kernel/tools/perf/util/probe-finder.c, branch linux-4.3.y

perf probe: Support probing at absolute address

2015-08-26T13:41:12Z

It should be useful to allow 'perf probe' probe at absolute offset of a target. For example, when (u)probing at a instruction of a shared object in a embedded system where debuginfo is not avaliable but we know the offset of that instruction by manually digging. This patch enables following perf probe command syntax: # perf probe 0xffffffff811e6615 And # perf probe /lib/x86_64-linux-gnu/libc-2.19.so 0xeb860 In the above example, we don't need a anchor symbol, so it is possible to compute absolute addresses using other methods and then use 'perf probe' to create the probing points. v1 -> v2: Drop the leading '+' in cmdline; Allow uprobing at offset 0x0; Improve 'perf probe -l' result when uprobe at area without debuginfo. v2 -> v3: Split bugfix to a separated patch. Test result: # perf probe 0xffffffff8119d175 %ax # perf probe sys_write %ax # perf probe /lib64/libc-2.18.so 0x0 %ax # perf probe /lib64/libc-2.18.so 0x5 %ax # perf probe /lib64/libc-2.18.so 0xd8e40 %ax # perf probe /lib64/libc-2.18.so __write %ax # perf probe /lib64/libc-2.18.so 0xd8e49 %ax # cat /sys/kernel/debug/tracing/uprobe_events p:probe_libc/abs_0 /lib64/libc-2.18.so:0x (null) arg1=%ax p:probe_libc/abs_5 /lib64/libc-2.18.so:0x0000000000000005 arg1=%ax p:probe_libc/abs_d8e40 /lib64/libc-2.18.so:0x00000000000d8e40 arg1=%ax p:probe_libc/__write /lib64/libc-2.18.so:0x00000000000d8e40 arg1=%ax p:probe_libc/abs_d8e49 /lib64/libc-2.18.so:0x00000000000d8e49 arg1=%ax # cat /sys/kernel/debug/tracing/kprobe_events p:probe/abs_ffffffff8119d175 0xffffffff8119d175 arg1=%ax p:probe/sys_write _text+1692016 arg1=%ax # perf probe -l Failed to find debug information for address 5 probe:abs_ffffffff8119d175 (on sys_write+5 with arg1) probe:sys_write (on sys_write with arg1) probe_libc:__write (on @unix/syscall-template.S:81 in /lib64/libc-2.18.so with arg1) probe_libc:abs_0 (on 0x0 in /lib64/libc-2.18.so with arg1) probe_libc:abs_5 (on 0x5 in /lib64/libc-2.18.so with arg1) probe_libc:abs_d8e40 (on @unix/syscall-template.S:81 in /lib64/libc-2.18.so with arg1) probe_libc:abs_d8e49 (on __GI___libc_write+9 in /lib64/libc-2.18.so with arg1) Signed-off-by: Wang Nan Acked-by: Masami Hiramatsu Cc: Namhyung Kim Cc: Steven Rostedt Cc: Zefan Li Cc: pi3orama@163.com Link: http://lkml.kernel.org/r/1440586666-235233-7-git-send-email-wangnan0@huawei.com Signed-off-by: Arnaldo Carvalho de Melo

perf strlist: Make dupstr be the default and part of an extensible config parm

2015-07-20T15:13:34Z

So that we can pass more info to strlist__new() without having to change its function signature, just adding entries to the strlist_config struct with sensible defaults for when those fields are not specified. Cc: Adrian Hunter Cc: Borislav Petkov Cc: David Ahern Cc: Frederic Weisbecker Cc: Jiri Olsa Cc: Namhyung Kim Cc: Stephane Eranian Link: http://lkml.kernel.org/n/tip-5uaaler4931i0s9sedxjquhq@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Reference count struct dso

2015-06-08T13:31:40Z

This has a different model than the 'thread' and 'map' struct lifetimes: there is not a definitive "don't use this DSO anymore" event, i.e. we may get many 'struct map' holding references to the '/usr/lib64/libc-2.20.so' DSO but then at some point some DSO may have no references but we still don't want to straight away release its resources, because "soon" we may get a new 'struct map' that needs it and we want to reuse its symtab or other resources. So we need some way to garbage collect it when crossing some memory usage threshold, which is left for anoter patch, for now it is sufficient to release it when calling dsos__exit(), i.e. when deleting the whole list as part of deleting the 'struct machine' containing it, which will leave only referenced objects being used. Cc: Adrian Hunter Cc: David Ahern Cc: Jiri Olsa Cc: Namhyung Kim Link: http://lkml.kernel.org/n/tip-majzgz07cm90t2tejrjy4clf@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf probe: Ignore tail calls to probed functions

