Revert "FROMLIST: arm64: Introduce uaccess_{disable,enable} functionality based on TTBR0_EL1"

This reverts commit 1911d36b27ba58ee18592df25b7ee636d4d4c41d.

Bug: 31432001
Change-Id: Iee77eed8454f379b948dbbaf65c105952ea30bef
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

10 files changed, 13 insertions, 134 deletions

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index aeb4554b3af3..9d3e77a5cf07 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -53,15 +53,6 @@
 	msr	daifclr, #2
 	.endm
 
-	.macro	save_and_disable_irq, flags
-	mrs	\flags, daif
-	msr	daifset, #2
-	.endm
-
-	.macro	restore_irq, flags
-	msr	daif, \flags
-	.endm
-
 /*
  * Enable and disable debug exceptions.
  */
@@ -372,13 +363,6 @@ alternative_endif
 	.endm
 
 /*
- * Return the current thread_info.
- */
-	.macro	get_thread_info, rd
-	mrs	\rd, sp_el0
-	.endm
-
-/*
  * Errata workaround post TTBR0_EL1 update.
  */
 	.macro	post_ttbr0_update_workaround
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 8e1f826caf99..1695f77d8bf2 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -189,12 +189,6 @@ static inline bool system_supports_mixed_endian_el0(void)
 	return id_aa64mmfr0_mixed_endian_el0(read_system_reg(SYS_ID_AA64MMFR0_EL1));
 }
 
-static inline bool system_uses_ttbr0_pan(void)
-{
-	return IS_ENABLED(CONFIG_ARM64_SW_TTBR0_PAN) &&
-		!cpus_have_cap(ARM64_HAS_PAN);
-}
-
 #endif /* __ASSEMBLY__ */
 
 #endif
diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 7803343e5881..7e51d1b57c0c 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -19,7 +19,6 @@
 #ifndef __ASM_KERNEL_PGTABLE_H
 #define __ASM_KERNEL_PGTABLE_H
 
-#include <asm/pgtable.h>
 #include <asm/sparsemem.h>
 
 /*
@@ -55,12 +54,6 @@
 #define SWAPPER_DIR_SIZE	(SWAPPER_PGTABLE_LEVELS * PAGE_SIZE)
 #define IDMAP_DIR_SIZE		(IDMAP_PGTABLE_LEVELS * PAGE_SIZE)
 
-#ifdef CONFIG_ARM64_SW_TTBR0_PAN
-#define RESERVED_TTBR0_SIZE	(PAGE_SIZE)
-#else
-#define RESERVED_TTBR0_SIZE	(0)
-#endif
-
 /* Initial memory map size */
 #if ARM64_SWAPPER_USES_SECTION_MAPS
 #define SWAPPER_BLOCK_SHIFT	SECTION_SHIFT
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index b3325a9cb90f..abd64bd1f6d9 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -47,9 +47,6 @@ typedef unsigned long mm_segment_t;
 struct thread_info {
 	unsigned long		flags;		/* low level flags */
 	mm_segment_t		addr_limit;	/* address limit */
-#ifdef CONFIG_ARM64_SW_TTBR0_PAN
-	u64			ttbr0;		/* saved TTBR0_EL1 */
-#endif
 	struct task_struct	*task;		/* main task structure */
 	int			preempt_count;	/* 0 => preemptable, <0 => bug */
 	int			cpu;		/* cpu */
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index c37c064d7cdd..c8ef22a9a83b 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -28,7 +28,6 @@
 
 #include <asm/alternative.h>
 #include <asm/cpufeature.h>
-#include <asm/kernel-pgtable.h>
 #include <asm/ptrace.h>
 #include <asm/sysreg.h>
 #include <asm/errno.h>
@@ -129,57 +128,16 @@ static inline void set_fs(mm_segment_t fs)
 /*
  * User access enabling/disabling.
  */
-#ifdef CONFIG_ARM64_SW_TTBR0_PAN
-static inline void uaccess_ttbr0_disable(void)
-{
-	unsigned long ttbr;
-
-	/* reserved_ttbr0 placed at the end of swapper_pg_dir */
-	ttbr = read_sysreg(ttbr1_el1) + SWAPPER_DIR_SIZE;
-	write_sysreg(ttbr, ttbr0_el1);
-	isb();
-}
-
-static inline void uaccess_ttbr0_enable(void)
-{
-	unsigned long flags;
-
-	/*
-	 * Disable interrupts to avoid preemption between reading the 'ttbr0'
-	 * variable and the MSR. A context switch could trigger an ASID
-	 * roll-over and an update of 'ttbr0'.
-	 */
-	local_irq_save(flags);
-	write_sysreg(current_thread_info()->ttbr0, ttbr0_el1);
-	isb();
-	local_irq_restore(flags);
-}
-#else
-static inline void uaccess_ttbr0_disable(void)
-{
-}
-
-static inline void uaccess_ttbr0_enable(void)
-{
-}
-#endif
-
 #define __uaccess_disable(alt)						\
 do {									\
-	if (system_uses_ttbr0_pan())					\
-		uaccess_ttbr0_disable();				\
-	else								\
-		asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,		\
-				CONFIG_ARM64_PAN));			\
+	asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,			\
+			CONFIG_ARM64_PAN));				\
 } while (0)
 
