[v2,3/3] x86/EFI: don't have an overly large image size

Commit Message

Jan Beulich April 23, 2021, 11:04 a.m. UTC

While without debug info the difference is benign (so far), since we pad
the image to 16Mb anyway, forcing the .reloc section to a 2Mb boundary
causes subsequent .debug_* sections to go farther beyond 16Mb than
needed. There's no reason to advance . for establishing __2M_rwdata_end,
as all data past _end is of no interest at runtime anymore anyway.

Signed-off-by: Jan Beulich <[e-mail]>
Reviewed-by: Roger Pau Monné <[e-mail]>
---
This makes more explicit a possible latent problem with the ELF image:
It ends at _end, not __2M_rwdata_end (advancing . as was done here does
not have the effect of increasing the image size). Interestingly the
conversion xen-syms => xen rounds up the program header specified size
suitably, as per the comment "Do not use p_memsz: it does not include
BSS alignment padding" in mkelf32.c. I do think this would instead want
taking care of in the linker script. Commit 7a95e0a2c572 ("x86: properly
calculate xen ELF end of image address") clearly only hacked an existing
hack rather than addressing the root cause. Thoughts?

Patch

--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -303,8 +303,7 @@  SECTIONS
   } PHDR(text)
   _end = . ;
 
-  . = ALIGN(SECTION_ALIGN);
-  __2M_rwdata_end = .;
+  __2M_rwdata_end = ALIGN(SECTION_ALIGN);
 
 #ifdef EFI
   .reloc ALIGN(4) : {