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* kexec broken with STACKLEAK enabled
@ 2019-09-22 17:32 Arvind Sankar
  2019-09-23 16:15 ` Nick Desaulniers
  0 siblings, 1 reply; 6+ messages in thread
From: Arvind Sankar @ 2019-09-22 17:32 UTC (permalink / raw)
  To: linux-kernel; +Cc: Nick Desaulniers

Hi, since commit b059f801a937 (x86/purgatory: Use CFLAGS_REMOVE rather
than reset KBUILD_CFLAGS) kexec is broken if GCC_PLUGIN_STACKLEAK is
enabled, as the purgatory contains undefined references to
stackleak_track_stack.

Attempting to load a kexec kernel results in an error:

	kexec: Undefined symbol: stackleak_track_stack
	kexec-bzImage64: Loading purgatory failed

Adding $(DISABLE_STACKLEAK_PLUGIN) to PURGATORY_CFLAGS in
arch/x86/purgatory/Makefile fixes this.

Not sure if that's the best fix or if other architectures also require a
similar one.

Thanks.

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: kexec broken with STACKLEAK enabled
  2019-09-22 17:32 kexec broken with STACKLEAK enabled Arvind Sankar
@ 2019-09-23 16:15 ` Nick Desaulniers
  2019-09-23 17:17   ` [PATCH] x86/purgatory: Add $(DISABLE_STACKLEAK_PLUGIN) Arvind Sankar
  0 siblings, 1 reply; 6+ messages in thread
From: Nick Desaulniers @ 2019-09-23 16:15 UTC (permalink / raw)
  To: Arvind Sankar
  Cc: LKML, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
	H. Peter Anvin, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)

On Sun, Sep 22, 2019 at 10:32 AM Arvind Sankar <nivedita@alum.mit.edu> wrote:
>
> Hi, since commit b059f801a937 (x86/purgatory: Use CFLAGS_REMOVE rather
> than reset KBUILD_CFLAGS) kexec is broken if GCC_PLUGIN_STACKLEAK is
> enabled, as the purgatory contains undefined references to
> stackleak_track_stack.
>
> Attempting to load a kexec kernel results in an error:
>
>         kexec: Undefined symbol: stackleak_track_stack
>         kexec-bzImage64: Loading purgatory failed
>
> Adding $(DISABLE_STACKLEAK_PLUGIN) to PURGATORY_CFLAGS in
> arch/x86/purgatory/Makefile fixes this.

Hi Arvind,
Thanks for the report.  That sounds like a straightforward fix.  Would
you like to send a patch for that?  I'd be happy to help review it.

>
> Not sure if that's the best fix or if other architectures also require a
> similar one.

The commit you reference should be x86 only.
-- 
Thanks,
~Nick Desaulniers

^ permalink raw reply	[flat|nested] 6+ messages in thread
* [PATCH] x86/purgatory: Add $(DISABLE_STACKLEAK_PLUGIN)
  2019-09-23 16:15 ` Nick Desaulniers
@ 2019-09-23 17:17   ` Arvind Sankar
  2019-09-23 17:25     ` Nick Desaulniers
                       ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Arvind Sankar @ 2019-09-23 17:17 UTC (permalink / raw)
  To: Nick Desaulniers
  Cc: Arvind Sankar, LKML, Thomas Gleixner, Ingo Molnar,
	Borislav Petkov, H. Peter Anvin,
	maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)

Since commit b059f801a937 ("x86/purgatory: Use CFLAGS_REMOVE rather than
reset KBUILD_CFLAGS") kexec breaks is GCC_PLUGIN_STACKLEAK is enabled, as
the purgatory contains undefined references to stackleak_track_stack.
Attempting to load a kexec kernel results in:
	kexec: Undefined symbol: stackleak_track_stack
	kexec-bzImage64: Loading purgatory failed

Fix this by disabling the stackleak plugin for purgatory.

