From 6063a8fbcf4311f82d7fec7326878f0d349670a0 Mon Sep 17 00:00:00 2001 From: Thomas Petazzoni Date: Sun, 14 Sep 2014 11:49:59 +0200 Subject: [PATCH] toolchain: switch to a two stage gcc build Currently, the internal toolchain backend does a three stage gcc build, with the following sequence of builds: - build gcc-initial - configure libc, install headers and start files - build gcc-intermediate - build libc - build gcc-final However, it turns out that this is not necessary, and only a two stage gcc build is needed. At some point, it was believed that a three stage gcc build was needed for NPTL based toolchains with old gcc versions, but even a gcc 4.4 build with a NPTL toolchain works fine. So, this commit switches the internal toolchain backend to use a two stage gcc build: just gcc-initial and gcc-final. It does so by: * Removing the custom dependency of all C libraries build step to host-gcc-intermediate. Now the C library packages simply have to depend on host-gcc-initial as a normal dependency (which they already do), and that's it. * Build and install both gcc *and* libgcc in host-gcc-initial. Previously, only gcc was built and installed in host-gcc-initial. libgcc was only done in host-gcc-intermediate, but now we need libgcc to build the C library. * Pass appropriate environment variables to get SSP (Stack Smashing Protection) to work properly: - Tell the compiler that the libc will provide the SSP support, by passing gcc_cv_libc_provides_ssp=yes. In Buildroot, we have chosen to use the SSP support from the C library instead of the SSP support from the compiler (this is not changed by this patch series, it was already the case). - Tell glibc to *not* build its own programs with SSP support. The issue is that if glibc detects that the compiler supports -fstack-protector, then glibc uses it to build a few things with SSP. However, at this point, the support is not complete (we only have host-gcc-initial, and the C library is not completely built). So, we pass libc_cv_ssp=no to tell the C library to not use SSP support itself. Note that this is not a big loss: only a few parts of the C library were built with -fstack-protector, not the entire library. * A special change is needed for ARC, because its libgcc depends on the C library, which breaks building libgcc in host-gcc-initial. This looks like a bug in the ARC compiler, as it does not obey the inhibit_libc variable which tells the compiler build process to *not* enable things that depend on the C library. So for now, in host-gcc-initial, we simply disable the build of libgmon.a for ARC. It's going to be built as part of host-gcc-final, so the final compiler will have gmon support. Signed-off-by: Thomas Petazzoni Signed-off-by: Peter Korsgaard --- package/gcc/gcc-initial/gcc-initial.mk | 20 ++++++++++++++++++-- package/glibc/glibc.mk | 4 +--- package/musl/musl.mk | 3 --- package/uclibc/uclibc.mk | 3 --- 4 files changed, 19 insertions(+), 11 deletions(-) diff --git a/package/gcc/gcc-initial/gcc-initial.mk b/package/gcc/gcc-initial/gcc-initial.mk index bc5ad26328..4470477a14 100644 --- a/package/gcc/gcc-initial/gcc-initial.mk +++ b/package/gcc/gcc-initial/gcc-initial.mk @@ -24,11 +24,24 @@ HOST_GCC_INITIAL_SUBDIR = build HOST_GCC_INITIAL_PRE_CONFIGURE_HOOKS += HOST_GCC_CONFIGURE_SYMLINK +# gcc on ARC has a bug: in its libgcc, even when no C library is +# available (--with-newlib is passed, and therefore inhibit_libc is +# defined), it tries to use the C library for the libgmon +# library. Since it's not needed in gcc-initial, we disabled it here. +ifeq ($(BR2_GCC_VERSION_4_8_ARC),y) +define HOST_GCC_INITIAL_DISABLE_LIBGMON + $(SED) 's/crtbeginS.o libgmon.a crtg.o/crtbeginS.o crtg.o/' \ + $(@D)/libgcc/config.host +endef +HOST_GCC_INITIAL_POST_PATCH_HOOKS += HOST_GCC_INITIAL_DISABLE_LIBGMON +endif + HOST_GCC_INITIAL_CONF_OPT = \ $(HOST_GCC_COMMON_CONF_OPT) \ --enable-languages=c \ --disable-shared \ --without-headers \ + --disable-threads \ --with-newlib \ --disable-largefile \ --disable-nls \ @@ -37,7 +50,10 @@ HOST_GCC_INITIAL_CONF_OPT = \ HOST_GCC_INITIAL_CONF_ENV = \ $(HOST_GCC_COMMON_CONF_ENV) -HOST_GCC_INITIAL_MAKE_OPT = all-gcc -HOST_GCC_INITIAL_INSTALL_OPT = install-gcc +# We need to tell gcc that the C library will be providing the ssp +# support, as it can't guess it since the C library hasn't been built +# yet (we're gcc-initial). +HOST_GCC_INITIAL_MAKE_OPT = $(if $(BR2_TOOLCHAIN_HAS_SSP),gcc_cv_libc_provides_ssp=yes) all-gcc all-target-libgcc +HOST_GCC_INITIAL_INSTALL_OPT = install-gcc install-target-libgcc $(eval $(host-autotools-package)) diff --git a/package/glibc/glibc.mk b/package/glibc/glibc.mk index 4cbca88579..0f634451dd 100644 --- a/package/glibc/glibc.mk +++ b/package/glibc/glibc.mk @@ -79,6 +79,7 @@ define GLIBC_CONFIGURE_CMDS $(SHELL) $(@D)/$(GLIBC_SRC_SUBDIR)/configure \ ac_cv_path_BASH_SHELL=/bin/bash \ libc_cv_forced_unwind=yes \ + libc_cv_ssp=no \ --target=$(GNU_TARGET_NAME) \ --host=$(GNU_TARGET_NAME) \ --build=$(GNU_HOST_NAME) \ @@ -127,6 +128,3 @@ define GLIBC_INSTALL_TARGET_CMDS endef $(eval $(autotools-package)) - -# Before (e)glibc is built, we must have the second stage cross-compiler -$(GLIBC_TARGET_BUILD): | host-gcc-intermediate diff --git a/package/musl/musl.mk b/package/musl/musl.mk index 63607f9528..2eccb3da4a 100644 --- a/package/musl/musl.mk +++ b/package/musl/musl.mk @@ -68,6 +68,3 @@ define MUSL_INSTALL_TARGET_CMDS endef $(eval $(generic-package)) - -# Before musl is built, we must have the second stage cross-compiler -$(MUSL_TARGET_BUILD): | host-gcc-intermediate diff --git a/package/uclibc/uclibc.mk b/package/uclibc/uclibc.mk index c68dc5627d..31ff47b3e0 100644 --- a/package/uclibc/uclibc.mk +++ b/package/uclibc/uclibc.mk @@ -534,6 +534,3 @@ define UCLIBC_INSTALL_STAGING_CMDS endef $(eval $(kconfig-package)) - -# Before uClibc is built, we must have the second stage cross-compiler -$(UCLIBC_TARGET_BUILD): | host-gcc-intermediate