Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1705789 > unrolled thread

[PATCH 00/14] arm64: VMAP_STACK support

Back to article view | Back to linux.kernel

Contents

  [PATCH 00/14] arm64: VMAP_STACK support Mark Rutland <mark.rutland@arm.com> - 2017-08-07 20:40 +0200
    [PATCH 03/14] arm64: kernel: remove {THREAD,IRQ_STACK}_START_SP Mark Rutland <mark.rutland@arm.com> - 2017-08-07 20:40 +0200
    [PATCH 06/14] arm64: clean up irq stack definitions Mark Rutland <mark.rutland@arm.com> - 2017-08-07 20:40 +0200
    [PATCH 08/14] efi/arm64: add EFI_KIMG_ALIGN Mark Rutland <mark.rutland@arm.com> - 2017-08-07 20:40 +0200
    [PATCH 14/14] arm64: add VMAP_STACK overflow detection Mark Rutland <mark.rutland@arm.com> - 2017-08-07 20:40 +0200
    [PATCH 13/14] arm64: add on_accessible_stack() Mark Rutland <mark.rutland@arm.com> - 2017-08-07 20:40 +0200
    [PATCH 07/14] arm64: move SEGMENT_ALIGN to <asm/memory.h> Mark Rutland <mark.rutland@arm.com> - 2017-08-07 20:50 +0200
    [PATCH 04/14] arm64: factor out PAGE_* and CONT_* definitions Mark Rutland <mark.rutland@arm.com> - 2017-08-07 20:50 +0200

#1705789 — [PATCH 00/14] arm64: VMAP_STACK support

Hi,

Ard and I have worked together to implement vmap stack support for
arm64. This supersedes our earlier vmap stack RFCs [0,1]. The git author
stats are a little misleading, as I've teased parts out into smaller
patches for review.

The series is based on our stack dump rework [2,3], which can be found
in the arm64/exception-stack branch [4] of my kernel.org repo. This
series can be found in the arm64/vmap-stack branch [5] of the same repo.

On arm64, there is no double-fault exception, as software saves
exception context to the stack. An erroneous memory access taken during
exception handling results in a data abort, as with any other erroneous
memory access. To avoid taking these recursively, we must detect
overflow by checking the SP before we attempt to store any context to
the stack. Doing this efficiently requires a couple of tricks.

For a naturally aligned stack, bits THREAD_SHIFT-1:0 of a valid SP may
contain any arbitrary value:

	0bXX .. 11111111111111
	0bXX .. 11011001011100
	0bXX .. 00000000000000

By aligning stacks to double their natural alignment, we know that the
THREAD_SHIFT bit of any valid SP must be zero:

	0bXX .. 0 11111111111111
	0bXX .. 0 11011001011100
	0bXX .. 0 00000000000000

... while an overflow will result in this bit flipping, along with
(some) other high-order bits:

	0bXX .. 0 00000000000000
	< SP -= 1 >
	0bXX .. 1 11111111111111

... and thus, we can detect overflows of up to THREAD_SIZE by testing
the THREAD_SHIFT bit of the SP value.

Provided we can get the SP into a general purpose register, we can
perform this test with a single TBNZ instruction. We don't have scratch
space to store a GPR, but we can (partially) swap the SP with a GPR
using arithmetic to perform the test:

	add	sp, sp, x0		// sp' = sp + x0
	sub	x0, sp, x0		// x0' = sp' - x0 = (sp + x0) - x0 = sp
	tbnz	x0, #THREAD_SHIFT, overflow_handler
	sub	x0, sp, x0		// sp' - x0' = (sp + x0) - sp = x0
	sub	sp, sp, x0		// sp' - x0 = (sp + x0) - x0 = sp

This series implements this approach, along with the other requisite
changes required to make this work.

The SP test is performed for all exceptions, after compensating for the
size of the exception registers, allowing the original exception context
to be preserved in entirety. The tests themselves are folded into the
exception vectors, minimizing their impact.

To ensure that IRQ stack overflows are detected and handled, IRQ stacks
are now dynamically allocated, with guard pages.

I've given the series some light testing with LKDTM, Syzkaller, Vince
Weaver's perf fuzzer, and a few combinations of debug options. I haven't
compared performance of the entire series to a baseline kernel, but from
testing so far the cost of the SP test falls in the noise for a kernel
build workload on Cortex-A57.

Many thanks to Ard for putting up with my meddling, and also to Laura
and James for their testing and comments on prior patches.

Thanks,
Mark.

[0] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-July/518368.html
[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-July/518434.html
[2] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-July/520705.html
[3] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-July/521435.html
[4] git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git arm64/exception-stack
[5] git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git arm64/vmap-stack

Ard Biesheuvel (2):
  arm64: kernel: remove {THREAD,IRQ_STACK}_START_SP
  arm64: assembler: allow adr_this_cpu to use the stack pointer

