ARM: 9384/2: mm: Make tlbflush routines CFI safe

Instead of avoiding CFI entirely on the TLB flush helpers, reorganize
the code so that the CFI machinery can deal with it. The important
things to take into account are:
- functions in asm called indirectly from C need to be defined using
  SYM_TYPED_FUNC_START()
- a reference to the asm function needs to be visible to the compiler,
  in order to get it to emit the typeid symbol.

The latter means that defining the cpu_tlb_fns structs is best done from
C code, so that the references in the static initializers will be
visible to the compiler.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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>

Author: ardbiesheuvel

arch/arm/mm/Makefile

@@ -62,6 +62,7 @@ obj-$(CONFIG_CPU_TLB_FEROCEON)	+= tlb-v4wbi.o	# reuse v4wbi TLB functions
 obj-$(CONFIG_CPU_TLB_V6)	+= tlb-v6.o
 obj-$(CONFIG_CPU_TLB_V7)	+= tlb-v7.o
 obj-$(CONFIG_CPU_TLB_FA)	+= tlb-fa.o
+obj-y				+= tlb.o
 
 obj-$(CONFIG_CPU_ARM7TDMI)	+= proc-arm7tdmi.o
 obj-$(CONFIG_CPU_ARM720T)	+= proc-arm720.o

arch/arm/mm/proc-macros.S

@@ -338,21 +338,6 @@ ENTRY(\name\()_cache_fns)
 	.size	\name\()_cache_fns, . - \name\()_cache_fns
 .endm
 
-.macro define_tlb_functions name:req, flags_up:req, flags_smp
-	.type	\name\()_tlb_fns, #object
-	.align 2
-ENTRY(\name\()_tlb_fns)
-	.long	\name\()_flush_user_tlb_range
-	.long	\name\()_flush_kern_tlb_range
-	.ifnb \flags_smp
-		ALT_SMP(.long	\flags_smp )
-		ALT_UP(.long	\flags_up )
-	.else
-		.long	\flags_up
-	.endif
-	.size	\name\()_tlb_fns, . - \name\()_tlb_fns
-.endm
-
 .macro globl_equ x, y
 	.globl	\x
 	.equ	\x, \y

arch/arm/mm/tlb-fa.S

@@ -15,6 +15,7 @@
  */
 #include <linux/linkage.h>
 #include <linux/init.h>
+#include <linux/cfi_types.h>
 #include <asm/assembler.h>
 #include <asm/asm-offsets.h>
 #include <asm/tlbflush.h>
@@ -31,7 +32,7 @@
  *	- mm    - mm_struct describing address space
  */
 	.align	4
-ENTRY(fa_flush_user_tlb_range)
+SYM_TYPED_FUNC_START(fa_flush_user_tlb_range)
 	vma_vm_mm ip, r2
 	act_mm	r3				@ get current->active_mm
 	eors	r3, ip, r3			@ == mm ?
@@ -46,9 +47,10 @@ ENTRY(fa_flush_user_tlb_range)
 	blo	1b
 	mcr	p15, 0, r3, c7, c10, 4		@ data write barrier
 	ret	lr
+SYM_FUNC_END(fa_flush_user_tlb_range)
 
 
-ENTRY(fa_flush_kern_tlb_range)
+SYM_TYPED_FUNC_START(fa_flush_kern_tlb_range)
 	mov	r3, #0
 	mcr	p15, 0, r3, c7, c10, 4		@ drain WB
 	bic	r0, r0, #0x0ff
@@ -60,8 +62,4 @@ ENTRY(fa_flush_kern_tlb_range)
 	mcr	p15, 0, r3, c7, c10, 4		@ data write barrier
 	mcr	p15, 0, r3, c7, c5, 4		@ prefetch flush (isb)
 	ret	lr
-
-	__INITDATA
-
-	/* define struct cpu_tlb_fns (see <asm/tlbflush.h> and proc-macros.S) */
-	define_tlb_functions fa, fa_tlb_flags
+SYM_FUNC_END(fa_flush_kern_tlb_range)

arch/arm/mm/tlb-v4.S

@@ -11,6 +11,7 @@
  */
 #include <linux/linkage.h>
 #include <linux/init.h>
+#include <linux/cfi_types.h>
 #include <asm/assembler.h>
 #include <asm/asm-offsets.h>
 #include <asm/tlbflush.h>
@@ -27,7 +28,7 @@
  *	- mm    - mm_struct describing address space
  */
 	.align	5
-ENTRY(v4_flush_user_tlb_range)
+SYM_TYPED_FUNC_START(v4_flush_user_tlb_range)
 	vma_vm_mm ip, r2
 	act_mm	r3				@ get current->active_mm
 	eors	r3, ip, r3				@ == mm ?
@@ -40,6 +41,7 @@ ENTRY(v4_flush_user_tlb_range)
 	cmp	r0, r1
 	blo	1b
 	ret	lr
+SYM_FUNC_END(v4_flush_user_tlb_range)
 
