Messages in this thread | | | Date | Wed, 21 Nov 2012 15:16:27 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH] arch_check_bp_in_kernelspace: fix the range check |
| |
Hi Amnon,
Please read my previous email ;) http://marc.info/?l=linux-kernel&m=135342649119153
On 11/21, u3557@miso.sublimeip.com wrote: > > Hi Oleg, > > > Or. Perhaps we can define TRAP_VSYSCALL and change emulate_vsyscall() to > > do > > > > > > if (current->ptrace && test_thread_flag(TIF_SYSCALL_TRACE)) > > send_sigtrap(TRAP_VSYSCALL, ...); > > > > if it returns true? > > > > I wish it were possible, but the vsyscall page is entered in user-mode,
Only in NATIVE mode. emulate_vsyscall() runs in kernel mode.
And in the NATIVE mode PTRACE_SYSCALL should work just fine, because:
> The vsyscall page was designed in order to avoid user/kernel context > switches,
True, it was. But not today. Please look at __vsyscall_page:
__vsyscall_page:
mov $__NR_gettimeofday, %rax syscall ret
If you want the "fast" sys_time() without entering the kernel, you can use __vdso_time(). And since vdso has the user-space mapping you can insert "int3" or use hw breakpoints.
At least this is my understanding after I glanced at the new implementation.
However. It is not that I think that TRAP_VSYSCALL is really good idea. At least it needs another option...
Oleg.
| |