On Sat, Sep 26, 2026 at 5:29 AM Jason A. Donenfeld <[email protected]> wrote: > > On Sat, Sep 26, 2026 at 12:55:34PM +0200, Christophe Leroy (CS GROUP) wrote: > > Hi Jason, > > > > Le 26/09/2026 à 12:02, Jason A. Donenfeld a écrit : > > > Apparently not on RISCV, which is what prompted this patch in the first > > > place. So I suspect Nathan's v2 here is the way to go. > > > > > > Don't you have -fno-builtin on RISCV like we have on powerpc ? > > I think Nick mentioned this led to other problems and didn't exactly > solve the problem.
Sorry, been very busy. Getting blasted from a fire hose of AI generated patches to review... arch/arm64/kvm/hyp/nvhe/Makefile has this pattern for exactly the same problem I suspect. Maybe that's the right tool in the toolbox? ``` diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile index 8dbf2532a573..27fa72d8fb86 100644 --- a/arch/riscv/kernel/vdso/Makefile +++ b/arch/riscv/kernel/vdso/Makefile @@ -27,7 +27,7 @@ asflags-y += -DVDSO_CFI=1 endif # Files to link into the vdso -obj-vdso = $(patsubst %, %.o, $(vdso-syms)) note.o +obj-vdso = $(patsubst %, %.o, $(vdso-syms)) note.o ../../lib/memset.o ifdef CONFIG_VDSO_GETRANDOM obj-vdso += vgetrandom-chacha.o ``` Fixes `make -skj"$(nproc)" ARCH=riscv LLVM=1 mrproper allmodconfig vdso_prepare` for me, as per https://github.com/ClangBuiltLinux/linux/issues/2183 (Nathan, don't forget to link to that in the commit message) I'm surprised I didn't need -fno-semantic-interposition (or one of the related flags... -fvisibility=hidden) If we want to get better, (if performance matters here and we want to trade source+build system complexity for absolute code perf) I would start with that, then worry about clawing back performance via things like: - __builtin_memset_inline - -finline-stringops=memset - -ffunction-sections+-Wl,--gc-sections to dead code eliminate the out of line copy of memset, though IIRC there's potential for wasted space due to alignment requirements (maybe the out of line copy of memset is smaller...idk) -- Thanks, ~Nick Desaulniers
