On Fri, Mar 19, 2021 at 1:25 PM Catalin Marinas <catalin.mari...@arm.com> wrote: > On Thu, Mar 18, 2021 at 09:41:54AM +0100, Arnd Bergmann wrote: > > On Wed, Mar 17, 2021 at 5:18 PM Catalin Marinas <catalin.mari...@arm.com> > > wrote: > > > On Wed, Mar 17, 2021 at 02:37:57PM +0000, Catalin Marinas wrote: > > > > On Thu, Feb 25, 2021 at 12:20:56PM +0100, Arnd Bergmann wrote: > > > > > diff --git a/arch/arm64/kernel/vmlinux.lds.S > > > > > b/arch/arm64/kernel/vmlinux.lds.S > > > > > index bad2b9eaab22..926cdb597a45 100644 > > > > > --- a/arch/arm64/kernel/vmlinux.lds.S > > > > > +++ b/arch/arm64/kernel/vmlinux.lds.S > > > > > @@ -217,7 +217,7 @@ SECTIONS > > > > > INIT_CALLS > > > > > CON_INITCALL > > > > > INIT_RAM_FS > > > > > - *(.init.altinstructions .init.bss .init.bss.*) /* from > > > > > the EFI stub */ > > > > > + *(.init.altinstructions .init.data.* .init.bss > > > > > .init.bss.*) /* from the EFI stub */ > > > > > > > > INIT_DATA already covers .init.data and .init.data.*, so I don't think > > > > we need this change. > > > > > > Ah, INIT_DATA only covers init.data.* (so no dot in front). The above > > > is needed for the EFI stub. > > > > I wonder if that is just a typo in INIT_DATA. Nico introduced it as part of > > 266ff2a8f51f ("kbuild: Fix asm-generic/vmlinux.lds.h for > > LD_DEAD_CODE_DATA_ELIMINATION"), so perhaps that should have > > been .init.data.* instead. > > I think it was the other Nicholas ;) (with an 'h'). The vmlinux.lds.h > change indeed looks like a typo (it's been around since 4.18).
Right, my mistake. > > It looks like pointer authentication gone wrong, which ended up > > with dereferencing the broken pointer in x22, and it explains why > > it only happens with -cpu max. Presumably this also only happens > > on secondary CPUs, so maybe the bit that initializes PAC on > > secondary CPUs got discarded? > > I seems that the whole alternative instructions section is gone, so any > run-time code patching that the kernel does won't work. The kernel boots > with the diff below but I'm not convinced we don't miss anything else. > In some cases you get a linker warning about gc sections but not in this > case. Maybe we need some more asserts to ensure that certain sections > are not empty. > > diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S > index 11909782ee3e..036cc59033d3 100644 > --- a/arch/arm64/kernel/vmlinux.lds.S > +++ b/arch/arm64/kernel/vmlinux.lds.S > @@ -203,7 +203,7 @@ SECTIONS > . = ALIGN(4); > .altinstructions : { > __alt_instructions = .; > - *(.altinstructions) > + KEEP(*(.altinstructions)) > __alt_instructions_end = .; > } > > Do we need a KEEP(.init.altinstructions) as well? I would guess so. Whatever causes the .altinstructions to get dropped presumably also leads to the same happening to .init.altinstructions. Ideally each use of altinstructions would cause a reference to a particular symbol so that one gets kept, while any .altinstructions for unused functions get discarded. Arnd