|On some architectures, when the kernel loads any userspace program it
|maps an ELF DSO into that program's address space. This DSO is called
|the vDSO and it often contains useful and highly-optimized alternatives
|to real syscalls.
|These functions are called just like ordinary C function according to
|your platform's ABI. Call them from a sensible context. (For example,
|if you set CS on x86 to something strange, the vDSO functions are
|within their rights to crash.) In addition, if you pass a bad
|pointer to a vDSO function, you might get SIGSEGV instead of -EFAULT.
|To find the DSO, parse the auxiliary vector passed to the program's
|entry point. The AT_SYSINFO_EHDR entry will point to the vDSO.
|The vDSO uses symbol versioning; whenever you request a symbol from the
|vDSO, specify the version you are expecting.
|Programs that dynamically link to glibc will use the vDSO automatically.
|Otherwise, you can use the reference parser in Documentation/vDSO/parse_vdso.c.
|Unless otherwise noted, the set of symbols with any given version and the
|ABI of those symbols is considered stable. It may vary across architectures,
|(As of this writing, this ABI documentation as been confirmed for x86_64.
| The maintainers of the other vDSO-using architectures should confirm
| that it is correct for their architecture.)