Re: sign extension for 32bit syscalls on ppc64
From: Stephen Rothwell <hidden>
Date: 2006-05-01 03:44:56
On Mon, 1 May 2006 10:05:18 +1000 Stephen Rothwell [off-list ref] wrote:
Try mkdirat. openat has a compat wrapper that has the dfd paramater declared as a unsigned int and passes it to sys_openat, whose first paramter is decalred to be int, so the sign extension gets done.
OK, I actually tried this and it works! :-( I traced the code path and it turns out that the place we check for the -100 (in do_path_lookup), the compiler has used a cmpwi instruction and so ignores the top 32 bits. Thus we get away with the ABI abuse! -- Cheers, Stephen Rothwell sfr@canb.auug.org.au http://www.canb.auug.org.au/~sfr/
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