kernel/tools/testing/selftests/rseq/rseq-x86.h, branch linux-6.2.y

selftests/rseq: Change type of rseq_offset to ptrdiff_t

2022-02-11T22:30:08Z

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

2022-02-02T12:11:37Z

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

2022-02-02T12:11:37Z

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

2022-02-02T12:11:37Z

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

2022-02-02T12:11:36Z

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

2022-02-02T12:11:36Z

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

2022-02-02T12:11:35Z

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()

2020-09-25T12:23:27Z

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

rseq/selftests: x86: use ud1 instruction as RSEQ_SIG opcode

2019-05-07T21:32:05Z

Use ud1 as the guard instruction for the restartable sequence abort handler. Its benefit compared to nopl is to trap execution if the program ends up trying to execute it by mistake, which makes debugging easier. The 4-byte signature per se is unchanged (it is the instruction operand). Only the opcode is changed from nopl to ud1. Signed-off-by: Mathieu Desnoyers Suggested-by: Peter Zijlstra CC: Peter Zijlstra CC: Thomas Gleixner CC: Joel Fernandes CC: Catalin Marinas CC: Dave Watson CC: Will Deacon CC: Shuah Khan CC: Andi Kleen CC: linux-kselftest@vger.kernel.org CC: "H . Peter Anvin" CC: Chris Lameter CC: Russell King CC: Michael Kerrisk CC: "Paul E . McKenney" CC: Paul Turner CC: Boqun Feng CC: Josh Triplett CC: Steven Rostedt CC: Ben Maurer CC: linux-api@vger.kernel.org CC: Andy Lutomirski CC: Andrew Morton CC: Linus Torvalds Signed-off-by: Shuah Khan

rseq/selftests: Introduce __rseq_cs_ptr_array, rename __rseq_table to __rseq_cs

2019-05-07T21:31:36Z

The entries within __rseq_table are aligned on 32 bytes due to linux/rseq.h struct rseq_cs uapi requirements, but the start of the __rseq_table section is not guaranteed to be 32-byte aligned. It can cause padding to be added at the start of the section, which makes it hard to use as an array of items by debuggers. Considering that __rseq_table does not really consist of a table due to the presence of padding, rename this section to __rseq_cs. Create a new __rseq_cs_ptr_array section which contains 64-bit packed pointers to entries within the __rseq_cs section. Signed-off-by: Mathieu Desnoyers CC: Thomas Gleixner CC: Joel Fernandes CC: Peter Zijlstra CC: Catalin Marinas CC: Dave Watson CC: Will Deacon CC: Shuah Khan CC: Andi Kleen CC: linux-kselftest@vger.kernel.org CC: "H . Peter Anvin" CC: Chris Lameter CC: Russell King CC: Michael Kerrisk CC: "Paul E . McKenney" CC: Paul Turner CC: Boqun Feng CC: Josh Triplett CC: Steven Rostedt CC: Ben Maurer CC: linux-api@vger.kernel.org CC: Andy Lutomirski CC: Andrew Morton CC: Linus Torvalds Signed-off-by: Shuah Khan