linux-kernel - [PATCH] [Rebased for 4.9] powerpc/32: Fix boot failure with GCC latent entropy plugin

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Date:   Sun, 30 Jan 2022 09:45:11 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Christophe Leroy <christophe.leroy@...roup.eu>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        Erhard Furtner <erhard_f@...lbox.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH] [Rebased for 4.9] powerpc/32: Fix boot failure with GCC
 latent entropy plugin

This is backport for 4.9

(cherry picked from commit bba496656a73fc1d1330b49c7f82843836e9feb1)

Boot fails with GCC latent entropy plugin enabled.

This is due to early boot functions trying to access 'latent_entropy'
global data while the kernel is not relocated at its final
destination yet.

As there is no way to tell GCC to use PTRRELOC() to access it,
disable latent entropy plugin in early_32.o and feature-fixups.o and
code-patching.o

Fixes: 38addce8b600 ("gcc-plugins: Add latent_entropy plugin")
Cc: stable@...r.kernel.org # v4.9+
Reported-by: Erhard Furtner <erhard_f@...lbox.org>
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215217
Link: https://lore.kernel.org/r/2bac55483b8daf5b1caa163a45fa5f9cdbe18be4.1640178426.git.christophe.leroy@csgroup.eu
---
 arch/powerpc/kernel/Makefile | 1 +
 arch/powerpc/lib/Makefile    | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index d80fbf0884ff..bc6c85788b84 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -14,6 +14,7 @@ CFLAGS_prom_init.o      += -fPIC
 CFLAGS_btext.o		+= -fPIC
 endif
 
+CFLAGS_setup_32.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
 CFLAGS_cputable.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
 CFLAGS_prom_init.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
 CFLAGS_btext.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index 309361e86523..3e3370d126ae 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -9,6 +9,9 @@ ccflags-$(CONFIG_PPC64)	:= $(NO_MINIMAL_TOC)
 CFLAGS_REMOVE_code-patching.o = $(CC_FLAGS_FTRACE)
 CFLAGS_REMOVE_feature-fixups.o = $(CC_FLAGS_FTRACE)
 
+CFLAGS_code-patching.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
+CFLAGS_feature-fixups.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
+
 obj-y += string.o alloc.o crtsavres.o code-patching.o \
 	 feature-fixups.o
 
-- 
2.33.1