rtld: introduce STATIC_TLS_EXTRA

[stevek]

Summary

The new STATIC_TLS_EXTRA variable provides a means for applications to increases the size of the extra static TLS space allocated by rtld beyond the default of '128'. This extra static TLS space is used for objects loaded with dlopen.

The value specified in the variable must be no less than the default value and no greater than the maximum allowed value for size_t type.

If an invalid value is specified, rtld will ignore it and just use the default value.

The rtld(1) man page is updated to document this new option.

Obtained from: Juniper Networks, Inc.

[kib]

libexec/rtld-elf/arm/reloc.c

458

Why not have ld_optional_static_tls always valid? Initialize it to RTLD_STATIC_TLS_EXTRA statically, and re-init if the env var is set. Then you do not need these conditional expressions.

Then it is probably more logical to call it ld_static_tls_extra.

libexec/rtld-elf/rtld.c

750

We do not do this, usually we either ignore invalid values or at worst issue a warning. See another comment for this file.

6119–6120

I recommend to print out the static_tls_extra value there.

[stevek]

Made changes per review comments.

[stevek]

Updated environment variable to match the variables used internally.
Instead of OPTIONAL_STATIC_TLS, the name is now STATIC_TLS_EXTRA.
Updated the man page also.

[kib]

You also need to rename the vars in the summary.

[stevek]

Updated the review summary from the commit log

[stevek]

In D42025#967445, @kib wrote:

You also need to rename the vars in the summary.

Yes, it seems that "git arc update" doesn't update the summary from the commit log. I just updated the review with the contents of my commit log.