[PATCH] uml: fix compilation and execution with hardened GCC
To make some half-assembly stubs compile, disable various "hardened" GCC
features:
*) we can't make it build PIC code as we need %ebx to do syscalls and GCC
wants it free for PIC
*) we can't leave stack protection as the stub is moved (not relocated!) in
memory so the RIP-relative access to the canary tries reading from an
unmapped address and causes a segfault, since we move the stub of various
megabytes (the exact amount will be decided at runtime) away from the
link-time address.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Acked-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/um/Makefile b/arch/um/Makefile
index 930e006..bed604a 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -118,6 +118,10 @@
LINK-$(CONFIG_LD_SCRIPT_STATIC) += -static
LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib
+CFLAGS_NO_HARDENING := $(call cc-option, -fno-PIC,) $(call cc-option, -fno-pic,) \
+ $(call cc-option, -fno-stack-protector,) \
+ $(call cc-option, -fno-stack-protector-all,)
+
CPP_MODE-$(CONFIG_MODE_TT) := -DMODE_TT
CONFIG_KERNEL_STACK_ORDER ?= 2
STACK_SIZE := $(shell echo $$[ 4096 * (1 << $(CONFIG_KERNEL_STACK_ORDER)) ] )
@@ -227,4 +231,4 @@
@echo ' SYMLINK $@'
$(Q)ln -sf ../../../include/asm-um/asm-offsets.h $@
-export SUBARCH USER_CFLAGS OS
+export SUBARCH USER_CFLAGS CFLAGS_NO_HARDENING OS