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selftests/rseq: introduce own copy of rseq uapi header

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The Linux kernel rseq uapi header has a broken layout for the
rseq_cs.ptr field on 32-bit little endian architectures. The entire
rseq_cs.ptr field is planned for removal, leaving only the 64-bit
rseq_cs.ptr64 field available.

Both glibc and librseq use their own copy of the Linux kernel uapi
header, where they introduce proper union fields to access to the 32-bit
low order bits of the rseq_cs pointer on 32-bit architectures.

Introduce a copy of the Linux kernel uapi headers in the Linux kernel
selftests.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220124171253.22072-2-mathieu.desnoyers@efficios.com
This commit is contained in:
Mathieu Desnoyers 2022-01-24 12:12:39 -05:00 committed by Peter Zijlstra
parent ec24445306
commit 5c105d55a9
3 changed files with 161 additions and 14 deletions
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151
tools/testing/selftests/rseq/rseq-abi.h Normal file
View File

@ -0,0 +1,151 @@
/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
#ifndef _RSEQ_ABI_H
#define _RSEQ_ABI_H
/*
* rseq-abi.h
*
* Restartable sequences system call API
*
* Copyright (c) 2015-2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
*/
#include <linux/types.h>
#include <asm/byteorder.h>
enum rseq_abi_cpu_id_state {
RSEQ_ABI_CPU_ID_UNINITIALIZED = -1,
RSEQ_ABI_CPU_ID_REGISTRATION_FAILED = -2,
};
enum rseq_abi_flags {
RSEQ_ABI_FLAG_UNREGISTER = (1 << 0),
};
enum rseq_abi_cs_flags_bit {
RSEQ_ABI_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT = 0,
RSEQ_ABI_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT = 1,
RSEQ_ABI_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT = 2,
};
enum rseq_abi_cs_flags {
RSEQ_ABI_CS_FLAG_NO_RESTART_ON_PREEMPT =
(1U << RSEQ_ABI_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT),
RSEQ_ABI_CS_FLAG_NO_RESTART_ON_SIGNAL =
(1U << RSEQ_ABI_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT),
RSEQ_ABI_CS_FLAG_NO_RESTART_ON_MIGRATE =
(1U << RSEQ_ABI_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT),
};
/*
* struct rseq_abi_cs is aligned on 4 * 8 bytes to ensure it is always
* contained within a single cache-line. It is usually declared as
* link-time constant data.
*/
struct rseq_abi_cs {
/* Version of this structure. */
__u32 version;
/* enum rseq_abi_cs_flags */
__u32 flags;
__u64 start_ip;
/* Offset from start_ip. */
__u64 post_commit_offset;
__u64 abort_ip;
} __attribute__((aligned(4 * sizeof(__u64))));
/*
* struct rseq_abi is aligned on 4 * 8 bytes to ensure it is always
* contained within a single cache-line.
*
* A single struct rseq_abi per thread is allowed.
*/
struct rseq_abi {
/*
* Restartable sequences cpu_id_start field. Updated by the
* kernel. Read by user-space with single-copy atomicity
* semantics. This field should only be read by the thread which
* registered this data structure. Aligned on 32-bit. Always
* contains a value in the range of possible CPUs, although the
* value may not be the actual current CPU (e.g. if rseq is not
* initialized). This CPU number value should always be compared
* against the value of the cpu_id field before performing a rseq
* commit or returning a value read from a data structure indexed
* using the cpu_id_start value.
*/
__u32 cpu_id_start;
/*
* Restartable sequences cpu_id field. Updated by the kernel.
* Read by user-space with single-copy atomicity semantics. This
* field should only be read by the thread which registered this
* data structure. Aligned on 32-bit. Values
* RSEQ_CPU_ID_UNINITIALIZED and RSEQ_CPU_ID_REGISTRATION_FAILED
* have a special semantic: the former means "rseq uninitialized",
* and latter means "rseq initialization failed". This value is
* meant to be read within rseq critical sections and compared
* with the cpu_id_start value previously read, before performing
* the commit instruction, or read and compared with the
* cpu_id_start value before returning a value loaded from a data
* structure indexed using the cpu_id_start value.
*/
__u32 cpu_id;
/*
* Restartable sequences rseq_cs field.
*
* Contains NULL when no critical section is active for the current
* thread, or holds a pointer to the currently active struct rseq_cs.
*
* Updated by user-space, which sets the address of the currently
* active rseq_cs at the beginning of assembly instruction sequence
* block, and set to NULL by the kernel when it restarts an assembly
* instruction sequence block, as well as when the kernel detects that
* it is preempting or delivering a signal outside of the range
* targeted by the rseq_cs. Also needs to be set to NULL by user-space
* before reclaiming memory that contains the targeted struct rseq_cs.
*
* Read and set by the kernel. Set by user-space with single-copy
* atomicity semantics. This field should only be updated by the
* thread which registered this data structure. Aligned on 64-bit.
*/
union {
__u64 ptr64;
/*
* The "arch" field provides architecture accessor for
* the ptr field based on architecture pointer size and
* endianness.
*/
struct {
#ifdef __LP64__
__u64 ptr;
#elif defined(__BYTE_ORDER) ? (__BYTE_ORDER == __BIG_ENDIAN) : defined(__BIG_ENDIAN)
__u32 padding; /* Initialized to zero. */
__u32 ptr;
#else
__u32 ptr;
__u32 padding; /* Initialized to zero. */
#endif
} arch;
} rseq_cs;
/*
* Restartable sequences flags field.
*
* This field should only be updated by the thread which
* registered this data structure. Read by the kernel.
* Mainly used for single-stepping through rseq critical sections
* with debuggers.
*
* - RSEQ_ABI_CS_FLAG_NO_RESTART_ON_PREEMPT
* Inhibit instruction sequence block restart on preemption
* for this thread.
* - RSEQ_ABI_CS_FLAG_NO_RESTART_ON_SIGNAL
* Inhibit instruction sequence block restart on signal
* delivery for this thread.
* - RSEQ_ABI_CS_FLAG_NO_RESTART_ON_MIGRATE
* Inhibit instruction sequence block restart on migration for
* this thread.
*/
__u32 flags;
} __attribute__((aligned(4 * sizeof(__u64))));
#endif /* _RSEQ_ABI_H */

