Re: [PATCH 2/5] x86/pvh: Make PVH entrypoint PIC for x86-64

Jason Andryuk
2024-04-11T15:26:19Z

On 2024-04-10 17:00, Brian Gerst wrote:
> On Wed, Apr 10, 2024 at 3:50 PM Jason Andryuk <jason.andryuk@amd.com> wrote:

>> /* 64-bit entry point. */
>> .code64
>> 1:
>> + UNWIND_HINT_END_OF_STACK
>> +
>> /* Set base address in stack canary descriptor. */
>> mov $MSR_GS_BASE,%ecx
>> - mov $_pa(canary), %eax
>> + leal rva(canary)(%ebp), %eax
>
> Since this is in 64-bit mode, RIP-relative addressing can be used.
>
>> xor %edx, %edx
>> wrmsr
>>
>> call xen_prepare_pvh
>>
>> /* startup_64 expects boot_params in %rsi. */
>> - mov $_pa(pvh_bootparams), %rsi
>> - mov $_pa(startup_64), %rax
>> + lea rva(pvh_bootparams)(%ebp), %rsi
>> + lea rva(startup_64)(%ebp), %rax
>
> RIP-relative here too.

Yes, thanks for catching that. With the RIP-relative conversion, there
is now:
vmlinux.o: warning: objtool: pvh_start_xen+0x10d: relocation to !ENDBR:
startup_64+0x0

I guess RIP-relative made it visible. That can be quieted by adding
ANNOTATE_NOENDBR to startup_64.

Thanks,
Jason