[PATCH 06/23] x86, kaiser: introduce user-mapped percpu areas

From: Dave Hansen
Date: Tue Oct 31 2017 - 18:36:35 EST

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These patches are based on work from a team at Graz University of
Technology posted here: https://github.com/IAIK/KAISER

The KAISER approach keeps two copies of the page tables: one for running
in the kernel and one for running userspace. But, there are a few
structures that are needed for switching in and out of the kernel and
a good subset of *those* are per-cpu data.

This patch creates a new kind of per-cpu data that is mapped and can be
used no matter which copy of the page tables we are using.

Thanks to Hugh Dickins for cleanups to this code.

Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Moritz Lipp <moritz.lipp@xxxxxxxxxxxxxx>
Cc: Daniel Gruss <daniel.gruss@xxxxxxxxxxxxxx>
Cc: Michael Schwarz <michael.schwarz@xxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
---

b/arch/x86/include/asm/desc.h | 2 +-
b/arch/x86/include/asm/hw_irq.h | 2 +-
b/arch/x86/include/asm/processor.h | 2 +-
b/arch/x86/kernel/cpu/common.c | 4 ++--
b/arch/x86/kernel/irqinit.c | 2 +-
b/arch/x86/kernel/process.c | 2 +-
b/include/asm-generic/vmlinux.lds.h | 7 +++++++
b/include/linux/percpu-defs.h | 32 +++++++++++++++++++++++++++++++-
8 files changed, 45 insertions(+), 8 deletions(-)

diff -puN arch/x86/include/asm/desc.h~kaiser-prep-user-mapped-percpu arch/x86/include/asm/desc.h
--- a/arch/x86/include/asm/desc.h~kaiser-prep-user-mapped-percpu 2017-10-31 15:03:51.046146272 -0700
+++ b/arch/x86/include/asm/desc.h 2017-10-31 15:03:51.066147217 -0700
@@ -45,7 +45,7 @@ struct gdt_page {
struct desc_struct gdt[GDT_ENTRIES];
} __attribute__((aligned(PAGE_SIZE)));

-DECLARE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page);
+DECLARE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(struct gdt_page, gdt_page);

/* Provide the original GDT */
static inline struct desc_struct *get_cpu_gdt_rw(unsigned int cpu)
diff -puN arch/x86/include/asm/hw_irq.h~kaiser-prep-user-mapped-percpu arch/x86/include/asm/hw_irq.h
--- a/arch/x86/include/asm/hw_irq.h~kaiser-prep-user-mapped-percpu 2017-10-31 15:03:51.048146366 -0700
+++ b/arch/x86/include/asm/hw_irq.h 2017-10-31 15:03:51.066147217 -0700
@@ -160,7 +160,7 @@ extern char irq_entries_start[];
#define VECTOR_RETRIGGERED ((void *)~0UL)

typedef struct irq_desc* vector_irq_t[NR_VECTORS];
-DECLARE_PER_CPU(vector_irq_t, vector_irq);
+DECLARE_PER_CPU_USER_MAPPED(vector_irq_t, vector_irq);

#endif /* !ASSEMBLY_ */

diff -puN arch/x86/include/asm/processor.h~kaiser-prep-user-mapped-percpu arch/x86/include/asm/processor.h
--- a/arch/x86/include/asm/processor.h~kaiser-prep-user-mapped-percpu 2017-10-31 15:03:51.051146508 -0700
+++ b/arch/x86/include/asm/processor.h 2017-10-31 15:03:51.067147264 -0700
@@ -348,7 +348,7 @@ struct tss_struct {

} ____cacheline_aligned;

-DECLARE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss);
+DECLARE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(struct tss_struct, cpu_tss);

/*
* sizeof(unsigned long) coming from an extra "long" at the end
diff -puN arch/x86/kernel/cpu/common.c~kaiser-prep-user-mapped-percpu arch/x86/kernel/cpu/common.c
--- a/arch/x86/kernel/cpu/common.c~kaiser-prep-user-mapped-percpu 2017-10-31 15:03:51.053146603 -0700
+++ b/arch/x86/kernel/cpu/common.c 2017-10-31 15:03:51.067147264 -0700
@@ -98,7 +98,7 @@ static const struct cpu_dev default_cpu

static const struct cpu_dev *this_cpu = &default_cpu;

-DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = {
+DEFINE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(struct gdt_page, gdt_page) = { .gdt = {
#ifdef CONFIG_X86_64
/*
* We need valid kernel segments for data and code in long mode too
@@ -1345,7 +1345,7 @@ static const unsigned int exception_stac
[DEBUG_STACK - 1] = DEBUG_STKSZ
};

-static DEFINE_PER_CPU_PAGE_ALIGNED(char, exception_stacks
+DEFINE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(char, exception_stacks
[(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]);

/* May not be marked __init: used by software suspend */
diff -puN arch/x86/kernel/irqinit.c~kaiser-prep-user-mapped-percpu arch/x86/kernel/irqinit.c
--- a/arch/x86/kernel/irqinit.c~kaiser-prep-user-mapped-percpu 2017-10-31 15:03:51.055146697 -0700
+++ b/arch/x86/kernel/irqinit.c 2017-10-31 15:03:51.068147312 -0700
@@ -51,7 +51,7 @@ static struct irqaction irq2 = {
.flags = IRQF_NO_THREAD,
};

