Re: [PATCH 11/70] x86/boot/compressed/64: Disable red-zone usage
From: Borislav Petkov <bp@alien8.de>
Date: 2020-03-31 13:16:16
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kvm, lkml
On Thu, Mar 19, 2020 at 10:13:08AM +0100, Joerg Roedel wrote:
From: Joerg Roedel <redacted> 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
^^ That 10 is the footnote number from the pdf. :)
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
I could use some blurb as to what the problem is, for future reference.
quoted hunk ↗ jump to hunk
pre-decompression boot code. Signed-off-by: Joerg Roedel <redacted> --- 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 := ndiff --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
That last chunk is not needed anymore after
c2d0b470154c ("efi/libstub/x86: Incorporate eboot.c into libstub")
AFAICT.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette