On 06/07/2016 12:19 AM, Oleg Nesterov wrote:
On 06/01, Dmitry Safonov wrote:
Note, that this will work only if application has changed it's CS.
So, suppose it changes it's CS and crashes,
If the application does 32-bit syscall with __USER_CS, ptrace
@@ -1355,7 +1355,7 @@ void update_regset_xstate_info(unsigned int size, u64
xstate_mask)
const struct user_regset_view *task_user_regset_view(struct task_struct *task)
{
#ifdef CONFIG_IA32_EMULATION
- if (test_tsk_thread_flag(task, TIF_IA32))
+ if (!user_64bit_mode(task_pt_regs(task)))
#endif
then coredump will do fill_elf_header(view->e_machine) and use EM_X86_64
instead of EM_386, or vice versa...
I simply can't understand is this better or worse, I guess gdb or any
other tool which looks at this coredump will be confused anyway.
Oleg, thanks for your reply!
At least, gdb will have all registers at that moment.
Firstly, I did it for returning with GET_REGSET corresponding
register set. So ptrace-attaching to a task with 64-bit code
selector would return 64-bit register set and contrariwise.
(as task may use all 64-bit registers, that seems logical
for me even if it has been loaded as 32-bit ELF)
And for coredump -- I guess it will show full register set
on the crash moment and show proper disasm around that place.
And for my purpose -- that's really what I need, to generate
32-bit ELF core file on crash after changing CS.
I did it for C/R of 32-bit application with changing code
selector from 64-bit. So last thing restorer does - unmap
itself (it's pie blob) and sigreturn to application.
So if the application crashes after it - it will be good
to have 32-bit coredump as for the original application.
Thanks,
Dmitry Safonov