14
tools/testing/selftests/rseq/rseq.c
View File

@ -30,8 +30,8 @@
#include "../kselftest.h" #include "../kselftest.h"
#include "rseq.h" #include "rseq.h"
__thread volatile struct rseq __rseq_abi = { __thread volatile struct rseq_abi __rseq_abi = {
.cpu_id = RSEQ_CPU_ID_UNINITIALIZED, .cpu_id = RSEQ_ABI_CPU_ID_UNINITIALIZED,
}; };
/* /*
@ -66,7 +66,7 @@ static void signal_restore(sigset_t oldset)
abort(); abort();
} }
static int sys_rseq(volatile struct rseq *rseq_abi, uint32_t rseq_len, static int sys_rseq(volatile struct rseq_abi *rseq_abi, uint32_t rseq_len,
int flags, uint32_t sig) int flags, uint32_t sig)
{ {
return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig); return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig);
@ -86,13 +86,13 @@ int rseq_register_current_thread(void)
} }
if (__rseq_refcount++) if (__rseq_refcount++)
goto end; goto end;
rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), 0, RSEQ_SIG); rc = sys_rseq(&__rseq_abi, sizeof(struct rseq_abi), 0, RSEQ_SIG);
if (!rc) { if (!rc) {
assert(rseq_current_cpu_raw() >= 0); assert(rseq_current_cpu_raw() >= 0);
goto end; goto end;
} }
if (errno != EBUSY) if (errno != EBUSY)
__rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED; __rseq_abi.cpu_id = RSEQ_ABI_CPU_ID_REGISTRATION_FAILED;
ret = -1; ret = -1;
__rseq_refcount--; __rseq_refcount--;
end: end:
@ -114,8 +114,8 @@ int rseq_unregister_current_thread(void)
} }
if (--__rseq_refcount) if (--__rseq_refcount)
goto end; goto end;
rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), rc = sys_rseq(&__rseq_abi, sizeof(struct rseq_abi),
RSEQ_FLAG_UNREGISTER, RSEQ_SIG); RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG);
if (!rc) if (!rc)
goto end; goto end;
__rseq_refcount = 1; __rseq_refcount = 1;

10
tools/testing/selftests/rseq/rseq.h
View File

@ -16,7 +16,7 @@
#include <errno.h> #include <errno.h>
#include <stdio.h> #include <stdio.h>
#include <stdlib.h> #include <stdlib.h>
#include <linux/rseq.h> #include "rseq-abi.h"
/* /*
* Empty code injection macros, override when testing. * Empty code injection macros, override when testing.
@ -43,7 +43,7 @@
#define RSEQ_INJECT_FAILED #define RSEQ_INJECT_FAILED
#endif #endif
extern __thread volatile struct rseq __rseq_abi; extern __thread volatile struct rseq_abi __rseq_abi;
extern int __rseq_handled; extern int __rseq_handled;
#define rseq_likely(x) __builtin_expect(!!(x), 1) #define rseq_likely(x) __builtin_expect(!!(x), 1)
@ -139,11 +139,7 @@ static inline uint32_t rseq_current_cpu(void)
static inline void rseq_clear_rseq_cs(void) static inline void rseq_clear_rseq_cs(void)
{ {
#ifdef __LP64__ __rseq_abi.rseq_cs.arch.ptr = 0;
__rseq_abi.rseq_cs.ptr = 0;
#else
__rseq_abi.rseq_cs.ptr.ptr32 = 0;
#endif
} }
/* /*