linux-kernel - [PATCH 3/3] compiler-gcc: Remove obsolete RELOC

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20251223202038.91200-4-ubizjak@gmail.com>
Date: Tue, 23 Dec 2025 21:18:58 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: x86@...nel.org,
	linux-kernel@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3/3] compiler-gcc: Remove obsolete RELOC_HIDE() macro

Remove the RELOC_HIDE() macro from include/linux/compiler-gcc.h.

The GCC specific macro was historically used to workaround very old
compiler bugs (including pre-4.1 ppc64 GCC). These compilers are long
obsolete.

The generic RELOC_HIDE() macro should be used instead.

The removal of the GCC specific macro results in the
following code size reduction:

     text    data     bss     dec     hex filename
  28526453        4823511  737108 34087072        20820a0 vmlinux-old.o
  28520945        4823463  737108 34081516        2080aec vmlinux-new.o

  ./bloat-o-meter vmlinux-old.o vmlinux-new.o
  add/remove: 4/14 grow/shrink: 189/674 up/down: 4433/-7865 (-3432)
  ...
  Total: Before=24103512, After=24100080, chg -0.01%

Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
---
 include/linux/compiler-gcc.h | 25 -------------------------
 1 file changed, 25 deletions(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 5de824a0b3d7..081e658754b9 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -10,31 +10,6 @@
 		     + __GNUC_MINOR__ * 100	\
 		     + __GNUC_PATCHLEVEL__)
 
-/*
- * This macro obfuscates arithmetic on a variable address so that gcc
- * shouldn't recognize the original var, and make assumptions about it.
- *
- * This is needed because the C standard makes it undefined to do
- * pointer arithmetic on "objects" outside their boundaries and the
- * gcc optimizers assume this is the case. In particular they
- * assume such arithmetic does not wrap.
- *
- * A miscompilation has been observed because of this on PPC.
- * To work around it we hide the relationship of the pointer and the object
- * using this macro.
- *
- * Versions of the ppc64 compiler before 4.1 had a bug where use of
- * RELOC_HIDE could trash r30. The bug can be worked around by changing
- * the inline assembly constraint from =g to =r, in this particular
- * case either is valid.
- */
-#define RELOC_HIDE(ptr, off)						\
-({									\
-	unsigned long __ptr;						\
-	__asm__ ("" : "=r"(__ptr) : "0"(ptr));				\
-	(typeof(ptr)) (__ptr + (off));					\
-})
-
 #if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
 #define __latent_entropy __attribute__((latent_entropy))
 #endif
-- 
2.52.0