linux-dev/arch/riscv/kernel/vdso/Makefile, branch master

RISC-V: vdso: Do not add missing symbols to version section in linker script

2022-11-10T23:06:14Z

Recently, ld.lld moved from '--undefined-version' to '--no-undefined-version' as the default, which breaks the compat vDSO build: ld.lld: error: version script assignment of 'LINUX_4.15' to symbol '__vdso_gettimeofday' failed: symbol not defined ld.lld: error: version script assignment of 'LINUX_4.15' to symbol '__vdso_clock_gettime' failed: symbol not defined ld.lld: error: version script assignment of 'LINUX_4.15' to symbol '__vdso_clock_getres' failed: symbol not defined These symbols are not present in the compat vDSO or the regular vDSO for 32-bit but they are unconditionally included in the version section of the linker script, which is prohibited with '--no-undefined-version'. Fix this issue by only including the symbols that are actually exported in the version section of the linker script. Link: https://github.com/ClangBuiltLinux/linux/issues/1756 Signed-off-by: Nathan Chancellor Tested-by: Conor Dooley Link: https://lore.kernel.org/r/20221108171324.3377226-1-nathan@kernel.org/ Signed-off-by: Palmer Dabbelt

riscv: vdso: fix build with llvm

2022-11-10T21:58:36Z

Even after commit 89fd4a1df829 ("riscv: jump_label: mark arguments as const to satisfy asm constraints"), building with CC_OPTIMIZE_FOR_SIZE + LLVM=1 can reproduce below build error: CC arch/riscv/kernel/vdso/vgettimeofday.o In file included from :4: In file included from lib/vdso/gettimeofday.c:5: In file included from include/vdso/datapage.h:17: In file included from include/vdso/processor.h:10: In file included from arch/riscv/include/asm/vdso/processor.h:7: In file included from include/linux/jump_label.h:112: arch/riscv/include/asm/jump_label.h:42:3: error: invalid operand for inline asm constraint 'i' " .option push \n\t" ^ 1 error generated. I think the problem is when "-Os" is passed as CFLAGS, it's removed by "CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os" which is introduced in commit e05d57dcb8c7 ("riscv: Fixup __vdso_gettimeofday broke dynamic ftrace"), thus no optimization at all for vgettimeofday.c arm64 does remove "-Os" as well, but it forces "-O2" after removing "-Os". I compared the generated vgettimeofday.o with "-O2" and "-Os", I think no big performance difference. So let's tell the kbuild not to remove "-Os" rather than follow arm64 style. vdso related performance can be improved a lot when building kernel with CC_OPTIMIZE_FOR_SIZE after this commit, ("-Os" VS no optimization) Fixes: e05d57dcb8c7 ("riscv: Fixup __vdso_gettimeofday broke dynamic ftrace") Signed-off-by: Jisheng Zhang Tested-by: Conor Dooley Link: https://lore.kernel.org/r/20221031182943.2453-1-jszhang@kernel.org Signed-off-by: Palmer Dabbelt

riscv: explicitly use symbol offsets for VDSO

2021-08-25T04:45:47Z

The current implementation of the `__rt_sigaction` reference computed an absolute offset relative to the mapped base of the VDSO. While this can be handled in the medlow model, the medany model cannot handle this as it is meant to be position independent. The current implementation relied on the BFD linker relaxing the PC-relative relocation into an absolute relocation as it was a near-zero address allowing it to be referenced relative to `zero`. We now extract the offsets and create a generated header allowing the build with LLVM and lld to succeed as we no longer depend on the linker rewriting address references near zero. This change was largely modelled after the ARM64 target which does something similar. Signed-off-by: Saleem Abdulrasool Tested-by: Nathan Chancellor Signed-off-by: Palmer Dabbelt

riscv: Enable Undefined Behavior Sanitizer UBSAN

2021-08-25T03:59:10Z

Select ARCH_HAS_UBSAN_SANITIZE_ALL in order to allow the user to enable CONFIG_UBSAN_SANITIZE_ALL and instrument the entire kernel for ubsan checks. VDSO is excluded because its build doesn't include the __ubsan_handle_*() functions from lib/ubsan.c, and the VDSO has no sane way to report errors even if it has definitions of these functions. Passed lib/test_ubsan.c test. Signed-off-by: Jisheng Zhang Signed-off-by: Palmer Dabbelt

riscv: vdso: fix and clean-up Makefile

2021-04-26T15:25:19Z

Running "make" on an already compiled kernel tree will rebuild the kernel even without any modifications: CALL linux/scripts/checksyscalls.sh CALL linux/scripts/atomic/check-atomics.sh CHK include/generated/compile.h SO2S arch/riscv/kernel/vdso/vdso-syms.S AS arch/riscv/kernel/vdso/vdso-syms.o AR arch/riscv/kernel/vdso/built-in.a AR arch/riscv/kernel/built-in.a AR arch/riscv/built-in.a GEN .version CHK include/generated/compile.h UPD include/generated/compile.h CC init/version.o AR init/built-in.a LD vmlinux.o The reason is "Any target that utilizes if_changed must be listed in $(targets), otherwise the command line check will fail, and the target will always be built" as explained by Documentation/kbuild/makefiles.rst Fix this build bug by adding vdso-syms.S to $(targets) At the same time, there are two trivial clean up modifications: - the vdso-dummy.o is not needed any more after so remove it. - vdso.lds is a generated file, so it should be prefixed with $(obj)/ instead of $(src)/ Fixes: c2c81bb2f691 ("RISC-V: Fix the VDSO symbol generaton for binutils-2.35+") Cc: stable@vger.kernel.org Signed-off-by: Jisheng Zhang Signed-off-by: Palmer Dabbelt

