X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=include%2Fringbuffer%2Fbackend.h;h=d01400dae97d93e8b1ddafda410adc85b0638b57;hb=refs%2Ftags%2Ffor-upstreaming-review-1;hp=48641606a4abbf6aa0bf0084df6a98820ed57f64;hpb=369708f464bedc0682151df9308cebfa14dbdb2b;p=lttng-modules.git

diff --git a/include/ringbuffer/backend.h b/include/ringbuffer/backend.h
index 48641606..d01400da 100644
--- a/include/ringbuffer/backend.h
+++ b/include/ringbuffer/backend.h
@@ -1,2 +1,463 @@
-/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only) */
-#include <lib/ringbuffer/backend.h>
+/* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
+ *
+ * lib/ringbuffer/backend.h
+ *
+ * Ring buffer backend (API).
+ *
+ * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by
+ * the reader in flight recorder mode.
+ */
+
+#ifndef _LIB_RING_BUFFER_BACKEND_H
+#define _LIB_RING_BUFFER_BACKEND_H
+
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+#include <linux/wait.h>
+#include <linux/poll.h>
+#include <linux/list.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/uaccess.h>
+
+/* Internal helpers */
+#include <ringbuffer/backend_internal.h>
+#include <ringbuffer/frontend_internal.h>
+
+/* Ring buffer backend API */
+
+/* Ring buffer backend access (read/write) */
+
+extern size_t lib_ring_buffer_read(struct lib_ring_buffer_backend *bufb,
+				   size_t offset, void *dest, size_t len);
+
+extern int __lib_ring_buffer_copy_to_user(struct lib_ring_buffer_backend *bufb,
+					  size_t offset, void __user *dest,
+					  size_t len);
+
+extern int lib_ring_buffer_read_cstr(struct lib_ring_buffer_backend *bufb,
+				     size_t offset, void *dest, size_t len);
+
+extern unsigned long *
+lib_ring_buffer_read_get_pfn(struct lib_ring_buffer_backend *bufb, size_t offset,
+			      void ***virt);
+
+/*
+ * Return the address where a given offset is located.
+ * Should be used to get the current subbuffer header pointer. Given we know
+ * it's never on a page boundary, it's safe to write directly to this address,
+ * as long as the write is never bigger than a page size.
+ */
+extern void *
+lib_ring_buffer_offset_address(struct lib_ring_buffer_backend *bufb,
+			       size_t offset);
+extern void *
+lib_ring_buffer_read_offset_address(struct lib_ring_buffer_backend *bufb,
+				    size_t offset);
+
+/**
+ * lib_ring_buffer_write - write 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
+ *
+ * This function copies "len" bytes of data from a source pointer to a buffer
+ * backend, at the current context offset. This is more or less a buffer
+ * backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write)
+ * if copy is crossing a page boundary.
+ */
+static inline __attribute__((always_inline))
+void lib_ring_buffer_write(const struct lib_ring_buffer_config *config,
+			   struct lib_ring_buffer_ctx *ctx,
+			   const void *src, size_t len)
+{
+	struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
+	struct channel_backend *chanb = &ctx->chan->backend;
+	size_t index, pagecpy;
+	size_t offset = ctx->buf_offset;
+	struct lib_ring_buffer_backend_pages *backend_pages;
+
+	if (unlikely(!len))
+		return;
+	backend_pages =
+		lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
+	offset &= chanb->buf_size - 1;
+	index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
+	pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK);
+	if (likely(pagecpy == len))
+		lib_ring_buffer_do_copy(config,
+					backend_pages->p[index].virt
+					    + (offset & ~PAGE_MASK),
+					src, len);
+	else
+		_lib_ring_buffer_write(bufb, offset, src, len, 0);
+	ctx->buf_offset += len;
+}
+
+/**
+ * lib_ring_buffer_memset - write len bytes of c to a buffer backend
+ * @config : ring buffer instance configuration
+ * @bufb : ring buffer backend
+ * @offset : offset within the buffer
+ * @c : the byte to copy
+ * @len : number of bytes to copy
+ *
+ * This function writes "len" bytes of "c" to a buffer backend, at a specific
+ * offset. This is more or less a buffer backend-specific memset() operation.
+ * Calls the slow path (_ring_buffer_memset) if write is crossing a page
+ * boundary.
