On 25/10/2023 8:22 am, Peter Zijlstra wrote: > On Tue, Oct 24, 2023 at 11:28:18PM -0700, Pawan Gupta wrote: > >> With .text.entry section I am getting getting below warnings and an >> error: >> >> ----------------------------------------------------------------- >> LD vmlinux.o >> vmlinux.o: warning: objtool: .text.entry+0x0: unreachable instruction >> vmlinux.o: warning: objtool: .text.entry+0x40: unreachable instruction >> vmlinux.o: warning: objtool: .text.entry+0x80: unreachable instruction >> vmlinux.o: warning: objtool: .text.entry+0xc0: unreachable instruction >> vmlinux.o: warning: objtool: .text.entry+0x100: unreachable instruction >> vmlinux.o: warning: objtool: .text.entry+0x140: unreachable instruction >> vmlinux.o: warning: objtool: .text.entry+0x180: unreachable instruction >> vmlinux.o: warning: objtool: .text.entry+0x1c0: unreachable instruction >> vmlinux.o: warning: objtool: .text.entry+0x200: unreachable instruction >> vmlinux.o: warning: objtool: .text.entry+0x240: unreachable instruction >> vmlinux.o: warning: objtool: .text.entry+0x280: unreachable instruction >> vmlinux.o: warning: objtool: .text.entry+0x2c0: unreachable instruction >> vmlinux.o: warning: objtool: .text.entry+0x300: unreachable instruction >> vmlinux.o: warning: objtool: .altinstr_replacement+0x2c: relocation to !ENDBR: .text.entry+0x0 >> vmlinux.o: warning: objtool: .altinstr_replacement+0x1c4: relocation to !ENDBR: .text.entry+0x0 >> vmlinux.o: warning: objtool: .altinstr_replacement+0x1d0: relocation to !ENDBR: .text.entry+0x0 >> vmlinux.o: warning: objtool: .altinstr_replacement+0x2d2: relocation to !ENDBR: .text.entry+0x80 >> vmlinux.o: warning: objtool: .altinstr_replacement+0x5d5: relocation to !ENDBR: .text.entry+0xc0 >> OBJCOPY modules.builtin.modinfo >> GEN modules.builtin >> MODPOST vmlinux.symvers >> UPD include/generated/utsversion.h >> CC init/version-timestamp.o >> LD .tmp_vmlinux.kallsyms1 >> ld: error: unplaced orphan section `.text.entry' from `vmlinux.o' >> make[2]: *** [scripts/Makefile.vmlinux:36: vmlinux] Error 1 >> ----------------------------------------------------------------- >> >> ... because my config has CONFIG_LD_ORPHAN_WARN_LEVEL="error" and >> objtool needs to be told about this entry. >> >> Do you think its worth fighting these warnings and error, or simply use >> .rodata section for verw memory operand? > I'm thinking you need to at the very least stay in a section that's > actually still mapped with PTI :-) Sorry. Xen and Linux have this section named opposite ways around. > diff --git a/arch/x86/entry/entry.S b/arch/x86/entry/entry.S > index bfb7bcb362bc..9eb2b532c92a 100644 > --- a/arch/x86/entry/entry.S > +++ b/arch/x86/entry/entry.S > @@ -20,3 +22,16 @@ SYM_FUNC_END(entry_ibpb) > EXPORT_SYMBOL_GPL(entry_ibpb); > > .popsection > + > +.pushsection .entry.text, "ax" > + > +.align 64 > +SYM_CODE_START_NOALIGN(mds_verw_sel) > + UNWIND_HINT_UNDEFINED > + ANNOTATE_NOENDBR > +1: > + .word __KERNEL_DS > + .skip 64 - (. - 1b), 0xcc The 1 label aliases mds_verw_sel and this must remain like this for the construct to work. So instead of .skip, why not simply .align 64, 0xcc and get rid of the 1: label? Do we have a suitably named constant cacheline size, rather than opencoding 64? > +SYM_CODE_END(mds_verw_sel); Given that KVM needs it, this probably needs an EXPORT_SYMBOL_GPL() on it. ~Andrew
