diff options
| -rw-r--r-- | fs/binfmt_elf.c | 3 | ||||
| -rw-r--r-- | include/linux/rseq.h | 12 | ||||
| -rw-r--r-- | include/uapi/linux/rseq.h | 26 | ||||
| -rw-r--r-- | kernel/rseq.c | 3 |
4 files changed, 38 insertions, 6 deletions
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 8e89cc5b2820..fb857faaf0d6 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -47,6 +47,7 @@ #include <linux/dax.h> #include <linux/uaccess.h> #include <uapi/linux/rseq.h> +#include <linux/rseq.h> #include <asm/param.h> #include <asm/page.h> @@ -286,7 +287,7 @@ create_elf_tables(struct linux_binprm *bprm, const struct elfhdr *exec, } #ifdef CONFIG_RSEQ NEW_AUX_ENT(AT_RSEQ_FEATURE_SIZE, offsetof(struct rseq, end)); - NEW_AUX_ENT(AT_RSEQ_ALIGN, __alignof__(struct rseq)); + NEW_AUX_ENT(AT_RSEQ_ALIGN, rseq_alloc_align()); #endif #undef NEW_AUX_ENT /* AT_NULL is zero; clear the rest too */ diff --git a/include/linux/rseq.h b/include/linux/rseq.h index 7a01a0760405..b9d62fc2140d 100644 --- a/include/linux/rseq.h +++ b/include/linux/rseq.h @@ -146,6 +146,18 @@ static inline void rseq_fork(struct task_struct *t, u64 clone_flags) t->rseq = current->rseq; } +/* + * Value returned by getauxval(AT_RSEQ_ALIGN) and expected by rseq + * registration. This is the active rseq area size rounded up to next + * power of 2, which guarantees that the rseq structure will always be + * aligned on the nearest power of two large enough to contain it, even + * as it grows. + */ +static inline unsigned int rseq_alloc_align(void) +{ + return 1U << get_count_order(offsetof(struct rseq, end)); +} + #else /* CONFIG_RSEQ */ static inline void rseq_handle_slowpath(struct pt_regs *regs) { } static inline void rseq_signal_deliver(struct ksignal *ksig, struct pt_regs *regs) { } diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h index 863c4a00a66b..f69344fe6c08 100644 --- a/include/uapi/linux/rseq.h +++ b/include/uapi/linux/rseq.h @@ -87,10 +87,17 @@ struct rseq_slice_ctrl { }; /* - * struct rseq is aligned on 4 * 8 bytes to ensure it is always - * contained within a single cache-line. + * The original size and alignment of the allocation for struct rseq is + * 32 bytes. * - * A single struct rseq per thread is allowed. + * The allocation size needs to be greater or equal to + * max(getauxval(AT_RSEQ_FEATURE_SIZE), 32), and the allocation needs to + * be aligned on max(getauxval(AT_RSEQ_ALIGN), 32). + * + * As an alternative, userspace is allowed to use both the original size + * and alignment of 32 bytes for backward compatibility. + * + * A single active struct rseq registration per thread is allowed. */ struct rseq { /* @@ -181,9 +188,20 @@ struct rseq { struct rseq_slice_ctrl slice_ctrl; /* + * Before rseq became extensible, its original size was 32 bytes even + * though the active rseq area was only 20 bytes. + * Exposing a 32 bytes feature size would make life needlessly painful + * for userspace. Therefore, add a reserved byte after byte 32 + * to bump the rseq feature size from 32 to 33. + * The next field to be added to the rseq area will be larger + * than one byte, and will replace this reserved byte. + */ + __u8 __reserved; + + /* * Flexible array member at end of structure, after last feature field. */ char end[]; -} __attribute__((aligned(4 * sizeof(__u64)))); +} __attribute__((aligned(32))); #endif /* _UAPI_LINUX_RSEQ_H */ diff --git a/kernel/rseq.c b/kernel/rseq.c index e349f86cc945..38d3ef540760 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -80,6 +80,7 @@ #include <linux/syscalls.h> #include <linux/uaccess.h> #include <linux/types.h> +#include <linux/rseq.h> #include <asm/ptrace.h> #define CREATE_TRACE_POINTS @@ -456,7 +457,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, int, flags, u32 */ if (rseq_len < ORIG_RSEQ_SIZE || (rseq_len == ORIG_RSEQ_SIZE && !IS_ALIGNED((unsigned long)rseq, ORIG_RSEQ_SIZE)) || - (rseq_len != ORIG_RSEQ_SIZE && (!IS_ALIGNED((unsigned long)rseq, __alignof__(*rseq)) || + (rseq_len != ORIG_RSEQ_SIZE && (!IS_ALIGNED((unsigned long)rseq, rseq_alloc_align()) || rseq_len < offsetof(struct rseq, end)))) return -EINVAL; if (!access_ok(rseq, rseq_len)) |