[Libunwind-devel] _UPT_access_* functions don't seem to work.

[Abhishek Kulkarni]

Hello,

Are the _UPT_access_* functions from libunwind-ptrace deprecated? The man-page documentation[1] for these functions is lacking and I don't really understand why they should be used over the corresponding unw_get_* functions. It seems like the former don't work as expected in some cases.

Like the documentation suggests, I am creating an address-space, a UPT-info structure and doing the remote initialization (using unw_init_remote) and then with:

 while (unw_step(&cursor) > 0) {

  _UPT_access_reg(uaddrspace, UNW_REG_IP, &ip, 0, upt_info);

  _UPT_get_proc_name(uaddrspace, ip, name, 128, &val, upt_info);

 printf("-- fn = %s, ip = %lx\n", name, (long)ip);

 }

I was hoping to get the backtrace of the remote process, but it just prints the same thing multiple times (I tried to flush the cache explicitly but it didn't make a difference). Instead, I can get the backtrace successfully using the following:

 while (unw_step(&cursor) > 0) {

 unw_get_reg(&cursor, UNW_REG_IP, &ip);

 unw_get_proc_name(&cursor, name, 128, 0);

 //_UPT_access_reg(uaddrspace, UNW_REG_IP, &ip, 0, upt_info);

 //_UPT_get_proc_name(uaddrspace, ip, name, 128, &val, upt_info);

 printf("-- fn = %s, ip = %lx\n", name, (long)ip);

 }

Am I missing something with how the _UPT_access_* functions are to be used?

Thanks,

Abhishek

[1] http://www.nongnu.org/libunwind/man/libunwind-ptrace(3).html