New setre*id functions broken on alpha

[Mariusz Mazur <mmazur at kernel dot pl>]

Note: this bug together with bugs #467 and #461 render glibc 
unbuildable/broken on sparc, ia64 and alpha.


Up to 2004-09-19 setreuid, setresuid, setregid and setresgid functions (and 
lots of others) on alpha where generated from a couple of macros, that due to 
the way function arguments are passed on alpha, generated stub functions 
(literally a couple of lines of asm code) that just issued a syscall without 
even touching the passed arguments. That worked fine.
But on that day fulltime C functions where added (ci log: "Call callback to 
set IDs in all other threads as well.") which broke above functions on alpha.

Stub functions aren't used any more, now C compiler has controll of the what's 
going on. Those functions take gid_t or uid_t as arguments and those types 
are defines as unsigned int (32 bit). Later they are casted to type long to 
put them into appropriate registers before making a syscall. The problem is 
that although those are unsigned ints we're using, the kernel expects to get 
a '-1' value in some cases (ask the designers what where they thinking). Now 
according to "Calling Standard for Alpha Systems"* when passing a 32bit 
signed to a function (that is putting it into a 64bit register) the signed 
stuff should get expanded to full 64bits (0xffffffff should become 
0xffffffffffffffff). But that doesn't happen, since those are unsigned ints 
the compiler is handling, so it doesn't expand the signed stuff, but just 
zeroes the first four bytes. So we're doing setreuid(-1, -1), but the kernel 
gets setreuid(4294967295, 4294967295) and doesn't treat that as -1. Casting 
that value to signed int before casting it to long fixes the problem. Here's 
my patch: 
http://cvs.pld-linux.org/cgi-bin/cvsweb/SOURCES/glibc-alpha_giduidfix.patch?rev=1.1


* 
http://www.cs.arizona.edu/computer.help/policy/DIGITAL_unix/AA-PY8AC-TET1_html/callCH4.html#BLOCK52


-- 
In the year eighty five ten
God is gonna shake his mighty head
He'll either say,
"I'm pleased where man has been"
Or tear it down, and start again