Mark Rutland (12):
  arm64: remove __die()'s stack dump
  fork: allow arch-override of VMAP stack alignment
  arm64: factor out PAGE_* and CONT_* definitions
  arm64: clean up THREAD_* definitions
  arm64: clean up irq stack definitions
  arm64: move SEGMENT_ALIGN to <asm/memory.h>
  efi/arm64: add EFI_KIMG_ALIGN
  arm64: factor out entry stack manipulation
  arm64: use an irq stack pointer
  arm64: add basic VMAP_STACK support
  arm64: add on_accessible_stack()
  arm64: add VMAP_STACK overflow detection

 arch/arm64/Kconfig                        |   1 +
 arch/arm64/include/asm/assembler.h        |   3 +-
 arch/arm64/include/asm/efi.h              |   8 +++
 arch/arm64/include/asm/irq.h              |  25 -------
 arch/arm64/include/asm/memory.h           |  53 ++++++++++++++
 arch/arm64/include/asm/page-def.h         |  34 +++++++++
 arch/arm64/include/asm/page.h             |  12 +---
 arch/arm64/include/asm/processor.h        |   2 +-
 arch/arm64/include/asm/stacktrace.h       |  62 ++++++++++++++++-
 arch/arm64/include/asm/thread_info.h      |  10 +--
 arch/arm64/kernel/entry.S                 | 110 +++++++++++++++++++++++-------
 arch/arm64/kernel/irq.c                   |  40 ++++++++++-
 arch/arm64/kernel/ptrace.c                |   1 +
 arch/arm64/kernel/smp.c                   |   2 +-
 arch/arm64/kernel/stacktrace.c            |   7 +-
 arch/arm64/kernel/traps.c                 |  44 ++++++++++--
 arch/arm64/kernel/vmlinux.lds.S           |  18 +----
 drivers/firmware/efi/libstub/arm64-stub.c |   6 +-
 kernel/fork.c                             |   5 +-
 19 files changed, 339 insertions(+), 104 deletions(-)
 create mode 100644 arch/arm64/include/asm/page-def.h

-- 
1.9.1

[toc] | [next] | [standalone]

#1705791 — [PATCH 03/14] arm64: kernel: remove {THREAD,IRQ_STACK}_START_SP

From: Ard Biesheuvel <ard.biesheuvel@linaro.org>

For historical reasons, we leave the top 16 bytes of our task and IRQ
stacks unused, a practice used to ensure that the SP can always be
masked to find the base of the current stack (historically, where
thread_info could be found).

However, this is not necessary, as:

* When an exception is taken from a task stack, we decrement the SP by
  S_FRAME_SIZE and stash the exception registers before we compare the
  SP against the task stack. In such cases, the SP must be at least
  S_FRAME_SIZE below the limit, and can be safely masked to determine
  whether the task stack is in use.

* When transitioning to an IRQ stack, we'll place a dummy frame onto the
  IRQ stack before enabling asynchronous exceptions, or executing code
  we expect to trigger faults. Thus, if an exception is taken from the
  IRQ stack, the SP must be at least 16 bytes below the limit.

* We no longer mask the SP to find the thread_info, which is now found
  via sp_el0. Note that historically, the offset was critical to ensure
  that cpu_switch_to() found the correct stack for new threads that
  hadn't yet executed ret_from_fork().

Given that, this initial offset serves no purpose, and can be removed.
This brings us in-line with other architectures (e.g. x86) which do not
rely on this masking.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
[Mark: rebase, kill THREAD_START_SP, commit msg additions]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/irq.h         | 5 ++---
 arch/arm64/include/asm/processor.h   | 2 +-
 arch/arm64/include/asm/thread_info.h | 1 -
 arch/arm64/kernel/entry.S            | 2 +-
 arch/arm64/kernel/smp.c              | 2 +-
 5 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
index 8ba89c4..1ebe202 100644
--- a/arch/arm64/include/asm/irq.h
+++ b/arch/arm64/include/asm/irq.h
@@ -2,7 +2,6 @@
 #define __ASM_IRQ_H
 
 #define IRQ_STACK_SIZE			THREAD_SIZE
-#define IRQ_STACK_START_SP		THREAD_START_SP
 
 #ifndef __ASSEMBLER__
 
@@ -26,9 +25,9 @@ static inline int nr_legacy_irqs(void)
 static inline bool on_irq_stack(unsigned long sp)
 {
 	unsigned long low = (unsigned long)raw_cpu_ptr(irq_stack);
-	unsigned long high = low + IRQ_STACK_START_SP;
+	unsigned long high = low + IRQ_STACK_SIZE;
 
-	return (low <= sp && sp <= high);
+	return (low <= sp && sp < high);
 }
 
 static inline bool on_task_stack(struct task_struct *tsk, unsigned long sp)
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 64c9e78..6687dd2 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -159,7 +159,7 @@ extern struct task_struct *cpu_switch_to(struct task_struct *prev,
 					 struct task_struct *next);
 
 #define task_pt_regs(p) \
-	((struct pt_regs *)(THREAD_START_SP + task_stack_page(p)) - 1)
+	((struct pt_regs *)(THREAD_SIZE + task_stack_page(p)) - 1)
 
 #define KSTK_EIP(tsk)	((unsigned long)task_pt_regs(tsk)->pc)
 #define KSTK_ESP(tsk)	user_stack_pointer(task_pt_regs(tsk))
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 46c3b93..b29ab0e 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -30,7 +30,6 @@
 #endif
 
 #define THREAD_SIZE		16384
-#define THREAD_START_SP		(THREAD_SIZE - 16)
 