Fixes: b059f801a937 ("x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS")
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
---
 arch/x86/purgatory/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index 527749066d31..fb4ee5444379 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -25,6 +25,7 @@ KCOV_INSTRUMENT := n
 
 PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
 PURGATORY_CFLAGS := -mcmodel=large -ffreestanding -fno-zero-initialized-in-bss
+PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN)
 
 # Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
 # in turn leaves some undefined symbols like __fentry__ in purgatory and not
-- 
2.21.0


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* Re: [PATCH] x86/purgatory: Add $(DISABLE_STACKLEAK_PLUGIN)
  2019-09-23 17:17   ` [PATCH] x86/purgatory: Add $(DISABLE_STACKLEAK_PLUGIN) Arvind Sankar
@ 2019-09-23 17:25     ` Nick Desaulniers
  2019-09-23 17:52     ` [tip: x86/urgent] x86/purgatory: Disable the stackleak GCC plugin for the purgatory tip-bot2 for Arvind Sankar
  2019-09-23 17:52     ` tip-bot2 for Arvind Sankar
  2 siblings, 0 replies; 6+ messages in thread
From: Nick Desaulniers @ 2019-09-23 17:25 UTC (permalink / raw)
  To: Arvind Sankar
  Cc: LKML, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
	H. Peter Anvin, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT),
	Ard Biesheuvel

On Mon, Sep 23, 2019 at 10:17 AM Arvind Sankar <nivedita@alum.mit.edu> wrote:
>
> Since commit b059f801a937 ("x86/purgatory: Use CFLAGS_REMOVE rather than
> reset KBUILD_CFLAGS") kexec breaks is GCC_PLUGIN_STACKLEAK is enabled, as
> the purgatory contains undefined references to stackleak_track_stack.
> Attempting to load a kexec kernel results in:
>         kexec: Undefined symbol: stackleak_track_stack
>         kexec-bzImage64: Loading purgatory failed
>
> Fix this by disabling the stackleak plugin for purgatory.
>
> Fixes: b059f801a937 ("x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS")
> Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
(Sorry for the fallout from b059f801a937, but this is giving us a
pretty good idea about what "runtime" requirements certain configs
have.  It would be cool to eventually have some kind of kexec test
case that folks could run in QEMU).

> ---
>  arch/x86/purgatory/Makefile | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
> index 527749066d31..fb4ee5444379 100644
> --- a/arch/x86/purgatory/Makefile
> +++ b/arch/x86/purgatory/Makefile
> @@ -25,6 +25,7 @@ KCOV_INSTRUMENT := n
>
>  PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
>  PURGATORY_CFLAGS := -mcmodel=large -ffreestanding -fno-zero-initialized-in-bss
> +PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN)
>
>  # Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
>  # in turn leaves some undefined symbols like __fentry__ in purgatory and not
> --
> 2.21.0
>


-- 
Thanks,
~Nick Desaulniers

^ permalink raw reply	[flat|nested] 6+ messages in thread
* [tip: x86/urgent] x86/purgatory: Disable the stackleak GCC plugin for the purgatory
  2019-09-23 17:17   ` [PATCH] x86/purgatory: Add $(DISABLE_STACKLEAK_PLUGIN) Arvind Sankar
  2019-09-23 17:25     ` Nick Desaulniers
@ 2019-09-23 17:52     ` tip-bot2 for Arvind Sankar
  2019-09-23 17:52     ` tip-bot2 for Arvind Sankar
  2 siblings, 0 replies; 6+ messages in thread
From: tip-bot2 for Arvind Sankar @ 2019-09-23 17:52 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Arvind Sankar, Nick Desaulniers, Borislav Petkov, H. Peter Anvin,
	Linus Torvalds, Peter Zijlstra, Thomas Gleixner, Ingo Molnar,
	linux-kernel

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     ca14c996afe7228ff9b480cf225211cc17212688
Gitweb:        https://git.kernel.org/tip/ca14c996afe7228ff9b480cf225211cc17212688
Author:        Arvind Sankar <nivedita@alum.mit.edu>
AuthorDate:    Mon, 23 Sep 2019 13:17:54 -04:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 23 Sep 2019 19:48:02 +02:00

x86/purgatory: Disable the stackleak GCC plugin for the purgatory

Since commit:

  b059f801a937 ("x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS")

kexec breaks if GCC_PLUGIN_STACKLEAK=y is enabled, as the purgatory
contains undefined references to stackleak_track_stack.

