diff options
author | Stephen Rothwell <sfr@canb.auug.org.au> | 2011-07-25 13:59:46 -0400 |
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committer | Trond Myklebust <Trond.Myklebust@netapp.com> | 2011-07-25 14:53:52 -0400 |
commit | 5f00bcb38ef9a980a33c6dbdc0044964b05f22dd (patch) | |
tree | 3175fb9375aecb50bde1be0bf4fa8aa8155131d6 /Documentation/ABI/stable/vdso | |
parent | 34006cee28f7344f9557a4be3816c7891b1bbab1 (diff) | |
parent | b6844e8f64920cdee620157252169ba63afb0c89 (diff) |
Merge branch 'master' into devel and apply fixup from Stephen Rothwell:
vfs/nfs: fixup for nfs_open_context change
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'Documentation/ABI/stable/vdso')
-rw-r--r-- | Documentation/ABI/stable/vdso | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/Documentation/ABI/stable/vdso b/Documentation/ABI/stable/vdso new file mode 100644 index 000000000000..8a1cbb594497 --- /dev/null +++ b/Documentation/ABI/stable/vdso @@ -0,0 +1,27 @@ +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, +though. + +(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.)
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