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authorNathan Chancellor <natechancellor@gmail.com>2020-04-29 01:14:18 +0300
committerThomas Bogendoerfer <tsbogend@alpha.franken.de>2020-05-12 11:02:00 +0300
commit2ff906994b6c2b949c5bf65330a8abb5dde9c8e5 (patch)
tree882ef88349ce87ad12e482b68b9658e392ba8276 /arch/mips/vdso
parentfd9d0ca2cc4f3c26877eb336a7d26d705ff42b8a (diff)
downloadlinux-2ff906994b6c2b949c5bf65330a8abb5dde9c8e5.tar.xz
MIPS: VDSO: Use $(LD) instead of $(CC) to link VDSO
Currently, the VDSO is being linked through $(CC). This does not match how the rest of the kernel links objects, which is through the $(LD) variable. When clang is built in a default configuration, it first attempts to use the target triple's default linker then the system's default linker, unless told otherwise through -fuse-ld=... We do not use -fuse-ld= because it can be brittle and we have support for invoking $(LD) directly. See commit fe00e50b2db8c ("ARM: 8858/1: vdso: use $(LD) instead of $(CC) to link VDSO") and commit 691efbedc60d2 ("arm64: vdso: use $(LD) instead of $(CC) to link VDSO") for examples of doing this in the VDSO. Do the same thing here. Replace the custom linking logic with $(cmd_ld) and ldflags-y so that $(LD) is respected. We need to explicitly add two flags to the linker that were implicitly passed by the compiler: -G 0 (which comes from ccflags-vdso) and --eh-frame-hdr. Before this patch (generated by adding '-v' to VDSO_LDFLAGS): <gcc_prefix>/libexec/gcc/mips64-linux/9.3.0/collect2 \ -plugin <gcc_prefix>/libexec/gcc/mips64-linux/9.3.0/liblto_plugin.so \ -plugin-opt=<gcc_prefix>/libexec/gcc/mips64-linux/9.3.0/lto-wrapper \ -plugin-opt=-fresolution=/tmp/ccGEi5Ka.res \ --eh-frame-hdr \ -G 0 \ -EB \ -mips64r2 \ -shared \ -melf64btsmip \ -o arch/mips/vdso/vdso.so.dbg.raw \ -L<gcc_prefix>/lib/gcc/mips64-linux/9.3.0/64 \ -L<gcc_prefix>/lib/gcc/mips64-linux/9.3.0 \ -L<gcc_prefix>/lib/gcc/mips64-linux/9.3.0/../../../../mips64-linux/lib \ -Bsymbolic \ --no-undefined \ -soname=linux-vdso.so.1 \ -EB \ --hash-style=sysv \ --build-id \ -T arch/mips/vdso/vdso.lds \ arch/mips/vdso/elf.o \ arch/mips/vdso/vgettimeofday.o \ arch/mips/vdso/sigreturn.o After this patch: <gcc_prefix>/bin/mips64-linux-ld \ -m elf64btsmip \ -Bsymbolic \ --no-undefined \ -soname=linux-vdso.so.1 \ -EB \ -nostdlib \ -shared \ -G 0 \ --eh-frame-hdr \ --hash-style=sysv \ --build-id \ -T arch/mips/vdso/vdso.lds \ arch/mips/vdso/elf.o \ arch/mips/vdso/vgettimeofday.o arch/mips/vdso/sigreturn.o \ -o arch/mips/vdso/vdso.so.dbg.raw Note that we leave behind -mips64r2. Turns out that ld ignores it (see get_emulation in ld/ldmain.c). This is true of current trunk and 2.23, which is the minimum supported version for the kernel: https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=ld/ldmain.c;hb=aa4209e7b679afd74a3860ce25659e71cc4847d5#l593 https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=ld/ldmain.c;hb=a55e30b51bc6227d8d41f707654d0a5620978dcf#l641 Before this patch, LD=ld.lld did nothing: $ llvm-readelf -p.comment arch/mips/vdso/vdso.so.dbg | sed 's/(.*//' String dump of section '.comment': [ 0] ClangBuiltLinux clang version 11.0.0 After this patch, it does: $ llvm-readelf -p.comment arch/mips/vdso/vdso.so.dbg | sed 's/(.*//' String dump of section '.comment': [ 0] Linker: LLD 11.0.0 [ 62] ClangBuiltLinux clang version 11.0.0 Link: https://github.com/ClangBuiltLinux/linux/issues/785 Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Diffstat (limited to 'arch/mips/vdso')
-rw-r--r--arch/mips/vdso/Makefile13
1 files changed, 4 insertions, 9 deletions
diff --git a/arch/mips/vdso/Makefile b/arch/mips/vdso/Makefile
index 92b53d1df42c..2e64c7600eea 100644
--- a/arch/mips/vdso/Makefile
+++ b/arch/mips/vdso/Makefile
@@ -60,10 +60,9 @@ ifdef CONFIG_MIPS_DISABLE_VDSO
endif
# VDSO linker flags.
-VDSO_LDFLAGS := \
- -Wl,-Bsymbolic -Wl,--no-undefined -Wl,-soname=linux-vdso.so.1 \
- $(addprefix -Wl$(comma),$(filter -E%,$(KBUILD_CFLAGS))) \
- -nostdlib -shared -Wl,--hash-style=sysv -Wl,--build-id
+ldflags-y := -Bsymbolic --no-undefined -soname=linux-vdso.so.1 \
+ $(filter -E%,$(KBUILD_CFLAGS)) -nostdlib -shared \
+ -G 0 --eh-frame-hdr --hash-style=sysv --build-id -T
CFLAGS_REMOVE_vdso.o = -pg
@@ -82,11 +81,7 @@ quiet_cmd_vdso_mips_check = VDSOCHK $@
#
quiet_cmd_vdsold_and_vdso_check = LD $@
- cmd_vdsold_and_vdso_check = $(cmd_vdsold); $(cmd_vdso_check); $(cmd_vdso_mips_check)
-
-quiet_cmd_vdsold = VDSO $@
- cmd_vdsold = $(CC) $(c_flags) $(VDSO_LDFLAGS) \
- -Wl,-T $(filter %.lds,$^) $(filter %.o,$^) -o $@
+ cmd_vdsold_and_vdso_check = $(cmd_ld); $(cmd_vdso_check); $(cmd_vdso_mips_check)
quiet_cmd_vdsoas_o_S = AS $@
cmd_vdsoas_o_S = $(CC) $(a_flags) -c -o $@ $<