[PATCH 11/70] x86/boot/compressed/64: Disable red-zone usage

Joerg Roedel
2020-03-19T09:19:58Z

From: Joerg Roedel <jroedel@suse.de>

The x86-64 ABI defines a red-zone on the stack:

The 128-byte area beyond the location pointed to by %rsp is
considered to be reserved and shall not be modified by signal or
interrupt handlers. 10 Therefore, functions may use this area for
temporary data that is not needed across function calls. In
particular, leaf functions may use this area for their entire stack
frame, rather than adjusting the stack pointer in the prologue and
epilogue. This area is known as the red zone.

This is not compatible with exception handling, so disable it for the
pre-decompression boot code.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/boot/Makefile | 2 +-
arch/x86/boot/compressed/Makefile | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index 012b82fc8617..8f55e4ce1ccc 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -65,7 +65,7 @@ clean-files += cpustr.h

# ---------------------------------------------------------------------------

-KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP
+KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP -mno-red-zone
KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
GCOV_PROFILE := n
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 26050ae0b27e..e186cc0b628d 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -30,7 +30,7 @@ KBUILD_CFLAGS := -m$(BITS) -O2
KBUILD_CFLAGS += -fno-strict-aliasing $(call cc-option, -fPIE, -fPIC)
KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
cflags-$(CONFIG_X86_32) := -march=i386
-cflags-$(CONFIG_X86_64) := -mcmodel=small
+cflags-$(CONFIG_X86_64) := -mcmodel=small -mno-red-zone
KBUILD_CFLAGS += $(cflags-y)
KBUILD_CFLAGS += -mno-mmx -mno-sse
KBUILD_CFLAGS += $(call cc-option,-ffreestanding)
@@ -87,7 +87,7 @@ endif

vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o

-$(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone
+$(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar

vmlinux-objs-$(CONFIG_EFI_STUB) += $(obj)/eboot.o \
$(objtree)/drivers/firmware/efi/libstub/lib.a
--
2.17.1