From 88903c464321cdbc2d473c24cbf311f576cf05bc Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Wed, 15 May 2019 14:38:30 +0900 Subject: tracing/probe: Add ustring type for user-space string Add "ustring" type for fetching user-space string from kprobe event. User can specify ustring type at uprobe event, and it is same as "string" for uprobe. Note that probe-event provides this option but it doesn't choose the correct type automatically since we have not way to decide the address is in user-space or not on some arch (and on some other arch, you can fetch the string by "string" type). So user must carefully check the target code (e.g. if you see __user on the target variable) and use this new type. Link: http://lkml.kernel.org/r/155789871009.26965.14167558859557329331.stgit@devnote2 Acked-by: Ingo Molnar Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware) --- Documentation/trace/kprobetrace.rst | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'Documentation/trace') diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst index 235ce2ab131a..a3ac7c9ac242 100644 --- a/Documentation/trace/kprobetrace.rst +++ b/Documentation/trace/kprobetrace.rst @@ -55,7 +55,8 @@ Synopsis of kprobe_events NAME=FETCHARG : Set NAME as the argument name of FETCHARG. FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types - (x8/x16/x32/x64), "string" and bitfield are supported. + (x8/x16/x32/x64), "string", "ustring" and bitfield + are supported. (\*1) only for the probe on function entry (offs == 0). (\*2) only for return probe. @@ -77,7 +78,11 @@ apply it to registers/stack-entries etc. (for example, '$stack1:x8[8]' is wrong, but '+8($stack):x8[8]' is OK.) String type is a special type, which fetches a "null-terminated" string from kernel space. This means it will fail and store NULL if the string container -has been paged out. +has been paged out. "ustring" type is an alternative of string for user-space. +Note that kprobe-event provides string/ustring types, but doesn't change it +automatically. So user has to decide if the targe string in kernel or in user +space carefully. On some arch, if you choose wrong one, it always fails to +record string data. The string array type is a bit different from other types. For other base types, [1] is equal to (e.g. +0(%di):x32[1] is same as +0(%di):x32.) But string[1] is not equal to string. The string type itself -- cgit v1.2.3