 #ifndef __ASSEMBLY__
 
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 4ddb8d7..1c0f787 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -268,7 +268,7 @@ alternative_else_nop_endif
 	cbnz	x25, 9998f
 
 	adr_this_cpu x25, irq_stack, x26
-	mov	x26, #IRQ_STACK_START_SP
+	mov	x26, #IRQ_STACK_SIZE
 	add	x26, x25, x26
 
 	/* switch to the irq stack */
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index dc66e6e..f13ddb2 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -154,7 +154,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 	 * page tables.
 	 */
 	secondary_data.task = idle;
-	secondary_data.stack = task_stack_page(idle) + THREAD_START_SP;
+	secondary_data.stack = task_stack_page(idle) + THREAD_SIZE;
 	update_cpu_boot_status(CPU_MMU_OFF);
 	__flush_dcache_area(&secondary_data, sizeof(secondary_data));
 
-- 
1.9.1

[toc] | [prev] | [next] | [standalone]

#1705792 — [PATCH 06/14] arm64: clean up irq stack definitions

Before we add yet another stack to the kernel, it would be nice to
ensure that we consistently organise stack definitions and related
helper functions.

This patch moves the basic IRQ stack defintions to <asm/memory.h> to
live with their task stack counterparts. Helpers used for unwinding are
moved into <asm/stacktrace.h>, where subsequent patches will add helpers
for other stacks. Includes are fixed up accordingly.

This patch is a pure refactoring -- there should be no functional
changes as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/irq.h        | 24 ------------------------
 arch/arm64/include/asm/memory.h     |  2 ++
 arch/arm64/include/asm/stacktrace.h | 25 ++++++++++++++++++++++++-
 arch/arm64/kernel/ptrace.c          |  1 +
 4 files changed, 27 insertions(+), 25 deletions(-)

diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
index 1ebe202..5e6f772 100644
--- a/arch/arm64/include/asm/irq.h
+++ b/arch/arm64/include/asm/irq.h
@@ -1,20 +1,12 @@
 #ifndef __ASM_IRQ_H
 #define __ASM_IRQ_H
 
-#define IRQ_STACK_SIZE			THREAD_SIZE
-
 #ifndef __ASSEMBLER__
 
-#include <linux/percpu.h>
-#include <linux/sched/task_stack.h>
-
 #include <asm-generic/irq.h>
-#include <asm/thread_info.h>
 
 struct pt_regs;
 
-DECLARE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack);
-
 extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
 
 static inline int nr_legacy_irqs(void)
@@ -22,21 +14,5 @@ static inline int nr_legacy_irqs(void)
 	return 0;
 }
 
-static inline bool on_irq_stack(unsigned long sp)
-{
-	unsigned long low = (unsigned long)raw_cpu_ptr(irq_stack);
-	unsigned long high = low + IRQ_STACK_SIZE;
-
-	return (low <= sp && sp < high);
-}
-
-static inline bool on_task_stack(struct task_struct *tsk, unsigned long sp)
-{
-	unsigned long low = (unsigned long)task_stack_page(tsk);
-	unsigned long high = low + THREAD_SIZE;
-
-	return (low <= sp && sp < high);
-}
-
 #endif /* !__ASSEMBLER__ */
 #endif
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 8ab4774..1fc2453 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -110,6 +110,8 @@
 
 #define THREAD_SIZE		(UL(1) << THREAD_SHIFT)
 
+#define IRQ_STACK_SIZE		THREAD_SIZE
+
 /*
  * Memory types available.
  */
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 3bebab3..000e2418 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -16,7 +16,12 @@
 #ifndef __ASM_STACKTRACE_H
 #define __ASM_STACKTRACE_H
 
-struct task_struct;
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+
+#include <asm/memory.h>
+#include <asm/ptrace.h>
 
 struct stackframe {
 	unsigned long fp;
@@ -31,4 +36,22 @@ extern void walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 			    int (*fn)(struct stackframe *, void *), void *data);
 extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk);
 
+DECLARE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack);
+
+static inline bool on_irq_stack(unsigned long sp)
+{
+	unsigned long low = (unsigned long)raw_cpu_ptr(irq_stack);
+	unsigned long high = low + IRQ_STACK_SIZE;
+
+	return (low <= sp && sp < high);
+}
+
+static inline bool on_task_stack(struct task_struct *tsk, unsigned long sp)
+{
+	unsigned long low = (unsigned long)task_stack_page(tsk);
+	unsigned long high = low + THREAD_SIZE;
+
+	return (low <= sp && sp < high);
+}
+
 #endif	/* __ASM_STACKTRACE_H */
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index baf0838..a9f8715 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -42,6 +42,7 @@
 #include <asm/compat.h>
 #include <asm/debug-monitors.h>
 #include <asm/pgtable.h>
+#include <asm/stacktrace.h>
 #include <asm/syscall.h>
 #include <asm/traps.h>
 #include <asm/system_misc.h>
-- 
1.9.1

[toc] | [prev] | [next] | [standalone]

#1705793 — [PATCH 08/14] efi/arm64: add EFI_KIMG_ALIGN

The EFI stub is intimately coupled with the kernel, and takes advantage
of this by relocating the kernel at a weaker alignment than the
documented boot protocol mandates.

However, it does so by assuming it can align the kernel to the segment
alignment, and assumes that this is 64K. In subsequent patches, we'll
have to consider other details to determine this de-facto alignment
constraint.

