CVS log for src/lib/libc/arch/mips/gen/_resumecontext.S

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Default branch: MAIN

Remove '_OFFSETOF' prefix for genassm(1) generate CPP identifers for
consistency with other arches.

NFCI and libc.so is the same before and after.

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Fix for [on]{32,64}

/usr/tests/lib/libc/sys/t_getcontext
/usr/tests/lib/libc/sys/t_swapcontext
/usr/tests/lib/libc/sys/t_ucontext
/usr/tests/lib/libpthread/t_swapcontext

All pass now.

Changes amount to

- saving GP from caller in context for n{32,64}
- performing (the equivalient of) PIC_PROLOGUE for swapcontext and
  __resumecontext
- Call setcontext via the PLT in __resumecontext

Add a NOP_L

PIC_TAILCALL on n32/n64 would mess up GP, so just use SYSTRAP to call
setcontext.

Fixes tests/lib/libc/sys/t_getcontext.c:setcontext_link

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sync with head

setcontext() used to be incompatible with -lpthread since it affected
the TLS pointer, therefore wrecking the pthread environement.

Some ports had _UC_TLSBASE flag or equivalent (_UC_UNIQUE on alpha)
that controlled whether setcontext() would change the TLS pointer.
This change let libpthread override setcontext() with its own version
that unsets _UC_TLSBASE, enabling safe usage of setcontext() with
-lpthread.

We also have the following required changes here:
- rename alpha's _UC_UNIQUE into _UC_TLSBASE
- add _UC_TLSBASE definition in header file for all ports
  (powerpc, sh3, sparc and sparc64 lack the implementation for now)
- introduce a libc stub that can be overriden for setcontext()
- modify MD libcs swapcontext() implementations so that they use the
  setcontext() libc stub instead of doing a plain system call.

While we are there:
- document various MD _UC_* flags in header file
- add libc and libpthread tests for swapcontext() behavior
  (hopefully helpful to spot MD problems introduced with this change)

Future work:
- Deciding whether kernel support or _UC_TLSBASE should be added for
  powerpc, sh3, sparc and sparc64 is left to portmasters
  sparc64

Approved by core@

Merge from matt-nb5-mips64.

Move to new ABI agnostic mechanisms.  Get rid of magic constants.
Use genassym.cf to generate them.

sync with head.

Remove clause 3 and 4 from TNF licenses

file _resumecontext.S was added on branch christos-time_t on 2008-04-28 20:22:57 +0000

Remove clause 3 and 4 from TNF licenses

optimize this: we can use %ra for relocation directly
(saves 1 insn)

get the offset to gp right

Merge the nathanw_sa branch.

Tidy up delay slot usage

_resumecontext was called by forcing the return address of a newly
created context.   The global pointer calculation requires the function
address to be in $t9 - because it was not a proper ABI call to
_resumecontext we need a helper function to build the correct $gp

file _resumecontext.S was initially added on branch nathanw_sa.