linux-kernel - [PATCH 4/4] x86, boot: Work around clang PR18415.

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 for Android: free password hash cracker in your pocket

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

Message-Id: <1389180083-23249-4-git-send-email-David.Woodhouse@intel.com>
Date:	Wed,  8 Jan 2014 11:21:23 +0000
From:	David Woodhouse <David.Woodhouse@...el.com>
To:	x86@...nel.org
Cc:	linux-kernel@...r.kernel.org, llvmlinux@...ts.linuxfoundation.org
Subject: [PATCH 4/4] x86, boot: Work around clang PR18415.

Clang's intrinsics ignore -mregparm=3 when they fall back to calling the
out-of-line implementations. Putting the args on the stack when memcpy()
expects them in registers is not a recipe for a happy kernel.

This bites with -m32 too, so clang is presumably catastrophically
broken for the i386 kernel until this is fixed, unless I'm missing
something.

For information/testing only; do not apply. With this, I can use
'clang -m16' to build all the kernel's 16-bit code and get a successful
boot.

Not-signed-off-by: David Woodhouse <David.Woodhouse@...el.com>
---
 arch/x86/boot/boot.h   | 2 ++
 arch/x86/boot/memory.c | 7 ++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index ef72bae..1182dc9 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -232,8 +232,10 @@ void *copy_from_gs(void *dst, addr_t src, size_t len);
 void *memcpy(void *dst, void *src, size_t len);
 void *memset(void *dst, int c, size_t len);

+#ifndef __clang__ /* PR18415 */
 #define memcpy(d,s,l) __builtin_memcpy(d,s,l)
 #define memset(d,c,l) __builtin_memset(d,c,l)
+#endif

 /* a20.c */
 int enable_a20(void);
diff --git a/arch/x86/boot/memory.c b/arch/x86/boot/memory.c
index db75d07..7af6504 100644
--- a/arch/x86/boot/memory.c
+++ b/arch/x86/boot/memory.c
@@ -63,8 +63,13 @@ static int detect_memory_e820(void)
 			count = 0;
 			break;
 		}
-
+#ifdef __clang__
+		/* PR18415 */
+		memcpy(desc, &buf, sizeof(*desc));
+		desc++;
+#else
 		*desc++ = buf;
+#endif
 		count++;
 	} while (ireg.ebx && count < ARRAY_SIZE(boot_params.e820_map));

-- 
1.8.4.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/