From 007ec26cdc9fefacbed85b592afc69413194499c Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 1 Nov 2018 23:34:29 +0000 Subject: vfs: Implement logging through fs_context Implement the ability for filesystems to log error, warning and informational messages through the fs_context. These can be extracted by userspace by reading from an fd created by fsopen(). Error messages are prefixed with "e ", warnings with "w " and informational messages with "i ". Inside the kernel, formatted messages are malloc'd but unformatted messages are not copied if they're either in the core .rodata section or in the .rodata section of the filesystem module pinned by fs_context::fs_type. The messages are only good till the fs_type is released. Note that the logging object is shared between duplicated fs_context structures. This is so that such as NFS which do a mount within a mount can get at least some of the errors from the inner mount. Five logging functions are provided for this: (1) void logfc(struct fs_context *fc, const char *fmt, ...); This logs a message into the context. If the buffer is full, the earliest message is discarded. (2) void errorf(fc, fmt, ...); This wraps logfc() to log an error. (3) void invalf(fc, fmt, ...); This wraps errorf() and returns -EINVAL for convenience. (4) void warnf(fc, fmt, ...); This wraps logfc() to log a warning. (5) void infof(fc, fmt, ...); This wraps logfc() to log an informational message. Signed-off-by: David Howells Signed-off-by: Al Viro --- include/linux/fs_context.h | 22 +++++++++++++++------- include/linux/module.h | 6 ++++++ 2 files changed, 21 insertions(+), 7 deletions(-) (limited to 'include/linux') diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h index 7ab8b44fab3e..1f966670c8dc 100644 --- a/include/linux/fs_context.h +++ b/include/linux/fs_context.h @@ -13,6 +13,7 @@ #define _LINUX_FS_CONTEXT_H #include +#include #include #include #include @@ -95,6 +96,7 @@ struct fs_context { struct user_namespace *user_ns; /* The user namespace for this mount */ struct net *net_ns; /* The network namespace for this mount */ const struct cred *cred; /* The mounter's credentials */ + struct fc_log *log; /* Logging buffer */ const char *source; /* The source name (eg. dev path) */ const char *subtype; /* The subtype to set on the superblock */ void *security; /* Linux S&M options */ @@ -151,15 +153,21 @@ extern int vfs_get_super(struct fs_context *fc, extern const struct file_operations fscontext_fops; -#ifdef CONFIG_PRINTK +/* + * Mount error, warning and informational message logging. This structure is + * shareable between a mount and a subordinate mount. + */ +struct fc_log { + refcount_t usage; + u8 head; /* Insertion index in buffer[] */ + u8 tail; /* Removal index in buffer[] */ + u8 need_free; /* Mask of kfree'able items in buffer[] */ + struct module *owner; /* Owner module for strings that don't then need freeing */ + char *buffer[8]; +}; + extern __attribute__((format(printf, 2, 3))) void logfc(struct fs_context *fc, const char *fmt, ...); -#else -static inline __attribute__((format(printf, 2, 3))) -void logfc(struct fs_context *fc, const char *fmt, ...) -{ -} -#endif /** * infof - Store supplementary informational message diff --git a/include/linux/module.h b/include/linux/module.h index 5bf5dcd91009..7dc4dc79b634 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -709,6 +709,12 @@ static inline bool is_module_text_address(unsigned long addr) return false; } +static inline bool within_module_core(unsigned long addr, + const struct module *mod) +{ + return false; +} + /* Get/put a kernel symbol (calls should be symmetric) */ #define symbol_get(x) ({ extern typeof(x) x __attribute__((weak)); &(x); }) #define symbol_put(x) do { } while (0) -- cgit v1.2.3