BMC/Intel-BMC/linux.git/arch/s390/kernel/vdso64, branch dev-5.8

s390/vdso: fix vDSO clock_getres()

2020-06-16T11:44:05+00:00

clock_getres in the vDSO library has to preserve the same behaviour of posix_get_hrtimer_res(). In particular, posix_get_hrtimer_res() does: sec = 0; ns = hrtimer_resolution; and hrtimer_resolution depends on the enablement of the high resolution timers that can happen either at compile or at run time. Fix the s390 vdso implementation of clock_getres keeping a copy of hrtimer_resolution in vdso data and using that directly. Link: https://lkml.kernel.org/r/20200324121027.21665-1-vincenzo.frascino@arm.com Signed-off-by: Vincenzo Frascino Acked-by: Martin Schwidefsky [heiko.carstens@de.ibm.com: use llgf for proper zero extension] Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/vdso: Use $(LD) instead of $(CC) to link vDSO

2020-06-16T11:44:05+00:00

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, which is just ld. However, the user can override this through the CLANG_DEFAULT_LINKER cmake define so that clang uses another linker by default, such as LLVM's own linker, ld.lld. This can be useful to get more optimized links across various different projects. However, this is problematic for the s390 vDSO because ld.lld does not have any s390 emulatiom support: https://github.com/llvm/llvm-project/blob/llvmorg-10.0.1-rc1/lld/ELF/Driver.cpp#L132-L150 Thus, if a user is using a toolchain with ld.lld as the default, they will see an error, even if they have specified ld.bfd through the LD make variable: $ make -j"$(nproc)" -s ARCH=s390 CROSS_COMPILE=s390x-linux-gnu- LLVM=1 \ LD=s390x-linux-gnu-ld \ defconfig arch/s390/kernel/vdso64/ ld.lld: error: unknown emulation: elf64_s390 clang-11: error: linker command failed with exit code 1 (use -v to see invocation) Normally, '-fuse-ld=bfd' could be used to get around this; however, this can be fragile, depending on paths and variable naming. The cleaner solution for the kernel is to take advantage of the fact that $(LD) can be invoked directly, which bypasses the heuristics of $(CC) and respects the user's choice. Similar changes have been done for ARM, ARM64, and MIPS. Link: https://lkml.kernel.org/r/20200602192523.32758-1-natechancellor@gmail.com Link: https://github.com/ClangBuiltLinux/linux/issues/1041 Signed-off-by: Nathan Chancellor Reviewed-by: Nick Desaulniers [heiko.carstens@de.ibm.com: add --build-id flag] Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

.gitignore: add SPDX License Identifier

2020-03-25T10:50:48+00:00

Add SPDX License Identifier to all .gitignore files. Signed-off-by: Masahiro Yamada Signed-off-by: Greg Kroah-Hartman

s390/vdso: fix getcpu

2019-11-30T09:52:44+00:00

getcpu reads the required values for cpu and node with two instructions. This might lead to an inconsistent result if user space gets preempted and migrated to a different CPU between the two instructions. Fix this by using just a single instruction to read both values at once. This is currently rather a theoretical bug, since there is no real NUMA support available (except for NUMA emulation). Reviewed-by: Christian Borntraeger Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/vdso: drop unnecessary cc-ldoption

2019-05-03T15:17:58+00:00

Towards the goal of removing cc-ldoption, it seems that --hash-style= was added to binutils 2.17.50.0.2 in 2006. The minimal required version of binutils for the kernel according to Documentation/process/changes.rst is 2.20. Link: https://gcc.gnu.org/ml/gcc/2007-01/msg01141.html Cc: clang-built-linux@googlegroups.com Suggested-by: Masahiro Yamada Signed-off-by: Nick Desaulniers Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/vdso: add missing FORCE to build targets

2018-10-26T08:19:40+00:00

According to Documentation/kbuild/makefiles.txt all build targets using if_changed should use FORCE as well. Add missing FORCE to make sure vdso targets are rebuild properly when not just immediate prerequisites have changed but also when build command differs. Reviewed-by: Philipp Rudo Signed-off-by: Vasily Gorbik Signed-off-by: Martin Schwidefsky

s390/kasan: avoid vdso instrumentation

2018-10-09T09:21:16+00:00

vdso is mapped into user space processes, which won't have kasan shodow mapped. Reviewed-by: Martin Schwidefsky Signed-off-by: Vasily Gorbik Signed-off-by: Martin Schwidefsky

s390/vdso: correct CFI annotations of vDSO functions

2018-09-20T11:20:29+00:00

Correct stack frame overhead for 31-bit vdso, which should be 96 rather then 160. This is done by reusing STACK_FRAME_OVERHEAD definition which contains correct value based on build flags. This fixes stack unwinding within vdso code for 31-bit processes. While at it replace all hard coded stack frame overhead values with the same definition in vdso64 as well. Reviewed-by: Hendrik Brueckner Signed-off-by: Vasily Gorbik Signed-off-by: Martin Schwidefsky

s390/vdso: revise CFI annotations of vDSO functions

2017-12-13T09:51:36+00:00

Revise and add CFI CFA and register rule annotations to the vDSO functions for proper stack unwinding and debugging. Because glibc might call the vDSO in special ways, the vDSO code does not rely on a stack frame created by the caller. The TOD clock value can be therefore not stored in the pre-allocated stack area and additional stack space is required. To correctly annotate these situations with CFI, the .cfi_val_offset directive is required to create relative offsets on the value of the stack register %r15. Because the .cfi_val_offset directive is available with recent GNU assembler versions only, additional checks are necessary. Note that if the vDSO is assembled with an older assembler version, stack unwinding and debugging from within the vDSO code might not be possible. Signed-off-by: Hendrik Brueckner Reviewed-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/kernel: emit CFI data in .debug_frame and discard .eh_frame sections

2017-12-13T09:51:35+00:00

Using perf probe and libdw on kernel modules failed to find CFI data for symbols. The CFI data is stored in the .eh_frame section. The elfutils libdw is not able to extract the CFI data correctly, because the .eh_frame section requires "non-simple" relocations for kernel modules. The suggestion is to avoid these "non-simple" relocations by emitting the CFI data in the .debug_frame section. Let gcc emit respective directives by specifying the -fno-asynchronous-unwind-tables option. Using the .debug_frame section for CFI data, the .eh_frame section becomes unused and, thus, discard it for kernel and modules builds The vDSO requires the .eh_frame section and, hence, emit the CFI data in both, the .eh_frame and .debug_frame sections. See also discussion on elfutils/libdw bugzilla: https://sourceware.org/bugzilla/show_bug.cgi?id=22452 Suggested-by: Mark Wielaard Signed-off-by: Hendrik Brueckner Reviewed-by: Heiko Carstens Signed-off-by: Martin Schwidefsky