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, 25 insertions, 17 deletions

diff --git a/arch/arm/mm/proc-arm940.S b/arch/arm/mm/proc-arm940.S
index cf9bfcc825ca..7e32ec271e8a 100644
--- a/arch/arm/mm/proc-arm940.S
+++ b/arch/arm/mm/proc-arm940.S
@@ -6,6 +6,7 @@
  */
 #include <linux/linkage.h>
 #include <linux/init.h>
+#include <linux/cfi_types.h>
 #include <linux/pgtable.h>
 #include <asm/assembler.h>
 #include <asm/hwcap.h>
@@ -71,26 +72,28 @@ ENTRY(cpu_arm940_do_idle)
  *
  *	Unconditionally clean and invalidate the entire icache.
  */
-ENTRY(arm940_flush_icache_all)
+SYM_TYPED_FUNC_START(arm940_flush_icache_all)
 	mov	r0, #0
 	mcr	p15, 0, r0, c7, c5, 0		@ invalidate I cache
 	ret	lr
-ENDPROC(arm940_flush_icache_all)
+SYM_FUNC_END(arm940_flush_icache_all)
 
 /*
  *	flush_user_cache_all()
  */
-ENTRY(arm940_flush_user_cache_all)
-	/* FALLTHROUGH */
+SYM_TYPED_FUNC_START(arm940_flush_user_cache_all)
+	b	arm940_flush_kern_cache_all
+SYM_FUNC_END(arm940_flush_user_cache_all)
 
 /*
  *	flush_kern_cache_all()
  *
  *	Clean and invalidate the entire cache.
  */
-ENTRY(arm940_flush_kern_cache_all)
+SYM_TYPED_FUNC_START(arm940_flush_kern_cache_all)
 	mov	r2, #VM_EXEC
-	/* FALLTHROUGH */
+	b	arm940_flush_user_cache_range
+SYM_FUNC_END(arm940_flush_kern_cache_all)
 
 /*
  *	flush_user_cache_range(start, end, flags)
@@ -102,7 +105,7 @@ ENTRY(arm940_flush_kern_cache_all)
  *	- end	- end address (exclusive)
  *	- flags	- vm_flags describing address space
  */
-ENTRY(arm940_flush_user_cache_range)
+SYM_TYPED_FUNC_START(arm940_flush_user_cache_range)
 	mov	ip, #0
 #ifdef CONFIG_CPU_DCACHE_WRITETHROUGH
 	mcr	p15, 0, ip, c7, c6, 0		@ flush D cache
@@ -119,6 +122,7 @@ ENTRY(arm940_flush_user_cache_range)
 	mcrne	p15, 0, ip, c7, c5, 0		@ invalidate I cache
 	mcrne	p15, 0, ip, c7, c10, 4		@ drain WB
 	ret	lr
+SYM_FUNC_END(arm940_flush_user_cache_range)
 
 /*
  *	coherent_kern_range(start, end)
@@ -130,8 +134,9 @@ ENTRY(arm940_flush_user_cache_range)
  *	- start	- virtual start address
  *	- end	- virtual end address
  */
-ENTRY(arm940_coherent_kern_range)
-	/* FALLTHROUGH */
+SYM_TYPED_FUNC_START(arm940_coherent_kern_range)
+	b	arm940_flush_kern_dcache_area
+SYM_FUNC_END(arm940_coherent_kern_range)
 
 /*
  *	coherent_user_range(start, end)
@@ -143,8 +148,9 @@ ENTRY(arm940_coherent_kern_range)
  *	- start	- virtual start address
  *	- end	- virtual end address
  */
-ENTRY(arm940_coherent_user_range)
-	/* FALLTHROUGH */
+SYM_TYPED_FUNC_START(arm940_coherent_user_range)
+	b	arm940_flush_kern_dcache_area
+SYM_FUNC_END(arm940_coherent_user_range)
 
 /*
  *	flush_kern_dcache_area(void *addr, size_t size)
@@ -155,7 +161,7 @@ ENTRY(arm940_coherent_user_range)
  *	- addr	- kernel address
  *	- size	- region size
  */
-ENTRY(arm940_flush_kern_dcache_area)
+SYM_TYPED_FUNC_START(arm940_flush_kern_dcache_area)
 	mov	r0, #0
 	mov	r1, #(CACHE_DSEGMENTS - 1) << 4	@ 4 segments
 1:	orr	r3, r1, #(CACHE_DENTRIES - 1) << 26 @ 64 entries
@@ -167,6 +173,7 @@ ENTRY(arm940_flush_kern_dcache_area)
 	mcr	p15, 0, r0, c7, c5, 0		@ invalidate I cache
 	mcr	p15, 0, r0, c7, c10, 4		@ drain WB
 	ret	lr
+SYM_FUNC_END(arm940_flush_kern_dcache_area)
 
 /*
  *	dma_inv_range(start, end)
@@ -222,7 +229,7 @@ ENTRY(cpu_arm940_dcache_clean_area)
  *	- start	- virtual start address
  *	- end	- virtual end address
  */
-ENTRY(arm940_dma_flush_range)
+SYM_TYPED_FUNC_START(arm940_dma_flush_range)
 	mov	ip, #0
 	mov	r1, #(CACHE_DSEGMENTS - 1) << 4	@ 4 segments
 1:	orr	r3, r1, #(CACHE_DENTRIES - 1) << 26 @ 64 entries
@@ -238,6 +245,7 @@ ENTRY(arm940_dma_flush_range)
 	bcs	1b				@ segments 7 to 0
 	mcr	p15, 0, ip, c7, c10, 4		@ drain WB
 	ret	lr
+SYM_FUNC_END(arm940_dma_flush_range)
 
 /*
  *	dma_map_area(start, size, dir)
@@ -245,13 +253,13 @@ ENTRY(arm940_dma_flush_range)
  *	- size	- size of region
  *	- dir	- DMA direction
  */
-ENTRY(arm940_dma_map_area)
+SYM_TYPED_FUNC_START(arm940_dma_map_area)
 	add	r1, r1, r0
 	cmp	r2, #DMA_TO_DEVICE
 	beq	arm940_dma_clean_range
 	bcs	arm940_dma_inv_range
 	b	arm940_dma_flush_range
-ENDPROC(arm940_dma_map_area)
+SYM_FUNC_END(arm940_dma_map_area)
 
 /*
  *	dma_unmap_area(start, size, dir)
@@ -259,9 +267,9 @@ ENDPROC(arm940_dma_map_area)
  *	- size	- size of region
  *	- dir	- DMA direction
  */
-ENTRY(arm940_dma_unmap_area)
+SYM_TYPED_FUNC_START(arm940_dma_unmap_area)
 	ret	lr
-ENDPROC(arm940_dma_unmap_area)
+SYM_FUNC_END(arm940_dma_unmap_area)
 
 	.globl	arm940_flush_kern_cache_louis
 	.equ	arm940_flush_kern_cache_louis, arm940_flush_kern_cache_all