On 16.03.2023 10:52, Oleksii wrote: >>> >>> Could you please explain what is x86 section asserts? >> >> If you look at the bottom of x86's xen.lds.S you'll find a number of >> assertions, among them one towards .got being empty. Some of the >> sections checked there may indeed not be applicable on arbitrary >> architectures, but I think .got is sufficiently universal. So I agree >> with Andrew that it may be worthwhile making some of this generic. > > I have question about 'SIZEOF(.got.plt) == 3 * 8': > > #ifndef EFI > ASSERT(!SIZEOF(.got), ".got non-empty") > /* > * At least GNU ld 2.30 and earlier fail to discard the generic part of > * .got.plt when no actual entries were allocated. Permit this case > alongside > * the section being empty. > */ > ASSERT(!SIZEOF(.got.plt) || SIZEOF(.got.plt) == 3 * 8, > "unexpected .got.plt size") > ASSERT(!SIZEOF(.igot.plt), ".igot.plt non-empty") > ASSERT(!SIZEOF(.iplt), ".iplt non-empty") > ASSERT(!SIZEOF(.plt), ".plt non-empty") > ASSERT(!SIZEOF(.rela), "leftover relocations") > #endif > > I assume that the check 'SIZEOF(.got.plt) == 3 * 8' was added to verify > the case when no real entries in .got.plt are needed but .got.plt still > has 3 entries. > > I commented the code where got entries are produced now: > --- a/xen/arch/riscv/riscv64/head.S > +++ b/xen/arch/riscv/riscv64/head.S > @@ -20,6 +20,7 @@ ENTRY(start) > csrc CSR_SSTATUS, t0 > > /* Clear the BSS */ > +/* > la t3, __bss_start > la t4, __bss_end > .L_clear_bss: > @@ -30,5 +31,6 @@ ENTRY(start) > la sp, cpu0_boot_stack > li t0, STACK_SIZE > add sp, sp, t0 > +*/ > > tail start_xen > > And I can't see .got.plt with 3 entries: > $ riscv64-linux-gnu-objdump -x xen/xen-syms | grep -i got > > What am I doing wrong? Or my understanding of the idea of the check is > wrong?
Did you read the comment next to it as to only older binutils being affected? I assume you use something newer than 2.30. Furthermore that specific behavior may very well have been x86-specific in the first place. So ... > And I assume that add !SIZEOF(.got) and !SIZEOF(.got.plt) would be > enough to RISC-V's xen.lds.S? ... quite likely: Yes. Jan
