x86/mpx: remove MPX from arch/x86

From: Dave Hansen <dave.hansen@linux.intel.com>

MPX is being removed from the kernel due to a lack of support
in the toolchain going forward (gcc).

This removes all the remaining (dead at this point) MPX handling
code remaining in the tree.  The only remaining code is the XSAVE
support for MPX state which is currently needd for KVM to handle
VMs which might use MPX.

Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: x86@kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>

arch/x86/include/asm/bugs.h

@@ -6,12 +6,6 @@
 
 extern void check_bugs(void);
 
-#if defined(CONFIG_CPU_SUP_INTEL)
-void check_mpx_erratum(struct cpuinfo_x86 *c);
-#else
-static inline void check_mpx_erratum(struct cpuinfo_x86 *c) {}
-#endif
-
 #if defined(CONFIG_CPU_SUP_INTEL) && defined(CONFIG_X86_32)
 int ppro_with_ram_bug(void);
 #else

arch/x86/include/asm/disabled-features.h

@@ -10,12 +10,6 @@
  * cpu_feature_enabled().
  */
 
-#ifdef CONFIG_X86_INTEL_MPX
-# define DISABLE_MPX	0
-#else
-# define DISABLE_MPX	(1<<(X86_FEATURE_MPX & 31))
-#endif
-
 #ifdef CONFIG_X86_SMAP
 # define DISABLE_SMAP	0
 #else
@@ -74,7 +68,7 @@
 #define DISABLED_MASK6	0
 #define DISABLED_MASK7	(DISABLE_PTI)
 #define DISABLED_MASK8	0
-#define DISABLED_MASK9	(DISABLE_MPX|DISABLE_SMAP)
+#define DISABLED_MASK9	(DISABLE_SMAP)
 #define DISABLED_MASK10	0
 #define DISABLED_MASK11	0
 #define DISABLED_MASK12	0

arch/x86/include/asm/mmu.h

@@ -50,10 +50,6 @@ typedef struct {
 	u16 pkey_allocation_map;
 	s16 execute_only_pkey;
 #endif
-#ifdef CONFIG_X86_INTEL_MPX
-	/* address of the bounds directory */
-	void __user *bd_addr;
-#endif
 } mm_context_t;
 
 #define INIT_MM_CONTEXT(mm)						\

arch/x86/include/asm/mmu_context.h

@@ -12,7 +12,6 @@
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
 #include <asm/paravirt.h>
-#include <asm/mpx.h>
 #include <asm/debugreg.h>
 
 extern atomic64_t last_mm_ctx_id;
@@ -275,25 +274,6 @@ static inline bool is_64bit_mm(struct mm_struct *mm)
 static inline void arch_unmap(struct mm_struct *mm, unsigned long start,
 			      unsigned long end)
 {
-	/*
-	 * mpx_notify_unmap() goes and reads a rarely-hot
-	 * cacheline in the mm_struct.  That can be expensive
-	 * enough to be seen in profiles.
-	 *
-	 * The mpx_notify_unmap() call and its contents have been
-	 * observed to affect munmap() performance on hardware
-	 * where MPX is not present.
-	 *
-	 * The unlikely() optimizes for the fast case: no MPX
-	 * in the CPU, or no MPX use in the process.  Even if
-	 * we get this wrong (in the unlikely event that MPX
-	 * is widely enabled on some system) the overhead of
-	 * MPX itself (reading bounds tables) is expected to
-	 * overwhelm the overhead of getting this unlikely()
-	 * consistently wrong.
-	 */
-	if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX)))
-		mpx_notify_unmap(mm, start, end);
 }
 
