[PATCH 0/2] arm64: stack helper cleanups

[PATCH 0/2] arm64: stack helper cleanups

[Mark Rutland]

Hi,

These two patches are minor cleanup for the stacktrace helpers, removing 
some dead code and making the header includes a bit easier to follow.

This is effectively some residual cleanup from the STACLKEAK rework in
v5.19, all local to arch/arm64.

Thanks,
Mark.

Mark Rutland (2):
  arm64: remove current_top_of_stack()
  arm64: move on_thread_stack() to <asm/stacktrace.h>

 arch/arm64/include/asm/processor.h  | 13 -------------
 arch/arm64/include/asm/stacktrace.h |  2 ++
 arch/arm64/kernel/irq.c             |  9 +++++----
 3 files changed, 7 insertions(+), 17 deletions(-)

-- 
2.30.2


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[PATCH 1/2] arm64: remove current_top_of_stack()

[Mark Rutland]

We no longer use current_top_of_stack() on arm64, so it can be removed.

We introduced current_top_of_stack() for STACKLEAK in commit:

  0b3e336601b82c6a ("arm64: Add support for STACKLEAK gcc plugin")

... then we figured out the intended semantics were unclear, and
reworked it in commit:

  e85094c31ddb794a ("arm64: stackleak: fix current_top_of_stack()")

... then we removed the only user in commit:

  0cfa2ccd285d98ad ("stackleak: rework stack high bound handling")

Given that it's no longer used, and it's very easy to misuse, this patch
removes current_top_of_stack(). For the moment, on_thread_stack() is
left where it is as moving it will change some header dependencies.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Will Deacon <will@kernel.org>
---
 arch/arm64/include/asm/processor.h | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 445aa3af3b76..cf4eefaacafc 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -396,17 +396,6 @@ long get_tagged_addr_ctrl(struct task_struct *task);
 #define GET_TAGGED_ADDR_CTRL()		get_tagged_addr_ctrl(current)
 #endif
 
-/*
- * For CONFIG_GCC_PLUGIN_STACKLEAK
- *
- * These need to be macros because otherwise we get stuck in a nightmare
- * of header definitions for the use of task_stack_page.
- */
-
-/*
- * The top of the current task's task stack
- */
-#define current_top_of_stack()	((unsigned long)current->stack + THREAD_SIZE)
 #define on_thread_stack()	(on_task_stack(current, current_stack_pointer, 1))
 
 #endif /* __ASSEMBLY__ */
-- 
2.30.2


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Re: [PATCH 1/2] arm64: remove current_top_of_stack()

[Mark Brown]

[-- Attachment #1.1: Type: text/plain, Size: 255 bytes --]

On Thu, Nov 17, 2022 at 12:09:01PM +0000, Mark Rutland wrote:
> We no longer use current_top_of_stack() on arm64, so it can be removed.
> 
> We introduced current_top_of_stack() for STACKLEAK in commit:

Reviewed-by: Mark Brown <broonie@kernel.org>

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Re: [PATCH 1/2] arm64: remove current_top_of_stack()

[Kees Cook]

On Thu, Nov 17, 2022 at 12:09:01PM +0000, Mark Rutland wrote:
> We no longer use current_top_of_stack() on arm64, so it can be removed.
> 
> We introduced current_top_of_stack() for STACKLEAK in commit:
> 
>   0b3e336601b82c6a ("arm64: Add support for STACKLEAK gcc plugin")
> 
> ... then we figured out the intended semantics were unclear, and
> reworked it in commit:
> 
>   e85094c31ddb794a ("arm64: stackleak: fix current_top_of_stack()")
> 
> ... then we removed the only user in commit:
> 
>   0cfa2ccd285d98ad ("stackleak: rework stack high bound handling")
> 
> Given that it's no longer used, and it's very easy to misuse, this patch
> removes current_top_of_stack(). For the moment, on_thread_stack() is
> left where it is as moving it will change some header dependencies.
> 
> There should be no functional change as a result of this patch.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
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[PATCH 2/2] arm64: move on_thread_stack() to <asm/stacktrace.h>

[Mark Rutland]

Currently on_thread_stack() is defined in <asm/processor.h>, depending
upon definitiong from <asm/stacktrace.h> despite this header not being
included. This ends up being fragile, and any user of on_thread_stack()
must include both <asm/processor.h> and <asm/stacktrace.h>.

We organised things this way due to header dependencies back in commit:

  0b3e336601b82c6a ("arm64: Add support for STACKLEAK gcc plugin")

... but now that we no longer use current_top_of_stack(), and given that
stackleak includes <asm/stacktrace.h> via <linux/stackleak.h>, we no
longer need the definition to live in <asm/processor.h>.