-DEFINE_PER_CPU(vector_irq_t, vector_irq) = {
+DEFINE_PER_CPU_USER_MAPPED(vector_irq_t, vector_irq) = {
[0 ... NR_VECTORS - 1] = VECTOR_UNUSED,
};

diff -puN arch/x86/kernel/process.c~kaiser-prep-user-mapped-percpu arch/x86/kernel/process.c
--- a/arch/x86/kernel/process.c~kaiser-prep-user-mapped-percpu 2017-10-31 15:03:51.057146792 -0700
+++ b/arch/x86/kernel/process.c 2017-10-31 15:03:51.068147312 -0700
@@ -46,7 +46,7 @@
* section. Since TSS's are completely CPU-local, we want them
* on exact cacheline boundaries, to eliminate cacheline ping-pong.
*/
-__visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = {
+__visible DEFINE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(struct tss_struct, cpu_tss) = {
.x86_tss = {
.sp0 = TOP_OF_INIT_STACK,
#ifdef CONFIG_X86_32
diff -puN include/asm-generic/vmlinux.lds.h~kaiser-prep-user-mapped-percpu include/asm-generic/vmlinux.lds.h
--- a/include/asm-generic/vmlinux.lds.h~kaiser-prep-user-mapped-percpu 2017-10-31 15:03:51.059146886 -0700
+++ b/include/asm-generic/vmlinux.lds.h 2017-10-31 15:03:51.068147312 -0700
@@ -807,7 +807,14 @@
*/
#define PERCPU_INPUT(cacheline) \
VMLINUX_SYMBOL(__per_cpu_start) = .; \
+ VMLINUX_SYMBOL(__per_cpu_user_mapped_start) = .; \
*(.data..percpu..first) \
+ . = ALIGN(cacheline); \
+ *(.data..percpu..user_mapped) \
+ *(.data..percpu..user_mapped..shared_aligned) \
+ . = ALIGN(PAGE_SIZE); \
+ *(.data..percpu..user_mapped..page_aligned) \
+ VMLINUX_SYMBOL(__per_cpu_user_mapped_end) = .; \
. = ALIGN(PAGE_SIZE); \
*(.data..percpu..page_aligned) \
. = ALIGN(cacheline); \
diff -puN include/linux/percpu-defs.h~kaiser-prep-user-mapped-percpu include/linux/percpu-defs.h
--- a/include/linux/percpu-defs.h~kaiser-prep-user-mapped-percpu 2017-10-31 15:03:51.062147028 -0700
+++ b/include/linux/percpu-defs.h 2017-10-31 15:03:51.069147359 -0700
@@ -35,6 +35,12 @@

#endif

+#ifdef CONFIG_KAISER
+#define USER_MAPPED_SECTION "..user_mapped"
+#else
+#define USER_MAPPED_SECTION ""
+#endif
+
/*
* Base implementations of per-CPU variable declarations and definitions, where
* the section in which the variable is to be placed is provided by the
@@ -115,6 +121,12 @@
#define DEFINE_PER_CPU(type, name) \
DEFINE_PER_CPU_SECTION(type, name, "")

+#define DECLARE_PER_CPU_USER_MAPPED(type, name) \
+ DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION)
+
+#define DEFINE_PER_CPU_USER_MAPPED(type, name) \
+ DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION)
+
/*
* Declaration/definition used for per-CPU variables that must come first in
* the set of variables.
@@ -144,6 +156,14 @@
DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
____cacheline_aligned_in_smp

+#define DECLARE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(type, name) \
+ DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION PER_CPU_SHARED_ALIGNED_SECTION) \
+ ____cacheline_aligned_in_smp
+
+#define DEFINE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(type, name) \
+ DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION PER_CPU_SHARED_ALIGNED_SECTION) \
+ ____cacheline_aligned_in_smp
+
#define DECLARE_PER_CPU_ALIGNED(type, name) \
DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
____cacheline_aligned
@@ -162,11 +182,21 @@
#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \
DEFINE_PER_CPU_SECTION(type, name, "..page_aligned") \
__aligned(PAGE_SIZE)
+/*
+ * Declaration/definition used for per-CPU variables that must be page aligned and need to be mapped in user mode.
+ */
+#define DECLARE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(type, name) \
+ DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION"..page_aligned") \
+ __aligned(PAGE_SIZE)
+
+#define DEFINE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(type, name) \
+ DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION"..page_aligned") \
+ __aligned(PAGE_SIZE)

/*
* Declaration/definition used for per-CPU variables that must be read mostly.
*/
-#define DECLARE_PER_CPU_READ_MOSTLY(type, name) \
+#define DECLARE_PER_CPU_READ_MOSTLY(type, name) \
DECLARE_PER_CPU_SECTION(type, name, "..read_mostly")

#define DEFINE_PER_CPU_READ_MOSTLY(type, name) \
_

Next message: Dave Hansen: "[PATCH 02/23] x86, kaiser: do not set _PAGE_USER for init_mm page tables"
Previous message: Matthias Kaehlcke: "Re: [PATCH v2] sched/sysctl: Fix attributes of some extern declarations"
In reply to: Dave Hansen: "[PATCH 10/23] x86, kaiser: make sure static PGDs are 8k in size"
Next in thread: Dave Hansen: "[PATCH 02/23] x86, kaiser: do not set _PAGE_USER for init_mm page tables"
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