ia64 has two stacks:
- memory stack (or stack), pointed at by by r12
- register backing store (register stack), pointed at by
ar.bsp/ar.bspstore with complications around dirty
register frame on CPU.
In [1] Dmitry noticed that PTRACE_GET_SYSCALL_INFO returns the register
stack instead memory stack.
The bug comes from the fact that user_stack_pointer() and
current_user_stack_pointer() don't return the same register:
ulong user_stack_pointer(struct pt_regs *regs) { return regs->ar_bspstore; }
#define current_user_stack_pointer() (current_pt_regs()->r12)
The change gets both back in sync.
I think ptrace(PTRACE_GET_SYSCALL_INFO) is the only affected user by
this bug on ia64.
The change fixes 'rt_sigreturn.gen.test' strace test where it was
observed initially.
Link: https://bugs.gentoo.org/769614 [1]
Link: https://lkml.kernel.org/r/20210331084447.2561532-1-slyfox@gentoo.org
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Reported-by: Dmitry V. Levin <ldv@altlinux.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
7ad1e36616