arm64: add on_accessible_stack()

Both unwind_frame() and dump_backtrace() try to check whether a stack
address is sane to access, with very similar logic. Both will need
updating in order to handle overflow stacks.

Factor out this logic into a helper, so that we can avoid further
duplication when we add overflow stacks.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>

diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 4c68d8a..92ddb6d 100644 (file)
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -57,4 +57,20 @@ static inline bool on_task_stack(struct task_struct *tsk, unsigned long sp)
        return (low <= sp && sp < high);
 }
 
+/*
+ * We can only safely access per-cpu stacks from current in a non-preemptible
+ * context.
+ */
+static inline bool on_accessible_stack(struct task_struct *tsk, unsigned long sp)
+{
+       if (on_task_stack(tsk, sp))
+               return true;
+       if (tsk != current || preemptible())
+               return false;
+       if (on_irq_stack(sp))
+               return true;
+
+       return false;
+}
+
 #endif /* __ASM_STACKTRACE_H */

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 35588ca..3144584 100644 (file)
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -50,12 +50,7 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
        if (!tsk)
                tsk = current;
 
-       /*
-        * Switching between stacks is valid when tracing current and in
-        * non-preemptible context.
-        */
-       if (!(tsk == current && !preemptible() && on_irq_stack(fp)) &&
-           !on_task_stack(tsk, fp))
+       if (!on_accessible_stack(tsk, fp))
                return -EINVAL;
 
        frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 9633773..d01c598 100644 (file)
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -193,8 +193,7 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
                if (in_entry_text(frame.pc)) {
                        stack = frame.fp - offsetof(struct pt_regs, stackframe);
 
-                       if (on_task_stack(tsk, stack) ||
-                           (tsk == current && !preemptible() && on_irq_stack(stack)))
+                       if (on_accessible_stack(tsk, stack))
                                dump_mem("", "Exception stack", stack,
                                         stack + sizeof(struct pt_regs));
                }