 /*

arch/x86/include/asm/mpx.h

-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _ASM_X86_MPX_H
-#define _ASM_X86_MPX_H
-
-#include <linux/types.h>
-#include <linux/mm_types.h>
-
-#include <asm/ptrace.h>
-#include <asm/insn.h>
-
-/*
- * NULL is theoretically a valid place to put the bounds
- * directory, so point this at an invalid address.
- */
-#define MPX_INVALID_BOUNDS_DIR	((void __user *)-1)
-#define MPX_BNDCFG_ENABLE_FLAG	0x1
-#define MPX_BD_ENTRY_VALID_FLAG	0x1
-
-/*
- * The upper 28 bits [47:20] of the virtual address in 64-bit
- * are used to index into bounds directory (BD).
- *
- * The directory is 2G (2^31) in size, and with 8-byte entries
- * it has 2^28 entries.
- */
-#define MPX_BD_SIZE_BYTES_64	(1UL<<31)
-#define MPX_BD_ENTRY_BYTES_64	8
-#define MPX_BD_NR_ENTRIES_64	(MPX_BD_SIZE_BYTES_64/MPX_BD_ENTRY_BYTES_64)
-
-/*
- * The 32-bit directory is 4MB (2^22) in size, and with 4-byte
- * entries it has 2^20 entries.
- */
-#define MPX_BD_SIZE_BYTES_32	(1UL<<22)
-#define MPX_BD_ENTRY_BYTES_32	4
-#define MPX_BD_NR_ENTRIES_32	(MPX_BD_SIZE_BYTES_32/MPX_BD_ENTRY_BYTES_32)
-
-/*
- * A 64-bit table is 4MB total in size, and an entry is
- * 4 64-bit pointers in size.
- */
-#define MPX_BT_SIZE_BYTES_64	(1UL<<22)
-#define MPX_BT_ENTRY_BYTES_64	32
-#define MPX_BT_NR_ENTRIES_64	(MPX_BT_SIZE_BYTES_64/MPX_BT_ENTRY_BYTES_64)
-
-/*
- * A 32-bit table is 16kB total in size, and an entry is
- * 4 32-bit pointers in size.
- */
-#define MPX_BT_SIZE_BYTES_32	(1UL<<14)
-#define MPX_BT_ENTRY_BYTES_32	16
-#define MPX_BT_NR_ENTRIES_32	(MPX_BT_SIZE_BYTES_32/MPX_BT_ENTRY_BYTES_32)
-
-#define MPX_BNDSTA_TAIL		2
-#define MPX_BNDCFG_TAIL		12
-#define MPX_BNDSTA_ADDR_MASK	(~((1UL<<MPX_BNDSTA_TAIL)-1))
-#define MPX_BNDCFG_ADDR_MASK	(~((1UL<<MPX_BNDCFG_TAIL)-1))
-#define MPX_BNDSTA_ERROR_CODE	0x3
-
-struct mpx_fault_info {
-	void __user *addr;
-	void __user *lower;
-	void __user *upper;
-};
-
-#ifdef CONFIG_X86_INTEL_MPX
-
-extern int mpx_fault_info(struct mpx_fault_info *info, struct pt_regs *regs);
-extern int mpx_handle_bd_fault(void);
-
-static inline int kernel_managing_mpx_tables(struct mm_struct *mm)
-{
-	return (mm->context.bd_addr != MPX_INVALID_BOUNDS_DIR);
-}
-
-static inline void mpx_mm_init(struct mm_struct *mm)
-{
-	/*
-	 * NULL is theoretically a valid place to put the bounds
-	 * directory, so point this at an invalid address.
-	 */
-	mm->context.bd_addr = MPX_INVALID_BOUNDS_DIR;
-}
-
-extern void mpx_notify_unmap(struct mm_struct *mm, unsigned long start, unsigned long end);
-extern unsigned long mpx_unmapped_area_check(unsigned long addr, unsigned long len, unsigned long flags);
-
-#else
-static inline int mpx_fault_info(struct mpx_fault_info *info, struct pt_regs *regs)
-{
-	return -EINVAL;
-}
-static inline int mpx_handle_bd_fault(void)
-{
-	return -EINVAL;
-}
-static inline int kernel_managing_mpx_tables(struct mm_struct *mm)
-{
-	return 0;
-}
-static inline void mpx_mm_init(struct mm_struct *mm)
-{
-}
-static inline void mpx_notify_unmap(struct mm_struct *mm,
-				    unsigned long start, unsigned long end)
-{
-}
-
-static inline unsigned long mpx_unmapped_area_check(unsigned long addr,
-		unsigned long len, unsigned long flags)
-{
-	return addr;
-}
-#endif /* CONFIG_X86_INTEL_MPX */
-
-#endif /* _ASM_X86_MPX_H */

