wiki:jazz/08-11-16

  1. 2008-11-16
    1. Event: SC'08
    2. BUGFIX: jfbterm (2)
    3. UCIMF - jfbterm patch (中文輸入)
    4. Debian
    5. 職場態度
    6. Web Service
    7. Open Source

2008-11-16

Event: SC'08

BUGFIX: jfbterm (2)

  • （續 08-11-15@GMT-6）尋找合理懷疑對象: 
    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);

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。
  • 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

UCIMF - jfbterm patch (中文輸入)

Debian

職場態度

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Web Service

Open Source

Last modified 16 years ago Last modified on Nov 18, 2008, 3:43:17 AM