2015-05-14T13:05:09Z

perf probe currently errors out if there are any tail calls to probed functions: [root@rhel71be]# perf probe do_fork Failed to find probe point in any functions. Error: Failed to add events. Fix this by teaching perf to ignore tail calls. Without patch: [root@rhel71be perf]# ./perf probe -v do_fork probe-definition(0): do_fork symbol:do_fork file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Looking at the vmlinux_path (7 entries long) symsrc__init: build id mismatch for /boot/vmlinux. Using /usr/lib/debug/lib/modules/3.10.0-201.el7.ppc64/vmlinux for symbols Open Debuginfo file: /usr/lib/debug/lib/modules/3.10.0-201.el7.ppc64/vmlinux Try to find probe point from debuginfo. found inline addr: 0xc0000000000bb9b0 Probe point found: do_fork+0 found inline addr: 0xc0000000000bbe20 Probe point found: kernel_thread+48 found inline addr: 0xc0000000000bbe5c Probe point found: sys_fork+28 found inline addr: 0xc0000000000bbfac Probe point found: sys_vfork+44 found inline addr: 0xc0000000000bc27c Failed to find probe point in any functions. An error occurred in debuginfo analysis (-2). Error: Failed to add events. Reason: No such file or directory (Code: -2) With patch: [root@rhel71be perf]# ./perf probe -v do_fork probe-definition(0): do_fork symbol:do_fork file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Looking at the vmlinux_path (7 entries long) symsrc__init: build id mismatch for /boot/vmlinux. Using /usr/lib/debug/lib/modules/3.10.0-201.el7.ppc64/vmlinux for symbols Open Debuginfo file: /usr/lib/debug/lib/modules/3.10.0-201.el7.ppc64/vmlinux Try to find probe point from debuginfo. found inline addr: 0xc0000000000bb9b0 Probe point found: do_fork+0 found inline addr: 0xc0000000000bbe20 Probe point found: kernel_thread+48 found inline addr: 0xc0000000000bbe5c Probe point found: sys_fork+28 found inline addr: 0xc0000000000bbfac Probe point found: sys_vfork+44 found inline addr: 0xc0000000000bc27c Ignoring tail call from SyS_clone Found 4 probe_trace_events. Opening /sys/kernel/debug/tracing/kprobe_events write=1 No kprobe blacklist support, ignored Added new events: Writing event: p:probe/do_fork _text+768432 Failed to write event: Invalid argument Error: Failed to add events. Reason: Invalid argument (Code: -22) [Ignore the error about failure to write event - this kernel is missing a patch to resolve _text properly] The reason to ignore tail calls is that the address does not belong to any function frame. In the example above, the address in SyS_clone is 0xc0000000000bc27c, but looking at the debug-info: <1><830081>: Abbrev Number: 133 (DW_TAG_subprogram) <830083> DW_AT_external : 1 <830083> DW_AT_name : (indirect string, offset: 0x3cea3): SyS_clone <830087> DW_AT_decl_file : 7 <830088> DW_AT_decl_line : 1689 <83008a> DW_AT_prototyped : 1 <83008a> DW_AT_type : <0x8110eb> <83008e> DW_AT_low_pc : 0xc0000000000bc270 <830096> DW_AT_high_pc : 0xc <83009e> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa) <8300a0> DW_AT_GNU_all_call_sites: 1 <8300a0> DW_AT_sibling : <0x830178> <3><830147>: Abbrev Number: 125 (DW_TAG_GNU_call_site) <830148> DW_AT_low_pc : 0xc0000000000bc27c <830150> DW_AT_GNU_tail_call: 1 <830150> DW_AT_abstract_origin: <0x82e7e1> The frame ends at 0xc0000000000bc27c. I suppose this is why this particular call is a "tail" call. FWIW, systemtap seems to ignore these as well and requires users to explicitly place probes at these call sites if necessary. I print out the caller so that users know. Signed-off-by: Naveen N. Rao Acked-by: Masami Hiramatsu Link: http://lkml.kernel.org/r/1430394151-15928-1-git-send-email-naveen.n.rao@linux.vnet.ibm.com Signed-off-by: Arnaldo Carvalho de Melo

perf probe: Show better error message when failed to find variable

2015-05-12T12:59:50Z

Indicate to check variable location range in error message when we got failed to find the variable. Before this patch: $ perf probe --add 'generic_perform_write+118 bytes' Failed to find the location of bytes at this address. Perhaps, it has been optimized out. Error: Failed to add events. After this patch: $ perf probe --add 'generic_perform_write+118 bytes' Failed to find the location of the 'bytes' variable at this address. Perhaps it has been optimized out. Use -V with the --range option to show 'bytes' location range. Error: Failed to add events. Signed-off-by: He Kuang Acked-by: Masami Hiramatsu Cc: Jiri Olsa Cc: Peter Zijlstra Cc: Wang Nan Link: http://lkml.kernel.org/r/1431336304-16863-3-git-send-email-hekuang@huawei.com [ Improve the error message based on lkml thread ] Signed-off-by: Arnaldo Carvalho de Melo

