Messages in this thread | | | Date | Thu, 2 Feb 2006 12:01:10 +0000 | From | Ralf Baechle <> | Subject | Re: [PATCH] compat: fix compat_sys_openat and friends |
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On Wed, Feb 01, 2006 at 09:36:40PM -0800, Linus Torvalds wrote:
> > Most of the 64 bit architectures will zero extend the first argument to > > compat_sys_{openat,newfstatat,futimesat} which will fail if the 32 bit > > syscall was passed AT_FDCWD (which is a small negative number). Declare > > the first argument to be an unsigned int which will force the correct > > sign extension when the internal functions are called in each case. > > Umm. > > Wouldn't it be _much_ better to declare the argument as a "long", since > some architectures (alpha, for example) may assume that 32-bit arguments > have been _sign_extended, not zero-extended.
> Then, when the "compat_sys_xxxx()" function passes the "long" down to the > _real_ function (which takes an "int"), those architectures (and only > those architectures) that actually have assumptions about high bits will > have the compiler automatically do the right zero- or sign-extensions at > that call-site.
MIPS is one of those architectures where variables are always held sign-extended to the full 32-bit or 64-bit size of the register. The signed-ness of the C data type doesn't matter at all here so Stephen's change is a nop for MIPS.
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