+ */
+static inline
+void lib_ring_buffer_memset(const struct lib_ring_buffer_config *config,
+			    struct lib_ring_buffer_ctx *ctx, int c, size_t len)
+{
+
+	struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
+	struct channel_backend *chanb = &ctx->chan->backend;
+	size_t index, pagecpy;
+	size_t offset = ctx->buf_offset;
+	struct lib_ring_buffer_backend_pages *backend_pages;
+
+	if (unlikely(!len))
+		return;
+	backend_pages =
+		lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
+	offset &= chanb->buf_size - 1;
+	index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
+	pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK);
+	if (likely(pagecpy == len))
+		lib_ring_buffer_do_memset(backend_pages->p[index].virt
+					  + (offset & ~PAGE_MASK),
+					  c, len);
+	else
+		_lib_ring_buffer_memset(bufb, offset, c, len, 0);
+	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 __attribute__((always_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 = READ_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 __attribute__((always_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 = __copy_from_user_inatomic(&c, src + count, 1);
+		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 index, pagecpy;
+	size_t offset = ctx->buf_offset;
+	struct lib_ring_buffer_backend_pages *backend_pages;
+
+	if (unlikely(!len))
+		return;
+	backend_pages =
+		lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
+	offset &= chanb->buf_size - 1;
+	index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
+	pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK);
+	if (likely(pagecpy == len)) {
+		size_t count;
+
+		count = lib_ring_buffer_do_strcpy(config,
+					backend_pages->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(backend_pages->p[index].virt
+						+ (offset & ~PAGE_MASK),
+					pad, pad_len);
+			offset += pad_len;
+		}
+		/* Ending '\0' */
+		lib_ring_buffer_do_memset(backend_pages->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
+ * @ctx: ring buffer context. (input arguments only)
+ * @src : userspace source pointer to copy from
+ * @len : length of data to copy
+ *
+ * This function copies "len" bytes of data from a userspace pointer to a
+ * buffer backend, at the current context offset. This is more or less a buffer
+ * backend-specific memcpy() operation. Calls the slow path
+ * (_ring_buffer_write_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 __attribute__((always_inline))
+void lib_ring_buffer_copy_from_user_inatomic(const struct lib_ring_buffer_config *config,
+				    struct lib_ring_buffer_ctx *ctx,
+				    const void __user *src, size_t len)
+{
+	struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
+	struct channel_backend *chanb = &ctx->chan->backend;
+	size_t index, pagecpy;
+	size_t offset = ctx->buf_offset;
+	struct lib_ring_buffer_backend_pages *backend_pages;
+	unsigned long ret;
+	mm_segment_t old_fs = get_fs();
+
+	if (unlikely(!len))
+		return;
+	backend_pages =
+		lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
+	offset &= chanb->buf_size - 1;
+	index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
+	pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK);
+
+	set_fs(KERNEL_DS);
+	pagefault_disable();
+	if (unlikely(!access_ok(src, len)))
+		goto fill_buffer;
+
+	if (likely(pagecpy == len)) {
+		ret = lib_ring_buffer_do_copy_from_user_inatomic(
+			backend_pages->p[index].virt + (offset & ~PAGE_MASK),
+			src, len);
+		if (unlikely(ret > 0)) {
+			/* Copy failed. */
+			goto fill_buffer;
+		}
+	} else {
+		_lib_ring_buffer_copy_from_user_inatomic(bufb, offset, src, len, 0);
+	}
+	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, 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 index, pagecpy;
+	size_t offset = ctx->buf_offset;
+	struct lib_ring_buffer_backend_pages *backend_pages;
+	mm_segment_t old_fs = get_fs();
+
+	if (unlikely(!len))
+		return;
+	backend_pages =
+		lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
+	offset &= chanb->buf_size - 1;
+	index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
+	pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK);
+
+	set_fs(KERNEL_DS);
+	pagefault_disable();
+	if (unlikely(!access_ok(src, len)))
+		goto fill_buffer;
+
+	if (likely(pagecpy == len)) {
+		size_t count;
+
+		count = lib_ring_buffer_do_strcpy_from_user_inatomic(config,
+					backend_pages->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(backend_pages->p[index].virt
+						+ (offset & ~PAGE_MASK),
+					pad, pad_len);
+			offset += pad_len;
+		}
+		/* Ending '\0' */
+		lib_ring_buffer_do_memset(backend_pages->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
+ * concurrently.
+ */
+static inline
+unsigned long lib_ring_buffer_get_records_unread(
+				const struct lib_ring_buffer_config *config,
+				struct lib_ring_buffer *buf)
+{
+	struct lib_ring_buffer_backend *bufb = &buf->backend;
+	struct lib_ring_buffer_backend_pages *pages;
+	unsigned long records_unread = 0, sb_bindex, id;
+	unsigned int i;
+
+	for (i = 0; i < bufb->chan->backend.num_subbuf; i++) {
+		id = bufb->buf_wsb[i].id;
+		sb_bindex = subbuffer_id_get_index(config, id);
+		pages = bufb->array[sb_bindex];
+		records_unread += v_read(config, &pages->records_unread);
+	}
+	if (config->mode == RING_BUFFER_OVERWRITE) {
+		id = bufb->buf_rsb.id;
+		sb_bindex = subbuffer_id_get_index(config, id);
+		pages = bufb->array[sb_bindex];
+		records_unread += v_read(config, &pages->records_unread);
+	}
+	return records_unread;
+}
+
+/*
+ * We use __copy_from_user_inatomic to copy userspace data after
+ * checking with access_ok() and disabling page faults.
+ *
+ * Return 0 if OK, nonzero on error.
+ */
+static inline
+unsigned long lib_ring_buffer_copy_from_user_check_nofault(void *dest,
+						const void __user *src,
+						unsigned long len)
+{
+	unsigned long ret;
+	mm_segment_t old_fs;
+
+	if (!access_ok(src, len))
+		return 1;
+	old_fs = get_fs();
+	set_fs(KERNEL_DS);
+	pagefault_disable();
+	ret = __copy_from_user_inatomic(dest, src, len);
+	pagefault_enable();
+	set_fs(old_fs);
+	return ret;
+}
+
+#endif /* _LIB_RING_BUFFER_BACKEND_H */