riscv: Use $(LD) instead of $(CC) to link vDSO

2021-04-26T15:24:59Z

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 linking with clang, there are a couple of warnings about flags that will not be used during the link: clang-12: warning: argument unused during compilation: '-no-pie' [-Wunused-command-line-argument] clang-12: warning: argument unused during compilation: '-pg' [-Wunused-command-line-argument] '-no-pie' was added in commit 85602bea297f ("RISC-V: build vdso-dummy.o with -no-pie") to override '-pie' getting added to the ld command from distribution versions of GCC that enable PIE by default. It is technically no longer needed after commit c2c81bb2f691 ("RISC-V: Fix the VDSO symbol generaton for binutils-2.35+"), which removed vdso-dummy.o in favor of generating vdso-syms.S from vdso.so with $(NM) but this also resolves the issue in case it ever comes back due to having full control over the $(LD) command. '-pg' is for function tracing, it is not used during linking as clang states. These flags could be removed/filtered to fix the warnings but it is easier to just match the rest of the kernel and use $(LD) directly for linking. See commits fe00e50b2db8 ("ARM: 8858/1: vdso: use $(LD) instead of $(CC) to link VDSO") 691efbedc60d ("arm64: vdso: use $(LD) instead of $(CC) to link VDSO") 2ff906994b6c ("MIPS: VDSO: Use $(LD) instead of $(CC) to link VDSO") 2b2a25845d53 ("s390/vdso: Use $(LD) instead of $(CC) to link vDSO") for more information. The flags are converted to linker flags and '--eh-frame-hdr' is added to match what is added by GCC implicitly, which can be seen by adding '-v' to GCC's invocation. Additionally, since this area is being modified, use the $(OBJCOPY) variable instead of an open coded $(CROSS_COMPILE)objcopy so that the user's choice of objcopy binary is respected. Link: https://github.com/ClangBuiltLinux/linux/issues/803 Link: https://github.com/ClangBuiltLinux/linux/issues/970 Signed-off-by: Nathan Chancellor Reviewed-by: Fangrui Song Signed-off-by: Palmer Dabbelt

riscv: Disable KSAN_SANITIZE for vDSO

2021-02-23T01:51:23Z

We use the generic C VDSO implementations of a handful of clock-related functions. When kasan is enabled this results in asan stub calls that are unlikely to be resolved by userspace, this just disables KASAN when building the VDSO. Verified the fix on a kernel with KASAN enabled using vDSO selftests. Link: https://lore.kernel.org/lkml/CACT4Y+ZNJBnkKHXUf=tm_yuowvZvHwN=0rmJ=7J+xFd+9r_6pQ@mail.gmail.com/ Tested-by: Tobias Klauser Signed-off-by: Tobias Klauser Tested-by: Dmitry Vyukov [Palmer: commit text] Fixes: ad5d1122b82f ("riscv: use vDSO common flow to reduce the latency of the time-related functions") Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt

riscv: Explicitly specify the build id style in vDSO Makefile again

2020-11-25T17:44:14Z

Commit a96843372331 ("kbuild: explicitly specify the build id style") explicitly set the build ID style to SHA1. Commit c2c81bb2f691 ("RISC-V: Fix the VDSO symbol generaton for binutils-2.35+") undid this change, likely unintentionally. Restore it so that the build ID style stays consistent across the tree regardless of linker. Fixes: c2c81bb2f691 ("RISC-V: Fix the VDSO symbol generaton for binutils-2.35+") Signed-off-by: Nathan Chancellor Reviewed-by: Nick Desaulniers Reviewed-by: Bill Wendling Signed-off-by: Palmer Dabbelt

RISC-V: Fix the VDSO symbol generaton for binutils-2.35+

2020-11-06T08:03:48Z

We were relying on GNU ld's ability to re-link executable files in order to extract our VDSO symbols. This behavior was deemed a bug as of binutils-2.35 (specifically the binutils-gdb commit a87e1817a4 ("Have the linker fail if any attempt to link in an executable is made."), but as that has been backported to at least Debian's binutils-2.34 in may manifest in other places. The previous version of this was a bit of a mess: we were linking a static executable version of the VDSO, containing only a subset of the input symbols, which we then linked into the kernel. This worked, but certainly wasn't a supported path through the toolchain. Instead this new version parses the textual output of nm to produce a symbol table. Both rely on near-zero addresses being linkable, but as we rely on weak undefined symbols being linkable elsewhere I don't view this as a major issue. Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API") Signed-off-by: Palmer Dabbelt

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