| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.1 33/78] ARM: 8384/1: VDSO: force use of BFD linker | Date | Fri, 11 Sep 2015 15:49:34 -0700 |
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4.1-stable review patch. If anyone has any objections, please let me know.
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From: Nathan Lynch <nathan_lynch@mentor.com>
commit d2b30cd4b7223a96e606dfc8120626f66d81e091 upstream.
When using a toolchain with gold as the default linker, the VDSO build fails:
VDSO arch/arm/vdso/vdso.so.raw HOSTCC arch/arm/vdso/vdsomunge MUNGE arch/arm/vdso/vdso.so.dbg OBJCOPY arch/arm/vdso/vdso.so BFD: arch/arm/vdso/vdso.so: Not enough room for program headers, try linking with -N
For whatever reason, ld.gold is omitting an exidx program header that ld.bfd emits, and even when I work around that, I don't get a working VDSO.
For now, instead of supporting gold (which will fail to link the kernel anyway since it does not implement --pic-veneer), direct the compiler to use the traditional bfd linker. This is accomplished by using -fuse-ld, which is implemented in GCC 4.8 and later.
Note: one limitation of this is that if the toolchain is configured to use gold by default, and the bfd linker is not in $PATH, the VDSO build will fail:
VDSO arch/arm/vdso/vdso.so.raw collect2: fatal error: cannot find 'ld'
This will happen if CROSS_COMPILE begins with a path such as /opt/bin/arm-linux-gnu- but /opt/bin is not in $PATH. This is considered an acceptable corner-case limitation and is easily worked around.
Additonal note: we use cc-option instead of cc-ldoption so that -fuse-ld=bfd is placed in the command line if the compiler recognizes the option. Using cc-ldoption results in an attempt to link, which fails in the situation just described, causing -fuse-ld=bfd to be omitted and gold to be used for the VDSO link, which is what we're trying to prevent.
Reported-by: Stefan Agner <stefan@agner.ch> Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Cc: Alexander Kochetkov <al.kochet@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- arch/arm/vdso/Makefile | 1 + 1 file changed, 1 insertion(+)
--- a/arch/arm/vdso/Makefile +++ b/arch/arm/vdso/Makefile @@ -14,6 +14,7 @@ VDSO_LDFLAGS += -Wl,-z,max-page-size=409 VDSO_LDFLAGS += -nostdlib -shared VDSO_LDFLAGS += $(call cc-ldoption, -Wl$(comma)--hash-style=sysv) VDSO_LDFLAGS += $(call cc-ldoption, -Wl$(comma)--build-id) +VDSO_LDFLAGS += $(call cc-option, -fuse-ld=bfd) obj-$(CONFIG_VDSO) += vdso.o extra-$(CONFIG_VDSO) += vdso.lds
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