Re: Patch to main() invocation in mips/crt0.S

["J. Johnston" <jjohnstn at redhat dot com>]

Richard Sandiford wrote:
> This patch makes mips/crt0.S call main() with the equivalent of:
>
>         char *argv[1] = { 0 };
>         char *envp[1] = { 0 };
>         main (0, argv, envp);
>
> Tested 6 ABIs (o32, o64, EABI32, EABI32/long64, EABI64, EABI64/long32)
> with a mips64vrel-elf build.  OK to install?
Yes.

-- Jeff J.

> Richard
>
>
> 	* mips/crt0.S (_start): Allocate 64 bytes of stack instead of 32.
> 	Pass an empty argv and envp to main().
>
> Index: libgloss/mips/crt0.S
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/crt0.S,v
> retrieving revision 1.5
> diff -c -d -p -F^[(a-zA-Z0-9_^#] -r1.5 crt0.S
> *** libgloss/mips/crt0.S	12 Nov 2002 23:14:24 -0000	1.5
> --- libgloss/mips/crt0.S	17 Dec 2002 10:46:50 -0000
> *************** 3:
> *** 157,172 ****
>   	lw	t0,0(a0)			# last address of memory available
>   	la	t1,K0BASE			# cached kernel memory
>   	addu	t0,t0,t1			# get the end of memory address
> ! 	/* We must subtract 24 bytes for the 3 8 byte arguments to main, in
> ! 	   case main wants to write them back to the stack.  The caller is
> ! 	   supposed to allocate stack space for parameters in registers in
> ! 	   the old MIPS ABIs.  We must do this even though we aren't passing
> ! 	   arguments, because main might be declared to have them.
> ! 
> ! 	   Some ports need a larger alignment for the stack, so we subtract
> ! 	   32, which satisifes the stack for the arguments and keeps the
> ! 	   stack pointer better aligned.  */
> ! 	subu	t0,t0,32			# and generate a starting stack-pointer
>   4:
>   	move	sp,t0				# set stack pointer
>   	sw	sp,__stackbase			# keep this for future ref
> --- 157,166 ----
>   	lw	t0,0(a0)			# last address of memory available
>   	la	t1,K0BASE			# cached kernel memory
>   	addu	t0,t0,t1			# get the end of memory address
> ! 	/* Allocate 32 bytes for the register parameters.  Allocate 16
> ! 	   bytes for a null argv and envp.  Round the result up to 64
> ! 	   bytes to preserve alignment.  */
> ! 	subu	t0,t0,64
>   4:
>   	move	sp,t0				# set stack pointer
>   	sw	sp,__stackbase			# keep this for future ref
> *************** #endif
> *** 213,221 ****
>   	jal	_init				# run global constructors
>   	nop
>   
> ! 	move	a0,zero				# set argc to 0
>   	jal	main				# call the program start function
> ! 	nop
>   
>   	# fall through to the "exit" routine
>   	jal	exit				# call libc exit to run the G++
> --- 207,223 ----
>   	jal	_init				# run global constructors
>   	nop
>   
> ! 	addiu	a1,sp,32			# argv = sp + 32
> ! 	addiu	a2,sp,40			# envp = sp + 40
> ! #if __mips64
> ! 	sd	zero,(a1)			# argv[argc] = 0
> ! 	sd	zero,(a2)			# envp[0] = 0
> ! #else
> ! 	sw	zero,(a1)
> ! 	sw	zero,(a2)
> ! #endif
>   	jal	main				# call the program start function
> ! 	move	a0,zero				# set argc to 0
>   
>   	# fall through to the "exit" routine
>   	jal	exit				# call libc exit to run the G++