 /*
  *	v4_flush_kern_tlb_range(start, end)
@@ -50,10 +52,11 @@ ENTRY(v4_flush_user_tlb_range)
  *	- start - virtual address (may not be aligned)
  *	- end   - virtual address (may not be aligned)
  */
+#ifdef CONFIG_CFI_CLANG
+SYM_TYPED_FUNC_START(v4_flush_kern_tlb_range)
+	b	.v4_flush_kern_tlb_range
+SYM_FUNC_END(v4_flush_kern_tlb_range)
+#else
 .globl v4_flush_kern_tlb_range
 .equ v4_flush_kern_tlb_range, .v4_flush_kern_tlb_range
-
-	__INITDATA
-
-	/* define struct cpu_tlb_fns (see <asm/tlbflush.h> and proc-macros.S) */
-	define_tlb_functions v4, v4_tlb_flags
+#endif

arch/arm/mm/tlb-v4wb.S

@@ -11,6 +11,7 @@
  */
 #include <linux/linkage.h>
 #include <linux/init.h>
+#include <linux/cfi_types.h>
 #include <asm/assembler.h>
 #include <asm/asm-offsets.h>
 #include <asm/tlbflush.h>
@@ -27,7 +28,7 @@
  *	- mm    - mm_struct describing address space
  */
 	.align	5
-ENTRY(v4wb_flush_user_tlb_range)
+SYM_TYPED_FUNC_START(v4wb_flush_user_tlb_range)
 	vma_vm_mm ip, r2
 	act_mm	r3				@ get current->active_mm
 	eors	r3, ip, r3				@ == mm ?
@@ -43,6 +44,7 @@ ENTRY(v4wb_flush_user_tlb_range)
 	cmp	r0, r1
 	blo	1b
 	ret	lr
+SYM_FUNC_END(v4wb_flush_user_tlb_range)
 
 /*
  *	v4_flush_kern_tlb_range(start, end)
@@ -53,7 +55,7 @@ ENTRY(v4wb_flush_user_tlb_range)
  *	- start - virtual address (may not be aligned)
  *	- end   - virtual address (may not be aligned)
  */
-ENTRY(v4wb_flush_kern_tlb_range)
+SYM_TYPED_FUNC_START(v4wb_flush_kern_tlb_range)
 	mov	r3, #0
 	mcr	p15, 0, r3, c7, c10, 4		@ drain WB
 	bic	r0, r0, #0x0ff
@@ -64,8 +66,4 @@ ENTRY(v4wb_flush_kern_tlb_range)
 	cmp	r0, r1
 	blo	1b
 	ret	lr
-
-	__INITDATA
-
-	/* define struct cpu_tlb_fns (see <asm/tlbflush.h> and proc-macros.S) */
-	define_tlb_functions v4wb, v4wb_tlb_flags
+SYM_FUNC_END(v4wb_flush_kern_tlb_range)

arch/arm/mm/tlb-v4wbi.S

@@ -11,6 +11,7 @@
  */
 #include <linux/linkage.h>
 #include <linux/init.h>
+#include <linux/cfi_types.h>
 #include <asm/assembler.h>
 #include <asm/asm-offsets.h>
 #include <asm/tlbflush.h>
@@ -26,7 +27,7 @@
  *	- mm    - mm_struct describing address space
  */
 	.align	5
-ENTRY(v4wbi_flush_user_tlb_range)
+SYM_TYPED_FUNC_START(v4wbi_flush_user_tlb_range)
 	vma_vm_mm ip, r2
 	act_mm	r3				@ get current->active_mm
 	eors	r3, ip, r3			@ == mm ?
@@ -43,8 +44,9 @@ ENTRY(v4wbi_flush_user_tlb_range)
 	cmp	r0, r1
 	blo	1b
 	ret	lr
+SYM_FUNC_END(v4wbi_flush_user_tlb_range)
 
