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authorHemant Kumar <hemant@linux.vnet.ibm.com>2016-07-01 17:03:46 +0900
committerArnaldo Carvalho de Melo <acme@redhat.com>2016-07-04 19:38:59 -0300
commit060fa0c7a3e0bb4f1426ee79dfd38e2a4c80067a (patch)
treef671a7986f7476f435d358d4c60ed610d5576249 /tools/perf/util/symbol.h
parent2492c465ad3ae6860ebfff1c9032865017835e70 (diff)
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perf sdt: ELF support for SDT
This patch serves the initial support to identify and list SDT events in binaries. When programs containing SDT markers are compiled, gcc with the help of assembler directives identifies them and places them in the section ".note.stapsdt". To find these markers from the binaries, one needs to traverse through this section and parse the relevant details like the name, type and location of the marker. Also, the original location could be skewed due to the effect of prelinking. If that is the case, the locations need to be adjusted. The functions in this patch open a given ELF, find out the SDT section, parse the relevant details, adjust the location (if necessary) and populate them in a list. A typical note entry in ".note.stapsdt" section is as follows : |--nhdr.n_namesz--| ------------------------------------ | nhdr | "stapsdt" | ----- |----------------------------------| | | <location> <base_address> | | | <semaphore> | nhdr.n_descsize | "provider_name" "note_name" | | | <args> | ----- |----------------------------------| | nhdr | "stapsdt" | |... The above shows an excerpt from the section ".note.stapsdt". 'nhdr' is a structure which has the note name size (n_namesz), note description size (n_desc_sz) and note type (n_type). So, in order to parse the note note info, we need nhdr to tell us where to start from. As can be seen from <sys/sdt.h>, the name of the SDT notes given is "stapsdt". But this is not the identifier of the note. After that, we go to description of the note to find out its location, the address of the ".stapsdt.base" section and the semaphore address. Then, we find the provider name and the SDT marker name and then follow the arguments. Signed-off-by: Hemant Kumar <hemant@linux.vnet.ibm.com> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Acked-by: Namhyung Kim <namhyung@kernel.org> Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com> Cc: Brendan Gregg <brendan.d.gregg@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/146736022628.27797.1201368329092908163.stgit@devbox Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/util/symbol.h')
-rw-r--r--tools/perf/util/symbol.h22
1 files changed, 22 insertions, 0 deletions
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index b10d558a8803..699f7cbcfe72 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -342,4 +342,26 @@ void arch__sym_update(struct symbol *s, GElf_Sym *sym);
int arch__choose_best_symbol(struct symbol *syma, struct symbol *symb);
+/* structure containing an SDT note's info */
+struct sdt_note {
+ char *name; /* name of the note*/
+ char *provider; /* provider name */
+ bool bit32; /* whether the location is 32 bits? */
+ union { /* location, base and semaphore addrs */
+ Elf64_Addr a64[3];
+ Elf32_Addr a32[3];
+ } addr;
+ struct list_head note_list; /* SDT notes' list */
+};
+
+int get_sdt_note_list(struct list_head *head, const char *target);
+int cleanup_sdt_note_list(struct list_head *sdt_notes);
+int sdt_notes__get_count(struct list_head *start);
+
+#define SDT_BASE_SCN ".stapsdt.base"
+#define SDT_NOTE_SCN ".note.stapsdt"
+#define SDT_NOTE_TYPE 3
+#define SDT_NOTE_NAME "stapsdt"
+#define NR_ADDR 3
+
#endif /* __PERF_SYMBOL */