perf probe: Add --range option to show a variable's location range

2015-05-12T12:59:50Z

It is not easy for users to get the accurate byte offset or the line number where a local variable can be probed. With '--range' option, local variables in the scope of the probe point are showed with a byte offset range, and can be added according to this range information. For example, there are some variables in the function generic_perform_write(): 0 ssize_t generic_perform_write(struct file *file, 1 struct iov_iter *i, loff_t pos) 2 { 3 struct address_space *mapping = file->f_mapping; 4 const struct address_space_operations *a_ops = mapping->a_ops; ... 42 status = a_ops->write_begin(file, mapping, pos, bytes, flags, &page, &fsdata); 44 if (unlikely(status < 0)) But we fail when we try to probe the variable 'a_ops' at line 42 or 44. $ perf probe --add 'generic_perform_write:42 a_ops' Failed to find the location of a_ops at this address. Perhaps, it has been optimized out. This is because the source code do not match the assembly, so a variable may not be available in the source code line where it appears. After this patch, we can lookup the accurate byte offset range of a variable, 'INV' indicates that this variable is not valid at the given point, but available in the scope: $ perf probe --vars 'generic_perform_write:42' --range Available variables at generic_perform_write:42 @ [INV] ssize_t written @ [INV] struct address_space_operations* a_ops @ [VAL] (unknown_type) fsdata @ [VAL] loff_t pos @ [VAL] long int status @ [VAL] long unsigned int bytes @ [VAL] struct address_space* mapping @ [VAL] struct iov_iter* i @ [VAL] struct page* page @ Then it is more clear for us to add a probe with this variable: $ perf probe --add 'generic_perform_write+170 a_ops' Added new event: probe:generic_perform_write (on generic_perform_write+170 with a_ops) Signed-off-by: He Kuang Acked-by: Masami Hiramatsu Cc: Jiri Olsa Cc: Peter Zijlstra Cc: Wang Nan Link: http://lkml.kernel.org/r/1431336304-16863-2-git-send-email-hekuang@huawei.com Signed-off-by: Arnaldo Carvalho de Melo

perf probe: Remove length limitation for showing available variables

2015-05-12T12:59:49Z

Use struct strbuf instead of bare char[] to remove the length limitation of variables in variable_list, so they will not disappear due to overlength, and make preparation for adding more description for variables. Signed-off-by: He Kuang Acked-by: Masami Hiramatsu Cc: Jiri Olsa Cc: Peter Zijlstra Cc: Wang Nan Link: http://lkml.kernel.org/r/1431336304-16863-1-git-send-email-hekuang@huawei.com Signed-off-by: Arnaldo Carvalho de Melo

Merge branch 'perf/urgent' into perf/core, to resolve conflicts

2015-05-11T09:56:27Z

Conflicts: tools/perf/builtin-kmem.c Signed-off-by: Ingo Molnar

perf probe: Support glob wildcards for function name

2015-05-08T19:31:02Z

Support glob wildcards for function name when adding new probes. This will allow us to build caches of function-entry level information with $params. e.g. ---- # perf probe --no-inlines --add 'kmalloc* $params' Added new events: probe:kmalloc_slab (on kmalloc* with $params) probe:kmalloc_large_node (on kmalloc* with $params) probe:kmalloc_order_trace (on kmalloc* with $params) You can now use it in all perf tools, such as: perf record -e probe:kmalloc_order_trace -aR sleep 1 # perf probe --list probe:kmalloc_large_node (on kmalloc_large_node@mm/slub.c with size flags node) probe:kmalloc_order_trace (on kmalloc_order_trace@mm/slub.c with size flags order) probe:kmalloc_slab (on kmalloc_slab@mm/slab_common.c with size flags) ---- Signed-off-by: Masami Hiramatsu Tested-by: Arnaldo Carvalho de Melo Cc: Ananth N Mavinakayanahalli Cc: David Ahern Cc: Hemant Kumar Cc: Jiri Olsa Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20150508010335.24812.19972.stgit@localhost.localdomain Signed-off-by: Arnaldo Carvalho de Melo

perf probe: Add --no-inlines option to avoid searching inline functions

2015-05-08T19:26:44Z

Add --no-inlines(--inlines) option to avoid searching inline functions. Searching all functions which matches glob pattern can take a long time and find a lot of inline functions. With this option perf-probe searches target on the non-inlined functions. Signed-off-by: Masami Hiramatsu Cc: Ananth N Mavinakayanahalli Cc: David Ahern Cc: Hemant Kumar Cc: Jiri Olsa Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20150508010333.24812.86568.stgit@localhost.localdomain Signed-off-by: Arnaldo Carvalho de Melo