[PATCH 02/26] x86: Create CONFIG_MITIGATION_ADDRESS_SPACE_ISOLATION

[Brendan Jackman <jackmanb@google.com>]

Currently a nop config. Keeping as a separate commit for easy review of
the boring bits. Later commits will use and enable this new config.

This config is only added for non-UML x86_64 as other architectures do
not yet have pending implementations. It also has somewhat artificial
dependencies on !PARAVIRT and !KASAN which are explained in the Kconfig
file.

Co-developed-by: Junaid Shahid <junaids@google.com>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 arch/alpha/include/asm/Kbuild      |  1 +
 arch/arc/include/asm/Kbuild        |  1 +
 arch/arm/include/asm/Kbuild        |  1 +
 arch/arm64/include/asm/Kbuild      |  1 +
 arch/csky/include/asm/Kbuild       |  1 +
 arch/hexagon/include/asm/Kbuild    |  1 +
 arch/loongarch/include/asm/Kbuild  |  1 +
 arch/m68k/include/asm/Kbuild       |  1 +
 arch/microblaze/include/asm/Kbuild |  1 +
 arch/mips/include/asm/Kbuild       |  1 +
 arch/nios2/include/asm/Kbuild      |  1 +
 arch/openrisc/include/asm/Kbuild   |  1 +
 arch/parisc/include/asm/Kbuild     |  1 +
 arch/powerpc/include/asm/Kbuild    |  1 +
 arch/riscv/include/asm/Kbuild      |  1 +
 arch/s390/include/asm/Kbuild       |  1 +
 arch/sh/include/asm/Kbuild         |  1 +
 arch/sparc/include/asm/Kbuild      |  1 +
 arch/um/include/asm/Kbuild         |  1 +
 arch/x86/Kconfig                   | 19 +++++++++++++++++++
 arch/xtensa/include/asm/Kbuild     |  1 +
 include/asm-generic/asi.h          |  5 +++++
 22 files changed, 44 insertions(+)

diff --git a/arch/alpha/include/asm/Kbuild b/arch/alpha/include/asm/Kbuild
index 396caece6d6d9..ca72ce3baca13 100644
--- a/arch/alpha/include/asm/Kbuild
+++ b/arch/alpha/include/asm/Kbuild
@@ -5,3 +5,4 @@ generic-y += agp.h
 generic-y += asm-offsets.h
 generic-y += kvm_para.h
 generic-y += mcs_spinlock.h
+generic-y += asi.h
diff --git a/arch/arc/include/asm/Kbuild b/arch/arc/include/asm/Kbuild
index 3c1afa524b9c2..60bdeffa7c31e 100644
--- a/arch/arc/include/asm/Kbuild
+++ b/arch/arc/include/asm/Kbuild
@@ -4,3 +4,4 @@ generic-y += kvm_para.h
 generic-y += mcs_spinlock.h
 generic-y += parport.h
 generic-y += user.h
+generic-y += asi.h
diff --git a/arch/arm/include/asm/Kbuild b/arch/arm/include/asm/Kbuild
index 03657ff8fbe3d..1e2c3d8dbbd99 100644
--- a/arch/arm/include/asm/Kbuild
+++ b/arch/arm/include/asm/Kbuild
@@ -6,3 +6,4 @@ generic-y += parport.h
 
 generated-y += mach-types.h
 generated-y += unistd-nr.h
+generic-y += asi.h
diff --git a/arch/arm64/include/asm/Kbuild b/arch/arm64/include/asm/Kbuild
index 4b6d2d52053e4..f95699a559309 100644
--- a/arch/arm64/include/asm/Kbuild
+++ b/arch/arm64/include/asm/Kbuild
@@ -5,6 +5,7 @@ generic-y += qrwlock.h
 generic-y += qspinlock.h
 generic-y += parport.h
 generic-y += user.h
+generic-y += asi.h
 