This patch adds a new EFI_KIMG_ALIGN definition that will track the
kernel's de-facto alignment requirements. Subsequent patches will modify
this as required.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/efi.h              | 3 +++
 drivers/firmware/efi/libstub/arm64-stub.c | 6 ++++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index 8f3043a..0e8cc3b 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -4,6 +4,7 @@
 #include <asm/boot.h>
 #include <asm/cpufeature.h>
 #include <asm/io.h>
+#include <asm/memory.h>
 #include <asm/mmu_context.h>
 #include <asm/neon.h>
 #include <asm/ptrace.h>
@@ -48,6 +49,8 @@
  */
 #define EFI_FDT_ALIGN	SZ_2M   /* used by allocate_new_fdt_and_exit_boot() */
 
+#define EFI_KIMG_ALIGN	SEGMENT_ALIGN
+
 /* on arm64, the FDT may be located anywhere in system RAM */
 static inline unsigned long efi_get_max_fdt_addr(unsigned long dram_base)
 {
diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
index b4c2589..af6ae95 100644
--- a/drivers/firmware/efi/libstub/arm64-stub.c
+++ b/drivers/firmware/efi/libstub/arm64-stub.c
@@ -11,6 +11,7 @@
  */
 #include <linux/efi.h>
 #include <asm/efi.h>
+#include <asm/memory.h>
 #include <asm/sections.h>
 #include <asm/sysreg.h>
 
@@ -81,9 +82,10 @@ efi_status_t handle_kernel_image(efi_system_table_t *sys_table_arg,
 		/*
 		 * If CONFIG_DEBUG_ALIGN_RODATA is not set, produce a
 		 * displacement in the interval [0, MIN_KIMG_ALIGN) that
-		 * is a multiple of the minimal segment alignment (SZ_64K)
+		 * doesn't violate this kernel's de-facto alignment
+		 * constraints.
 		 */
-		u32 mask = (MIN_KIMG_ALIGN - 1) & ~(SZ_64K - 1);
+		u32 mask = (MIN_KIMG_ALIGN - 1) & ~(EFI_KIMG_ALIGN - 1);
 		u32 offset = !IS_ENABLED(CONFIG_DEBUG_ALIGN_RODATA) ?
 			     (phys_seed >> 32) & mask : TEXT_OFFSET;
 
-- 
1.9.1

[toc] | [prev] | [next] | [standalone]

#1705794 — [PATCH 14/14] arm64: add VMAP_STACK overflow detection

This patch adds stack overflow detection to arm64, usable when vmap'd stacks
are in use.

Overflow is detected in a small preamble executed for each exception entry,
which checks whether there is enough space on the current stack for the general
purpose registers to be saved. If there is not enough space, the overflow
handler is invoked on a per-cpu overflow stack. This approach preserves the
original exception information in ESR_EL1 (and where appropriate, FAR_EL1).

Task and IRQ stacks are aligned to double their size, enabling overflow to be
detected with a single bit test. For example, a 16K stack is aligned to 32K,
ensuring that bit 14 of the SP must be zero. On an overflow (or underflow),
this bit is flipped. Thus, overflow (of less than the size of the stack) can be
detected by testing whether this bit is set.

The overflow check is performed before any attempt is made to access the
stack, avoiding recursive faults (and the loss of exception information
these would entail). As logical operations cannot be performed on the SP
directly, the SP is temporarily swapped with a general purpose register
using arithmetic operations to enable the test to be performed.

This gives us a useful error message on stack overflow, as can be trigger with
the LKDTM overflow test:

