Re: powerpc64 context: aim/locore64.S __start TMPSTKSZ-48 vs. TMPSTKSZ-96 (-r277392 and later) vs. modern aim/trap_subr64.S cpu_reset_handler: (TMPSTKSZ-48)?

[I found yet another one, an implicit example: PC_SLBSTACK-48+1024.]

On 2019-May-8, at 15:10, Mark Millard <marklmi at yahoo.com> wrote:

> On 2019-May-8, at 13:53, Mark Millard <marklmi at yahoo.com> wrote:
> 
>> Should cpu_reset_handler have been updated to use (TMPSTKSZ-96) when
>> __start was changed to use TMPSTKSZ-96, back in 2015-Jan-19?
>> 
> 
> Looks like I should have listed more context: there is both
> (TMPSTKSZ-48) and (TRAPSTKSZ-48) for powerpc64:
> 
> /mnt/usr/src/sys/powerpc/aim/trap_subr32.S:     addi    %r1,%r1,TRAPSTKSZ-16
> /mnt/usr/src/sys/powerpc/aim/trap_subr64.S:     addi    %r1,%r1,(TMPSTKSZ-48)
> /mnt/usr/src/sys/powerpc/aim/trap_subr64.S:     addi    %r1,%r1,(TRAPSTKSZ-48)
> /mnt/usr/src/sys/powerpc/aim/locore32.S:#define TMPSTKSZ        8192            /* 8K temporary stack */
> /mnt/usr/src/sys/powerpc/aim/locore32.S:        .space  TMPSTKSZ
> /mnt/usr/src/sys/powerpc/aim/locore32.S:#define TRAPSTKSZ       4096            /* 4k trap stack */
> /mnt/usr/src/sys/powerpc/aim/locore32.S:        .space        TRAPSTKSZ
> /mnt/usr/src/sys/powerpc/aim/locore32.S:        addi    %r1,%r1,(8+TMPSTKSZ-40)
> /mnt/usr/src/sys/powerpc/aim/locore64.S:#define TMPSTKSZ        16384           /* 16K temporary stack */
> /mnt/usr/src/sys/powerpc/aim/locore64.S:        .space  TMPSTKSZ
> /mnt/usr/src/sys/powerpc/aim/locore64.S:#define TRAPSTKSZ       4096            /* 4k trap stack */
> /mnt/usr/src/sys/powerpc/aim/locore64.S:        .space        TRAPSTKSZ
> /mnt/usr/src/sys/powerpc/aim/locore64.S:        .llong  tmpstk + TMPSTKSZ - 96 - .
> /mnt/usr/src/sys/powerpc/ofw/ofwcall64.S:#define        OFWSTKSZ        4096            /* 4K Open Firmware stack */
> /mnt/usr/src/sys/powerpc/ofw/ofwcall64.S:       .space  OFWSTKSZ
> /mnt/usr/src/sys/powerpc/ofw/ofwcall64.S:       addi    %r7,%r7,OFWSTKSZ-40
> /mnt/usr/src/sys/powerpc/ofw/ofwcall32.S:#define        OFWSTKSZ        4096            /* 4K Open Firmware stack */
> /mnt/usr/src/sys/powerpc/ofw/ofwcall32.S:       .space  OFWSTKSZ
> /mnt/usr/src/sys/powerpc/ofw/ofwcall32.S:       addi    %r1,%r1,(OFWSTKSZ-32)
> 
> 
> It is not obvious what justifies the figures for
> powerpc64:
> 
> TMPSTKSZ - 96
> TMPSTKSZ-48
> TRAPSTKSZ-48
> 
> Magic constants with no notes about how to figure out
> the correct (minimum?) figure to subtract.
> 
> My question about the 48 vs. 96 may apply to more
> than the TMPSTKSZ-48 usage.

There is also:

       addi    %r1,%r1,PC_SLBSTACK-48+1024

with 1024 being the ???STKSZ and having another
magic 48 that I wonder about if it should be
96.



===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)


===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)

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