porting latest newlib 4.4.0

[effbiae]

I started porting the latest newlib 4.4.0* to BareMetal using BareMetal-newlib (the port of 3.0.0) as a starting point. I patched the build system (which is a bit simpler than 3.0.0) and got it to start building, then I got stuck.

Taking a different approach, I thought I'd look at the FAQ for newlib to see the recommended steps to porting to a new platform. It's FAQ 6 and the first step is to add setjmp/longjmp code. I don't see any code for setjmp in BareMetal-newlib. I have no idea why jumping is so important to newlib, but here we are as step one of the port and the FAQ says "give me jumping."

Can setjmp/longjmp be easily implemented? I imagine it's not a lot of work but I'm new to BareMetal and OS development in general. I append the newlib/libc/machine/fr30/setjmp.S mentioned in the FAQ from the newlib 4.4.0 tree so you can see how fr30 implements setjmp/longjmp.

I thought I'd ask as the last thing I do before I go to bed in the hope that I'll get an answer in my morning... but it is Sunday, so we'll see. I'm in Eastern Australia, GMT+11

[*] latest version is 4.4.0.20231231 - there's no 4.4.0 version, so going with this

$ cat newlib/libc/machine/fr30/setjmp.S
# setjmp/longjmp for FR30.  The jmpbuf looks like this:
#	
# Register	jmpbuf offset
# R8		0x00
# R9		0x04
# R10		0x08
# R11		0x0c
# R12		0x10
# R13		0x14
# R14 (FP)	0x18
# R15 (SP)	0x1c
# RP            0x20
	
.macro save reg
	st	\reg,@r4
	add	#4,r4
.endm
	
.macro restore reg
	ld	@r4,\reg
	add	#4,r4
.endm


	.text
	.global	setjmp
setjmp:
	save	r8
	save	r9
	save	r10
	save	r11
	save	r12
	save	r13
	save	r14
	save	r15
	mov	RP,r5
	st	r5,@r4

# Return 0 to caller.
	ldi:8	#0,r4
	ret

	.global	longjmp
longjmp:
	restore	r8
	restore	r9
	restore	r10
	restore	r11
	restore	r12
	restore	r13
	restore	r14
	restore	r15
	ld	@r4,r4
	mov	r4,RP

# If caller attempted to return 0, return 1 instead.

	mov	r5,r4
	or	r4,r4
	bne	1f
	ldi:8	#1,r4
    1:
	ret

[IanSeyler]

Hello!

I think it's just showing mn10300 (Matsushita?) or fr30 (RISC-V?) as examples for adding new hardware support. Newlib already has support for x86-64 so that is what should be used I think.

It's unfortunate that they shuffled things around so much in Newlib. Porting was easier in the earlier version.

-Ian