Hey Alex, clang/llvm folk, On Fri, Feb 24, 2023 at 11:02:18AM +0100, Alexandre Ghiti wrote: > Add 2 early command line parameters that allow to downgrade satp mode > (using the same naming as x86): > - "no5lvl": use a 4-level page table (down from sv57 to sv48) > - "no4lvl": use a 3-level page table (down from sv57/sv48 to sv39) > > Note that going through the device tree to get the kernel command line > works with ACPI too since the efi stub creates a device tree anyway with > the command line. > > In KASAN kernels, we can't use the libfdt that early in the boot process > since we are not ready to execute instrumented functions. So instead of > using the "generic" libfdt, we compile our own versions of those functions > that are not instrumented and that are prefixed so that they do not > conflict with the generic ones. We also need the non-instrumented versions > of the string functions and the prefixed versions of memcpy/memmove. > > This is largely inspired by commit aacd149b6238 ("arm64: head: avoid > relocating the kernel twice for KASLR") from which I removed compilation > flags that were not relevant to RISC-V at the moment (LTO, SCS, pie). > > Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx> > Tested-by: Björn Töpel <bjorn@xxxxxxxxxxxx> > Reviewed-by: Björn Töpel <bjorn@xxxxxxxxxxxx> > --- > .../admin-guide/kernel-parameters.txt | 5 +- > arch/riscv/kernel/Makefile | 2 + > arch/riscv/kernel/pi/Makefile | 37 +++++++++++ > arch/riscv/kernel/pi/cmdline_early.c | 62 +++++++++++++++++++ + 4 ld.lld: warning: vmlinux.a(arch/riscv/kernel/pi/string.pi.o):(.init.sdata) is being placed in '.init.sdata' I'm getting 4 new linker warnings with LLVM=1 clang-15 allmodconfig builds - but I don't really understand this issue. Is this spurious, and a just consequence of... > diff --git a/arch/riscv/kernel/pi/Makefile b/arch/riscv/kernel/pi/Makefile > new file mode 100644 > index 000000000000..4002ed94b6d3 > --- /dev/null > +++ b/arch/riscv/kernel/pi/Makefile > @@ -0,0 +1,37 @@ > +# SPDX-License-Identifier: GPL-2.0 > +# This file was copied from arm64/kernel/pi/Makefile. > + > +KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ > + -Os -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK_PLUGIN) \ > + $(call cc-option,-mbranch-protection=none) \ > + -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \ > + -D__DISABLE_EXPORTS -ffreestanding \ > + -fno-asynchronous-unwind-tables -fno-unwind-tables \ > + $(call cc-option,-fno-addrsig) > + > +CFLAGS_cmdline_early.o += -D__NO_FORTIFY > +CFLAGS_lib-fdt_ro.o += -D__NO_FORTIFY > + > +GCOV_PROFILE := n > +KASAN_SANITIZE := n > +KCSAN_SANITIZE := n > +UBSAN_SANITIZE := n > +KCOV_INSTRUMENT := n > + > +$(obj)/%.pi.o: OBJCOPYFLAGS := --prefix-symbols=__pi_ \ > + --remove-section=.note.gnu.property \ > + --prefix-alloc-sections=.init ...this? > +$(obj)/%.pi.o: $(obj)/%.o FORCE > + $(call if_changed,objcopy) > + > +$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE > + $(call if_changed_rule,cc_o_c) > + > +$(obj)/string.o: $(srctree)/lib/string.c FORCE > + $(call if_changed_rule,cc_o_c) > + > +$(obj)/ctype.o: $(srctree)/lib/ctype.c FORCE > + $(call if_changed_rule,cc_o_c) > + > +obj-y := cmdline_early.pi.o string.pi.o ctype.pi.o lib-fdt.pi.o lib-fdt_ro.pi.o > +extra-y := $(patsubst %.pi.o,%.o,$(obj-y))
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