arch/x86/include/asm/processor.h

@@ -915,24 +915,6 @@ extern int set_tsc_mode(unsigned int val);
 
 DECLARE_PER_CPU(u64, msr_misc_features_shadow);
 
-/* Register/unregister a process' MPX related resource */
-#define MPX_ENABLE_MANAGEMENT()	mpx_enable_management()
-#define MPX_DISABLE_MANAGEMENT()	mpx_disable_management()
-
-#ifdef CONFIG_X86_INTEL_MPX
-extern int mpx_enable_management(void);
-extern int mpx_disable_management(void);
-#else
-static inline int mpx_enable_management(void)
-{
-	return -EINVAL;
-}
-static inline int mpx_disable_management(void)
-{
-	return -EINVAL;
-}
-#endif /* CONFIG_X86_INTEL_MPX */
-
 #ifdef CONFIG_CPU_SUP_AMD
 extern u16 amd_get_nb_id(int cpu);
 extern u32 amd_get_nodes_per_socket(void);

arch/x86/include/asm/trace/mpx.h

-/* SPDX-License-Identifier: GPL-2.0 */
-#undef TRACE_SYSTEM
-#define TRACE_SYSTEM mpx
-
-#if !defined(_TRACE_MPX_H) || defined(TRACE_HEADER_MULTI_READ)
-#define _TRACE_MPX_H
-
-#include <linux/tracepoint.h>
-
-#ifdef CONFIG_X86_INTEL_MPX
-
-TRACE_EVENT(mpx_bounds_register_exception,
-
-	TP_PROTO(void __user *addr_referenced,
-		 const struct mpx_bndreg *bndreg),
-	TP_ARGS(addr_referenced, bndreg),
-
-	TP_STRUCT__entry(
-		__field(void __user *, addr_referenced)
-		__field(u64, lower_bound)
-		__field(u64, upper_bound)
-	),
-
-	TP_fast_assign(
-		__entry->addr_referenced = addr_referenced;
-		__entry->lower_bound = bndreg->lower_bound;
-		__entry->upper_bound = bndreg->upper_bound;
-	),
-	/*
-	 * Note that we are printing out the '~' of the upper
-	 * bounds register here.  It is actually stored in its
-	 * one's complement form so that its 'init' state
-	 * corresponds to all 0's.  But, that looks like
-	 * gibberish when printed out, so print out the 1's
-	 * complement instead of the actual value here.  Note
-	 * though that you still need to specify filters for the
-	 * actual value, not the displayed one.
-	 */
-	TP_printk("address referenced: 0x%p bounds: lower: 0x%llx ~upper: 0x%llx",
-		__entry->addr_referenced,
-		__entry->lower_bound,
-		~__entry->upper_bound
-	)
-);
-
-TRACE_EVENT(bounds_exception_mpx,
-
-	TP_PROTO(const struct mpx_bndcsr *bndcsr),
-	TP_ARGS(bndcsr),
-
-	TP_STRUCT__entry(
-		__field(u64, bndcfgu)
-		__field(u64, bndstatus)
-	),
-
-	TP_fast_assign(
-		/* need to get rid of the 'const' on bndcsr */
-		__entry->bndcfgu   = (u64)bndcsr->bndcfgu;
-		__entry->bndstatus = (u64)bndcsr->bndstatus;
-	),
-
