我使用bt命令查看堆栈跟踪.输出是
(gdb) bt #0 0x001ae4cd in Debugger (message=0x1 "???\a") at /SourceCache/xnu/xnu-1228.7.58/osfmk/i386/AT386/model_dep.c:705 #1 0x3bf97000 in ?? () #2 0x0012b0fa in panic (str=0x5ef "") at /SourceCache/xnu/xnu-1228.7.58/osfmk/kern/debug.c:274 #3 0x001a8cd4 in kernel_trap (state=0x51a67c80) at /SourceCache/xnu/xnu-1228.7.58/osfmk/i386/trap.c:680 #4 0x0019ede5 in return_from_trap () at pmap.h:176 #5 0x00132bea in __doprnt (fmt=<value temporarily unavailable,due to optimizations>,argp=0x51a67e6c,putc=0x38ad24 <kvprintf+33>,arg=0x51a67e48,radix=10) at /SourceCache/xnu/xnu-1228.7.58/osfmk/kern/printf.c:439 #6 0x0038ad11 in kvprintf (fmt=0x1 "???\a",func=0x1,arg=0x1,radix=1,ap=0x51a67e84 "\\?\034I\"") at /SourceCache/xnu/xnu-1228.7.58/bsd/kern/subr_prf.c:525 #7 0x491b5dac in com_my_drv_Log (format=0x491cbff8 "%s::%s:%n\n") at Logger.cpp:37 #8 0x491b3d36 in MyDrv::init (this=0x5c1f200,properties=0x58a8040) at MyDrv.cpp:34 #9 0x00412887 in IOService::probeCandidates (this=0x599a980,matches=0x58ade80) at /SourceCache/xnu/xnu-1228.7.58/iokit/Kernel/IOService.cpp:2512 #10 0x004124ab in IOService::doServiceMatch (this=0x534180,options=8) at /SourceCache/xnu/xnu-1228.7.58/iokit/Kernel/IOService.cpp:2921 #11 0x00411127 in _IOConfigThread::main (self=0x58c6790) at /SourceCache/xnu/xnu-1228.7.58/iokit/Kernel/IOService.cpp:3125 (gdb)
在框架
#7 0x491b5dac in com_my_drv_Log
我如何查看通过签名传递给我的com_my_drv_Log的参数
void com_my_drv_Log (const char* format,...); /* with the variable argument list */
？
解决方法
看起来像这样可以做一个简单的程序：
#include <stdarg.h> #include <stdio.h> void myfunc(const char *fmt,...) { va_list args; va_start(args,fmt); vprintf(fmt,args); va_end(args); return; } int main(int argc,char *argv[]) { myfunc("test 1: %s %s\n","one","two"); myfunc("test 2: %s %d %c\n","apple",222,'y'); return 0; }
这是gdb会话示例：
$gdb testprog GNU gdb (GDB) 7.1-debian [snip] Reading symbols from /home/user/testprog...done. (gdb) break myfunc Breakpoint 1 at 0x400552: file testprog.c,line 7. (gdb) run Starting program: /home/user/testprog Breakpoint 1,myfunc (fmt=0x4006f4 "test 1: %s %s\n") at testprog.c:7 7 va_start(args,fmt); (gdb) # initialize args to hold correct values: (gdb) step 8 vprintf(fmt,args); (gdb) # print first argument in "..." list which we know is a char*: (gdb) p *(char **)(((char *)args[0].reg_save_area)+args[0].gp_offset) $1 = 0x4006f0 "one"
