Nathan Chancellor 2ff906994b 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 fe00e50b2d ("ARM: 8858/1: vdso: use $(LD) instead of $(CC) to link VDSO") and commit 691efbedc6 ("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>		2020-05-12 10:02:00 +02:00
..
.gitignore	.gitignore: add SPDX License Identifier	2020-03-25 11:50:48 +01:00
config-n32-o32-env.c	mips: compat: vdso: Use legacy syscalls as fallback	2019-09-03 15:35:23 +01:00
elf.S	mips: Add support for generic vDSO	2019-07-25 21:45:05 -07:00
genvdso.c	mips/vdso: Support mremap() for vDSO	2020-01-15 10:44:14 -08:00
genvdso.h	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00
Kconfig	MIPS: VDSO: Move disabling the VDSO logic to Kconfig	2020-05-12 10:01:45 +02:00
Makefile	MIPS: VDSO: Use $(LD) instead of $(CC) to link VDSO	2020-05-12 10:02:00 +02:00
sigreturn.S	mips: Add support for generic vDSO	2019-07-25 21:45:05 -07:00
vdso.lds.S	MIPS: VDSO: Move disabling the VDSO logic to Kconfig	2020-05-12 10:01:45 +02:00
vgettimeofday.c	mips: Fix gettimeofday() in the vdso library	2019-12-02 10:50:37 -08:00