| Message ID | 20240814083428.3012-5-frediano.ziglio@cloud.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Support EFI multiboot loading using PE binary | expand |
On 14.08.2024 10:34, Frediano Ziglio wrote: > If code is loaded by EFI the loader will relocate the image > under 4GB. This causes offsets in x86 code generated by > sym_offs(SYMBOL) to be relocated too (basically they won't be > offsets from image base). In turn meaning that ... > --- a/xen/arch/x86/boot/head.S > +++ b/xen/arch/x86/boot/head.S > @@ -380,7 +380,8 @@ x86_32_switch: > lgdt gdt_boot_descr(%rip) > > /* Store Xen image load base address in place accessible for 32-bit code. */ > - lea __image_base__(%rip),%esi > + lea __image_base__(%rip), %esi > + sub $sym_offs(__image_base__), %esi ... the comment needs updating too then, as %esi won't necessarily hold the load base address any longer (if I understand correctly what's going on here). Jan
diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S index 666e341bc5..86805389f9 100644 --- a/xen/arch/x86/boot/head.S +++ b/xen/arch/x86/boot/head.S @@ -380,7 +380,8 @@ x86_32_switch: lgdt gdt_boot_descr(%rip) /* Store Xen image load base address in place accessible for 32-bit code. */ - lea __image_base__(%rip),%esi + lea __image_base__(%rip), %esi + sub $sym_offs(__image_base__), %esi /* Reload code selector. */ pushq $BOOT_CS32
If code is loaded by EFI the loader will relocate the image under 4GB. This causes offsets in x86 code generated by sym_offs(SYMBOL) to be relocated too (basically they won't be offsets from image base). In order to get wanted address when using sym_offs an sym_esi compensate the difference in %esi. Signed-off-by: Frediano Ziglio <frediano.ziglio@cloud.com> --- xen/arch/x86/boot/head.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- Changes since v1: - Completely different way to cope with the issue, much more easier.