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authorBeau Belgrave <beaub@linux.microsoft.com>2024-02-22 03:18:05 +0300
committerSteven Rostedt (Google) <rostedt@goodmis.org>2024-03-18 17:13:03 +0300
commit64805e4039f1687b9857034123a9ec10bb9abddd (patch)
treeddef503d796b1b14c4b61d10278b054249472e5a /include/uapi
parent1e953de9e9b4ca77a9ce0fc17a0778eba3a4ca64 (diff)
downloadlinux-64805e4039f1687b9857034123a9ec10bb9abddd.tar.xz
tracing/user_events: Introduce multi-format events
Currently user_events supports 1 event with the same name and must have the exact same format when referenced by multiple programs. This opens an opportunity for malicious or poorly thought through programs to create events that others use with different formats. Another scenario is user programs wishing to use the same event name but add more fields later when the software updates. Various versions of a program may be running side-by-side, which is prevented by the current single format requirement. Add a new register flag (USER_EVENT_REG_MULTI_FORMAT) which indicates the user program wishes to use the same user_event name, but may have several different formats of the event. When this flag is used, create the underlying tracepoint backing the user_event with a unique name per-version of the format. It's important that existing ABI users do not get this logic automatically, even if one of the multi format events matches the format. This ensures existing programs that create events and assume the tracepoint name will match exactly continue to work as expected. Add logic to only check multi-format events with other multi-format events and single-format events to only check single-format events during find. Change system name of the multi-format event tracepoint to ensure that multi-format events are isolated completely from single-format events. This prevents single-format names from conflicting with multi-format events if they end with the same suffix as the multi-format events. Add a register_name (reg_name) to the user_event struct which allows for split naming of events. We now have the name that was used to register within user_events as well as the unique name for the tracepoint. Upon registering events ensure matches based on first the reg_name, followed by the fields and format of the event. This allows for multiple events with the same registered name to have different formats. The underlying tracepoint will have a unique name in the format of {reg_name}.{unique_id}. For example, if both "test u32 value" and "test u64 value" are used with the USER_EVENT_REG_MULTI_FORMAT the system would have 2 unique tracepoints. The dynamic_events file would then show the following: u:test u64 count u:test u32 count The actual tracepoint names look like this: test.0 test.1 Both would be under the new user_events_multi system name to prevent the older ABI from being used to squat on multi-formatted events and block their use. Deleting events via "!u:test u64 count" would only delete the first tracepoint that matched that format. When the delete ABI is used all events with the same name will be attempted to be deleted. If per-version deletion is required, user programs should either not use persistent events or delete them via dynamic_events. Link: https://lore.kernel.org/linux-trace-kernel/20240222001807.1463-3-beaub@linux.microsoft.com Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'include/uapi')
-rw-r--r--include/uapi/linux/user_events.h6
1 files changed, 5 insertions, 1 deletions
diff --git a/include/uapi/linux/user_events.h b/include/uapi/linux/user_events.h
index f74f3aedd49c..a03de03dccbc 100644
--- a/include/uapi/linux/user_events.h
+++ b/include/uapi/linux/user_events.h
@@ -12,6 +12,7 @@
#include <linux/ioctl.h>
#define USER_EVENTS_SYSTEM "user_events"
+#define USER_EVENTS_MULTI_SYSTEM "user_events_multi"
#define USER_EVENTS_PREFIX "u:"
/* Create dynamic location entry within a 32-bit value */
@@ -22,8 +23,11 @@ enum user_reg_flag {
/* Event will not delete upon last reference closing */
USER_EVENT_REG_PERSIST = 1U << 0,
+ /* Event will be allowed to have multiple formats */
+ USER_EVENT_REG_MULTI_FORMAT = 1U << 1,
+
/* This value or above is currently non-ABI */
- USER_EVENT_REG_MAX = 1U << 1,
+ USER_EVENT_REG_MAX = 1U << 2,
};
/*