arm64: factor out entry stack manipulation

In subsequent patches, we will detect stack overflow in our exception
entry code, by verifying the SP after it has been decremented to make
space for the exception regs.

This verification code is small, and we can minimize its impact by
placing it directly in the vectors. To avoid redundant modification of
the SP, we also need to move the initial decrement of the SP into the
vectors.

As a preparatory step, this patch introduces kernel_ventry, which
performs this decrement, and updates the entry code accordingly.
Subsequent patches will fold SP verification into kernel_ventry.

There should be no functional change as a result of this patch.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
[Mark: turn into prep patch, expand commit msg]
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: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index f31c7b26a6869cd78a1905f39e539a936e17f679..58eba94279c53ec473b3d7b04d7aa8ccb5958636 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -69,8 +69,13 @@
 #define BAD_FIQ                2
 #define BAD_ERROR      3
 
-       .macro  kernel_entry, el, regsize = 64
+       .macro kernel_ventry    label
+       .align 7
        sub     sp, sp, #S_FRAME_SIZE
+       b       \label
+       .endm
+
+       .macro  kernel_entry, el, regsize = 64
        .if     \regsize == 32
        mov     w0, w0                          // zero upper 32 bits of x0
        .endif
@@ -319,31 +324,31 @@ tsk       .req    x28             // current thread_info
 
        .align  11
 ENTRY(vectors)
-       ventry  el1_sync_invalid                // Synchronous EL1t
-       ventry  el1_irq_invalid                 // IRQ EL1t
-       ventry  el1_fiq_invalid                 // FIQ EL1t
-       ventry  el1_error_invalid               // Error EL1t
+       kernel_ventry   el1_sync_invalid                // Synchronous EL1t
+       kernel_ventry   el1_irq_invalid                 // IRQ EL1t
+       kernel_ventry   el1_fiq_invalid                 // FIQ EL1t
+       kernel_ventry   el1_error_invalid               // Error EL1t
 
-       ventry  el1_sync                        // Synchronous EL1h
-       ventry  el1_irq                         // IRQ EL1h
-       ventry  el1_fiq_invalid                 // FIQ EL1h
-       ventry  el1_error_invalid               // Error EL1h
+       kernel_ventry   el1_sync                        // Synchronous EL1h
+       kernel_ventry   el1_irq                         // IRQ EL1h
+       kernel_ventry   el1_fiq_invalid                 // FIQ EL1h
+       kernel_ventry   el1_error_invalid               // Error EL1h
 
-       ventry  el0_sync                        // Synchronous 64-bit EL0
-       ventry  el0_irq                         // IRQ 64-bit EL0
-       ventry  el0_fiq_invalid                 // FIQ 64-bit EL0
-       ventry  el0_error_invalid               // Error 64-bit EL0
+       kernel_ventry   el0_sync                        // Synchronous 64-bit EL0
+       kernel_ventry   el0_irq                         // IRQ 64-bit EL0
+       kernel_ventry   el0_fiq_invalid                 // FIQ 64-bit EL0
+       kernel_ventry   el0_error_invalid               // Error 64-bit EL0
 
 #ifdef CONFIG_COMPAT
-       ventry  el0_sync_compat                 // Synchronous 32-bit EL0
-       ventry  el0_irq_compat                  // IRQ 32-bit EL0
-       ventry  el0_fiq_invalid_compat          // FIQ 32-bit EL0
-       ventry  el0_error_invalid_compat        // Error 32-bit EL0
+       kernel_ventry   el0_sync_compat                 // Synchronous 32-bit EL0
+       kernel_ventry   el0_irq_compat                  // IRQ 32-bit EL0
+       kernel_ventry   el0_fiq_invalid_compat          // FIQ 32-bit EL0
+       kernel_ventry   el0_error_invalid_compat        // Error 32-bit EL0
 #else
-       ventry  el0_sync_invalid                // Synchronous 32-bit EL0
-       ventry  el0_irq_invalid                 // IRQ 32-bit EL0
-       ventry  el0_fiq_invalid                 // FIQ 32-bit EL0
-       ventry  el0_error_invalid               // Error 32-bit EL0
+       kernel_ventry   el0_sync_invalid                // Synchronous 32-bit EL0
+       kernel_ventry   el0_irq_invalid                 // IRQ 32-bit EL0
+       kernel_ventry   el0_fiq_invalid                 // FIQ 32-bit EL0
+       kernel_ventry   el0_error_invalid               // Error 32-bit EL0
 #endif
 END(vectors)