root@ribbensteg:/sys/kernel/debug/provoke-crash# echo OVERFLOW > DIRECT
[  116.249161] lkdtm: Performing direct entry OVERFLOW
[  116.254048] Insufficient stack space to handle exception!
[  116.254059] CPU: 4 PID: 2269 Comm: bash Not tainted 4.13.0-rc3-00020-g307fec7 #197
[  116.266913] Hardware name: ARM Juno development board (r1) (DT)
[  116.272783] task: ffff800976bf0e00 task.stack: ffff00000d540000
[  116.278660] PC is at recursive_loop+0x10/0x50
[  116.282981] LR is at recursive_loop+0x34/0x50
[  116.287300] pc : [<ffff000008597778>] lr : [<ffff00000859779c>] pstate: 40000145
[  116.294633] sp : ffff00000d53ff30
[  116.297916] x29: ffff00000d540350 x28: ffff800976bf0e00
[  116.303188] x27: ffff000008981000 x26: ffff000008f701f8
[  116.308458] x25: ffff00000d543eb8 x24: ffff00000d543eb8
[  116.313729] x23: ffff000008f6ff30 x22: 0000000000000009
[  116.318999] x21: ffff800975c43000 x20: ffff000008f6ff80
[  116.324269] x19: 0000000000000013 x18: 0000000000000010
[  116.329539] x17: 0000ffffb24cf6a4 x16: ffff0000081fbc40
[  116.334820] x15: 0000000000000006 x14: ffff000088fc637f
[  116.340099] x13: ffff000008fc638d x12: ffff000008ec2460
[  116.345379] x11: ffff00000d543a30 x10: 0000000005f5e0ff
[  116.350659] x9 : 00000000ffffffd0 x8 : ffff00000d540770
[  116.355939] x7 : 1313131313131313 x6 : 000000000000019c
[  116.361218] x5 : 0000000000000000 x4 : 0000000000000000
[  116.366497] x3 : 0000000000000000 x2 : 0000000000000400
[  116.371777] x1 : 0000000000000013 x0 : 0000000000000012
[  116.377058] Task stack:     [0xffff00000d540000..0xffff00000d544000]
[  116.383366] IRQ stack:      [0xffff000008020000..0xffff000008024000]
[  116.389675] Overflow stack: [0xffff80097ffa54e0..0xffff80097ffa64e0]
[  116.395984] ESR: 0x96000047 -- DABT (current EL)
[  116.400569] FAR: 0xffff00000d53ff30
[  116.404036] Kernel panic - not syncing: kernel stack overflow
[  116.409744] CPU: 4 PID: 2269 Comm: bash Not tainted 4.13.0-rc3-00020-g307fec7 #197
[  116.417268] Hardware name: ARM Juno development board (r1) (DT)
[  116.423146] Call trace:
[  116.425587] [<ffff0000080883a0>] dump_backtrace+0x0/0x268
[  116.430955] [<ffff0000080886cc>] show_stack+0x14/0x20
[  116.435976] [<ffff00000894e138>] dump_stack+0x98/0xb8
[  116.440997] [<ffff0000080c1e44>] panic+0x118/0x28c
[  116.445758] [<ffff0000080c1a84>] nmi_panic+0x6c/0x70
[  116.450693] [<ffff000008088f88>] handle_bad_stack+0x118/0x128
[  116.456401] Exception stack(0xffff80097ffa63a0 to 0xffff80097ffa64e0)
[  116.462799] 63a0: 0000000000000012 0000000000000013 0000000000000400 0000000000000000
[  116.470585] 63c0: 0000000000000000 0000000000000000 000000000000019c 1313131313131313
[  116.478372] 63e0: ffff00000d540770 00000000ffffffd0 0000000005f5e0ff ffff00000d543a30
[  116.486157] 6400: ffff000008ec2460 ffff000008fc638d ffff000088fc637f 0000000000000006
[  116.493943] 6420: ffff0000081fbc40 0000ffffb24cf6a4 0000000000000010 0000000000000013
[  116.501730] 6440: ffff000008f6ff80 ffff800975c43000 0000000000000009 ffff000008f6ff30
[  116.509516] 6460: ffff00000d543eb8 ffff00000d543eb8 ffff000008f701f8 ffff000008981000
[  116.517302] 6480: ffff800976bf0e00 ffff00000d540350 ffff00000859779c ffff00000d53ff30
[  116.525087] 64a0: ffff000008597778 0000000040000145 0000000000000000 0000000000000000
[  116.532874] 64c0: 0001000000000000 0000000000000000 ffff00000d540350 ffff000008597778
[  116.540660] [<ffff00000808205c>] __bad_stack+0x88/0x8c
[  116.545767] [<ffff000008597778>] recursive_loop+0x10/0x50
[  116.551132] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.556497] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.561862] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.567228] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.572592] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.577957] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.583322] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.588687] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.594051] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.599416] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.604781] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.610146] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.615511] [<ffff00000859779c>] recursive_loop+0x34/0x50
[  116.620876] [<ffff00000859782c>] lkdtm_OVERFLOW+0x14/0x20
[  116.626241] [<ffff000008597760>] lkdtm_do_action+0x1c/0x24
[  116.631693] [<ffff0000085975d0>] direct_entry+0xe0/0x168
[  116.636974] [<ffff000008340f98>] full_proxy_write+0x60/0xa8
[  116.642511] [<ffff0000081f93dc>] __vfs_write+0x1c/0x118
[  116.647704] [<ffff0000081fa824>] vfs_write+0x9c/0x1a8
[  116.652723] [<ffff0000081fbc84>] SyS_write+0x44/0xa0
[  116.657655] Exception stack(0xffff00000d543ec0 to 0xffff00000d544000)
[  116.664053] 3ec0: 0000000000000001 000000001952d808 0000000000000009 0000000000000000
[  116.671838] 3ee0: 0000000000000000 0000000000000000 0000ffffb24d6c6c 0dfefefefeff07ff
[  116.679624] 3f00: 0000000000000040 fefefefefefefeff 0000000019555b28 0000000000000008
[  116.687411] 3f20: 0000000000000000 0000000000000018 ffffffffffffffff 00000ca9b8000000
[  116.695196] 3f40: 0000000000000000 0000ffffb24cf6a4 0000ffffd8d00e40 0000000000000009
[  116.702983] 3f60: 000000001952d808 0000ffffb25ad178 0000000000000009 0000000000000000
[  116.710768] 3f80: 0000000000000001 00000000004c9c98 00000000004ca628 00000000004ed000
[  116.718554] 3fa0: 00000000004ea8e0 0000ffffd8d00fe0 0000ffffb24d674c 0000ffffd8d00fe0
[  116.726340] 3fc0: 0000ffffb2524fec 0000000060000000 0000000000000001 0000000000000040
[  116.734125] 3fe0: 0000000000000000 0000000000000000 0000000000000000 0000ffffb2524fec
[  116.741912] [<ffff000008082fb0>] el0_svc_naked+0x24/0x28
[  116.747189] [<0000ffffb2524fec>] 0xffffb2524fec
[  116.751695] SMP: stopping secondary CPUs
[  116.755909] Kernel Offset: disabled
[  116.759375] CPU features: 0x002086
[  116.762753] Memory Limit: none
[  116.765795] ---[ end Kernel panic - not syncing: kernel stack overflow

