linux-kernel - [PATCH] [Rebased for 5.16 and 5.15] powerpc/32: Fix boot failure with GCC latent entropy plugin

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Date:   Sun, 30 Jan 2022 09:45:12 +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 5.16 and 5.15] powerpc/32: Fix boot failure with
 GCC latent entropy plugin

This is backport for 5.16 and 5.15

(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 5fa68c2ef1f8..36f3f5a8868d 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -11,6 +11,7 @@ CFLAGS_prom_init.o      += -fPIC
 CFLAGS_btext.o		+= -fPIC
 endif
 
+CFLAGS_early_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 9e5d0f413b71..0b08e85d3839 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -19,6 +19,9 @@ CFLAGS_code-patching.o += -DDISABLE_BRANCH_PROFILING
 CFLAGS_feature-fixups.o += -DDISABLE_BRANCH_PROFILING
 endif
 
+CFLAGS_code-patching.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
+CFLAGS_feature-fixups.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
+
 obj-y += alloc.o code-patching.o feature-fixups.o pmem.o test_code-patching.o
 
 ifndef CONFIG_KASAN
-- 
2.33.1