X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=lib%2Fringbuffer%2Fbackend.h;h=aadc9c37b1d2b3f7870a2ad87f184ae736c0aafc;hb=bfe529f90b1354246b5d8a18f49e30595c612041;hp=826be933fe61bb45efbe96a7738823e3ae46af9e;hpb=7b8ea3a503536c9d00f8bb14958a150cbf7370c0;p=lttng-modules.git diff --git a/lib/ringbuffer/backend.h b/lib/ringbuffer/backend.h index 826be933..aadc9c37 100644 --- a/lib/ringbuffer/backend.h +++ b/lib/ringbuffer/backend.h @@ -90,12 +90,13 @@ void lib_ring_buffer_write(const struct lib_ring_buffer_config *config, { struct lib_ring_buffer_backend *bufb = &ctx->buf->backend; struct channel_backend *chanb = &ctx->chan->backend; - size_t sbidx, index; + size_t sbidx, index, pagecpy; size_t offset = ctx->buf_offset; - ssize_t pagecpy; struct lib_ring_buffer_backend_pages *rpages; unsigned long sb_bindex, id; + if (unlikely(!len)) + return; offset &= chanb->buf_size - 1; sbidx = offset >> chanb->subbuf_size_order; index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT; @@ -136,12 +137,13 @@ void lib_ring_buffer_memset(const struct lib_ring_buffer_config *config, struct lib_ring_buffer_backend *bufb = &ctx->buf->backend; struct channel_backend *chanb = &ctx->chan->backend; - size_t sbidx, index; + size_t sbidx, index, pagecpy; size_t offset = ctx->buf_offset; - ssize_t pagecpy; struct lib_ring_buffer_backend_pages *rpages; unsigned long sb_bindex, id; + if (unlikely(!len)) + return; offset &= chanb->buf_size - 1; sbidx = offset >> chanb->subbuf_size_order; index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT; @@ -161,6 +163,127 @@ void lib_ring_buffer_memset(const struct lib_ring_buffer_config *config, ctx->buf_offset += len; } +/* + * Copy up to @len string bytes from @src to @dest. Stop whenever a NULL + * terminating character is found in @src. Returns the number of bytes + * copied. Does *not* terminate @dest with NULL terminating character. + */ +static inline +size_t lib_ring_buffer_do_strcpy(const struct lib_ring_buffer_config *config, + char *dest, const char *src, size_t len) +{ + size_t count; + + for (count = 0; count < len; count++) { + char c; + + /* + * Only read source character once, in case it is + * modified concurrently. + */ + c = ACCESS_ONCE(src[count]); + if (!c) + break; + lib_ring_buffer_do_copy(config, &dest[count], &c, 1); + } + return count; +} + +/* + * Copy up to @len string bytes from @src to @dest. Stop whenever a NULL + * terminating character is found in @src, or when a fault occurs. + * Returns the number of bytes copied. Does *not* terminate @dest with + * NULL terminating character. + * + * This function deals with userspace pointers, it should never be called + * directly without having the src pointer checked with access_ok() + * previously. + */ +static inline +size_t lib_ring_buffer_do_strcpy_from_user_inatomic(const struct lib_ring_buffer_config *config, + char *dest, const char __user *src, size_t len) +{ + size_t count; + + for (count = 0; count < len; count++) { + int ret; + char c; + + ret = __get_user(c, &src[count]); + if (ret || !c) + break; + lib_ring_buffer_do_copy(config, &dest[count], &c, 1); + } + return count; +} + +/** + * lib_ring_buffer_strcpy - write string data to a buffer backend + * @config : ring buffer instance configuration + * @ctx: ring buffer context. (input arguments only) + * @src : source pointer to copy from + * @len : length of data to copy + * @pad : character to use for padding + * + * This function copies @len - 1 bytes of string data from a source + * pointer to a buffer backend, followed by a terminating '\0' + * character, at the current context offset. This is more or less a + * buffer backend-specific strncpy() operation. If a terminating '\0' + * character is found in @src before @len - 1 characters are copied, pad + * the buffer with @pad characters (e.g. '#'). Calls the slow path + * (_ring_buffer_strcpy) if copy is crossing a page boundary. + */ +static inline +void lib_ring_buffer_strcpy(const struct lib_ring_buffer_config *config, + struct lib_ring_buffer_ctx *ctx, + const char *src, size_t len, int pad) +{ + struct lib_ring_buffer_backend *bufb = &ctx->buf->backend; + struct channel_backend *chanb = &ctx->chan->backend; + size_t sbidx, index, pagecpy; + size_t offset = ctx->buf_offset; + struct lib_ring_buffer_backend_pages *rpages; + unsigned long sb_bindex, id; + + if (unlikely(!len)) + return; + offset &= chanb->buf_size - 1; + sbidx = offset >> chanb->subbuf_size_order; + index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT; + pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK); + id = bufb->buf_wsb[sbidx].id; + sb_bindex = subbuffer_id_get_index(config, id); + rpages = bufb->array[sb_bindex]; + CHAN_WARN_ON(ctx->chan, + config->mode == RING_BUFFER_OVERWRITE + && subbuffer_id_is_noref(config, id)); + if (likely(pagecpy == len)) { + size_t count; + + count = lib_ring_buffer_do_strcpy(config, + rpages->p[index].virt + + (offset & ~PAGE_MASK), + src, len - 1); + offset += count; + /* Padding */ + if (unlikely(count < len - 1)) { + size_t pad_len = len - 1 - count; + + lib_ring_buffer_do_memset(rpages->p[index].virt + + (offset & ~PAGE_MASK), + pad, pad_len); + offset += pad_len; + } + /* Ending '\0' */ + lib_ring_buffer_do_memset(rpages->p[index].virt + + (offset & ~PAGE_MASK), + '\0', 1); + } else { + _lib_ring_buffer_strcpy(bufb, offset, src, len, 0, pad); + } + ctx->buf_offset += len; +} + /** * lib_ring_buffer_copy_from_user_inatomic - write userspace data to a buffer backend * @config : ring buffer instance configuration @@ -181,14 +304,15 @@ void lib_ring_buffer_copy_from_user_inatomic(const struct lib_ring_buffer_config { struct lib_ring_buffer_backend *bufb = &ctx->buf->backend; struct channel_backend *chanb = &ctx->chan->backend; - size_t sbidx, index; + size_t sbidx, index, pagecpy; size_t offset = ctx->buf_offset; - ssize_t pagecpy; struct lib_ring_buffer_backend_pages *rpages; unsigned long sb_bindex, id; unsigned long ret; mm_segment_t old_fs = get_fs(); + if (unlikely(!len)) + return; offset &= chanb->buf_size - 1; sbidx = offset >> chanb->subbuf_size_order; index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT; @@ -233,6 +357,98 @@ fill_buffer: _lib_ring_buffer_memset(bufb, offset, 0, len, 0); } +/** + * lib_ring_buffer_strcpy_from_user_inatomic - write userspace string data to a buffer backend + * @config : ring buffer instance configuration + * @ctx: ring buffer context (input arguments only) + * @src : userspace source pointer to copy from + * @len : length of data to copy + * @pad : character to use for padding + * + * This function copies @len - 1 bytes of string data from a userspace + * source pointer to a buffer backend, followed by a terminating '\0' + * character, at the current context offset. This is more or less a + * buffer backend-specific strncpy() operation. If a terminating '\0' + * character is found in @src before @len - 1 characters are copied, pad + * the buffer with @pad characters (e.g. '#'). Calls the slow path + * (_ring_buffer_strcpy_from_user_inatomic) if copy is crossing a page + * boundary. Disable the page fault handler to ensure we never try to + * take the mmap_sem. + */ +static inline +void lib_ring_buffer_strcpy_from_user_inatomic(const struct lib_ring_buffer_config *config, + struct lib_ring_buffer_ctx *ctx, + const void __user *src, size_t len, int pad) +{ + struct lib_ring_buffer_backend *bufb = &ctx->buf->backend; + struct channel_backend *chanb = &ctx->chan->backend; + size_t sbidx, index, pagecpy; + size_t offset = ctx->buf_offset; + struct lib_ring_buffer_backend_pages *rpages; + unsigned long sb_bindex, id; + mm_segment_t old_fs = get_fs(); + + if (unlikely(!len)) + return; + offset &= chanb->buf_size - 1; + sbidx = offset >> chanb->subbuf_size_order; + index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT; + pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK); + id = bufb->buf_wsb[sbidx].id; + sb_bindex = subbuffer_id_get_index(config, id); + rpages = bufb->array[sb_bindex]; + CHAN_WARN_ON(ctx->chan, + config->mode == RING_BUFFER_OVERWRITE + && subbuffer_id_is_noref(config, id)); + + set_fs(KERNEL_DS); + pagefault_disable(); + if (unlikely(!access_ok(VERIFY_READ, src, len))) + goto fill_buffer; + + if (likely(pagecpy == len)) { + size_t count; + + count = lib_ring_buffer_do_strcpy_from_user_inatomic(config, + rpages->p[index].virt + + (offset & ~PAGE_MASK), + src, len - 1); + offset += count; + /* Padding */ + if (unlikely(count < len - 1)) { + size_t pad_len = len - 1 - count; + + lib_ring_buffer_do_memset(rpages->p[index].virt + + (offset & ~PAGE_MASK), + pad, pad_len); + offset += pad_len; + } + /* Ending '\0' */ + lib_ring_buffer_do_memset(rpages->p[index].virt + + (offset & ~PAGE_MASK), + '\0', 1); + } else { + _lib_ring_buffer_strcpy_from_user_inatomic(bufb, offset, src, + len, 0, pad); + } + pagefault_enable(); + set_fs(old_fs); + ctx->buf_offset += len; + + return; + +fill_buffer: + pagefault_enable(); + set_fs(old_fs); + /* + * In the error path we call the slow path version to avoid + * the pollution of static inline code. + */ + _lib_ring_buffer_memset(bufb, offset, pad, len - 1, 0); + offset += len - 1; + _lib_ring_buffer_memset(bufb, offset, '\0', 1, 0); +} + /* * This accessor counts the number of unread records in a buffer. * It only provides a consistent value if no reads not writes are performed @@ -263,9 +479,4 @@ unsigned long lib_ring_buffer_get_records_unread( return records_unread; } -ssize_t lib_ring_buffer_file_splice_read(struct file *in, loff_t *ppos, - struct pipe_inode_info *pipe, - size_t len, unsigned int flags); -loff_t lib_ring_buffer_no_llseek(struct file *file, loff_t offset, int origin); - #endif /* _LIB_RING_BUFFER_BACKEND_H */