This patch was co-authored by Ard Biesheuvel and Mark Rutland.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/memory.h     |  2 ++
 arch/arm64/include/asm/stacktrace.h | 18 +++++++++++
 arch/arm64/kernel/entry.S           | 59 +++++++++++++++++++++++++++++++++++++
 arch/arm64/kernel/traps.c           | 39 ++++++++++++++++++++++++
 4 files changed, 118 insertions(+)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index c5cd2c5..1a025b7 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -133,6 +133,8 @@
 
 #define IRQ_STACK_SIZE		THREAD_SIZE
 
+#define OVERFLOW_STACK_SIZE	SZ_4K
+
 /*
  * Alignment of kernel segments (e.g. .text, .data).
  */
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 92ddb6d..ee19563 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -57,6 +57,22 @@ static inline bool on_task_stack(struct task_struct *tsk, unsigned long sp)
 	return (low <= sp && sp < high);
 }
 
+#ifdef CONFIG_VMAP_STACK
+DECLARE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack);
+
+#define OVERFLOW_STACK_PTR() ((unsigned long)this_cpu_ptr(overflow_stack) + OVERFLOW_STACK_SIZE)
+
+static inline bool on_overflow_stack(unsigned long sp)
+{
+	unsigned long low = (unsigned long)this_cpu_ptr(overflow_stack);
+	unsigned long high = low + OVERFLOW_STACK_SIZE;
+
+	return (low <= sp && sp < high);
+}
+#else
+static inline bool on_overflow_stack(unsigned long sp) { return false; }
+#endif
+
 /*
  * We can only safely access per-cpu stacks from current in a non-preemptible
  * context.
@@ -69,6 +85,8 @@ static inline bool on_accessible_stack(struct task_struct *tsk, unsigned long sp
 		return false;
 	if (on_irq_stack(sp))
 		return true;
+	if (on_overflow_stack(sp))
+		return true;
 
 	return false;
 }
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index e5aa866..44a27c3 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -72,6 +72,37 @@
 	.macro kernel_ventry	label
 	.align 7
 	sub	sp, sp, #S_FRAME_SIZE
+#ifdef CONFIG_VMAP_STACK
+	add	sp, sp, x0			// sp' = sp + x0
+	sub	x0, sp, x0			// x0' = sp' - x0 = (sp + x0) - x0 = sp
+	tbnz	x0, #THREAD_SHIFT, 0f
+	sub	x0, sp, x0			// sp' - x0' = (sp + x0) - sp = x0
+	sub	sp, sp, x0			// sp' - x0 = (sp + x0) - x0 = sp
+	b	\label
+
+	/* Stash the original SP value in tpidr_el0 */
+0:	msr	tpidr_el0, x0
+
+	/* Recover the original x0 value and stash it in tpidrro_el0 */
+	sub	x0, sp, x0
+	msr	tpidrro_el0, x0
+
+	/* Switch to the overflow stack */
+	adr_this_cpu sp, overflow_stack + OVERFLOW_STACK_SIZE, x0
+
+	/*
+	 * Check whether we were already on the overflow stack. This may happen
+	 * after panic() re-enables interrupts.
+	 */
+	mrs	x0, tpidr_el0			// sp of interrupted context
+	sub	x0, sp, x0			// delta with top of overflow stack
+	tst	x0, #~(OVERFLOW_STACK_SIZE - 1)	// within range?
+	b.ne	__bad_stack			// no? -> bad stack pointer
+
+	/* We were already on the overflow stack. Restore sp/x0 and carry on. */
+	sub	sp, sp, x0
+	mrs	x0, tpidrro_el0
+#endif
 	b	\label
 	.endm
 
@@ -348,6 +379,34 @@ ENTRY(vectors)
 #endif
 END(vectors)
 
+#ifdef CONFIG_VMAP_STACK
+	/*
+	 * We detected an overflow in kernel_ventry, which switched to the
+	 * overflow stack. Stash the exception regs, and head to our overflow
+	 * handler.
+	 */
+__bad_stack:
+	/* Restore the original x0 value */
+	mrs	x0, tpidrro_el0
+
+	/*
+	 * Store the original GPRs to the new stack. The orginial SP (minus
+	 * S_FRAME_SIZE) was stashed in tpidr_el0 by kernel_ventry.
+	 */
+	sub	sp, sp, #S_FRAME_SIZE
+	kernel_entry 1
+	mrs	x0, tpidr_el0
+	add	x0, x0, #S_FRAME_SIZE
+	str	x0, [sp, #S_SP]
+
+	/* Stash the regs for handle_bad_stack */
+	mov	x0, sp
+
+	/* Time to die */
+	bl	handle_bad_stack
+	ASM_BUG()
+#endif /* CONFIG_VMAP_STACK */
+
 /*
  * Invalid mode handlers
  */
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index d01c598..2c80a11 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -32,6 +32,7 @@
 #include <linux/sched/signal.h>
 #include <linux/sched/debug.h>
 #include <linux/sched/task_stack.h>
+#include <linux/sizes.h>
 #include <linux/syscalls.h>
 #include <linux/mm_types.h>
 
