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, 23 insertions, 22 deletions

diff --git a/arch/arm/mm/cache-v7m.S b/arch/arm/mm/cache-v7m.S
index eb60b5e5e2ad..5a62b9a224e1 100644
--- a/arch/arm/mm/cache-v7m.S
+++ b/arch/arm/mm/cache-v7m.S
@@ -11,6 +11,7 @@
  */
 #include <linux/linkage.h>
 #include <linux/init.h>
+#include <linux/cfi_types.h>
 #include <asm/assembler.h>
 #include <asm/errno.h>
 #include <asm/unwind.h>
@@ -159,10 +160,10 @@ ENDPROC(v7m_invalidate_l1)
  *	Registers:
  *	r0 - set to 0
  */
-ENTRY(v7m_flush_icache_all)
+SYM_TYPED_FUNC_START(v7m_flush_icache_all)
 	invalidate_icache r0
 	ret	lr
-ENDPROC(v7m_flush_icache_all)
+SYM_FUNC_END(v7m_flush_icache_all)
 
 /*
  *	v7m_flush_dcache_all()
@@ -236,13 +237,13 @@ ENDPROC(v7m_flush_dcache_all)
  *  unification in a single instruction.
  *
  */
-ENTRY(v7m_flush_kern_cache_all)
+SYM_TYPED_FUNC_START(v7m_flush_kern_cache_all)
 	stmfd	sp!, {r4-r7, r9-r11, lr}
 	bl	v7m_flush_dcache_all
 	invalidate_icache r0
 	ldmfd	sp!, {r4-r7, r9-r11, lr}
 	ret	lr
-ENDPROC(v7m_flush_kern_cache_all)
+SYM_FUNC_END(v7m_flush_kern_cache_all)
 
 /*
  *	v7m_flush_cache_all()
@@ -251,8 +252,9 @@ ENDPROC(v7m_flush_kern_cache_all)
  *
  *	- mm    - mm_struct describing address space
  */
-ENTRY(v7m_flush_user_cache_all)
-	/*FALLTHROUGH*/
+SYM_TYPED_FUNC_START(v7m_flush_user_cache_all)
+	ret	lr
+SYM_FUNC_END(v7m_flush_user_cache_all)
 
 /*
  *	v7m_flush_cache_range(start, end, flags)
@@ -266,10 +268,9 @@ ENTRY(v7m_flush_user_cache_all)
  *	It is assumed that:
  *	- we have a VIPT cache.
  */
-ENTRY(v7m_flush_user_cache_range)
+SYM_TYPED_FUNC_START(v7m_flush_user_cache_range)
 	ret	lr
-ENDPROC(v7m_flush_user_cache_all)
-ENDPROC(v7m_flush_user_cache_range)
+SYM_FUNC_END(v7m_flush_user_cache_range)
 
 /*
  *	v7m_coherent_kern_range(start,end)
@@ -284,8 +285,9 @@ ENDPROC(v7m_flush_user_cache_range)
  *	It is assumed that:
  *	- the Icache does not read data from the write buffer
  */
-ENTRY(v7m_coherent_kern_range)
-	/* FALLTHROUGH */
+SYM_TYPED_FUNC_START(v7m_coherent_kern_range)
+	b	v7m_coherent_user_range
+SYM_FUNC_END(v7m_coherent_kern_range)
 
 /*
  *	v7m_coherent_user_range(start,end)
@@ -300,7 +302,7 @@ ENTRY(v7m_coherent_kern_range)
  *	It is assumed that:
  *	- the Icache does not read data from the write buffer
  */
-ENTRY(v7m_coherent_user_range)
+SYM_TYPED_FUNC_START(v7m_coherent_user_range)
  UNWIND(.fnstart		)
 	dcache_line_size r2, r3
 	sub	r3, r2, #1
@@ -328,8 +330,7 @@ ENTRY(v7m_coherent_user_range)
 	isb
 	ret	lr
  UNWIND(.fnend		)
-ENDPROC(v7m_coherent_kern_range)
-ENDPROC(v7m_coherent_user_range)
+SYM_FUNC_END(v7m_coherent_user_range)
 
 /*
  *	v7m_flush_kern_dcache_area(void *addr, size_t size)
@@ -340,7 +341,7 @@ ENDPROC(v7m_coherent_user_range)
  *	- addr	- kernel address
  *	- size	- region size
  */
-ENTRY(v7m_flush_kern_dcache_area)
+SYM_TYPED_FUNC_START(v7m_flush_kern_dcache_area)
 	dcache_line_size r2, r3
 	add	r1, r0, r1
 	sub	r3, r2, #1
@@ -352,7 +353,7 @@ ENTRY(v7m_flush_kern_dcache_area)
 	blo	1b
 	dsb	st
 	ret	lr
-ENDPROC(v7m_flush_kern_dcache_area)
+SYM_FUNC_END(v7m_flush_kern_dcache_area)
 
 /*
  *	v7m_dma_inv_range(start,end)
@@ -408,7 +409,7 @@ ENDPROC(v7m_dma_clean_range)
  *	- start   - virtual start address of region
  *	- end     - virtual end address of region
  */
-ENTRY(v7m_dma_flush_range)
+SYM_TYPED_FUNC_START(v7m_dma_flush_range)
 	dcache_line_size r2, r3
 	sub	r3, r2, #1
 	bic	r0, r0, r3
@@ -419,7 +420,7 @@ ENTRY(v7m_dma_flush_range)
 	blo	1b
 	dsb	st
 	ret	lr
-ENDPROC(v7m_dma_flush_range)
+SYM_FUNC_END(v7m_dma_flush_range)
 
 /*
  *	dma_map_area(start, size, dir)
@@ -427,12 +428,12 @@ ENDPROC(v7m_dma_flush_range)
  *	- size	- size of region
  *	- dir	- DMA direction
  */
-ENTRY(v7m_dma_map_area)
+SYM_TYPED_FUNC_START(v7m_dma_map_area)
 	add	r1, r1, r0
 	teq	r2, #DMA_FROM_DEVICE
 	beq	v7m_dma_inv_range
 	b	v7m_dma_clean_range
-ENDPROC(v7m_dma_map_area)
+SYM_FUNC_END(v7m_dma_map_area)
 
 /*
  *	dma_unmap_area(start, size, dir)
@@ -440,12 +441,12 @@ ENDPROC(v7m_dma_map_area)
  *	- size	- size of region
  *	- dir	- DMA direction
  */
-ENTRY(v7m_dma_unmap_area)
+SYM_TYPED_FUNC_START(v7m_dma_unmap_area)
 	add	r1, r1, r0
 	teq	r2, #DMA_TO_DEVICE
 	bne	v7m_dma_inv_range
 	ret	lr
-ENDPROC(v7m_dma_unmap_area)
+SYM_FUNC_END(v7m_dma_unmap_area)
 
 	.globl	v7m_flush_kern_cache_louis
 	.equ	v7m_flush_kern_cache_louis, v7m_flush_kern_cache_all