linux-kernel - [tip: x86/boot] x86/boot/compressed: Avoid gcc-11 -Wstringop-overread warning

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Date:   Mon, 22 Mar 2021 23:30:23 -0000
From:   "tip-bot2 for Arnd Bergmann" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Arnd Bergmann <arnd@...db.de>, Ingo Molnar <mingo@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Martin Sebor <msebor@...il.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/boot] x86/boot/compressed: Avoid gcc-11 -Wstringop-overread warning

The following commit has been merged into the x86/boot branch of tip:

Commit-ID:     e14cfb3bdd0f82147d09e9f46bedda6302f28ee1
Gitweb:        https://git.kernel.org/tip/e14cfb3bdd0f82147d09e9f46bedda6302f28ee1
Author:        Arnd Bergmann <arnd@...db.de>
AuthorDate:    Mon, 22 Mar 2021 17:02:39 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 23 Mar 2021 00:16:25 +01:00

x86/boot/compressed: Avoid gcc-11 -Wstringop-overread warning

GCC gets confused by the comparison of a pointer to an integer literal,
with the assumption that this is an offset from a NULL pointer and that
dereferencing it is invalid:

  In file included from arch/x86/boot/compressed/misc.c:18:
  In function ‘parse_elf’,
      inlined from ‘extract_kernel’ at arch/x86/boot/compressed/misc.c:442:2:
  arch/x86/boot/compressed/../string.h:15:23: error: ‘__builtin_memcpy’ reading 64 bytes from a region of size 0 [-Werror=stringop-overread]
     15 | #define memcpy(d,s,l) __builtin_memcpy(d,s,l)
        |                       ^~~~~~~~~~~~~~~~~~~~~~~
  arch/x86/boot/compressed/misc.c:283:9: note: in expansion of macro ‘memcpy’
    283 |         memcpy(&ehdr, output, sizeof(ehdr));
        |         ^~~~~~

I could not find any good workaround for this, but as this is only
a warning for a failure during early boot, removing the line entirely
works around the warning.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Martin Sebor <msebor@...il.com>
Link: https://lore.kernel.org/r/20210322160253.4032422-2-arnd@kernel.org
---
 arch/x86/boot/compressed/misc.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 267e7f9..1945b8a 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -430,8 +430,6 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 		error("Destination address too large");
 #endif
 #ifndef CONFIG_RELOCATABLE
-	if ((unsigned long)output != LOAD_PHYSICAL_ADDR)
-		error("Destination address does not match LOAD_PHYSICAL_ADDR");
 	if (virt_addr != LOAD_PHYSICAL_ADDR)
 		error("Destination virtual address changed when not relocatable");
 #endif