+++ /dev/null
-/* 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 <wrapper/uaccess.h>
-
-/* Internal helpers */
-#include <wrapper/ringbuffer/backend_internal.h>
-#include <wrapper/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(!lttng_access_ok(VERIFY_READ, 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(!lttng_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,
- 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 (!lttng_access_ok(VERIFY_READ, 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 */
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