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 --- tools/testing/selftests/rseq/rseq-abi.h | 151 ++++++++++++++++++++++++ tools/testing/selftests/rseq/rseq.c | 14 +-- tools/testing/selftests/rseq/rseq.h | 10 +- 3 files changed, 161 insertions(+), 14 deletions(-) create mode 100644 tools/testing/selftests/rseq/rseq-abi.h
diff --git a/tools/testing/selftests/rseq/rseq-abi.h b/tools/testing/selftests/rseq/rseq-abi.h new file mode 100644 index 000000000000..a8c44d9af71f --- /dev/null +++ b/tools/testing/selftests/rseq/rseq-abi.h @@ -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 */ diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c index fb440dfca158..bfe1b2692ffc 100644 --- a/tools/testing/selftests/rseq/rseq.c +++ b/tools/testing/selftests/rseq/rseq.c @@ -30,8 +30,8 @@ #include "../kselftest.h" #include "rseq.h"
-__thread volatile struct rseq __rseq_abi = { - .cpu_id = RSEQ_CPU_ID_UNINITIALIZED, +__thread volatile struct rseq_abi __rseq_abi = { + .cpu_id = RSEQ_ABI_CPU_ID_UNINITIALIZED, };
/* @@ -66,7 +66,7 @@ static void signal_restore(sigset_t oldset) 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) { return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig); @@ -86,13 +86,13 @@ int rseq_register_current_thread(void) } if (__rseq_refcount++) 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) { assert(rseq_current_cpu_raw() >= 0); goto end; } if (errno != EBUSY) - __rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED; + __rseq_abi.cpu_id = RSEQ_ABI_CPU_ID_REGISTRATION_FAILED; ret = -1; __rseq_refcount--; end: @@ -114,8 +114,8 @@ int rseq_unregister_current_thread(void) } if (--__rseq_refcount) goto end; - rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), - RSEQ_FLAG_UNREGISTER, RSEQ_SIG); + rc = sys_rseq(&__rseq_abi, sizeof(struct rseq_abi), + RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG); if (!rc) goto end; __rseq_refcount = 1; diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h index 3f63eb362b92..cb6bbc53b586 100644 --- a/tools/testing/selftests/rseq/rseq.h +++ b/tools/testing/selftests/rseq/rseq.h @@ -16,7 +16,7 @@ #include <errno.h> #include <stdio.h> #include <stdlib.h> -#include <linux/rseq.h> +#include "rseq-abi.h"
/* * Empty code injection macros, override when testing. @@ -43,7 +43,7 @@ #define RSEQ_INJECT_FAILED #endif
-extern __thread volatile struct rseq __rseq_abi; +extern __thread volatile struct rseq_abi __rseq_abi; extern int __rseq_handled;
#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) { -#ifdef __LP64__ - __rseq_abi.rseq_cs.ptr = 0; -#else - __rseq_abi.rseq_cs.ptr.ptr32 = 0; -#endif + __rseq_abi.rseq_cs.arch.ptr = 0; }
/*