[v3,11/75] x86/boot/compressed/64: Disable red-zone usage
diff mbox series

Message ID 20200428151725.31091-12-joro@8bytes.org
State New
Headers show
  • x86: SEV-ES Guest Support
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Commit Message

Joerg Roedel April 28, 2020, 3:16 p.m. UTC
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. 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, because the IRET frame
written by the hardware at the stack pointer and the functions to handle
the exception will overwrite the temporary variables of the interrupted
function, causing undefined behavior. So disable red-zones for the
pre-decompression boot code.

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

diff mbox series

diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index e17be90ab312..93f1320fc7bf 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -65,7 +65,7 @@  clean-files += cpustr.h
 # ---------------------------------------------------------------------------
 KBUILD_CFLAGS	+= $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
 KBUILD_CFLAGS	+= -fno-asynchronous-unwind-tables
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 5f7c262bcc99..085d5f083f50 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 $(call cc-option, -fPIE, -fPIC)
 cflags-$(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)