i#5431: Support glibc's rseq support

[abhinav92003]

Fixes issues with DR's rseq handling in glibc 2.35+.

Glibc 2.35 added support for the Linux rseq feature. See
https://lwn.net/Articles/883104/ for details. TLDR; glibc registers
its own struct rseq at init time, and stores its offset from the
thread pointer in __rseq_offset. The glibc-registered struct rseq is
present in the struct pthread. If glibc's rseq support isn't
available, either due to some issue or because the user disabled
it by exporting GLIBC_TUNABLES=glibc.pthread.rseq=0, it will
set __rseq_size to zero.

Improves the heuristic to find the registered struct rseq. For the
glibc-support case: on AArch64, it is at a -ve offset from app lib
seg base, whereas on x86 it's at a +ve offset. On both AArch64
and x86, the offset is of the opposite sign than what it would be
if the app registered the struct rseq manually in its static TLS
(which happens for older glibc and when glibc's rseq support
is disabled).

Detects whether the glibc rseq support is enabled by looking at
the sign of the struct rseq offset.

Removes the drrun -disable_rseq workaround added by #5695.

Adjusts the linux.rseq test to get the struct rseq registered by
glibc, when it's available. Also fixes some issues in the test.

Adds the Ubuntu_22 tag to rseq tests so that they are enabled.

Our Ubuntu-20 CI tests the case without rseq support in glibc,
where the app registers the struct rseq. This also helps test the
case where the app is not using glibc.

Also, our Ubuntu-22 CI tests the case with Glibc rseq support.
Manually tested the disabled rseq support case on glibc 2.35,
but not adding a CI version of it.

Fixes #5431

[abhinav92003]

On AArch64 with glibc 2.35 (not in our CI), the tool.drcacheoff.rseq test is failing with

238:   Trace invariant failure in T-1 at ref # 0: Serial schedule entry count does
238:   not match trace

But I see the same failure without this change and glibc's rseq disabled. So it's probably unrelated.

[derekbruening]

On AArch64 with glibc 2.35 (not in our CI), the tool.drcacheoff.rseq test is failing with

238:   Trace invariant failure in T-1 at ref # 0: Serial schedule entry count does
238:   not match trace

But I see the same failure without this change and glibc's rseq disabled. So it's probably unrelated.

Please file an issue on this: never seen this before.

[abhinav92003]

I've created #5734 and #5733 for two test issues that happen even without this PR and seem unrelated to i#5431.

#5733 happens even on the Jenkins A64 machine with the older glibc, in addition to on an A64 VM with newer glibc.
#5734 happens with the newer glibc A64 VM only.

[abhinav92003]

run arm tests

[abhinav92003]

run arm tests

[abhinav92003]

attach_blocking and attach_test are timing out on A64.

[abhinav92003]

run arm tests

[derekbruening]

attach_blocking and attach_test are timing out on A64.

Please cite an existing issue or file a new one, as with any test failure.

[abhinav92003]

Please cite an existing issue or file a new one, as with any test failure.

Wasn't sure before if it's my PR that's causing it. But I ran it without these changes on the Jenkins machine and they still time out. Maybe it's related to the Jenkins machine update.

[abhinav92003]

Please cite an existing issue or file a new one, as with any test failure.

Wasn't sure before if it's my PR that's causing it. But I ran it without these changes on the Jenkins machine and they still time out. Maybe it's related to the Jenkins machine update.

#5740.

[abhinav92003]

Run arm tests