xtensa: Implement "current_stack_pointer"

To follow the existing per-arch conventions replace open-coded uses
of asm "sp" as "current_stack_pointer". This will let it be used in
non-arch places (like HARDENED_USERCOPY).

Cc: Chris Zankel <chris@zankel.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: linux-xtensa@linux-xtensa.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Link: https://lore.kernel.org/lkml/CAMo8BfJFJE-n3=AF+pb9_6oF3gzxX7a+7aBrASHjjNX5byqDqw@mail.gmail.com

diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index 8ac599aa6d994780f67445646ef0a571de0bed53..887432327613103c3a28a4a12d89e43dead50bff 100644 (file)
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -3,6 +3,7 @@ config XTENSA
        def_bool y
        select ARCH_32BIT_OFF_T
        select ARCH_HAS_BINFMT_FLAT if !MMU
+       select ARCH_HAS_CURRENT_STACK_POINTER
        select ARCH_HAS_DMA_PREP_COHERENT if MMU
        select ARCH_HAS_SYNC_DMA_FOR_CPU if MMU
        select ARCH_HAS_SYNC_DMA_FOR_DEVICE if MMU

diff --git a/arch/xtensa/include/asm/current.h b/arch/xtensa/include/asm/current.h
index 5d98a7ad4251b7ac4abd3a7416dd77bf994feaa9..08010dbf5e09a3cbc0c325c91dbe0b19764ddf6a 100644 (file)
--- a/arch/xtensa/include/asm/current.h
+++ b/arch/xtensa/include/asm/current.h
@@ -26,6 +26,8 @@ static inline struct task_struct *get_current(void)
 
 #define current get_current()
 
+register unsigned long current_stack_pointer __asm__("a1");
+
 #else
 
 #define GET_CURRENT(reg,sp)            \

diff --git a/arch/xtensa/include/asm/stacktrace.h b/arch/xtensa/include/asm/stacktrace.h
index fe06e8ed162b754ce2c6cceec4ddb9682030f088..a85e785a628884fad2e6ac0fcc4a0a2d27b40bcb 100644 (file)
--- a/arch/xtensa/include/asm/stacktrace.h
+++ b/arch/xtensa/include/asm/stacktrace.h
@@ -19,14 +19,14 @@ struct stackframe {
 
 static __always_inline unsigned long *stack_pointer(struct task_struct *task)
 {
-       unsigned long *sp;
+       unsigned long sp;
 
        if (!task || task == current)
-               __asm__ __volatile__ ("mov %0, a1\n" : "=a"(sp));
+               sp = current_stack_pointer;
        else
-               sp = (unsigned long *)task->thread.sp;
+               sp = task->thread.sp;
 
-       return sp;
+       return (unsigned long *)sp;
 }
 
 void walk_stackframe(unsigned long *sp,

diff --git a/arch/xtensa/kernel/irq.c b/arch/xtensa/kernel/irq.c
index 15051a8a153998efe65196aecbfbf6dc91af1e02..529fe9245821948823bc42883c6535f21ffbeb2b 100644 (file)
--- a/arch/xtensa/kernel/irq.c
+++ b/arch/xtensa/kernel/irq.c
@@ -36,9 +36,8 @@ asmlinkage void do_IRQ(int hwirq, struct pt_regs *regs)
 #ifdef CONFIG_DEBUG_STACKOVERFLOW
        /* Debugging check for stack overflow: is there less than 1KB free? */
        {
-               unsigned long sp;
+               unsigned long sp = current_stack_pointer;
 
-               __asm__ __volatile__ ("mov %0, a1\n" : "=a" (sp));
                sp &= THREAD_SIZE - 1;
 
                if (unlikely(sp < (sizeof(thread_info) + 1024)))