@@ -41,6 +42,7 @@
 #include <asm/esr.h>
 #include <asm/insn.h>
 #include <asm/traps.h>
+#include <asm/smp.h>
 #include <asm/stack_pointer.h>
 #include <asm/stacktrace.h>
 #include <asm/exception.h>
@@ -666,6 +668,43 @@ asmlinkage void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr)
 	force_sig_info(info.si_signo, &info, current);
 }
 
+#ifdef CONFIG_VMAP_STACK
+
+DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack)
+	__aligned(16);
+
+asmlinkage void handle_bad_stack(struct pt_regs *regs)
+{
+	unsigned long tsk_stk = (unsigned long)current->stack;
+	unsigned long irq_stk = (unsigned long)this_cpu_read(irq_stack_ptr);
+	unsigned long ovf_stk = (unsigned long)this_cpu_ptr(overflow_stack);
+	unsigned int esr = read_sysreg(esr_el1);
+	unsigned long far = read_sysreg(far_el1);
+
+	console_verbose();
+	pr_emerg("Insufficient stack space to handle exception!");
+
+	__show_regs(regs);
+
+	pr_emerg("Task stack:     [0x%016lx..0x%016lx]\n",
+		 tsk_stk, tsk_stk + THREAD_SIZE);
+	pr_emerg("IRQ stack:      [0x%016lx..0x%016lx]\n",
+		 irq_stk, irq_stk + THREAD_SIZE);
+	pr_emerg("Overflow stack: [0x%016lx..0x%016lx]\n",
+		 ovf_stk, ovf_stk + OVERFLOW_STACK_SIZE);
+
+	pr_emerg("ESR: 0x%08x -- %s\n", esr, esr_get_class_string(esr));
+	pr_emerg("FAR: 0x%016lx\n", far);
+
+	/*
+	 * We use nmi_panic to limit the potential for recusive overflows, and
+	 * to get a better stack trace.
+	 */
+	nmi_panic(NULL, "kernel stack overflow");
+	cpu_park_loop();
+}
+#endif
+
 void __pte_error(const char *file, int line, unsigned long val)
 {
 	pr_err("%s:%d: bad pte %016lx.\n", file, line, val);
-- 
1.9.1

[toc] | [prev] | [next] | [standalone]

#1705795 — [PATCH 13/14] arm64: add on_accessible_stack()

Both unwind_frame() and dump_backtrace() try to check whether a stack
address is sane to access, with very similar logic. Both will need
updating in order to handle overflow stacks.

Factor out this logic into a helper, so that we can avoid further
duplication when we add overflow stacks.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/stacktrace.h | 16 ++++++++++++++++
 arch/arm64/kernel/stacktrace.c      |  7 +------
 arch/arm64/kernel/traps.c           |  3 +--
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 4c68d8a..92ddb6d 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -57,4 +57,20 @@ static inline bool on_task_stack(struct task_struct *tsk, unsigned long sp)
 	return (low <= sp && sp < high);
 }
 
+/*
+ * We can only safely access per-cpu stacks from current in a non-preemptible
+ * context.
+ */
+static inline bool on_accessible_stack(struct task_struct *tsk, unsigned long sp)
+{
+	if (on_task_stack(tsk, sp))
+		return true;
+	if (tsk != current || preemptible())
+		return false;
+	if (on_irq_stack(sp))
+		return true;
+
+	return false;
+}
+
 #endif	/* __ASM_STACKTRACE_H */
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 54f3463..d9b80eb 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -50,12 +50,7 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
 	if (!tsk)
 		tsk = current;
 
-	/*
-	 * Switching between stacks is valid when tracing current and in
-	 * non-preemptible context.
-	 */
-	if (!(tsk == current && !preemptible() && on_irq_stack(fp)) &&
-	    !on_task_stack(tsk, fp))
+	if (!on_accessible_stack(tsk, fp))
 		return -EINVAL;
 
 	frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 9633773..d01c598 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -193,8 +193,7 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 		if (in_entry_text(frame.pc)) {
 			stack = frame.fp - offsetof(struct pt_regs, stackframe);
 
-			if (on_task_stack(tsk, stack) ||
-			    (tsk == current && !preemptible() && on_irq_stack(stack)))
+			if (on_accessible_stack(tsk, stack))
 				dump_mem("", "Exception stack", stack,
 					 stack + sizeof(struct pt_regs));
 		}
-- 
1.9.1

[toc] | [prev] | [next] | [standalone]

#1705800 — [PATCH 07/14] arm64: move SEGMENT_ALIGN to <asm/memory.h>

Currently we define SEGMENT_ALIGN directly in our vmlinux.lds.S.

This is unfortunate, as the EFI stub currently open-codes the same
number, and in future we'll want to fiddle with this.

