linux-dev/arch/mips/vdso/Makefile, branch master

mips: Enable KCSAN

2022-02-07T17:31:57Z

This patch enables KCSAN for the 64-bit version. Updated rules for the incompatible compilation units (vdso, boot/compressed). Signed-off-by: Nemanja Rakovic Signed-off-by: Thomas Bogendoerfer

MIPS: VDSO: remove -nostdlib compiler flag

2021-11-09T15:09:37Z

The -nostdlib option requests the compiler to not use the standard system startup files or libraries when linking. It is effective only when $(CC) is used as a linker driver. Since commit 2ff906994b6c ("MIPS: VDSO: Use $(LD) instead of $(CC) to link VDSO"), $(LD) is directly used, hence -nostdlib is unneeded. Signed-off-by: Masahiro Yamada Signed-off-by: Thomas Bogendoerfer

MIPS: Makefile: Replace -pg with CC_FLAGS_FTRACE

2021-04-21T11:44:35Z

This patch replaces the "open-coded" -pg compile flag with a CC_FLAGS_FTRACE makefile variable which architectures can override if a different option should be used for code generation. Signed-off-by: zhaoxiao Signed-off-by: Thomas Bogendoerfer

MIPS: VDSO: Use CLANG_FLAGS instead of filtering out '--target='

2021-01-18T14:40:14Z

Commit ee67855ecd9d ("MIPS: vdso: Allow clang's --target flag in VDSO cflags") allowed the '--target=' flag from the main Makefile to filter through to the vDSO. However, it did not bring any of the other clang specific flags for controlling the integrated assembler and the GNU tools locations (--prefix=, --gcc-toolchain=, and -no-integrated-as). Without these, we will get a warning (visible with tinyconfig): arch/mips/vdso/elf.S:14:1: warning: DWARF2 only supports one section per compilation unit .pushsection .note.Linux, "a",@note ; .balign 4 ; .long 2f - 1f ; .long 4484f - 3f ; .long 0 ; 1:.asciz "Linux" ; 2:.balign 4 ; 3: ^ arch/mips/vdso/elf.S:34:2: warning: DWARF2 only supports one section per compilation unit .section .mips_abiflags, "a" ^ All of these flags are bundled up under CLANG_FLAGS in the main Makefile and exported so that they can be added to Makefiles that set their own CFLAGS. Use this value instead of filtering out '--target=' so there is no warning and all of the tools are properly used. Cc: stable@vger.kernel.org Fixes: ee67855ecd9d ("MIPS: vdso: Allow clang's --target flag in VDSO cflags") Link: https://github.com/ClangBuiltLinux/linux/issues/1256 Reported-by: Anders Roxell Signed-off-by: Nathan Chancellor Tested-by: Anders Roxell Signed-off-by: Thomas Bogendoerfer

kbuild: explicitly specify the build id style

2020-10-09T14:57:30Z

ld's --build-id defaults to "sha1" style, while lld defaults to "fast". The build IDs are very different between the two, which may confuse programs that reference them. Signed-off-by: Bill Wendling Acked-by: David S. Miller Signed-off-by: Masahiro Yamada

kbuild: remove cc-option test of -fno-stack-protector

2020-07-07T02:13:10Z

Some Makefiles already pass -fno-stack-protector unconditionally. For example, arch/arm64/kernel/vdso/Makefile, arch/x86/xen/Makefile. No problem report so far about hard-coding this option. So, we can assume all supported compilers know -fno-stack-protector. GCC 4.8 and Clang support this option (https://godbolt.org/z/_HDGzN) Get rid of cc-option from -fno-stack-protector. Remove CONFIG_CC_HAS_STACKPROTECTOR_NONE, which is always 'y'. Note: arch/mips/vdso/Makefile adds -fno-stack-protector twice, first unconditionally, and second conditionally. I removed the second one. Signed-off-by: Masahiro Yamada Reviewed-by: Kees Cook Acked-by: Ard Biesheuvel Reviewed-by: Nick Desaulniers

MIPS: VDSO: Use $(LD) instead of $(CC) to link VDSO

2020-05-12T08:02:00Z

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): /libexec/gcc/mips64-linux/9.3.0/collect2 \ -plugin /libexec/gcc/mips64-linux/9.3.0/liblto_plugin.so \ -plugin-opt=/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/lib/gcc/mips64-linux/9.3.0/64 \ -L/lib/gcc/mips64-linux/9.3.0 \ -L/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: /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 Signed-off-by: Thomas Bogendoerfer

MIPS: VDSO: Move disabling the VDSO logic to Kconfig

2020-05-12T08:01:45Z

After commit 9553d16fa671 ("init/kconfig: Add LD_VERSION Kconfig"), we have access to GNU ld's version at configuration time. As a result, we can make it clearer under what configuration circumstances the MIPS VDSO needs to be disabled. This is a prerequisite for getting rid of the MIPS VDSO binutils warning and linking the VDSO when LD is ld.lld. Wrapping the call to ld-ifversion with CONFIG_LD_IS_LLD does not work because the config values are wiped away during 'make clean'. Signed-off-by: Nathan Chancellor Signed-off-by: Thomas Bogendoerfer

MIPS: vdso: Wrap -mexplicit-relocs in cc-option

2020-02-19T18:30:10Z

Clang does not support this option and errors out: clang-11: error: unknown argument: '-mexplicit-relocs' Clang does not appear to need this flag like GCC does because the jalr check that was added in commit 976c23af3ee5 ("mips: vdso: add build time check that no 'jalr t9' calls left") passes just fine with $ make ARCH=mips CC=clang CROSS_COMPILE=mipsel-linux-gnu- malta_defconfig arch/mips/vdso/ even before commit d3f703c4359f ("mips: vdso: fix 'jalr t9' crash in vdso code"). -mrelax-pic-calls has been supported since clang 9, which is the earliest version that could build a working MIPS kernel, and it is the default for clang so just leave it be. Fixes: d3f703c4359f ("mips: vdso: fix 'jalr t9' crash in vdso code") Link: https://github.com/ClangBuiltLinux/linux/issues/890 Signed-off-by: Nathan Chancellor Reviewed-by: Nick Desaulniers Tested-by: Nick Desaulniers Signed-off-by: Paul Burton Cc: Ralf Baechle Cc: linux-mips@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: clang-built-linux@googlegroups.com

mips: vdso: add build time check that no 'jalr t9' calls left

2020-02-15T20:44:03Z

vdso shared object cannot have GOT based PIC 'jalr t9' calls because nobody set GOT table in vdso. Contributing into vdso .o files are compiled in PIC mode and as result for internal static functions calls compiler will generate 'jalr t9' instructions. Those are supposed to be converted into PC relative 'bal' calls by linker when relocation are processed. Mips global GOT entries do have dynamic relocations and they will be caught by cmd_vdso_check Makefile rule. Static PIC calls go through mips local GOT entries that do not have dynamic relocations. For those 'jalr t9' calls could be present but without dynamic relocations and they need to be converted to 'bal' calls by linker. Add additional build time check to make sure that no 'jalr t9' slip through because of some toolchain misconfiguration that prevents 'jalr t9' to 'bal' conversion. Signed-off-by: Victor Kamensky Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org Cc: Ralf Baechle Cc: James Hogan Cc: Vincenzo Frascino Cc: bruce.ashfield@gmail.com Cc: richard.purdie@linuxfoundation.org