[ktap] [PATCH 2/4] symbol: add helpers for sdt probes.
- From: Azat Khuzhin <a3at.mail@xxxxxxxxx>
- To: ktap@xxxxxxxxxxxxx
- Date: Sat, 9 Nov 2013 23:44:02 +0400
Next helpers was added:
- search_stapsdt_note()
- sdt_note_data()
- sdt_note_name()
- sdt_note_addr()
Based on this patch set: https://lkml.org/lkml/2013/10/23/10
Signed-off-by: Azat Khuzhin <a3at.mail@xxxxxxxxx>
---
userspace/symbol.c | 108 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 108 insertions(+)
diff --git a/userspace/symbol.c b/userspace/symbol.c
index dfbc40d..b7f677c 100644
--- a/userspace/symbol.c
+++ b/userspace/symbol.c
@@ -114,6 +114,114 @@ static vaddr_t search_symbol(Elf *elf, const char *symbol)
return 0;
}
+#define SDT_NOTE_TYPE 3
+#define SDT_NOTE_COUNT 3
+#define SDT_NOTE_SCN ".note.stapsdt"
+#define SDT_NOTE_NAME "stapsdt"
+
+static vaddr_t sdt_note_addr(Elf *elf, const char *data, size_t len, int type)
+{
+ vaddr_t vaddr;
+
+ /*
+ * dst and src are required for translation from file to memory
+ * representation
+ */
+ Elf_Data dst = {
+ .d_buf = &vaddr, .d_type = ELF_T_ADDR, .d_version = EV_CURRENT,
+ .d_size = gelf_fsize(elf, ELF_T_ADDR, SDT_NOTE_COUNT,
EV_CURRENT),
+ .d_off = 0, .d_align = 0
+ };
+
+ Elf_Data src = {
+ .d_buf = (void *) data, .d_type = ELF_T_ADDR,
+ .d_version = EV_CURRENT, .d_size = dst.d_size, .d_off = 0,
+ .d_align = 0
+ };
+
+ /* Check the type of each of the notes */
+ if (type != SDT_NOTE_TYPE)
+ return 0;
+
+ if (len < dst.d_size + SDT_NOTE_COUNT)
+ return 0;
+
+ /* Translation from file representation to memory representation */
+ if (gelf_xlatetom(elf, &dst, &src,
+ elf_getident(elf, NULL)[EI_DATA]) == NULL)
+ return 0; /* TODO */
+
+ return vaddr;
+}
+
+static const char *sdt_note_name(Elf *elf, GElf_Nhdr *nhdr, const char *data)
+{
+ const char *provider = data + gelf_fsize(elf,
+ ELF_T_ADDR, SDT_NOTE_COUNT, EV_CURRENT);
+ const char *name = (const char *)memchr(provider, '\0',
+ data + nhdr->n_descsz - provider);
+
+ if (name++ == NULL)
+ return NULL;
+
+ return name;
+}
+
+static const char *sdt_note_data(const Elf_Data *data, size_t off)
+{
+ return ((data->d_buf) + off);
+}
+
+static vaddr_t search_stapsdt_note(Elf *elf, const char *note)
+{
+ GElf_Ehdr ehdr;
+ Elf_Scn *scn = NULL;
+ Elf_Data *data;
+ GElf_Shdr shdr;
+ size_t shstrndx;
+ size_t next;
+ GElf_Nhdr nhdr;
+ size_t name_off, desc_off, offset;
+ vaddr_t vaddr = 0;
+
+ if (gelf_getehdr(elf, &ehdr) == NULL)
+ return 0;
+ if (elf_getshdrstrndx(elf, &shstrndx) != 0)
+ return 0;
+
+ /*
+ * Look for section type = SHT_NOTE, flags = no SHF_ALLOC
+ * and name = .note.stapsdt
+ */
+ scn = elf_section_by_name(elf, &ehdr, &shdr, SDT_NOTE_SCN);
+ if (!scn)
+ return 0;
+ if (!(shdr.sh_type == SHT_NOTE) || (shdr.sh_flags & SHF_ALLOC))
+ return 0;
+
+ data = elf_getdata(scn, NULL);
+
+ for (offset = 0;
+ (next = gelf_getnote(data, offset, &nhdr, &name_off,
&desc_off)) > 0;
+ offset = next) {
+ const char *name;
+
+ if (nhdr.n_namesz != sizeof(SDT_NOTE_NAME) ||
+ memcmp(data->d_buf + name_off, SDT_NOTE_NAME,
+ sizeof(SDT_NOTE_NAME)))
+ continue;
+
+ name = sdt_note_name(elf, &nhdr, sdt_note_data(data, desc_off));
+ if (!name || strcmp(name, note))
+ continue;
+
+ vaddr = sdt_note_addr(elf, sdt_note_data(data, desc_off),
+ nhdr.n_descsz, nhdr.n_type);
+ }
+
+ return vaddr;
+}
+
vaddr_t find_symbol(const char *exec, const char *symbol)
{
vaddr_t vaddr = 0;
--
1.8.4.rc3
Other related posts:
- » [ktap] [PATCH 2/4] symbol: add helpers for sdt probes. - Azat Khuzhin
