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author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-18 21:51:00 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-18 21:51:00 +0300 |
commit | 818e95c768c6607a1df4cf022c00c3c58e2f203e (patch) | |
tree | 453a2b891097c379f1f133f4821a46628d86002b /Documentation | |
parent | d4df33b0e9925c158b313a586fb1557cf29cfdf4 (diff) | |
parent | 0aeb1def44169cbe7119f26cf10b974a2046142e (diff) | |
download | linux-818e95c768c6607a1df4cf022c00c3c58e2f203e.tar.xz |
Merge tag 'trace-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing updates from Steven Rostedt:
"The main changes in this release include:
- Add user space specific memory reading for kprobes
- Allow kprobes to be executed earlier in boot
The rest are mostly just various clean ups and small fixes"
* tag 'trace-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (33 commits)
tracing: Make trace_get_fields() global
tracing: Let filter_assign_type() detect FILTER_PTR_STRING
tracing: Pass type into tracing_generic_entry_update()
ftrace/selftest: Test if set_event/ftrace_pid exists before writing
ftrace/selftests: Return the skip code when tracing directory not configured in kernel
tracing/kprobe: Check registered state using kprobe
tracing/probe: Add trace_event_call accesses APIs
tracing/probe: Add probe event name and group name accesses APIs
tracing/probe: Add trace flag access APIs for trace_probe
tracing/probe: Add trace_event_file access APIs for trace_probe
tracing/probe: Add trace_event_call register API for trace_probe
tracing/probe: Add trace_probe init and free functions
tracing/uprobe: Set print format when parsing command
tracing/kprobe: Set print format right after parsed command
kprobes: Fix to init kprobes in subsys_initcall
tracepoint: Use struct_size() in kmalloc()
ring-buffer: Remove HAVE_64BIT_ALIGNED_ACCESS
ftrace: Enable trampoline when rec count returns back to one
tracing/kprobe: Do not run kprobe boot tests if kprobe_event is on cmdline
tracing: Make a separate config for trace event self tests
...
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 13 | ||||
-rw-r--r-- | Documentation/trace/kprobetrace.rst | 42 | ||||
-rw-r--r-- | Documentation/trace/uprobetracer.rst | 10 |
3 files changed, 58 insertions, 7 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a5f4004e8705..f0461456d910 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2011,6 +2011,19 @@ Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, the default is off. + kprobe_event=[probe-list] + [FTRACE] Add kprobe events and enable at boot time. + The probe-list is a semicolon delimited list of probe + definitions. Each definition is same as kprobe_events + interface, but the parameters are comma delimited. + For example, to add a kprobe event on vfs_read with + arg1 and arg2, add to the command line; + + kprobe_event=p,vfs_read,$arg1,$arg2 + + See also Documentation/trace/kprobetrace.rst "Kernel + Boot Parameter" section. + kpti= [ARM64] Control page table isolation of user and kernel address spaces. Default: enabled on cores which need mitigation. diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst index 7d2b0178d3f3..fbb314bfa112 100644 --- a/Documentation/trace/kprobetrace.rst +++ b/Documentation/trace/kprobetrace.rst @@ -51,15 +51,17 @@ Synopsis of kprobe_events $argN : Fetch the Nth function argument. (N >= 1) (\*1) $retval : Fetch return value.(\*2) $comm : Fetch current task comm. - +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(\*3) + +|-[u]OFFS(FETCHARG) : Fetch memory at FETCHARG +|- OFFS address.(\*3)(\*4) NAME=FETCHARG : Set NAME as the argument name of FETCHARG. FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types - (x8/x16/x32/x64), "string" and bitfield are supported. + (x8/x16/x32/x64), "string", "ustring" and bitfield + are supported. (\*1) only for the probe on function entry (offs == 0). (\*2) only for return probe. (\*3) this is useful for fetching a field of data structures. + (\*4) "u" means user-space dereference. See :ref:`user_mem_access`. Types ----- @@ -77,7 +79,8 @@ apply it to registers/stack-entries etc. (for example, '$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. +See :ref:`user_mem_access` for more info.. The string array type is a bit different from other types. For other base types, <base-type>[1] is equal to <base-type> (e.g. +0(%di):x32[1] is same as +0(%di):x32.) But string[1] is not equal to string. The string type itself @@ -92,6 +95,25 @@ Symbol type('symbol') is an alias of u32 or u64 type (depends on BITS_PER_LONG) which shows given pointer in "symbol+offset" style. For $comm, the default type is "string"; any other type is invalid. +.. _user_mem_access: +User Memory Access +------------------ +Kprobe events supports user-space memory access. For that purpose, you can use +either user-space dereference syntax or 'ustring' type. + +The user-space dereference syntax allows you to access a field of a data +structure in user-space. This is done by adding the "u" prefix to the +dereference syntax. For example, +u4(%si) means it will read memory from the +address in the register %si offset by 4, and the memory is expected to be in +user-space. You can use this for strings too, e.g. +u0(%si):string will read +a string from the address in the register %si that is expected to be in user- +space. 'ustring' is a shortcut way of performing the same task. That is, ++0(%si):ustring is equivalent to +u0(%si):string. + +Note that kprobe-event provides the user-memory access syntax but it doesn't +use it transparently. This means if you use normal dereference or string type +for user memory, it might fail, and may always fail on some archs. The user +has to carefully check if the target data is in kernel or user space. Per-Probe Event Filtering ------------------------- @@ -124,6 +146,20 @@ You can check the total number of probe hits and probe miss-hits via The first column is event name, the second is the number of probe hits, the third is the number of probe miss-hits. +Kernel Boot Parameter +--------------------- +You can add and enable new kprobe events when booting up the kernel by +"kprobe_event=" parameter. The parameter accepts a semicolon-delimited +kprobe events, which format is similar to the kprobe_events. +The difference is that the probe definition parameters are comma-delimited +instead of space. For example, adding myprobe event on do_sys_open like below + + p:myprobe do_sys_open dfd=%ax filename=%dx flags=%cx mode=+4($stack) + +should be below for kernel boot parameter (just replace spaces with comma) + + p:myprobe,do_sys_open,dfd=%ax,filename=%dx,flags=%cx,mode=+4($stack) + Usage examples -------------- diff --git a/Documentation/trace/uprobetracer.rst b/Documentation/trace/uprobetracer.rst index 0b21305fabdc..6e75a6c5a2c8 100644 --- a/Documentation/trace/uprobetracer.rst +++ b/Documentation/trace/uprobetracer.rst @@ -42,16 +42,18 @@ Synopsis of uprobe_tracer @+OFFSET : Fetch memory at OFFSET (OFFSET from same file as PATH) $stackN : Fetch Nth entry of stack (N >= 0) $stack : Fetch stack address. - $retval : Fetch return value.(*) + $retval : Fetch return value.(\*1) $comm : Fetch current task comm. - +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(**) + +|-[u]OFFS(FETCHARG) : Fetch memory at FETCHARG +|- OFFS address.(\*2)(\*3) 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. - (*) only for return probe. - (**) this is useful for fetching a field of data structures. + (\*1) only for return probe. + (\*2) this is useful for fetching a field of data structures. + (\*3) Unlike kprobe event, "u" prefix will just be ignored, becuse uprobe + events can access only user-space memory. Types ----- |