ARM: 9385/2: mm: Type-annotate all cache assembly routines

Tag all references to assembly functions with SYM_TYPED_FUNC_START()
and SYM_FUNC_END() so they also become CFI-safe.

When we add SYM_TYPED_FUNC_START() to assembly calls, a function
prototype signature will be emitted into the object file at
(pc-4) at the call site, so that the KCFI runtime check can compare
this to the expected call. Example:

8011ae38:       a540670c        .word   0xa540670c

8011ae3c <v7_flush_icache_all>:
8011ae3c:       e3a00000        mov     r0, #0
8011ae40:       ee070f11        mcr     15, 0, r0, cr7, cr1, {0}
8011ae44:       e12fff1e        bx      lr

This means no "fallthrough" code can enter a SYM_TYPED_FUNC_START()
call from above it: there will be a function prototype signature
there, so those are consistently converted to a branch or ret lr
depending on context.

Tested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

1 files changed, 28 insertions, 19 deletions

diff --git a/arch/arm/mm/cache-v4.S b/arch/arm/mm/cache-v4.S
index 7787057e4990..22d9c9d9e0d7 100644
--- a/arch/arm/mm/cache-v4.S
+++ b/arch/arm/mm/cache-v4.S
@@ -6,6 +6,7 @@
  */
 #include <linux/linkage.h>
 #include <linux/init.h>
+#include <linux/cfi_types.h>
 #include <asm/assembler.h>
 #include <asm/page.h>
 #include "proc-macros.S"
@@ -15,9 +16,9 @@
  *
  *	Unconditionally clean and invalidate the entire icache.
  */
-ENTRY(v4_flush_icache_all)
+SYM_TYPED_FUNC_START(v4_flush_icache_all)
 	ret	lr
-ENDPROC(v4_flush_icache_all)
+SYM_FUNC_END(v4_flush_icache_all)
 
 /*
  *	flush_user_cache_all()
@@ -27,21 +28,24 @@ ENDPROC(v4_flush_icache_all)
  *
  *	- mm	- mm_struct describing address space
  */
-ENTRY(v4_flush_user_cache_all)
-	/* FALLTHROUGH */
+SYM_TYPED_FUNC_START(v4_flush_user_cache_all)
+	b	v4_flush_kern_cache_all
+SYM_FUNC_END(v4_flush_user_cache_all)
+
 /*
  *	flush_kern_cache_all()
  *
  *	Clean and invalidate the entire cache.
  */
-ENTRY(v4_flush_kern_cache_all)
+SYM_TYPED_FUNC_START(v4_flush_kern_cache_all)
 #ifdef CONFIG_CPU_CP15
 	mov	r0, #0
 	mcr	p15, 0, r0, c7, c7, 0		@ flush ID cache
 	ret	lr
 #else
-	/* FALLTHROUGH */
+	ret	lr
 #endif
+SYM_FUNC_END(v4_flush_kern_cache_all)
 
 /*
  *	flush_user_cache_range(start, end, flags)
@@ -53,14 +57,15 @@ ENTRY(v4_flush_kern_cache_all)
  *	- end	- end address (exclusive, may not be aligned)
  *	- flags	- vma_area_struct flags describing address space
  */
-ENTRY(v4_flush_user_cache_range)
+SYM_TYPED_FUNC_START(v4_flush_user_cache_range)
 #ifdef CONFIG_CPU_CP15
 	mov	ip, #0
 	mcr	p15, 0, ip, c7, c7, 0		@ flush ID cache
 	ret	lr
 #else
-	/* FALLTHROUGH */
+	ret	lr
 #endif
+SYM_FUNC_END(v4_flush_user_cache_range)
 
 /*
  *	coherent_kern_range(start, end)
@@ -72,8 +77,9 @@ ENTRY(v4_flush_user_cache_range)
  *	- start  - virtual start address
  *	- end	 - virtual end address
  */
-ENTRY(v4_coherent_kern_range)
-	/* FALLTHROUGH */
+SYM_TYPED_FUNC_START(v4_coherent_kern_range)
+	ret	lr
+SYM_FUNC_END(v4_coherent_kern_range)
 
 /*
  *	coherent_user_range(start, end)
@@ -85,9 +91,10 @@ ENTRY(v4_coherent_kern_range)
  *	- start  - virtual start address
  *	- end	 - virtual end address
  */
-ENTRY(v4_coherent_user_range)
+SYM_TYPED_FUNC_START(v4_coherent_user_range)
 	mov	r0, #0
 	ret	lr
+SYM_FUNC_END(v4_coherent_user_range)
 
 /*
  *	flush_kern_dcache_area(void *addr, size_t size)
@@ -98,8 +105,9 @@ ENTRY(v4_coherent_user_range)
  *	- addr	- kernel address
  *	- size	- region size
  */
-ENTRY(v4_flush_kern_dcache_area)
-	/* FALLTHROUGH */
+SYM_TYPED_FUNC_START(v4_flush_kern_dcache_area)
+	b	v4_dma_flush_range
+SYM_FUNC_END(v4_flush_kern_dcache_area)
 
 /*
  *	dma_flush_range(start, end)
@@ -109,12 +117,13 @@ ENTRY(v4_flush_kern_dcache_area)
  *	- start  - virtual start address
  *	- end	 - virtual end address
  */
-ENTRY(v4_dma_flush_range)
+SYM_TYPED_FUNC_START(v4_dma_flush_range)
 #ifdef CONFIG_CPU_CP15
 	mov	r0, #0
 	mcr	p15, 0, r0, c7, c7, 0		@ flush ID cache
 #endif
 	ret	lr
+SYM_FUNC_END(v4_dma_flush_range)
 
 /*
  *	dma_unmap_area(start, size, dir)
@@ -122,10 +131,11 @@ ENTRY(v4_dma_flush_range)
  *	- size	- size of region
  *	- dir	- DMA direction
  */
-ENTRY(v4_dma_unmap_area)
+SYM_TYPED_FUNC_START(v4_dma_unmap_area)
 	teq	r2, #DMA_TO_DEVICE
 	bne	v4_dma_flush_range
-	/* FALLTHROUGH */
+	ret	lr
+SYM_FUNC_END(v4_dma_unmap_area)
 
 /*
  *	dma_map_area(start, size, dir)
@@ -133,10 +143,9 @@ ENTRY(v4_dma_unmap_area)
  *	- size	- size of region
  *	- dir	- DMA direction
  */
-ENTRY(v4_dma_map_area)
+SYM_TYPED_FUNC_START(v4_dma_map_area)
 	ret	lr
-ENDPROC(v4_dma_unmap_area)
-ENDPROC(v4_dma_map_area)
+SYM_FUNC_END(v4_dma_map_area)
 
 	.globl	v4_flush_kern_cache_louis
 	.equ	v4_flush_kern_cache_louis, v4_flush_kern_cache_all