From ad06e987b147dc272e683a419ce5b4c39b2bd16b Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Fri, 13 Mar 2015 09:38:16 +0000
Subject: [PATCH] The System V ABI for amd64 allows functions to use space in a
 128 byte redzone below the stack pointer for scratch space and requires
 interrupt and signal frames to avoid overwriting it. However, EFI uses the
 Windows ABI which does not support this. As a result, interrupt handlers in
 EFI push their interrupt frames directly on top of the stack pointer. If the
 compiler used the red zone in a function in the EFI loader, then a device
 interrupt that occurred while that function was running could trash its local
 variables.  In practice this happens fairly reliable when using gzipfs as an
 interrupt during decompression can trash the local variables in the
 inflate_table() function resulting in corrupted output or hangs.

Fix this by disabling the redzone for amd64 EFI binaries. This
requires building not only the loader but any libraries used by the
loader without redzone support.

Thanks to Jilles for pointing me at the redzone once I found the stack
corruption.

Differential Revision:	https://reviews.freebsd.org/D2054
Reviewed by:	imp
MFC after:	2 weeks
Sponsored by:	Cisco Systems, Inc.
---
 lib/libstand/Makefile        | 2 +-
 sys/boot/amd64/Makefile.inc  | 2 +-
 sys/boot/efi/libefi/Makefile | 2 +-
 sys/boot/ficl/Makefile       | 3 +++
 4 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/libstand/Makefile b/lib/libstand/Makefile
index 4a1fa2cca72..a5a135f7fd3 100644
--- a/lib/libstand/Makefile
+++ b/lib/libstand/Makefile
@@ -28,7 +28,7 @@ CFLAGS+=	-mno-mmx -mno-3dnow -mno-sse -mno-sse2 -mno-sse3 -msoft-float
 CFLAGS.gcc+=	-mpreferred-stack-boundary=2
 .endif
 .if ${MACHINE_CPUARCH} == "amd64"
-CFLAGS+=	-fPIC
+CFLAGS+=	-fPIC -mno-red-zone
 .endif
 .if ${MACHINE} == "pc98"
 CFLAGS+=	-Os
diff --git a/sys/boot/amd64/Makefile.inc b/sys/boot/amd64/Makefile.inc
index ee96a42abd8..7b10385928b 100644
--- a/sys/boot/amd64/Makefile.inc
+++ b/sys/boot/amd64/Makefile.inc
@@ -5,7 +5,7 @@
 BINDIR?=	/boot
 
 # See conf/kern.mk for the correct set of these
-CFLAGS+=	-ffreestanding
+CFLAGS+=	-ffreestanding -mno-red-zone
 CFLAGS+=	-mno-mmx -mno-sse -mno-aes -mno-avx -msoft-float
 LDFLAGS+=	-nostdlib
 
diff --git a/sys/boot/efi/libefi/Makefile b/sys/boot/efi/libefi/Makefile
index 3edeb22ea5a..bd753cff350 100644
--- a/sys/boot/efi/libefi/Makefile
+++ b/sys/boot/efi/libefi/Makefile
@@ -9,7 +9,7 @@ SRCS=	delay.c efi_console.c efinet.c efipart.c errno.c handles.c \
 SRCS+= nullconsole.c comconsole.c
 
 .if ${MACHINE_ARCH} == "amd64"
-CFLAGS+= -fPIC
+CFLAGS+= -fPIC -mno-red-zone
 .endif
 CFLAGS+= -I${.CURDIR}/../include
 CFLAGS+= -I${.CURDIR}/../include/${MACHINE_CPUARCH}
diff --git a/sys/boot/ficl/Makefile b/sys/boot/ficl/Makefile
index 833cf99d851..15baae3f490 100644
--- a/sys/boot/ficl/Makefile
+++ b/sys/boot/ficl/Makefile
@@ -21,6 +21,9 @@ CFLAGS+=	-ffreestanding
 CFLAGS+=	-march=i386
 CFLAGS.gcc+=	-mpreferred-stack-boundary=2
 .endif
+.if ${MACHINE_CPUARCH} == "amd64"
+CFLAGS+=	-mno-red-zone
+.endif
 .if ${MACHINE_CPUARCH} == "i386" || ${MACHINE_CPUARCH} == "amd64"
 CFLAGS+=	-mno-mmx -mno-3dnow -mno-sse -mno-sse2 -mno-sse3 -msoft-float
 .endif