 generated-y += cpucap-defs.h
 generated-y += sysreg-defs.h
diff --git a/arch/csky/include/asm/Kbuild b/arch/csky/include/asm/Kbuild
index 1117c28cb7e8a..5e49ccb571644 100644
--- a/arch/csky/include/asm/Kbuild
+++ b/arch/csky/include/asm/Kbuild
@@ -10,3 +10,4 @@ generic-y += qspinlock.h
 generic-y += parport.h
 generic-y += user.h
 generic-y += vmlinux.lds.h
+generic-y += asi.h
\ No newline at end of file
diff --git a/arch/hexagon/include/asm/Kbuild b/arch/hexagon/include/asm/Kbuild
index 3ece3c93fe086..744ffbeeb7ae4 100644
--- a/arch/hexagon/include/asm/Kbuild
+++ b/arch/hexagon/include/asm/Kbuild
@@ -3,3 +3,4 @@ generic-y += extable.h
 generic-y += iomap.h
 generic-y += kvm_para.h
 generic-y += mcs_spinlock.h
+generic-y += asi.h
diff --git a/arch/loongarch/include/asm/Kbuild b/arch/loongarch/include/asm/Kbuild
index 2dbec7853ae86..66fcd325d6083 100644
--- a/arch/loongarch/include/asm/Kbuild
+++ b/arch/loongarch/include/asm/Kbuild
@@ -27,3 +27,4 @@ generic-y += param.h
 generic-y += posix_types.h
 generic-y += resource.h
 generic-y += kvm_para.h
+generic-y += asi.h
diff --git a/arch/m68k/include/asm/Kbuild b/arch/m68k/include/asm/Kbuild
index 0dbf9c5c6faeb..faf0f135df4ab 100644
--- a/arch/m68k/include/asm/Kbuild
+++ b/arch/m68k/include/asm/Kbuild
@@ -4,3 +4,4 @@ generic-y += extable.h
 generic-y += kvm_para.h
 generic-y += mcs_spinlock.h
 generic-y += spinlock.h
+generic-y += asi.h
diff --git a/arch/microblaze/include/asm/Kbuild b/arch/microblaze/include/asm/Kbuild
index a055f5dbe00a3..012e4bf83c134 100644
--- a/arch/microblaze/include/asm/Kbuild
+++ b/arch/microblaze/include/asm/Kbuild
@@ -8,3 +8,4 @@ generic-y += parport.h
 generic-y += syscalls.h
 generic-y += tlb.h
 generic-y += user.h
+generic-y += asi.h
diff --git a/arch/mips/include/asm/Kbuild b/arch/mips/include/asm/Kbuild
index 7ba67a0d6c97b..3191699298d80 100644
--- a/arch/mips/include/asm/Kbuild
+++ b/arch/mips/include/asm/Kbuild
@@ -13,3 +13,4 @@ generic-y += parport.h
 generic-y += qrwlock.h
 generic-y += qspinlock.h
 generic-y += user.h
+generic-y += asi.h
diff --git a/arch/nios2/include/asm/Kbuild b/arch/nios2/include/asm/Kbuild
index 7fe7437555fb4..bfdc4026c5b16 100644
--- a/arch/nios2/include/asm/Kbuild
+++ b/arch/nios2/include/asm/Kbuild
@@ -5,3 +5,4 @@ generic-y += kvm_para.h
 generic-y += mcs_spinlock.h
 generic-y += spinlock.h
 generic-y += user.h
+generic-y += asi.h
diff --git a/arch/openrisc/include/asm/Kbuild b/arch/openrisc/include/asm/Kbuild
index c8c99b554ca4c..d137c4e08e369 100644
--- a/arch/openrisc/include/asm/Kbuild
+++ b/arch/openrisc/include/asm/Kbuild
@@ -7,3 +7,4 @@ generic-y += spinlock.h
 generic-y += qrwlock_types.h
 generic-y += qrwlock.h
 generic-y += user.h
+generic-y += asi.h
diff --git a/arch/parisc/include/asm/Kbuild b/arch/parisc/include/asm/Kbuild
index 4fb596d94c893..3cbb4eb14712c 100644
--- a/arch/parisc/include/asm/Kbuild
+++ b/arch/parisc/include/asm/Kbuild
@@ -5,3 +5,4 @@ generic-y += agp.h
 generic-y += kvm_para.h
 generic-y += mcs_spinlock.h
 generic-y += user.h
+generic-y += asi.h
diff --git a/arch/powerpc/include/asm/Kbuild b/arch/powerpc/include/asm/Kbuild
index 61a8d5555cd7e..103c7e2f66987 100644
--- a/arch/powerpc/include/asm/Kbuild
+++ b/arch/powerpc/include/asm/Kbuild
@@ -8,3 +8,4 @@ generic-y += mcs_spinlock.h
 generic-y += qrwlock.h
 generic-y += vtime.h
 generic-y += early_ioremap.h
+generic-y += asi.h
diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
index 504f8b7e72d41..08c199a56731e 100644
--- a/arch/riscv/include/asm/Kbuild
+++ b/arch/riscv/include/asm/Kbuild
@@ -9,3 +9,4 @@ generic-y += qrwlock.h
 generic-y += qrwlock_types.h
 generic-y += user.h
 generic-y += vmlinux.lds.h
+generic-y += asi.h
diff --git a/arch/s390/include/asm/Kbuild b/arch/s390/include/asm/Kbuild
index 4b904110d27cb..b5caf77e8d955 100644
--- a/arch/s390/include/asm/Kbuild
+++ b/arch/s390/include/asm/Kbuild
@@ -7,3 +7,4 @@ generated-y += unistd_nr.h
 generic-y += asm-offsets.h
 generic-y += kvm_types.h
 generic-y += mcs_spinlock.h
+generic-y += asi.h
diff --git a/arch/sh/include/asm/Kbuild b/arch/sh/include/asm/Kbuild
index fc44d9c88b419..ea19e45158285 100644
--- a/arch/sh/include/asm/Kbuild
+++ b/arch/sh/include/asm/Kbuild
@@ -3,3 +3,4 @@ generated-y += syscall_table.h
 generic-y += kvm_para.h
 generic-y += mcs_spinlock.h
 generic-y += parport.h
+generic-y += asi.h
diff --git a/arch/sparc/include/asm/Kbuild b/arch/sparc/include/asm/Kbuild
index 43b0ae4c2c211..cb9062c9be17f 100644
--- a/arch/sparc/include/asm/Kbuild
+++ b/arch/sparc/include/asm/Kbuild
@@ -4,3 +4,4 @@ generated-y += syscall_table_64.h
 generic-y += agp.h
 generic-y += kvm_para.h
 generic-y += mcs_spinlock.h
+generic-y += asi.h
diff --git a/arch/um/include/asm/Kbuild b/arch/um/include/asm/Kbuild
index b2d834a29f3a9..1bcb16b09dc49 100644
--- a/arch/um/include/asm/Kbuild
+++ b/arch/um/include/asm/Kbuild
@@ -28,3 +28,4 @@ generic-y += trace_clock.h
 generic-y += kprobes.h
 generic-y += mm_hooks.h
 generic-y += vga.h
+generic-y += asi.h
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 928820e61cb50..ff74aa53842ea 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2516,6 +2516,25 @@ config MITIGATION_PAGE_TABLE_ISOLATION
 
