在Linux中的用戶空間程序中，我通過堆中的分配獲得了一段內存，然後將指針分發給運行在其他線程中的許多其他組件。我希望在修改所述內存時得到通知。我當然可以開發一個自定義的用戶空間解決方案，供其他組件在嘗試修改內存時使用。在我的情況下，問題是這些是遺留組件，並且他們可以在很多場合寫入內存。所以我想知道是否有類似inotify的API（在文件發生變化時得到通知）或其他方法，以便在內存更改時得到通知。如何在Linux中的內存中獲取修改通知
我考慮過使用mmap和inotify，如果更改沒有刷新，顯然不會工作。任何建議表示讚賞:-)
唯一可以這樣工作的是一個調試硬件觀察點。
但是，如果沿着這條路線走下去，你會做錯事。
爲了在線程之間共享內存，您需要實現適當的鎖定和同步代碼。在這種情況下，您應該能夠在內存解鎖時添加更改通知。
您CAN添加一個inotify watch它將在mmap-ed文件上的msync()上觸發。
這需要將Linux內核修補到enable support for a new inotify watch。該補丁添加了一個新標誌IN_SYNC - 在mmap-ed文件上執行msync（）時觸發的新inotify事件。
修補程序已在Linux Kernel的v2.6.37上進行了測試。
From 83edf446e92c86c738337ca4a35eab48e2f4e0eb Mon Sep 17 00:00:00 2001
From: Chinmay V S <[email protected]>
Date: Mon, 17 Jun 2013 13:53:57 +0800
Subject: [PATCH] Add mmap-ed file support to inotify
This patch adds a new flag IN_SYNC. This is a new inotify event that is
triggered whenever msync() is carried out on a mmap-ed file.
Signed-off-by: Chinmay V S <[email protected]>
---
fs/sync.c | 5 +++++
include/linux/fsnotify.h | 16 ++++++++++++++++
include/linux/fsnotify_backend.h | 1 +
include/linux/inotify.h | 3 ++-
mm/msync.c | 4 ++++
5 files changed, 28 insertions(+), 3 deletions(-)
diff --git a/fs/sync.c b/fs/sync.c
index ba76b96..174c2af 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -16,6 +16,7 @@
#include <linux/buffer_head.h>
#include <linux/backing-dev.h>
#include "internal.h"
+#include <linux/fsnotify.h>
#define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
SYNC_FILE_RANGE_WAIT_AFTER)
@@ -190,6 +191,10 @@ static int do_fsync(unsigned int fd, int datasync)
ret = vfs_fsync(file, datasync);
fput(file);
}
+
+ if (!ret)
+ fsnotify_sync(file->f_path.dentry);
+
return ret;
}
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index b10bcde..ef211fb 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -224,6 +224,22 @@ static inline void fsnotify_modify(struct file *file)
}
/*
+ * fsnotify_sync - file was synced
+ */
+static inline void fsnotify_sync(struct dentry *dentry)
+{
+ struct inode *inode = dentry->d_inode;
+ u32 mask = FS_SYNC;
+
+ if (S_ISDIR(inode->i_mode))
+ mask |= FS_ISDIR;
+
+ fsnotify_parent(NULL, dentry, mask);
+ fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
+
+}
+
+/*
* fsnotify_open - file was opened
*/
static inline void fsnotify_open(struct file *file)
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 7380763..35b5cb8 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -36,6 +36,7 @@
#define FS_DELETE 0x00000200 /* Subfile was deleted */
#define FS_DELETE_SELF 0x00000400 /* Self was deleted */
#define FS_MOVE_SELF 0x00000800 /* Self was moved */
+#define FS_SYNC 0x00001000 /* File was synced */
#define FS_UNMOUNT 0x00002000 /* inode on umount fs */
#define FS_Q_OVERFLOW 0x00004000 /* Event queued overflowed */
diff --git a/include/linux/inotify.h b/include/linux/inotify.h
index d33041e..244a132 100644
--- a/include/linux/inotify.h
+++ b/include/linux/inotify.h
@@ -38,6 +38,7 @@ struct inotify_event {
#define IN_DELETE 0x00000200 /* Subfile was deleted */
#define IN_DELETE_SELF 0x00000400 /* Self was deleted */
#define IN_MOVE_SELF 0x00000800 /* Self was moved */
+#define IN_SYNC 0x00001000 /* File was synced */
/* the following are legal events. they are sent as needed to any watch */
#define IN_UNMOUNT 0x00002000 /* Backing fs was unmounted */
@@ -64,7 +65,7 @@ struct inotify_event {
#define IN_ALL_EVENTS (IN_ACCESS | IN_MODIFY | IN_ATTRIB | IN_CLOSE_WRITE | \
IN_CLOSE_NOWRITE | IN_OPEN | IN_MOVED_FROM | \
IN_MOVED_TO | IN_DELETE | IN_CREATE | IN_DELETE_SELF | \
- IN_MOVE_SELF)
+ IN_MOVE_SELF | IN_SYNC)
/* Flags for sys_inotify_init1. */
#define IN_CLOEXEC O_CLOEXEC
diff --git a/mm/msync.c b/mm/msync.c
index 632df45..b1665ac 100644
--- a/mm/msync.c
+++ b/mm/msync.c
@@ -13,6 +13,7 @@
#include <linux/file.h>
#include <linux/syscalls.h>
#include <linux/sched.h>
+#include <linux/fsnotify.h>
/*
* MS_SYNC syncs the entire file - including mappings.
@@ -83,6 +84,9 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
get_file(file);
up_read(&mm->mmap_sem);
error = vfs_fsync(file, 0);
+ if (!error)
+ fsnotify_sync(file->f_path.dentry);
+
fput(file);
if (error || start >= end)
goto out;
--
1.8.2
修補程序已在Linux Kernel的v2.6.37上進行了測試。
您可以對RAM中的相應頁面進行保護（將其設置爲只讀），並在寫入失敗時捕獲SIGSEGV信號。在信號處理程序中，您需要設置RAM讀寫以允許寫入成功（這主要是對用戶空間中的頁面錯誤作出反應）。然後，您需要重新保護RAM以檢測下一次寫入。
這是一個硬核C代碼，它是特定於架構的（不是便攜式的），但我過去做過（2001年在英特爾奔騰服務器上）。這是x86特定的，所以我不知道如何在x86_64上執行此操作。如果需要，我可以在我的檔案中做一些考古工作，讓你朝着正確的方向前進（發表評論，我會潛入舊代碼中）。