linux-kernel - [PATCH] powerpc: get rid of #include <generated/compile.h>

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Message-Id: <20220604085050.4078927-1-masahiroy@kernel.org>
Date:   Sat,  4 Jun 2022 17:50:50 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Diana Craciun <diana.craciun@....com>,
        Frank Rowand <frank.rowand@...y.com>,
        Jason Yan <yanaijie@...wei.com>, Rob Herring <robh@...nel.org>,
        Scott Wood <oss@...error.net>, linux-kernel@...r.kernel.org
Subject: [PATCH] powerpc: get rid of #include <generated/compile.h>

You cannot include <generated/compile.h> here because it is generated
in init/Makefile but there is no guarantee that it happens before
arch/powerpc/mm/nohash/kaslr_booke.c is compiled for parallel builds.

The places where you can reliably include <generated/compile.h> are:

  - init/          (because init/Makefile can specify the dependency)
  - arch/*/boot/   (because it is compiled after vmlinux)

Commit f231e4333312 ("hexagon: get rid of #include <generated/compile.h>")
fixed the last breakage at that time, but powerpc re-added this.

<genearated/compile.h> was unneeded because 'build_str' is almost the
same as 'linux_banner' defined in init/version.c

Let's copy the solution from MIPS.
(get_random_boot() in arch/mips/kernel/relocate.c)

Fixes: 6a38ea1d7b94 ("powerpc/fsl_booke/32: randomize the kernel image offset")
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

If this gets into the mainline before -rc2 or -rc3,
I will base my kbuild work on top of this.


 arch/powerpc/mm/nohash/kaslr_booke.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/mm/nohash/kaslr_booke.c b/arch/powerpc/mm/nohash/kaslr_booke.c
index 96c38f971603..5f81c076621f 100644
--- a/arch/powerpc/mm/nohash/kaslr_booke.c
+++ b/arch/powerpc/mm/nohash/kaslr_booke.c
@@ -18,7 +18,6 @@
 #include <asm/prom.h>
 #include <asm/kdump.h>
 #include <mm/mmu_decl.h>
-#include <generated/compile.h>
 #include <generated/utsrelease.h>
 
 struct regions {
@@ -36,10 +35,6 @@ struct regions {
 	int reserved_mem_size_cells;
 };
 
-/* Simplified build-specific string for starting entropy. */
-static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@"
-		LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION;
-
 struct regions __initdata regions;
 
 static __init void kaslr_get_cmdline(void *fdt)
@@ -70,7 +65,8 @@ static unsigned long __init get_boot_seed(void *fdt)
 {
 	unsigned long hash = 0;
 
-	hash = rotate_xor(hash, build_str, sizeof(build_str));
+	/* build-specific string for starting entropy. */
+	hash = rotate_xor(hash, linux_banner, strlen(linux_banner));
 	hash = rotate_xor(hash, fdt, fdt_totalsize(fdt));
 
 	return hash;
-- 
2.32.0