| Message ID | 20250401130840.72119-11-roger.pau@citrix.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | x86/EFI: prevent write-execute sections | expand |
On 01.04.2025 15:08, Roger Pau Monne wrote: > @@ -218,12 +214,15 @@ SECTIONS > */ > *(.altinstr_replacement) > > -#ifdef EFI /* EFI wants to merge all of .init.* ELF doesn't. */ > - . = ALIGN(SMP_CACHE_BYTES); > -#else > } PHDR(text) > - DECL_SECTION(.init.data) { > +#ifdef EFI > + /* > + * Align to prevent the data section from re-using the tail of an RX mapping > + * from the previous text section. > + */ > + . = ALIGN(SECTION_ALIGN); Does this need to be SECTION_ALIGN, growing image size by perhaps more than 1Mb (at least that's what I expect as an effect)? Wouldn't PAGE_SIZE suffice for our purposes? Jan > #endif > + DECL_SECTION(.init.data) { > *(.init.bss.stack_aligned) > > . = ALIGN(POINTER_ALIGN);
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S index 1191bf4e2ddd..852aa135a76c 100644 --- a/xen/arch/x86/xen.lds.S +++ b/xen/arch/x86/xen.lds.S @@ -201,11 +201,7 @@ SECTIONS __2M_init_start = .; /* Start of 2M superpages, mapped RWX (boot only). */ . = ALIGN(PAGE_SIZE); /* Init code and data */ __init_begin = .; -#ifdef EFI /* EFI wants to merge all of .init.* ELF doesn't. */ - DECL_SECTION(.init) { -#else DECL_SECTION(.init.text) { -#endif _sinittext = .; *(.init.text) *(.text.startup) @@ -218,12 +214,15 @@ SECTIONS */ *(.altinstr_replacement) -#ifdef EFI /* EFI wants to merge all of .init.* ELF doesn't. */ - . = ALIGN(SMP_CACHE_BYTES); -#else } PHDR(text) - DECL_SECTION(.init.data) { +#ifdef EFI + /* + * Align to prevent the data section from re-using the tail of an RX mapping + * from the previous text section. + */ + . = ALIGN(SECTION_ALIGN); #endif + DECL_SECTION(.init.data) { *(.init.bss.stack_aligned) . = ALIGN(POINTER_ALIGN);
As a result of having no relocations against text sections, there's no need for a single .init section that's read-write-execute, as .init.text is no longer modified. Remove the bodge and fallback to the layout used by ELF images with an .init.text and .init.data section. The resulting PE sections are: Sections: Idx Name Size VMA LMA File off Algn 0 .text 00193f6b ffff82d040200000 ffff82d040200000 00000480 2**4 CONTENTS, ALLOC, LOAD, READONLY, CODE 1 .rodata 0008a010 ffff82d040400000 ffff82d040400000 00194400 2**2 CONTENTS, ALLOC, LOAD, DATA 2 .buildid 00000035 ffff82d04048a010 ffff82d04048a010 0021e420 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 3 .init.text 00049e70 ffff82d040600000 ffff82d040600000 0021e460 2**2 CONTENTS, ALLOC, LOAD, READONLY, CODE 4 .init.data 000560a8 ffff82d040800000 ffff82d040800000 002682e0 2**2 CONTENTS, ALLOC, LOAD, DATA [...] Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> --- Changes since v1: - Align .init.text. - Clarify commit message. --- xen/arch/x86/xen.lds.S | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-)