 #define __uaccess_enable(alt)						\
 do {									\
-	if (system_uses_ttbr0_pan())					\
-		uaccess_ttbr0_enable();					\
-	else								\
-		asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,		\
-				CONFIG_ARM64_PAN));			\
+	asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,			\
+			CONFIG_ARM64_PAN));				\
 } while (0)
 
 static inline void uaccess_disable(void)
@@ -409,39 +367,12 @@ extern __must_check long strnlen_user(const char __user *str, long n);
 
 #include <asm/alternative.h>
 #include <asm/assembler.h>
-#include <asm/kernel-pgtable.h>
-
-/*
- * User access enabling/disabling macros.
- */
-	.macro	uaccess_ttbr0_disable, tmp1
-	mrs	\tmp1, ttbr1_el1		// swapper_pg_dir
-	add	\tmp1, \tmp1, #SWAPPER_DIR_SIZE	// reserved_ttbr0 at the end of swapper_pg_dir
-	msr	ttbr0_el1, \tmp1		// set reserved TTBR0_EL1
-	isb
-	.endm
-
-	.macro	uaccess_ttbr0_enable, tmp1
-	get_thread_info \tmp1
-	ldr	\tmp1, [\tmp1, #TI_TTBR0]	// load saved TTBR0_EL1
-	msr	ttbr0_el1, \tmp1		// set the non-PAN TTBR0_EL1
-	isb
-	.endm
 
 /*
- * These macros are no-ops when UAO is present.
+ * User access enabling/disabling macros. These are no-ops when UAO is
+ * present.
  */
 	.macro	uaccess_disable_not_uao, tmp1
-#ifdef CONFIG_ARM64_SW_TTBR0_PAN
-alternative_if_not ARM64_HAS_PAN
-	uaccess_ttbr0_disable \tmp1
-alternative_else
-	nop
-	nop
-	nop
-	nop
-alternative_endif
-#endif
 alternative_if_not ARM64_ALT_PAN_NOT_UAO
 	nop
 alternative_else
@@ -450,21 +381,6 @@ alternative_endif
 	.endm
 
 	.macro	uaccess_enable_not_uao, tmp1, tmp2
-#ifdef CONFIG_ARM64_SW_TTBR0_PAN
-alternative_if_not ARM64_HAS_PAN
-	save_and_disable_irq \tmp2		// avoid preemption
-	uaccess_ttbr0_enable \tmp1
-	restore_irq \tmp2
-alternative_else
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-alternative_endif
-#endif
 alternative_if_not ARM64_ALT_PAN_NOT_UAO
 	nop
 alternative_else
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index dac70c160289..2bb17bd556f8 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -38,9 +38,6 @@ int main(void)
   DEFINE(TI_FLAGS,		offsetof(struct thread_info, flags));
   DEFINE(TI_PREEMPT,		offsetof(struct thread_info, preempt_count));
   DEFINE(TI_ADDR_LIMIT,		offsetof(struct thread_info, addr_limit));
-#ifdef CONFIG_ARM64_SW_TTBR0_PAN
-  DEFINE(TI_TTBR0,		offsetof(struct thread_info, ttbr0));
-#endif
   DEFINE(TI_TASK,		offsetof(struct thread_info, task));
   DEFINE(TI_CPU,		offsetof(struct thread_info, cpu));
   BLANK();
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index cdf1dca64133..eda7d5915fbb 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -46,7 +46,6 @@ unsigned int compat_elf_hwcap2 __read_mostly;
 #endif
 
 DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS);
-EXPORT_SYMBOL(cpu_hwcaps);
 
 #define __ARM64_FTR_BITS(SIGNED, STRICT, TYPE, SHIFT, WIDTH, SAFE_VAL) \
 	{						\
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 8aa564f58b61..367e850ece4d 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -187,6 +187,10 @@ alternative_endif
 	eret					// return to kernel
 	.endm
 
+	.macro	get_thread_info, rd
+	mrs	\rd, sp_el0
+	.endm
+
 	.macro	irq_stack_entry
 	mov	x19, sp			// preserve the original sp
 
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 8cfd5ab37743..0ea9a97467a6 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -318,14 +318,14 @@ __create_page_tables:
 	 * dirty cache lines being evicted.
 	 */
 	mov	x0, x25
-	add	x1, x26, #SWAPPER_DIR_SIZE + RESERVED_TTBR0_SIZE
+	add	x1, x26, #SWAPPER_DIR_SIZE
 	bl	__inval_cache_range
 
 	/*
 	 * Clear the idmap and swapper page tables.
 	 */
 	mov	x0, x25
-	add	x6, x26, #SWAPPER_DIR_SIZE + RESERVED_TTBR0_SIZE
+	add	x6, x26, #SWAPPER_DIR_SIZE
 1:	stp	xzr, xzr, [x0], #16
 	stp	xzr, xzr, [x0], #16
 	stp	xzr, xzr, [x0], #16
@@ -404,7 +404,7 @@ __create_page_tables:
 	 * tables again to remove any speculatively loaded cache lines.
 	 */
 	mov	x0, x25
-	add	x1, x26, #SWAPPER_DIR_SIZE + RESERVED_TTBR0_SIZE
+	add	x1, x26, #SWAPPER_DIR_SIZE
 	dmb	sy
 	bl	__inval_cache_range
 
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 7a5228c7abdd..9442a51d3540 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -194,11 +194,6 @@ SECTIONS
 	swapper_pg_dir = .;
 	. += SWAPPER_DIR_SIZE;
 
-#ifdef CONFIG_ARM64_SW_TTBR0_PAN
-	reserved_ttbr0 = .;
-	. += RESERVED_TTBR0_SIZE;
-#endif
-
 	_end = .;
 
 	STABS_DEBUG