linux-kernel - [tip:x86/boot] x86/boot: Simplify pointer casting in choose_random

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Message-ID: <tip-549f90db68c9f8e21a40ec21c8047441984e7164@git.kernel.org>
Date:	Fri, 6 May 2016 23:35:43 -0700
From:	tip-bot for Borislav Petkov <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	peterz@...radead.org, bp@...e.de, luto@...capital.net,
	linux-kernel@...r.kernel.org, hpa@...or.com, tglx@...utronix.de,
	bp@...en8.de, dvlasenk@...hat.com, brgerst@...il.com,
	mingo@...nel.org, keescook@...omium.org,
	torvalds@...ux-foundation.org
Subject: [tip:x86/boot] x86/boot: Simplify pointer casting in
 choose_random_location()

Commit-ID:  549f90db68c9f8e21a40ec21c8047441984e7164
Gitweb:     http://git.kernel.org/tip/549f90db68c9f8e21a40ec21c8047441984e7164
Author:     Borislav Petkov <bp@...e.de>
AuthorDate: Fri, 6 May 2016 13:50:15 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sat, 7 May 2016 07:38:38 +0200

x86/boot: Simplify pointer casting in choose_random_location()

Pass them down as 'unsigned long' directly and get rid of more casting and
assignments.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: akpm@...ux-foundation.org
Cc: bhe@...hat.com
Cc: dyoung@...hat.com
Cc: linux-tip-commits@...r.kernel.org
Cc: luto@...nel.org
Cc: vgoyal@...hat.com
Cc: yinghai@...nel.org
Link: http://lkml.kernel.org/r/20160506115015.GI24044@pd.tnic
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/boot/compressed/kaslr.c | 17 ++++++-----------
 arch/x86/boot/compressed/misc.c  |  3 ++-
 arch/x86/boot/compressed/misc.h  | 10 +++++-----
 3 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 6392f00..ff12277 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -350,20 +350,15 @@ static unsigned long find_random_addr(unsigned long minimum,
 	return slots_fetch_random();
 }
 
-unsigned char *choose_random_location(unsigned char *input_ptr,
+/*
+ * Since this function examines addresses much more numerically,
+ * it takes the input and output pointers as 'unsigned long'.
+ */
+unsigned char *choose_random_location(unsigned long input,
 				      unsigned long input_size,
-				      unsigned char *output_ptr,
+				      unsigned long output,
 				      unsigned long output_size)
 {
-	/*
-	 * The caller of choose_random_location() uses unsigned char * for
-	 * buffer pointers since it performs decompression, elf parsing, etc.
-	 * Since this code examines addresses much more numerically,
-	 * unsigned long is used internally here. Instead of sprinkling
-	 * more casts into extract_kernel, do them here and at return.
-	 */
-	unsigned long input = (unsigned long)input_ptr;
-	unsigned long output = (unsigned long)output_ptr;
 	unsigned long choice = output;
 	unsigned long random_addr;
 
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 9536d77..f14db4e 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -366,7 +366,8 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 	 * the entire decompressed kernel plus relocation table, or the
 	 * entire decompressed kernel plus .bss and .brk sections.
 	 */
-	output = choose_random_location(input_data, input_len, output,
+	output = choose_random_location((unsigned long)input_data, input_len,
+					(unsigned long)output,
 					max(output_len, kernel_total_size));
 
 	/* Validate memory location choices. */
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 1f23d02..0112005a 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -67,20 +67,20 @@ int cmdline_find_option_bool(const char *option);
 
 #if CONFIG_RANDOMIZE_BASE
 /* kaslr.c */
-unsigned char *choose_random_location(unsigned char *input_ptr,
+unsigned char *choose_random_location(unsigned long input_ptr,
 				      unsigned long input_size,
-				      unsigned char *output_ptr,
+				      unsigned long output_ptr,
 				      unsigned long output_size);
 /* cpuflags.c */
 bool has_cpuflag(int flag);
 #else
 static inline
-unsigned char *choose_random_location(unsigned char *input_ptr,
+unsigned char *choose_random_location(unsigned long input_ptr,
 				      unsigned long input_size,
-				      unsigned char *output_ptr,
+				      unsigned long output_ptr,
 				      unsigned long output_size)
 {
-	return output_ptr;
+	return (unsigned char *)output_ptr;
 }
 #endif