This patch rebase the implementation of the breakpoints API on top of
perf events instances.
Each breakpoints are now perf events that handle the
register scheduling, thread/cpu attachment, etc..
The new layering is now made as follows:
ptrace kgdb ftrace perf syscall
\ | / /
\ | / /
/
Core breakpoint API /
/
| /
| /
Breakpoints perf events
|
|
Breakpoints PMU ---- Debug Register constraints handling
(Part of core breakpoint API)
|
|
Hardware debug registers
Reasons of this rewrite:
- Use the centralized/optimized pmu registers scheduling,
implying an easier arch integration
- More powerful register handling: perf attributes (pinned/flexible
events, exclusive/non-exclusive, tunable period, etc...)
Impact:
- New perf ABI: the hardware breakpoints counters
- Ptrace breakpoints setting remains tricky and still needs some per
thread breakpoints references.
Todo (in the order):
- Support breakpoints perf counter events for perf tools (ie: implement
perf_bpcounter_event())
- Support from perf tools
Changes in v2:
- Follow the perf "event " rename
- The ptrace regression have been fixed (ptrace breakpoint perf events
weren't released when a task ended)
- Drop the struct hw_breakpoint and store generic fields in
perf_event_attr.
- Separate core and arch specific headers, drop
asm-generic/hw_breakpoint.h and create linux/hw_breakpoint.h
- Use new generic len/type for breakpoint
- Handle off case: when breakpoints api is not supported by an arch
Changes in v3:
- Fix broken CONFIG_KVM, we need to propagate the breakpoint api
changes to kvm when we exit the guest and restore the bp registers
to the host.
Changes in v4:
- Drop the hw_breakpoint_restore() stub as it is only used by KVM
- EXPORT_SYMBOL_GPL hw_breakpoint_restore() as KVM can be built as a
module
- Restore the breakpoints unconditionally on kvm guest exit:
TIF_DEBUG_THREAD doesn't anymore cover every cases of running
breakpoints and vcpu->arch.switch_db_regs might not always be
set when the guest used debug registers.
(Waiting for a reliable optimization)
Changes in v5:
- Split-up the asm-generic/hw-breakpoint.h moving to
linux/hw_breakpoint.h into a separate patch
- Optimize the breakpoints restoring while switching from kvm guest
to host. We only want to restore the state if we have active
breakpoints to the host, otherwise we don't care about messed-up
address registers.
- Add asm/hw_breakpoint.h to Kbuild
- Fix bad breakpoint type in trace_selftest.c
Changes in v6:
- Fix wrong header inclusion in trace.h (triggered a build
error with CONFIG_FTRACE_SELFTEST
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jan Kiszka <jan.kiszka@web.de>
Cc: Jiri Slaby <jirislaby@gmail.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Paul Mundt <lethal@linux-sh.org>
The compiler warns us about:
kernel/trace/trace_ksym.c: In function ksym_hbp_handler:
kernel/trace/trace_ksym.c:92: attention : passing argument 1 of trace_buffer_lock_reserve from incompatible pointer type
kernel/trace/trace_ksym.c:106: attention : passing argument 1 of trace_buffer_unlock_commit from incompatible pointer type
Commit "e77405ad" (tracing: pass around ring buffer
instead of tracer) has changed the central tracing
APIs. And this change has updated every callsites of
these APIs except those that aren't in tracing/core,
such as the ksym tracer.
Cc: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
It's rather boring to clear symbol one by one in ksym_trace_filter
file, so, this patch will let ksym_trace_filter file support quickly
clear all break points. We can write "0" to this file and it will clear
all symbols
for example:
# cat ksym_trace_filter
ksym_filter_head:rw-
global_trace:rw-
# echo 0 > ksym_trace_filter
# cat ksym_trace_filter
#
Changelog v1->v2:
Add other ways to clear all breakpoints by writing NULL or "*:---"
to ksym_trace_filter file base on K.Prasad's suggestion
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
LKML-Reference: <4A67E092.3080202@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This patch fix 2 bugs:
- fix the return value of ksym_trace_filter_write() when we want to
clear symbol in ksym_trace_filter file
for example:
# echo global_trace:rw- > /debug/tracing/ksym_trace_filter
# echo global_trace:--- > /debug/tracing/ksym_trace_filter
-bash: echo: write error: Invalid argument
# cat /debug/tracing/ksym_trace_filter
#
We want to clear 'global_trace' in ksym_trace_filter, it complain
with "Invalid argument", but the operation is successful
- the "r--" access types is not allowed, but ksym_trace_filter file think
it OK
for example:
# echo ksym_tracer_mutex:r-- > ksym_trace_filter
-bash: echo: write error: Resource temporarily unavailable
# dmesg
ksym_tracer request failed. Try again later!!
The error occur at register_kernel_hw_breakpoint(), but It's should
at access types parser
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
LKML-Reference: <4A66863D.5090802@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
When access type is changed, the hw break point will be
unregistered and then be registered again with new access
type. But the registration may fail, in this case, -errno
should be returned.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "K.Prasad" <prasad@linux.vnet.ibm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A52E314.7070004@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Make sure the user input string is NULL-terminated.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "K.Prasad" <prasad@linux.vnet.ibm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A52E300.7020601@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Reading ksym_trace_filter gave me some arbitrary characters,
when it should show nothing. It's because buf is not initialized
when there's no filter.
Also reduce stack usage by about 512 bytes.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "K.Prasad" <prasad@linux.vnet.ibm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A52E2B4.6030706@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
struct trace_ksym is used as an entry in hbp list, and is also
used as trace_entry stored in ring buffer.
This is not necessary and is a waste of memory in ring buffer.
There is also a bug that dereferencing field->ksym_hbp in
ksym_trace_output() can be invalid.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "K.Prasad" <prasad@linux.vnet.ibm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A52E2A4.4050007@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
ksym_tracer_mutex is declared inside an #ifdef CONFIG_PROFILE_KSYM_TRACER
section. This makes it unavailable for the hardware breakpoint tracer if it is
configured without the breakpoint profiler.
This patch fixes the following build error:
kernel/trace/trace_ksym.c: In function ‘ksym_trace_filter_read’:
kernel/trace/trace_ksym.c:226: erreur: ‘ksym_tracer_mutex’ undeclared (first use in this function)
kernel/trace/trace_ksym.c:226: erreur: (Each undeclared identifier is reported only once
kernel/trace/trace_ksym.c:226: erreur: for each function it appears in.)
kernel/trace/trace_ksym.c: In function ‘ksym_trace_filter_write’:
kernel/trace/trace_ksym.c:273: erreur: ‘ksym_tracer_mutex’ undeclared (first use in this function)
kernel/trace/trace_ksym.c: In function ‘ksym_trace_reset’:
kernel/trace/trace_ksym.c:335: erreur: ‘ksym_tracer_mutex’ undeclared (first use in this function)
make[1]: *** [kernel/trace/trace_ksym.o] Erreur 1
[ Impact: fix a build error ]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This patch adds an ftrace plugin to detect and profile memory access over kernel
variables. It uses HW Breakpoint interfaces to 'watch memory addresses.
Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Frederic Weisbecker