From: Sergei Trofimovich slyfox@gentoo.org Subject: ia64: fix user_stack_pointer() for ptrace()
ia64 has two stacks: - memory stack (or stack), pointed at by by r12 - register backing store (register stack), pointed at ar.bsp/ar.bspstore with complications around dirty register frame on CPU.
In https://bugs.gentoo.org/769614 Dmitry noticed that PTRACE_GET_SYSCALL_INFO returns 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://lkml.kernel.org/r/20210331084447.2561532-1-slyfox@gentoo.org Link: https://bugs.gentoo.org/769614 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 ---
arch/ia64/include/asm/ptrace.h | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-)
--- a/arch/ia64/include/asm/ptrace.h~ia64-fix-user_stack_pointer-for-ptrace +++ a/arch/ia64/include/asm/ptrace.h @@ -54,8 +54,7 @@
static inline unsigned long user_stack_pointer(struct pt_regs *regs) { - /* FIXME: should this be bspstore + nr_dirty regs? */ - return regs->ar_bspstore; + return regs->r12; }
static inline int is_syscall_success(struct pt_regs *regs) @@ -79,11 +78,6 @@ static inline long regs_return_value(str unsigned long __ip = instruction_pointer(regs); \ (__ip & ~3UL) + ((__ip & 3UL) << 2); \ }) -/* - * Why not default? Because user_stack_pointer() on ia64 gives register - * stack backing store instead... - */ -#define current_user_stack_pointer() (current_pt_regs()->r12)
/* given a pointer to a task_struct, return the user's pt_regs */ # define task_pt_regs(t) (((struct pt_regs *) ((char *) (t) + IA64_STK_OFFSET)) - 1) _