Attempting to load a kexec kernel results in this failure:

  kexec: Undefined symbol: stackleak_track_stack
  kexec-bzImage64: Loading purgatory failed

Fix this by disabling the stackleak plugin for the purgatory.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: b059f801a937 ("x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS")
Link: https://lkml.kernel.org/r/20190923171753.GA2252517@rani.riverdale.lan
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/purgatory/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index 10fb42d..b81b517 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -23,6 +23,7 @@ KCOV_INSTRUMENT := n
 
 PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
 PURGATORY_CFLAGS := -mcmodel=large -ffreestanding -fno-zero-initialized-in-bss
+PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN)
 
 # Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
 # in turn leaves some undefined symbols like __fentry__ in purgatory and not

^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [tip: x86/urgent] x86/purgatory: Disable the stackleak GCC plugin for the purgatory
  2019-09-23 17:17   ` [PATCH] x86/purgatory: Add $(DISABLE_STACKLEAK_PLUGIN) Arvind Sankar
  2019-09-23 17:25     ` Nick Desaulniers
  2019-09-23 17:52     ` [tip: x86/urgent] x86/purgatory: Disable the stackleak GCC plugin for the purgatory tip-bot2 for Arvind Sankar
@ 2019-09-23 17:52     ` tip-bot2 for Arvind Sankar
  2 siblings, 0 replies; 6+ messages in thread
From: tip-bot2 for Arvind Sankar @ 2019-09-23 17:52 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Arvind Sankar, Nick Desaulniers, Borislav Petkov, H. Peter Anvin,
	Linus Torvalds, Peter Zijlstra, Thomas Gleixner, Ingo Molnar,
	linux-kernel

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     ca14c996afe7228ff9b480cf225211cc17212688
Gitweb:        https://git.kernel.org/tip/ca14c996afe7228ff9b480cf225211cc17212688
Author:        Arvind Sankar <nivedita@alum.mit.edu>
AuthorDate:    Mon, 23 Sep 2019 13:17:54 -04:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 23 Sep 2019 19:48:02 +02:00

x86/purgatory: Disable the stackleak GCC plugin for the purgatory

Since commit:

  b059f801a937 ("x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS")

kexec breaks if GCC_PLUGIN_STACKLEAK=y is enabled, as the purgatory
contains undefined references to stackleak_track_stack.

Attempting to load a kexec kernel results in this failure:

  kexec: Undefined symbol: stackleak_track_stack
  kexec-bzImage64: Loading purgatory failed

Fix this by disabling the stackleak plugin for the purgatory.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: b059f801a937 ("x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS")
Link: https://lkml.kernel.org/r/20190923171753.GA2252517@rani.riverdale.lan
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/purgatory/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index 10fb42d..b81b517 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -23,6 +23,7 @@ KCOV_INSTRUMENT := n
 
 PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
 PURGATORY_CFLAGS := -mcmodel=large -ffreestanding -fno-zero-initialized-in-bss
+PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN)
 
 # Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
 # in turn leaves some undefined symbols like __fentry__ in purgatory and not

^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-09-23 17:52 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-09-22 17:32 kexec broken with STACKLEAK enabled Arvind Sankar
2019-09-23 16:15 ` Nick Desaulniers
2019-09-23 17:17   ` [PATCH] x86/purgatory: Add $(DISABLE_STACKLEAK_PLUGIN) Arvind Sankar
2019-09-23 17:25     ` Nick Desaulniers
2019-09-23 17:52     ` [tip: x86/urgent] x86/purgatory: Disable the stackleak GCC plugin for the purgatory tip-bot2 for Arvind Sankar
2019-09-23 17:52     ` tip-bot2 for Arvind Sankar

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