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.
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: Oleg Nesterov <oleg@xxxxxxxxxx>
CC: linux-ia64@xxxxxxxxxxxxxxx
Bug: https://bugs.gentoo.org/769614
Reported-by: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
Signed-off-by: Sergei Trofimovich <slyfox@xxxxxxxxxx>
---
arch/ia64/include/asm/ptrace.h | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/arch/ia64/include/asm/ptrace.h b/arch/ia64/include/asm/ptrace.h
index b3aa46090101..08179135905c 100644
--- a/arch/ia64/include/asm/ptrace.h
+++ b/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(struct pt_regs *regs)
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)
--
2.31.1
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