__DATA_CONST & __TEXT_EXEC missing in binary... Causing panics about xnu

[adalric]

Well that solves it, that padding is the one messing the assert.

[zhuowei]

@aBradleyUno do we need to add some extra sectcreate arguments in the arm64 ldflags?

XNU/makedefs/MakeInc.def

Line 364 in 1eb20fd

-Wl,-sectcreate,__PRELINK_TEXT,__text,/dev/null \

[adalric]

Done, still, there is a panic every 15 LoC.

[zhuowei]

@aBradleyUno It seems that that isn't the right way to add a __DATA_CONST: https://github.com/apple-opensource/ld64/blob/master/src/ld/Options.cpp#L3808 says to pass in -data_const to the linker. Also, passing in -text_exec enables __TEXT_EXEC. https://github.com/apple-opensource/ld64/blob/master/src/ld/Options.cpp#L3816

My bad. :(

It looks like kexts are automatically compiled with these enabled (https://github.com/apple-opensource/ld64/blob/master/src/ld/Options.cpp#L4601), but there's no equivalent check for the kernel.

[adalric]

There is still the problem with the hardcoded offset. The assert still fails.

XNU/osfmk/arm64/arm_vm_init.c

Line 1338 in 1eb20fd

assert(segDATACONSTB == segTEXTB + segSizeTEXT);

[zhuowei]

@aBradleyUno we could try using -segment_order to reorder the segments manually

[adalric]

@zhuowei or -sectalign, I'm going to try both

[adalric]

-Wl,-segment_order,__TEXT:__DATA_CONST:__TEXT_EXEC:__KLD:__LAST:__DATA:__PRELINK_TEXT:__PLK_TEXT_EXEC:__PLK_DATA_CONST:__PRELINK_DATA:__PLK_LLVM_COV:__PLK_LINKEDIT:__PRELINK_INFO \

Am I missing something? @zhuowei

[zhuowei]

@aBradleyUno that looks fine.

[adalric]

@zhuowei still panics

[zhuowei]

@aBradleyUno What's the message now?

[adalric]

@zhuowei is still on the assert, the only difference are the value on the variables
Also check the segments, what does `__TEXT,initcode does?
Left Darm64 - Right iOS 11.2.5

[zhuowei]

There's only two mentions of initcode in darwin-xnu: both are in kern_memorystatus.h

Edit: can I see the compiled kernel?

[adalric]

Maybe XNU_KERNEL_PRIVATE?

[adalric]

So, if I comment out the first assert the second one works like a charm

[adalric]

XNU.zip

[zhuowei]

@aBradleyUno The __TEXT section ends at 0xfffffff007204000, but the __DATA_CONST starts at 0xfffffff007400000 - this gap is causing the first assert to fire. It's interesting that __data_const aligned itself to the nearest 0x200000 byte; there's this in the makefile that seems relevant:

XNU/makedefs/MakeInc.def

Line 460 in c099cbf

-Wl,-seg_page_size,__TEXT,0x200000 \