Move on_thread_stack() to <asm/stacktrace.h>, where all its dependencies
are guaranteed to be defined. This requires having arm64's irq.c
explicitly include <asm/stacktrace.h>, and I've taken the opportunity to
sort the includes, which were slightly out of order.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Will Deacon <will@kernel.org>
---
 arch/arm64/include/asm/processor.h  | 2 --
 arch/arm64/include/asm/stacktrace.h | 2 ++
 arch/arm64/kernel/irq.c             | 9 +++++----
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index cf4eefaacafc..b15fd6c11294 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -396,7 +396,5 @@ long get_tagged_addr_ctrl(struct task_struct *task);
 #define GET_TAGGED_ADDR_CTRL()		get_tagged_addr_ctrl(current)
 #endif
 
-#define on_thread_stack()	(on_task_stack(current, current_stack_pointer, 1))
-
 #endif /* __ASSEMBLY__ */
 #endif /* __ASM_PROCESSOR_H */
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 5a0edb064ea4..4e5354beafb0 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -57,6 +57,8 @@ static inline bool on_task_stack(const struct task_struct *tsk,
 	return stackinfo_on_stack(&info, sp, size);
 }
 
+#define on_thread_stack()	(on_task_stack(current, current_stack_pointer, 1))
+
 #ifdef CONFIG_VMAP_STACK
 DECLARE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack);
 
diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
index 38dbd3828f13..0c8e30ff8eaa 100644
--- a/arch/arm64/kernel/irq.c
+++ b/arch/arm64/kernel/irq.c
@@ -10,20 +10,21 @@
  * Copyright (C) 2012 ARM Ltd.
  */
 
-#include <linux/irq.h>
-#include <linux/memory.h>
-#include <linux/smp.h>
 #include <linux/hardirq.h>
 #include <linux/init.h>
+#include <linux/irq.h>
 #include <linux/irqchip.h>
 #include <linux/kprobes.h>
+#include <linux/memory.h>
 #include <linux/scs.h>
 #include <linux/seq_file.h>
+#include <linux/smp.h>
 #include <linux/vmalloc.h>
 #include <asm/daifflags.h>
 #include <asm/exception.h>
-#include <asm/vmap_stack.h>
 #include <asm/softirq_stack.h>
+#include <asm/stacktrace.h>
+#include <asm/vmap_stack.h>
 
 /* Only access this in an NMI enter/exit */
 DEFINE_PER_CPU(struct nmi_ctx, nmi_contexts);
-- 
2.30.2


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Re: [PATCH 2/2] arm64: move on_thread_stack() to <asm/stacktrace.h>

[Mark Brown]

[-- Attachment #1.1: Type: text/plain, Size: 390 bytes --]

On Thu, Nov 17, 2022 at 12:09:02PM +0000, Mark Rutland wrote:
> Currently on_thread_stack() is defined in <asm/processor.h>, depending
> upon definitiong from <asm/stacktrace.h> despite this header not being
> included. This ends up being fragile, and any user of on_thread_stack()
> must include both <asm/processor.h> and <asm/stacktrace.h>.

Reviewed-by: Mark Brown <broonie@kernel.org>

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Re: [PATCH 2/2] arm64: move on_thread_stack() to <asm/stacktrace.h>

[Kees Cook]

On Thu, Nov 17, 2022 at 12:09:02PM +0000, Mark Rutland wrote:
> Currently on_thread_stack() is defined in <asm/processor.h>, depending
> upon definitiong from <asm/stacktrace.h> despite this header not being
> included. This ends up being fragile, and any user of on_thread_stack()
> must include both <asm/processor.h> and <asm/stacktrace.h>.
> 
> We organised things this way due to header dependencies back in commit:
> 
>   0b3e336601b82c6a ("arm64: Add support for STACKLEAK gcc plugin")
> 
> ... but now that we no longer use current_top_of_stack(), and given that
> stackleak includes <asm/stacktrace.h> via <linux/stackleak.h>, we no
> longer need the definition to live in <asm/processor.h>.
> 
> Move on_thread_stack() to <asm/stacktrace.h>, where all its dependencies
> are guaranteed to be defined. This requires having arm64's irq.c
> explicitly include <asm/stacktrace.h>, and I've taken the opportunity to
> sort the includes, which were slightly out of order.
> 
> There should be no functional change as a result of this patch.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
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Re: [PATCH 0/2] arm64: stack helper cleanups

[Will Deacon]

On Thu, 17 Nov 2022 12:09:00 +0000, Mark Rutland wrote:
> These two patches are minor cleanup for the stacktrace helpers, removing
> some dead code and making the header includes a bit easier to follow.
> 
> This is effectively some residual cleanup from the STACLKEAK rework in
> v5.19, all local to arch/arm64.
> 
> Thanks,
> Mark.
> 
> [...]

Applied to arm64 (for-next/stacks), thanks!

[1/2] arm64: remove current_top_of_stack()
      https://git.kernel.org/arm64/c/c8c384d7b397
[2/2] arm64: move on_thread_stack() to <asm/stacktrace.h>
      https://git.kernel.org/arm64/c/4585a934203d

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

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