linux-toradex.git/tools/testing/selftests/rseq/rseq-x86.h, branch v6.3-rc5

selftests/rseq: x86: Template memory ordering and percpu access mode

2022-12-27T11:52:12+00:00

Introduce a rseq-x86-bits.h template header which is internally included
to generate the static inline functions covering:

- relaxed and release memory ordering,
- per-cpu-id and per-mm-cid per-cpu data access.

This introduces changes to the rseq.h selftests API which require to
update the rseq selftest programs. Similar API/templating changes need
to be done for other architectures.

Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20221122203932.231377-12-mathieu.desnoyers@efficios.com

selftests/rseq: Remove RSEQ_SKIP_FASTPATH code

2022-12-27T11:52:12+00:00

This code is not currently build by the test Makefile, adds complexity,
and is not overall useful considering that the abort handling loops to
retry the fast-path.

Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20221122203932.231377-10-mathieu.desnoyers@efficios.com

selftests/rseq: Change type of rseq_offset to ptrdiff_t

2022-02-11T22:30:08+00:00

Just before the 2.35 release of glibc, the __rseq_offset userspace ABI
was changed from int to ptrdiff_t.

Adapt to this change in the kernel selftests.

Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://sourceware.org/pipermail/libc-alpha/2022-February/136024.html

selftests/rseq: x86-32: use %gs segment selector for accessing rseq thread area

2022-02-02T12:11:37+00:00

Rather than use rseq_get_abi() and pass its result through a register to
the inline assembler, directly access the per-thread rseq area through a
memory reference combining the %gs segment selector, the constant offset
of the field in struct rseq, and the rseq_offset value (in a register).

Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20220124171253.22072-16-mathieu.desnoyers@efficios.com

selftests/rseq: x86-64: use %fs segment selector for accessing rseq thread area

2022-02-02T12:11:37+00:00

Rather than use rseq_get_abi() and pass its result through a register to
the inline assembler, directly access the per-thread rseq area through a
memory reference combining the %fs segment selector, the constant offset
of the field in struct rseq, and the rseq_offset value (in a register).

Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20220124171253.22072-15-mathieu.desnoyers@efficios.com

selftests/rseq: Fix: work-around asm goto compiler bugs

2022-02-02T12:11:37+00:00

gcc and clang each have their own compiler bugs with respect to asm
goto. Implement a work-around for compiler versions known to have those
bugs.

gcc prior to 4.8.2 miscompiles asm goto.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670

gcc prior to 8.1.0 miscompiles asm goto at O1.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103908

clang prior to version 13.0.1 miscompiles asm goto at O2.
https://github.com/llvm/llvm-project/issues/52735

Work around these issues by adding a volatile inline asm with
memory clobber in the fallthrough after the asm goto and at each
label target.  Emit this for all compilers in case other similar
issues are found in the future.

Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20220124171253.22072-14-mathieu.desnoyers@efficios.com

selftests/rseq: Fix warnings about #if checks of undefined tokens

2022-02-02T12:11:36+00:00

Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20220124171253.22072-12-mathieu.desnoyers@efficios.com

selftests/rseq: Fix ppc32 offsets by using long rather than off_t

2022-02-02T12:11:36+00:00

The semantic of off_t is for file offsets. We mean to use it as an
offset from a pointer. We really expect it to fit in a single register,
and not use a 64-bit type on 32-bit architectures.

Fix runtime issues on ppc32 where the offset is always 0 due to
inconsistency between the argument type (off_t -> 64-bit) and type
expected by the inline assembler (32-bit).

Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20220124171253.22072-11-mathieu.desnoyers@efficios.com

selftests/rseq: Introduce rseq_get_abi() helper

2022-02-02T12:11:35+00:00

This is done in preparation for the selftest uplift to become compatible
with glibc-2.35.

glibc-2.35 exposes the rseq per-thread data in the TCB, accessible
at an offset from the thread pointer, rather than through an actual
Thread-Local Storage (TLS) variable, as the kernel selftests initially
expected.

Introduce a rseq_get_abi() helper, initially using the __rseq_abi
TLS variable, in preparation for changing this userspace ABI for one
which is compatible with glibc-2.35.

Note that the __rseq_abi TLS and glibc-2.35's ABI for per-thread data
cannot actively coexist in a process, because the kernel supports only
a single rseq registration per thread.

Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20220124171253.22072-6-mathieu.desnoyers@efficios.com

rseq/selftests,x86_64: Add rseq_offset_deref_addv()

2020-09-25T12:23:27+00:00

This patch adds rseq_offset_deref_addv() function to
tools/testing/selftests/rseq/rseq-x86.h, to be used in a selftest in
the next patch in the patchset.

Once an architecture adds support for this function they should define
"RSEQ_ARCH_HAS_OFFSET_DEREF_ADDV".

Signed-off-by: Peter Oskolkov 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Mathieu Desnoyers 
Link: https://lkml.kernel.org/r/20200923233618.2572849-2-posk@google.com