### screen 1
root     pts/3    172.21.253.1     01:59    1:19m  0.12s  0.10s gdb ./jfbterm 3833                              ### from ssh for gdb
root     pts/2    -                01:59    1:46m  0.00s  0.21s ./jfbterm -f /etc/jfbterm.conf -e /root/test.sh ### fb created by jfbterm
root     pts/4    172.21.253.1     02:01    0.00s  0.02s  0.00s w                                               ### from ssh for this command `w'

Last modified 16 years ago Last modified on Feb 2, 2009, 2:18:44 AM

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