 	  See Documentation/arch/x86/pti.rst for more details.
 
+config MITIGATION_ADDRESS_SPACE_ISOLATION
+	bool "Allow code to run with a reduced kernel address space"
+	default n
+	depends on X86_64 && !PARAVIRT && !KASAN && !UML
+	help
+	  This feature provides the ability to run some kernel code
+	  with a reduced kernel address space. This can be used to
+	  mitigate some speculative execution attacks.
+
+	  The !PARAVIRT dependency is only because of lack of testing; in theory
+	  the code is written to work under paravirtualization. In practice
+	  there are likely to be unhandled cases, in particular concerning TLB
+	  flushes.
+
+	  The !KASAN dependency is mainly because ASI creates a secondary
+	  direct-map region in order to implement local-nonsensitive memory.
+	  This dependencies will later be removed with extensions to the KASAN
+	  implementation.
+
 config MITIGATION_RETPOLINE
 	bool "Avoid speculative indirect branches in kernel"
 	select OBJTOOL if HAVE_OBJTOOL
diff --git a/arch/xtensa/include/asm/Kbuild b/arch/xtensa/include/asm/Kbuild
index fa07c686cbcc2..07cea6902f980 100644
--- a/arch/xtensa/include/asm/Kbuild
+++ b/arch/xtensa/include/asm/Kbuild
@@ -8,3 +8,4 @@ generic-y += parport.h
 generic-y += qrwlock.h
 generic-y += qspinlock.h
 generic-y += user.h
+generic-y += asi.h
diff --git a/include/asm-generic/asi.h b/include/asm-generic/asi.h
new file mode 100644
index 0000000000000..c4d9a5ff860a9
--- /dev/null
+++ b/include/asm-generic/asi.h
@@ -0,0 +1,5 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_GENERIC_ASI_H
+#define __ASM_GENERIC_ASI_H
+
+#endif

-- 
2.45.2.993.g49e7a77208-goog