04da832e16
Linux/Alpha has two versions of several system call wrappers that take or return data of type "struct timeval" (possibly nested inside a larger structure). The GLIBC_2.0 version is a compat symbol that calls __NR_osf_foo or __NR_old_foo and uses a struct timeval with a 32-bit tv_sec field. The GLIBC_2.1 version is used for current code, calls __NR_foo, and uses a struct timeval with a 64-bit tv_sec field. This patch changes all of the compat symbols of this type to be wrappers around their GLIBC_2.1 counterparts; the compatibility system calls will no longer be used. It serves as a proposal for part of how we do the transition to 64-bit time_t on systems that currently use 32-bit time_t: * The patched glibc will NOT use system calls that involve 32-bit time_t to implement its compatibility symbols. This will make both our lives and the kernel maintainers' lives easier. The primary argument I've seen against it is that the kernel could warn about uses of the old system calls, helping people find old binaries that need to be recompiled. I think there are several other ways we could accomplish this, e.g. scripts to scan the filesystem for binaries with references to the old symbol versions, or issuing diagnostics ourselves. * The compat symbols do NOT report failure after the Y2038 deadline. An earlier revision of this patch had them return -1 and set errno to EOVERFLOW, but Adhemerval pointed out that many of them have already performed side effects at the point where we discover the overflow, so that would break more than it fixes. Also, we don't want people to be _checking_ for EOVERFLOW from these functions; we want them to recompile with 64-bit time_t. So it's not actually useful for them to report failure to the calling code. * What they do do, when they encounter overflow, is saturate the overflowed "struct timeval"(s): tv_sec is set to INT32_MAX and tv_nsec is set to 999999. That means time stops advancing for programs with 32-bit time_t when they reach the deadline. That's obviously going to break stuff, but I think wrapping around is probably going to break _more_ stuff. I'd be interested to hear arguments against, if anyone has one. The new header file tv32-compat.h is currently Alpha-specific but I mean for it to be reused to aid in writing wrappers for all affected architectures. I only put it in sysdeps/unix/sysv/linux/alpha for now because I haven't checked whether the various "foo32" structures it defines agree with the ABI for ports other than Linux/Alpha. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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