From 53cd885bc5c3ea283cc9c00ca6446c778f00bfba Mon Sep 17 00:00:00 2001 From: Song Liu Date: Tue, 19 Jul 2022 17:21:24 -0700 Subject: ftrace: Allow IPMODIFY and DIRECT ops on the same function IPMODIFY (livepatch) and DIRECT (bpf trampoline) ops are both important users of ftrace. It is necessary to allow them work on the same function at the same time. First, DIRECT ops no longer specify IPMODIFY flag. Instead, DIRECT flag is handled together with IPMODIFY flag in __ftrace_hash_update_ipmodify(). Then, a callback function, ops_func, is added to ftrace_ops. This is used by ftrace core code to understand whether the DIRECT ops can share with an IPMODIFY ops. To share with IPMODIFY ops, the DIRECT ops need to implement the callback function and adjust the direct trampoline accordingly. If DIRECT ops is attached before the IPMODIFY ops, ftrace core code calls ENABLE_SHARE_IPMODIFY_PEER on the DIRECT ops before registering the IPMODIFY ops. If IPMODIFY ops is attached before the DIRECT ops, ftrace core code calls ENABLE_SHARE_IPMODIFY_SELF in __ftrace_hash_update_ipmodify. Owner of the DIRECT ops may return 0 if the DIRECT trampoline can share with IPMODIFY, so error code otherwise. The error code is propagated to register_ftrace_direct_multi so that onwer of the DIRECT trampoline can handle it properly. For more details, please refer to comment before enum ftrace_ops_cmd. Signed-off-by: Song Liu Signed-off-by: Daniel Borkmann Reviewed-by: Steven Rostedt (Google) Link: https://lore.kernel.org/all/20220602193706.2607681-2-song@kernel.org/ Link: https://lore.kernel.org/all/20220718055449.3960512-1-song@kernel.org/ Link: https://lore.kernel.org/bpf/20220720002126.803253-3-song@kernel.org --- include/linux/ftrace.h | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) (limited to 'include') diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index acb35243ce5d..0b61371e287b 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -208,6 +208,43 @@ enum { FTRACE_OPS_FL_DIRECT = BIT(17), }; +/* + * FTRACE_OPS_CMD_* commands allow the ftrace core logic to request changes + * to a ftrace_ops. Note, the requests may fail. + * + * ENABLE_SHARE_IPMODIFY_SELF - enable a DIRECT ops to work on the same + * function as an ops with IPMODIFY. Called + * when the DIRECT ops is being registered. + * This is called with both direct_mutex and + * ftrace_lock are locked. + * + * ENABLE_SHARE_IPMODIFY_PEER - enable a DIRECT ops to work on the same + * function as an ops with IPMODIFY. Called + * when the other ops (the one with IPMODIFY) + * is being registered. + * This is called with direct_mutex locked. + * + * DISABLE_SHARE_IPMODIFY_PEER - disable a DIRECT ops to work on the same + * function as an ops with IPMODIFY. Called + * when the other ops (the one with IPMODIFY) + * is being unregistered. + * This is called with direct_mutex locked. + */ +enum ftrace_ops_cmd { + FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_SELF, + FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER, + FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER, +}; + +/* + * For most ftrace_ops_cmd, + * Returns: + * 0 - Success. + * Negative on failure. The return value is dependent on the + * callback. + */ +typedef int (*ftrace_ops_func_t)(struct ftrace_ops *op, enum ftrace_ops_cmd cmd); + #ifdef CONFIG_DYNAMIC_FTRACE /* The hash used to know what functions callbacks trace */ struct ftrace_ops_hash { @@ -250,6 +287,7 @@ struct ftrace_ops { unsigned long trampoline; unsigned long trampoline_size; struct list_head list; + ftrace_ops_func_t ops_func; #endif }; -- cgit v1.2.3