-ENTRY(v4wbi_flush_kern_tlb_range)
+SYM_TYPED_FUNC_START(v4wbi_flush_kern_tlb_range)
 	mov	r3, #0
 	mcr	p15, 0, r3, c7, c10, 4		@ drain WB
 	bic	r0, r0, #0x0ff
@@ -55,8 +57,4 @@ ENTRY(v4wbi_flush_kern_tlb_range)
 	cmp	r0, r1
 	blo	1b
 	ret	lr
-
-	__INITDATA
-
-	/* define struct cpu_tlb_fns (see <asm/tlbflush.h> and proc-macros.S) */
-	define_tlb_functions v4wbi, v4wbi_tlb_flags
+SYM_FUNC_END(v4wbi_flush_kern_tlb_range)

arch/arm/mm/tlb-v6.S

@@ -9,6 +9,7 @@
  */
 #include <linux/init.h>
 #include <linux/linkage.h>
+#include <linux/cfi_types.h>
 #include <asm/asm-offsets.h>
 #include <asm/assembler.h>
 #include <asm/page.h>
@@ -32,7 +33,7 @@
  *	- the "Invalidate single entry" instruction will invalidate
  *	  both the I and the D TLBs on Harvard-style TLBs
  */
-ENTRY(v6wbi_flush_user_tlb_range)
+SYM_TYPED_FUNC_START(v6wbi_flush_user_tlb_range)
 	vma_vm_mm r3, r2			@ get vma->vm_mm
 	mov	ip, #0
 	mmid	r3, r3				@ get vm_mm->context.id
@@ -56,6 +57,7 @@ ENTRY(v6wbi_flush_user_tlb_range)
 	blo	1b
 	mcr	p15, 0, ip, c7, c10, 4		@ data synchronization barrier
 	ret	lr
+SYM_FUNC_END(v6wbi_flush_user_tlb_range)
 
 /*
  *	v6wbi_flush_kern_tlb_range(start,end)
@@ -65,7 +67,7 @@ ENTRY(v6wbi_flush_user_tlb_range)
  *	- start - start address (may not be aligned)
  *	- end   - end address (exclusive, may not be aligned)
  */
-ENTRY(v6wbi_flush_kern_tlb_range)
+SYM_TYPED_FUNC_START(v6wbi_flush_kern_tlb_range)
 	mov	r2, #0
 	mcr	p15, 0, r2, c7, c10, 4		@ drain write buffer
 	mov	r0, r0, lsr #PAGE_SHIFT		@ align address
@@ -85,8 +87,4 @@ ENTRY(v6wbi_flush_kern_tlb_range)
 	mcr	p15, 0, r2, c7, c10, 4		@ data synchronization barrier
 	mcr	p15, 0, r2, c7, c5, 4		@ prefetch flush (isb)
 	ret	lr
-
-	__INIT
-
-	/* define struct cpu_tlb_fns (see <asm/tlbflush.h> and proc-macros.S) */
-	define_tlb_functions v6wbi, v6wbi_tlb_flags
+SYM_FUNC_END(v6wbi_flush_kern_tlb_range)

arch/arm/mm/tlb-v7.S

@@ -10,6 +10,7 @@
  */
 #include <linux/init.h>
 #include <linux/linkage.h>
+#include <linux/cfi_types.h>
 #include <asm/assembler.h>
 #include <asm/asm-offsets.h>
 #include <asm/page.h>
@@ -31,7 +32,7 @@
  *	- the "Invalidate single entry" instruction will invalidate
  *	  both the I and the D TLBs on Harvard-style TLBs
  */
-ENTRY(v7wbi_flush_user_tlb_range)
+SYM_TYPED_FUNC_START(v7wbi_flush_user_tlb_range)
 	vma_vm_mm r3, r2			@ get vma->vm_mm
 	mmid	r3, r3				@ get vm_mm->context.id
 	dsb	ish
@@ -57,7 +58,7 @@ ENTRY(v7wbi_flush_user_tlb_range)
 	blo	1b
 	dsb	ish
 	ret	lr
-ENDPROC(v7wbi_flush_user_tlb_range)
+SYM_FUNC_END(v7wbi_flush_user_tlb_range)
 
