svn commit: r218745 - head/sys/boot/i386/boot2

Ronald Klop ronald-freebsd8 at klop.yi.org
Wed Feb 16 23:04:31 UTC 2011


On Wed, 16 Feb 2011 23:41:26 +0100, Alexander Best <arundel at freebsd.org>  
wrote:

> On Wed Feb 16 11, Alexander Best wrote:
>> On Wed Feb 16 11, Alexander Best wrote:
>> > On Wed Feb 16 11, Warner Losh wrote:
>> > > Author: imp
>> > > Date: Wed Feb 16 18:05:10 2011
>> > > New Revision: 218745
>> > > URL: http://svn.freebsd.org/changeset/base/218745
>> > >
>> > > Log:
>> > >   Remove reading of symbols from a.out loaded files.  Since we are  
>> tight
>> > >   on space for clang and a.out support is only needed for  
>> /boot/loader,
>> > >   they are excess bytes that serve no useful purpose other than to
>> > >   support really old kernels (FreeBSD < 3.2 or so).  Prefer clang
>> > >   support over support for these old kernels and remove this code.   
>> We
>> > >   gain about 100 bytes of space this way.
>> >
>> > i think without this code uint32_t x serves no purpose any longer:
>> >
>> > /usr/git-freebsd-head/sys/boot/i386/boot2/boot2.c:322:20: warning:  
>> unused variable 'x' [-Wunused-variable]
>> >     uint32_t addr, x;
>> >                    ^
>>
>> also due to
>>
>> /usr/git-freebsd-head/sys/boot/i386/boot2/boot2.c:631:8: warning: cast  
>> from 'caddr_t' (aka 'char *') to 'uint32_t *' (aka 'unsigned int *')  
>> increases required alignment from 1 to 4 [-Wcast-align]
>>         t1 = *(uint32_t *)PTOV(0x46c);
>>               ^~~~~~~~~~~~~~~~~~~~~~~
>>
>> i think t0 and t1 can be turned into uint8_t's and PTOV(0x46c); can be  
>> casted
>> to (uint8_t *), instead of (uint32_t *).
>
> with this additional change the code fits when compiled with clang:
>
> diff --git a/sys/boot/i386/boot2/sio.S b/sys/boot/i386/boot2/sio.S
> index 7b8e9eb..d745129 100644
> --- a/sys/boot/i386/boot2/sio.S
> +++ b/sys/boot/i386/boot2/sio.S
> @@ -29,11 +29,11 @@
>  sio_init:      movw $SIO_PRT+0x3,%dx           # Data format reg
>                 movb $SIO_FMT|0x80,%al          # Set format
>                 outb %al,(%dx)                  #  and DLAB
> -               pushl %edx                      # Save
> +               pushb %dl                       # Save
>                 subb $0x3,%dl                   # Divisor latch reg
>                 movl 0x8(%esp),%eax             # Set
>                 outw %ax,(%dx)                  #  BPS
> -               popl %edx                       # Restore
> +               popb %dl                        # Restore
>                 movb $SIO_FMT,%al               # Clear
>                 outb %al,(%dx)                  #  DLAB
>                 incl %edx                       # Modem control reg
>
> ...since we're only modifying %dl in subb $0x3,%dl, we don't need to  
> push/pop
> a 32 bit value, but only 8 bits.


You guys are kings. :-) I heard they don't even teach assembly anymore at  
a lot of universities.










>
> cheers.
> alex
>
>>
>> cheers.
>> alex
>>
>> >
>> > cheers.
>> > alex
>> >
>> > >
>> > >   Reviewed by:	rdivacky@
>> > >
>> > > Modified:
>> > >   head/sys/boot/i386/boot2/boot2.c
>> > >
>> > > Modified: head/sys/boot/i386/boot2/boot2.c
>> > >  
>> ==============================================================================
>> > > --- head/sys/boot/i386/boot2/boot2.c	Wed Feb 16 17:50:21  
>> 2011	(r218744)
>> > > +++ head/sys/boot/i386/boot2/boot2.c	Wed Feb 16 18:05:10  
>> 2011	(r218745)
>> > > @@ -347,23 +347,6 @@ load(void)
>> > >  	p += roundup2(hdr.ex.a_text, PAGE_SIZE);
>> > >  	if (xfsread(ino, p, hdr.ex.a_data))
>> > >  	    return;
>> > > -	p += hdr.ex.a_data + roundup2(hdr.ex.a_bss, PAGE_SIZE);
>> > > -	bootinfo.bi_symtab = VTOP(p);
>> > > -	*(uint32_t*)p = hdr.ex.a_syms;
>> > > -	p += sizeof(hdr.ex.a_syms);
>> > > -	if (hdr.ex.a_syms) {
>> > > -	    if (xfsread(ino, p, hdr.ex.a_syms))
>> > > -		return;
>> > > -	    p += hdr.ex.a_syms;
>> > > -	    if (xfsread(ino, p, sizeof(int)))
>> > > -		return;
>> > > -	    x = *(uint32_t *)p;
>> > > -	    p += sizeof(int);
>> > > -	    x -= sizeof(int);
>> > > -	    if (xfsread(ino, p, x))
>> > > -		return;
>> > > -	    p += x;
>> > > -	}
>> > >      } else {
>> > >  	fs_off = hdr.eh.e_phoff;
>> > >  	for (j = i = 0; i < hdr.eh.e_phnum && j < 2; i++) {
>> > > @@ -395,8 +378,8 @@ load(void)
>> > >  	    }
>> > >  	}
>> > >  	addr = hdr.eh.e_entry & 0xffffff;
>> > > +	bootinfo.bi_esymtab = VTOP(p);
>> > >      }
>> > > -    bootinfo.bi_esymtab = VTOP(p);
>> > >      bootinfo.bi_kernelname = VTOP(kname);
>> > >      bootinfo.bi_bios_dev = dsk.drive;
>> > >      __exec((caddr_t)addr, RB_BOOTINFO | (opts & RBX_MASK),
>> >
>> > --
>> > a13x
>>
>> --
>> a13x


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