grub/asm-tests/i386-pc.S

/* on x86 old clang doesn't support .code16
   newer clang supports it but creates 6-byte jumps instead of 3-byte ones
   which makes us go over boot sector size.
   Starting with 3.9 clang emits 3-byte jumps but still creates 8-bytes movl
   instead of 5-bytes, so code overflows into data.  */

	.code16
	jmp far
	.org 4
	jmp nearer
	.org 6
	movl nearer, %ebx
	.org 11
	.space 100
nearer:
	.space 200
far:
	.byte 0
Relax requirements on asm for non-BIOS i386 platforms. These platforms don't have a hard limit on size of resulting code16 code, so we don't care if assembly is bigger than necessarry. 2015-02-21 19:18:18 +00:00			`/* on x86 old clang doesn't support .code16`
			`newer clang supports it but creates 6-byte jumps instead of 3-byte ones`
asm-tests/i386-pc: Check that movl is 5 bytes. LLVM 3.9 now emits short form of jump instructions, but it is still using 32 bit addresses for some movl instructions. Fortunately it was caught early: clang ... boot/i386/pc/boot.S clang -cc1as: fatal error: error in backend: invalid .org offset '440' (at offset '441') Add additional check to catch it during configure run and force -no-integrated-as. Closes: 49200 More details in https://lists.gnu.org/archive/html/grub-devel/2015-02/msg00099.html https://llvm.org/bugs/show_bug.cgi?id=22662 2016-09-28 17:31:04 +00:00			`which makes us go over boot sector size.`
			`Starting with 3.9 clang emits 3-byte jumps but still creates 8-bytes movl`
			`instead of 5-bytes, so code overflows into data. */`
Relax requirements on asm for non-BIOS i386 platforms. These platforms don't have a hard limit on size of resulting code16 code, so we don't care if assembly is bigger than necessarry. 2015-02-21 19:18:18 +00:00
			`.code16`
			`jmp far`
			`.org 4`
asm-tests/i386-pc: Check that near jumps are 2 bytes. We already check that jump over 300 bytes gap is 3 bytes in code16-mode. Some clang versions generate 3-byte opcode for short jumps which makes boot.img blow over 512-byte limit. Enforce -no-integrated-as in such cases 2015-11-11 17:58:57 +00:00			`jmp nearer`
			`.org 6`
asm-tests/i386-pc: Check that movl is 5 bytes. LLVM 3.9 now emits short form of jump instructions, but it is still using 32 bit addresses for some movl instructions. Fortunately it was caught early: clang ... boot/i386/pc/boot.S clang -cc1as: fatal error: error in backend: invalid .org offset '440' (at offset '441') Add additional check to catch it during configure run and force -no-integrated-as. Closes: 49200 More details in https://lists.gnu.org/archive/html/grub-devel/2015-02/msg00099.html https://llvm.org/bugs/show_bug.cgi?id=22662 2016-09-28 17:31:04 +00:00			`movl nearer, %ebx`
			`.org 11`
asm-tests/i386-pc: Check that near jumps are 2 bytes. We already check that jump over 300 bytes gap is 3 bytes in code16-mode. Some clang versions generate 3-byte opcode for short jumps which makes boot.img blow over 512-byte limit. Enforce -no-integrated-as in such cases 2015-11-11 17:58:57 +00:00			`.space 100`
			`nearer:`
			`.space 200`
Relax requirements on asm for non-BIOS i386 platforms. These platforms don't have a hard limit on size of resulting code16 code, so we don't care if assembly is bigger than necessarry. 2015-02-21 19:18:18 +00:00			`far:`
			`.byte 0`