linux-kernel - [PATCH AUTOSEL 5.2 28/63] x86/purgatory: Disable the stackleak GCC plugin for the purgatory

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Message-Id: <20191001164125.15398-28-sashal@kernel.org>
Date:   Tue,  1 Oct 2019 12:40:50 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 5.2 28/63] x86/purgatory: Disable the stackleak GCC plugin for the purgatory

From: Arvind Sankar <nivedita@...m.mit.edu>

[ Upstream commit ca14c996afe7228ff9b480cf225211cc17212688 ]

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@...m.mit.edu>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.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@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/purgatory/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index 10fb42da0007e..b81b5172cf994 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
-- 
2.20.1