-	TP_printk("bndcfgu:0x%llx bndstatus:0x%llx",
-		__entry->bndcfgu,
-		__entry->bndstatus)
-);
-
-DECLARE_EVENT_CLASS(mpx_range_trace,
-
-	TP_PROTO(unsigned long start,
-		 unsigned long end),
-	TP_ARGS(start, end),
-
-	TP_STRUCT__entry(
-		__field(unsigned long, start)
-		__field(unsigned long, end)
-	),
-
-	TP_fast_assign(
-		__entry->start = start;
-		__entry->end   = end;
-	),
-
-	TP_printk("[0x%p:0x%p]",
-		(void *)__entry->start,
-		(void *)__entry->end
-	)
-);
-
-DEFINE_EVENT(mpx_range_trace, mpx_unmap_zap,
-	TP_PROTO(unsigned long start, unsigned long end),
-	TP_ARGS(start, end)
-);
-
-DEFINE_EVENT(mpx_range_trace, mpx_unmap_search,
-	TP_PROTO(unsigned long start, unsigned long end),
-	TP_ARGS(start, end)
-);
-
-TRACE_EVENT(mpx_new_bounds_table,
-
-	TP_PROTO(unsigned long table_vaddr),
-	TP_ARGS(table_vaddr),
-
-	TP_STRUCT__entry(
-		__field(unsigned long, table_vaddr)
-	),
-
-	TP_fast_assign(
-		__entry->table_vaddr = table_vaddr;
-	),
-
-	TP_printk("table vaddr:%p", (void *)__entry->table_vaddr)
-);
-
-#else
-
-/*
- * This gets used outside of MPX-specific code, so we need a stub.
- */
-static inline
-void trace_bounds_exception_mpx(const struct mpx_bndcsr *bndcsr)
-{
-}
-
-#endif /* CONFIG_X86_INTEL_MPX */
-
-#undef TRACE_INCLUDE_PATH
-#define TRACE_INCLUDE_PATH asm/trace/
-#undef TRACE_INCLUDE_FILE
-#define TRACE_INCLUDE_FILE mpx
-#endif /* _TRACE_MPX_H */
-
-/* This part must be outside protection */
-#include <trace/define_trace.h>

arch/x86/kernel/cpu/common.c

@@ -165,22 +165,6 @@ DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = {
 } };
 EXPORT_PER_CPU_SYMBOL_GPL(gdt_page);
 
-static int __init x86_mpx_setup(char *s)
-{
-	/* require an exact match without trailing characters */
-	if (strlen(s))
-		return 0;
-
-	/* do not emit a message if the feature is not present */
-	if (!boot_cpu_has(X86_FEATURE_MPX))
-		return 1;
-
-	setup_clear_cpu_cap(X86_FEATURE_MPX);
-	pr_info("nompx: Intel Memory Protection Extensions (MPX) disabled\n");
-	return 1;
-}
-__setup("nompx", x86_mpx_setup);
-
 #ifdef CONFIG_X86_64
 static int __init x86_nopcid_setup(char *s)
 {
@@ -307,8 +291,6 @@ static inline void squash_the_stupid_serial_number(struct cpuinfo_x86 *c)
 static __init int setup_disable_smep(char *arg)
 {
 	setup_clear_cpu_cap(X86_FEATURE_SMEP);
-	/* Check for things that depend on SMEP being enabled: */
-	check_mpx_erratum(&boot_cpu_data);
 	return 1;
 }
 __setup("nosmep", setup_disable_smep);