 /*
  *	v7wbi_flush_kern_tlb_range(start,end)
@@ -67,7 +68,7 @@ ENDPROC(v7wbi_flush_user_tlb_range)
  *	- start - start address (may not be aligned)
  *	- end   - end address (exclusive, may not be aligned)
  */
-ENTRY(v7wbi_flush_kern_tlb_range)
+SYM_TYPED_FUNC_START(v7wbi_flush_kern_tlb_range)
 	dsb	ish
 	mov	r0, r0, lsr #PAGE_SHIFT		@ align address
 	mov	r1, r1, lsr #PAGE_SHIFT
@@ -86,9 +87,4 @@ ENTRY(v7wbi_flush_kern_tlb_range)
 	dsb	ish
 	isb
 	ret	lr
-ENDPROC(v7wbi_flush_kern_tlb_range)
-
-	__INIT
-
-	/* define struct cpu_tlb_fns (see <asm/tlbflush.h> and proc-macros.S) */
-	define_tlb_functions v7wbi, v7wbi_tlb_flags_up, flags_smp=v7wbi_tlb_flags_smp
+SYM_FUNC_END(v7wbi_flush_kern_tlb_range)

arch/arm/mm/tlb.c

@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright 2024 Google LLC
+// Author: Ard Biesheuvel <ardb@google.com>
+
+#include <linux/types.h>
+#include <asm/tlbflush.h>
+
+#ifdef CONFIG_CPU_TLB_V4WT
+void v4_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *);
+void v4_flush_kern_tlb_range(unsigned long, unsigned long);
+
+struct cpu_tlb_fns v4_tlb_fns __initconst = {
+	.flush_user_range	= v4_flush_user_tlb_range,
+	.flush_kern_range	= v4_flush_kern_tlb_range,
+	.tlb_flags		= v4_tlb_flags,
+};
+#endif
+
+#ifdef CONFIG_CPU_TLB_V4WB
+void v4wb_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *);
+void v4wb_flush_kern_tlb_range(unsigned long, unsigned long);
+
+struct cpu_tlb_fns v4wb_tlb_fns __initconst = {
+	.flush_user_range	= v4wb_flush_user_tlb_range,
+	.flush_kern_range	= v4wb_flush_kern_tlb_range,
+	.tlb_flags		= v4wb_tlb_flags,
+};
+#endif
+
+#if defined(CONFIG_CPU_TLB_V4WBI) || defined(CONFIG_CPU_TLB_FEROCEON)
+void v4wbi_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *);
+void v4wbi_flush_kern_tlb_range(unsigned long, unsigned long);
+
+struct cpu_tlb_fns v4wbi_tlb_fns __initconst = {
+	.flush_user_range	= v4wbi_flush_user_tlb_range,
+	.flush_kern_range	= v4wbi_flush_kern_tlb_range,
+	.tlb_flags		= v4wbi_tlb_flags,
+};
+#endif
+
+#ifdef CONFIG_CPU_TLB_V6
+void v6wbi_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *);
+void v6wbi_flush_kern_tlb_range(unsigned long, unsigned long);
+
+struct cpu_tlb_fns v6wbi_tlb_fns __initconst = {
+	.flush_user_range	= v6wbi_flush_user_tlb_range,
+	.flush_kern_range	= v6wbi_flush_kern_tlb_range,
+	.tlb_flags		= v6wbi_tlb_flags,
+};
+#endif
+
+#ifdef CONFIG_CPU_TLB_V7
+void v7wbi_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *);
+void v7wbi_flush_kern_tlb_range(unsigned long, unsigned long);
+
+struct cpu_tlb_fns v7wbi_tlb_fns __initconst = {
+	.flush_user_range	= v7wbi_flush_user_tlb_range,
+	.flush_kern_range	= v7wbi_flush_kern_tlb_range,
+	.tlb_flags		= IS_ENABLED(CONFIG_SMP) ? v7wbi_tlb_flags_smp
+							 : v7wbi_tlb_flags_up,
+};
+
+#ifdef CONFIG_SMP_ON_UP
+/* This will be run-time patched so the offset better be right */
+static_assert(offsetof(struct cpu_tlb_fns, tlb_flags) == 8);
+
+asm("	.pushsection	\".alt.smp.init\", \"a\"		\n" \
+    "	.align		2					\n" \
+    "	.long		v7wbi_tlb_fns + 8 - .			\n" \
+    "	.long "  	__stringify(v7wbi_tlb_flags_up) "	\n" \
+    "	.popsection						\n");
+#endif
+#endif
+
+#ifdef CONFIG_CPU_TLB_FA
+void fa_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *);
+void fa_flush_kern_tlb_range(unsigned long, unsigned long);
+
+struct cpu_tlb_fns fa_tlb_fns __initconst = {
+	.flush_user_range	= fa_flush_user_tlb_range,
+	.flush_kern_range	= fa_flush_kern_tlb_range,
+	.tlb_flags		= fa_tlb_flags,
+};
+#endif