This patch moves the definition to our <asm/memory.h>, where it can be
used by both vmlinux.lds.S and the EFI stub code.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/memory.h | 19 +++++++++++++++++++
 arch/arm64/kernel/vmlinux.lds.S | 16 ----------------
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 1fc2453..7fa6ad4 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -113,6 +113,25 @@
 #define IRQ_STACK_SIZE		THREAD_SIZE
 
 /*
+ * Alignment of kernel segments (e.g. .text, .data).
+ */
+#if defined(CONFIG_DEBUG_ALIGN_RODATA)
+/*
+ *  4 KB granule:   1 level 2 entry
+ * 16 KB granule: 128 level 3 entries, with contiguous bit
+ * 64 KB granule:  32 level 3 entries, with contiguous bit
+ */
+#define SEGMENT_ALIGN			SZ_2M
+#else
+/*
+ *  4 KB granule:  16 level 3 entries, with contiguous bit
+ * 16 KB granule:   4 level 3 entries, without contiguous bit
+ * 64 KB granule:   1 level 3 entry
+ */
+#define SEGMENT_ALIGN			SZ_64K
+#endif
+
+/*
  * Memory types available.
  */
 #define MT_DEVICE_nGnRnE	0
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 987a00e..7156538 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -72,22 +72,6 @@ PECOFF_FILE_ALIGNMENT = 0x200;
 #define PECOFF_EDATA_PADDING
 #endif
 
-#if defined(CONFIG_DEBUG_ALIGN_RODATA)
-/*
- *  4 KB granule:   1 level 2 entry
- * 16 KB granule: 128 level 3 entries, with contiguous bit
- * 64 KB granule:  32 level 3 entries, with contiguous bit
- */
-#define SEGMENT_ALIGN			SZ_2M
-#else
-/*
- *  4 KB granule:  16 level 3 entries, with contiguous bit
- * 16 KB granule:   4 level 3 entries, without contiguous bit
- * 64 KB granule:   1 level 3 entry
- */
-#define SEGMENT_ALIGN			SZ_64K
-#endif
-
 SECTIONS
 {
 	/*
-- 
1.9.1

[toc] | [prev] | [next] | [standalone]

#1705805 — [PATCH 04/14] arm64: factor out PAGE_* and CONT_* definitions

Some headers rely on PAGE_* definitions from <asm/page.h>, but cannot
include this due to potential circular includes. For example, a number
of definitions in <asm/memory.h> rely on PAGE_SHIFT, and <asm/page.h>
includes <asm/memory.h>.

This requires users of these definitions to include both headers, which
is fragile and error-prone.

This patch ameliorates matters by moving the basic definitions out to a
new header, <asm/page-def.h>. Both <asm/page.h> and <asm/memory.h> are
updated to include this, avoiding this fragility, and avoiding the
possibility of circular include dependencies.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/memory.h   |  1 +
 arch/arm64/include/asm/page-def.h | 34 ++++++++++++++++++++++++++++++++++
 arch/arm64/include/asm/page.h     | 12 +-----------
 3 files changed, 36 insertions(+), 11 deletions(-)
 create mode 100644 arch/arm64/include/asm/page-def.h

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 32f827233..77d55dc 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -25,6 +25,7 @@
 #include <linux/const.h>
 #include <linux/types.h>
 #include <asm/bug.h>
+#include <asm/page-def.h>
 #include <asm/sizes.h>
 
 /*
diff --git a/arch/arm64/include/asm/page-def.h b/arch/arm64/include/asm/page-def.h
new file mode 100644
index 0000000..01591a2
--- /dev/null
+++ b/arch/arm64/include/asm/page-def.h
@@ -0,0 +1,34 @@
+/*
+ * Based on arch/arm/include/asm/page.h
+ *
+ * Copyright (C) 1995-2003 Russell King
+ * Copyright (C) 2017 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_PAGE_DEF_H
+#define __ASM_PAGE_DEF_H
+
+#include <linux/const.h>
+
+/* PAGE_SHIFT determines the page size */
+/* CONT_SHIFT determines the number of pages which can be tracked together  */
+#define PAGE_SHIFT		CONFIG_ARM64_PAGE_SHIFT
+#define CONT_SHIFT		CONFIG_ARM64_CONT_SHIFT
+#define PAGE_SIZE		(_AC(1, UL) << PAGE_SHIFT)
+#define PAGE_MASK		(~(PAGE_SIZE-1))
+
+#define CONT_SIZE		(_AC(1, UL) << (CONT_SHIFT + PAGE_SHIFT))
+#define CONT_MASK		(~(CONT_SIZE-1))
+
+#endif /* __ASM_PAGE_DEF_H */
diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h
index 8472c6d..60d02c8 100644
--- a/arch/arm64/include/asm/page.h
+++ b/arch/arm64/include/asm/page.h
@@ -19,17 +19,7 @@
 #ifndef __ASM_PAGE_H
 #define __ASM_PAGE_H
 
-#include <linux/const.h>
-
-/* PAGE_SHIFT determines the page size */
-/* CONT_SHIFT determines the number of pages which can be tracked together  */
-#define PAGE_SHIFT		CONFIG_ARM64_PAGE_SHIFT
-#define CONT_SHIFT		CONFIG_ARM64_CONT_SHIFT
-#define PAGE_SIZE		(_AC(1, UL) << PAGE_SHIFT)
-#define PAGE_MASK		(~(PAGE_SIZE-1))
-
-#define CONT_SIZE		(_AC(1, UL) << (CONT_SHIFT + PAGE_SHIFT))
-#define CONT_MASK		(~(CONT_SIZE-1))
+#include <asm/page-def.h>
 
 #ifndef __ASSEMBLY__
 
-- 
1.9.1

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web