arch/x86/kernel/cpu/intel.c

@@ -31,41 +31,6 @@
 #include <asm/apic.h>
 #endif
 
-/*
- * Just in case our CPU detection goes bad, or you have a weird system,
- * allow a way to override the automatic disabling of MPX.
- */
-static int forcempx;
-
-static int __init forcempx_setup(char *__unused)
-{
-	forcempx = 1;
-
-	return 1;
-}
-__setup("intel-skd-046-workaround=disable", forcempx_setup);
-
-void check_mpx_erratum(struct cpuinfo_x86 *c)
-{
-	if (forcempx)
-		return;
-	/*
-	 * Turn off the MPX feature on CPUs where SMEP is not
-	 * available or disabled.
-	 *
-	 * Works around Intel Erratum SKD046: "Branch Instructions
-	 * May Initialize MPX Bound Registers Incorrectly".
-	 *
-	 * This might falsely disable MPX on systems without
-	 * SMEP, like Atom processors without SMEP.  But there
-	 * is no such hardware known at the moment.
-	 */
-	if (cpu_has(c, X86_FEATURE_MPX) && !cpu_has(c, X86_FEATURE_SMEP)) {
-		setup_clear_cpu_cap(X86_FEATURE_MPX);
-		pr_warn("x86/mpx: Disabling MPX since SMEP not present\n");
-	}
-}
-
 /*
  * Processors which have self-snooping capability can handle conflicting
  * memory type across CPUs by snooping its own cache. However, there exists
@@ -330,7 +295,6 @@ static void early_init_intel(struct cpuinfo_x86 *c)
 			c->x86_coreid_bits = get_count_order((ebx >> 16) & 0xff);
 	}
 
-	check_mpx_erratum(c);
 	check_memory_type_self_snoop_errata(c);
 
 	/*

arch/x86/kernel/setup.c

@@ -947,8 +947,6 @@ void __init setup_arch(char **cmdline_p)
 	init_mm.end_data = (unsigned long) _edata;
 	init_mm.brk = _brk_end;
 
-	mpx_mm_init(&init_mm);
-
 	code_resource.start = __pa_symbol(_text);
 	code_resource.end = __pa_symbol(_etext)-1;
 	data_resource.start = __pa_symbol(_etext);

arch/x86/kernel/sys_x86_64.c

@@ -22,7 +22,6 @@
 #include <asm/elf.h>
 #include <asm/ia32.h>
 #include <asm/syscalls.h>
-#include <asm/mpx.h>
 
 /*
  * Align a virtual address to avoid aliasing in the I$ on AMD F15h.
@@ -137,10 +136,6 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
 	struct vm_unmapped_area_info info;
 	unsigned long begin, end;
 
-	addr = mpx_unmapped_area_check(addr, len, flags);
-	if (IS_ERR_VALUE(addr))
-		return addr;
-
 	if (flags & MAP_FIXED)
 		return addr;
 
@@ -180,10 +175,6 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 	unsigned long addr = addr0;
 	struct vm_unmapped_area_info info;
 
-	addr = mpx_unmapped_area_check(addr, len, flags);
-	if (IS_ERR_VALUE(addr))
-		return addr;
-
 	/* requested length too big for entire address space */
 	if (len > TASK_SIZE)
 		return -ENOMEM;

arch/x86/mm/hugetlbpage.c

@@ -19,7 +19,6 @@
 #include <asm/tlbflush.h>
 #include <asm/pgalloc.h>
 #include <asm/elf.h>
-#include <asm/mpx.h>
 
 #if 0	/* This is just for testing */
 struct page *
@@ -151,10 +150,6 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 	if (len & ~huge_page_mask(h))
 		return -EINVAL;
 
-	addr = mpx_unmapped_area_check(addr, len, flags);
-	if (IS_ERR_VALUE(addr))
-		return addr;
-
 	if (len > TASK_SIZE)
 		return -ENOMEM;
 

arch/x86/mm/mmap.c

@@ -163,8 +163,6 @@ unsigned long get_mmap_base(int is_legacy)
 
 const char *arch_vma_name(struct vm_area_struct *vma)
 {
-	if (vma->vm_flags & VM_MPX)
-		return "[mpx]";
 	return NULL;
 }