On Fri, 12 Jan 2024 13:35:39 PST (-0800), Richard Henderson wrote: > On 1/12/24 08:49, Vineet Gupta wrote: >> Hi Richard, Alistair >> >> On 10/30/23 14:17, Richard Henderson wrote: >>> diff --git a/linux-user/riscv/Makefile.vdso b/linux-user/riscv/Makefile.vdso >>> new file mode 100644 >>> index 0000000000..2c257dbfda >>> --- /dev/null >>> +++ b/linux-user/riscv/Makefile.vdso >>> @@ -0,0 +1,15 @@ >>> +include $(BUILD_DIR)/tests/tcg/riscv64-linux-user/config-target.mak >>> + >>> +SUBDIR = $(SRC_PATH)/linux-user/riscv >>> +VPATH += $(SUBDIR) >>> + >>> +all: $(SUBDIR)/vdso-32.so $(SUBDIR)/vdso-64.so >>> + >>> +LDFLAGS = -nostdlib -shared -fpic -Wl,-h,linux-vdso.so.1 >>> -Wl,--build-id=sha1 \ >>> + -Wl,--hash-style=both -Wl,-T,$(SUBDIR)/vdso.ld >>> + >>> +$(SUBDIR)/vdso-32.so: vdso.S vdso.ld vdso-asmoffset.h >>> + $(CC) -o $@ $(LDFLAGS) -mabi=ilp32d -march=rv32g $< >>> + >>> +$(SUBDIR)/vdso-64.so: vdso.S vdso.ld vdso-asmoffset.h >>> + $(CC) -o $@ $(LDFLAGS) -mabi=lp64d -march=rv64g $< >> >> So by default qemu ships the vdso binary. How can one rebuild it ? >> >> From skimming the build files it seems following ought to do it >>    make update-linux-vdso >> >> with a prior configure cmd like below with PATH pointing to the cross >> compiler. >> ../configure --target-list=riscv64-linux-user >> --cross-cc-riscv64=riscv64-unknown-linux-gnu-gcc > > Yes, that should do it. > >> But it doesn't, I'm sure we are missing something basis here. > > Do you get an error message? > Did $(BUILD_DIR)/tests/tcg/riscv64-linux-user/config-target.mak get created > properly? > >> For starters we saw something that seems like a thinko in >> >> diff --git a/linux-user/riscv/vdso.S b/linux-user/riscv/vdso.S >> -#define sizeof_reg    (__riscv_xlen / 4) >> +#define sizeof_reg    (__riscv_xlen / 8) > > Oops. > >> As as aside, we also see that rt_sigreturn in kernel vdso elides the >> explicit the call frame information. Again we naively don't know if that >> is required in qemu. >> >>    .text >> ENTRY(__vdso_rt_sigreturn) >>    .cfi_startproc >>    .cfi_signal_frame >>    li a7, __NR_rt_sigreturn >>    ecall >>    .cfi_endproc >> ENDPROC(__vdso_rt_sigreturn) > > Perhaps it's not required, no. But I'd consider the lack of info from the > kernel to be a > bug. Lack of it means places like gcc have to have special cases.
Ya, I agree. We've tried to avoid too many RISC-V-specific hacks for this, but it's bitten me a few times in embedded codebases and it's always a headache. Reviewed-by: Palmer Dabbelt <pal...@rivosinc.com> Thanks! Looks like we've got essentially the same thing in Linux already, so I think we're safe over there. > > > > r~ > > -- > You received this message because you are subscribed to the Google Groups > "gnu-toolchain" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to gnu-toolchain+unsubscr...@rivosinc.com. > To view this discussion on the web visit > https://groups.google.com/a/rivosinc.com/d/msgid/gnu-toolchain/119848b9-0cd7-4d33-bc43-385c86069388%40linaro.org. > For more options, visit https://groups.google.com/a/rivosinc.com/d/optout.
