Changes between Version 3 and Version 4 of jazz/jfbterm

Timestamp:

Jan 15, 2009, 10:02:37 AM (17 years ago)

Author:

jazz

Comment:

--

jazz/jfbterm

@@ -298 +298 @@
                 die("cannot mmap(mmio)");
 }}}
+
+== BUGFIX: jfbterm (4) ==
+
+ * [wiki:jazz/09-01-4 09-01-14@GMT+8 原紀錄 BUGFIX: jfbterm (3)]
+
+ * 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 }
+}}}
+ * [http://lxr.linux.no/linux+v2.6.11/drivers/video/fbmem.c#L804 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;
+}}}
+ * [http://lxr.linux.no/linux+v2.6.27.7/drivers/video/fbmem.c#L1247 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