x86, vdso: Remove compat vdso support

The compat vDSO is a complicated hack that's needed to maintain
compatibility with a small range of glibc versions.

This removes it and replaces it with a much simpler hack: a config
option to disable the 32-bit vDSO by default.

This also changes the default value of CONFIG_COMPAT_VDSO to n --
users configuring kernels from scratch almost certainly want that
choice.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/4bb4690899106eb11430b1186d5cc66ca9d1660c.1394751608.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 16 insertions, 6 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7116fda7077f..86019750e15f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3409,14 +3409,24 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                                         of CONFIG_HIGHPTE.
 
         vdso=           [X86,SH]
-                        vdso=2: enable compat VDSO (default with COMPAT_VDSO)
-                        vdso=1: enable VDSO (default)
+                        On X86_32, this is an alias for vdso32=.  Otherwise:
+
+                        vdso=1: enable VDSO (the default)
                         vdso=0: disable VDSO mapping
 
-        vdso32=         [X86]
-                        vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
-                        vdso32=1: enable 32-bit VDSO (default)
-                        vdso32=0: disable 32-bit VDSO mapping
+        vdso32=         [X86] Control the 32-bit vDSO
+                        vdso32=1: enable 32-bit VDSO
+                        vdso32=0 or vdso32=2: disable 32-bit VDSO
+
+                        See the help text for CONFIG_COMPAT_VDSO for more
+                        details.  If CONFIG_COMPAT_VDSO is set, the default is
+                        vdso32=0; otherwise, the default is vdso32=1.
+
+                        For compatibility with older kernels, vdso32=2 is an
+                        alias for vdso32=0.
+
+                        Try vdso32=0 if you encounter an error that says:
+                        dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
 
         vector=         [IA-64,SMP]
                         vector=percpu: enable percpu vector domain