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Diffstat (limited to 'tools/lib/bpf/usdt.c')
-rw-r--r--tools/lib/bpf/usdt.c123
1 files changed, 63 insertions, 60 deletions
diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
index f1c9339cfbbc..5159207cbfd9 100644
--- a/tools/lib/bpf/usdt.c
+++ b/tools/lib/bpf/usdt.c
@@ -441,7 +441,7 @@ static int parse_elf_segs(Elf *elf, const char *path, struct elf_seg **segs, siz
return 0;
}
-static int parse_lib_segs(int pid, const char *lib_path, struct elf_seg **segs, size_t *seg_cnt)
+static int parse_vma_segs(int pid, const char *lib_path, struct elf_seg **segs, size_t *seg_cnt)
{
char path[PATH_MAX], line[PATH_MAX], mode[16];
size_t seg_start, seg_end, seg_off;
@@ -531,35 +531,40 @@ err_out:
return err;
}
-static struct elf_seg *find_elf_seg(struct elf_seg *segs, size_t seg_cnt, long addr, bool relative)
+static struct elf_seg *find_elf_seg(struct elf_seg *segs, size_t seg_cnt, long virtaddr)
{
struct elf_seg *seg;
int i;
- if (relative) {
- /* for shared libraries, address is relative offset and thus
- * should be fall within logical offset-based range of
- * [offset_start, offset_end)
- */
- for (i = 0, seg = segs; i < seg_cnt; i++, seg++) {
- if (seg->offset <= addr && addr < seg->offset + (seg->end - seg->start))
- return seg;
- }
- } else {
- /* for binaries, address is absolute and thus should be within
- * absolute address range of [seg_start, seg_end)
- */
- for (i = 0, seg = segs; i < seg_cnt; i++, seg++) {
- if (seg->start <= addr && addr < seg->end)
- return seg;
- }
+ /* for ELF binaries (both executables and shared libraries), we are
+ * given virtual address (absolute for executables, relative for
+ * libraries) which should match address range of [seg_start, seg_end)
+ */
+ for (i = 0, seg = segs; i < seg_cnt; i++, seg++) {
+ if (seg->start <= virtaddr && virtaddr < seg->end)
+ return seg;
}
+ return NULL;
+}
+static struct elf_seg *find_vma_seg(struct elf_seg *segs, size_t seg_cnt, long offset)
+{
+ struct elf_seg *seg;
+ int i;
+
+ /* for VMA segments from /proc/<pid>/maps file, provided "address" is
+ * actually a file offset, so should be fall within logical
+ * offset-based range of [offset_start, offset_end)
+ */
+ for (i = 0, seg = segs; i < seg_cnt; i++, seg++) {
+ if (seg->offset <= offset && offset < seg->offset + (seg->end - seg->start))
+ return seg;
+ }
return NULL;
}
-static int parse_usdt_note(Elf *elf, const char *path, long base_addr,
- GElf_Nhdr *nhdr, const char *data, size_t name_off, size_t desc_off,
+static int parse_usdt_note(Elf *elf, const char *path, GElf_Nhdr *nhdr,
+ const char *data, size_t name_off, size_t desc_off,
struct usdt_note *usdt_note);
static int parse_usdt_spec(struct usdt_spec *spec, const struct usdt_note *note, __u64 usdt_cookie);
@@ -568,8 +573,8 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *
const char *usdt_provider, const char *usdt_name, __u64 usdt_cookie,
struct usdt_target **out_targets, size_t *out_target_cnt)
{
- size_t off, name_off, desc_off, seg_cnt = 0, lib_seg_cnt = 0, target_cnt = 0;
- struct elf_seg *segs = NULL, *lib_segs = NULL;
+ size_t off, name_off, desc_off, seg_cnt = 0, vma_seg_cnt = 0, target_cnt = 0;
+ struct elf_seg *segs = NULL, *vma_segs = NULL;
struct usdt_target *targets = NULL, *target;
long base_addr = 0;
Elf_Scn *notes_scn, *base_scn;
@@ -613,8 +618,7 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *
struct elf_seg *seg = NULL;
void *tmp;
- err = parse_usdt_note(elf, path, base_addr, &nhdr,
- data->d_buf, name_off, desc_off, &note);
+ err = parse_usdt_note(elf, path, &nhdr, data->d_buf, name_off, desc_off, &note);
if (err)
goto err_out;
@@ -654,30 +658,29 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *
usdt_rel_ip += base_addr - note.base_addr;
}
- if (ehdr.e_type == ET_EXEC) {
- /* When attaching uprobes (which what USDTs basically
- * are) kernel expects a relative IP to be specified,
- * so if we are attaching to an executable ELF binary
- * (i.e., not a shared library), we need to calculate
- * proper relative IP based on ELF's load address
- */
- seg = find_elf_seg(segs, seg_cnt, usdt_abs_ip, false /* relative */);
- if (!seg) {
- err = -ESRCH;
- pr_warn("usdt: failed to find ELF program segment for '%s:%s' in '%s' at IP 0x%lx\n",
- usdt_provider, usdt_name, path, usdt_abs_ip);
- goto err_out;
- }
- if (!seg->is_exec) {
- err = -ESRCH;
- pr_warn("usdt: matched ELF binary '%s' segment [0x%lx, 0x%lx) for '%s:%s' at IP 0x%lx is not executable\n",
- path, seg->start, seg->end, usdt_provider, usdt_name,
- usdt_abs_ip);
- goto err_out;
- }
+ /* When attaching uprobes (which is what USDTs basically are)
+ * kernel expects file offset to be specified, not a relative
+ * virtual address, so we need to translate virtual address to
+ * file offset, for both ET_EXEC and ET_DYN binaries.
+ */
+ seg = find_elf_seg(segs, seg_cnt, usdt_abs_ip);
+ if (!seg) {
+ err = -ESRCH;
+ pr_warn("usdt: failed to find ELF program segment for '%s:%s' in '%s' at IP 0x%lx\n",
+ usdt_provider, usdt_name, path, usdt_abs_ip);
+ goto err_out;
+ }
+ if (!seg->is_exec) {
+ err = -ESRCH;
+ pr_warn("usdt: matched ELF binary '%s' segment [0x%lx, 0x%lx) for '%s:%s' at IP 0x%lx is not executable\n",
+ path, seg->start, seg->end, usdt_provider, usdt_name,
+ usdt_abs_ip);
+ goto err_out;
+ }
+ /* translate from virtual address to file offset */
+ usdt_rel_ip = usdt_abs_ip - seg->start + seg->offset;
- usdt_rel_ip = usdt_abs_ip - (seg->start - seg->offset);
- } else if (!man->has_bpf_cookie) { /* ehdr.e_type == ET_DYN */
+ if (ehdr.e_type == ET_DYN && !man->has_bpf_cookie) {
/* If we don't have BPF cookie support but need to
* attach to a shared library, we'll need to know and
* record absolute addresses of attach points due to
@@ -697,9 +700,9 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *
goto err_out;
}
- /* lib_segs are lazily initialized only if necessary */
- if (lib_seg_cnt == 0) {
- err = parse_lib_segs(pid, path, &lib_segs, &lib_seg_cnt);
+ /* vma_segs are lazily initialized only if necessary */
+ if (vma_seg_cnt == 0) {
+ err = parse_vma_segs(pid, path, &vma_segs, &vma_seg_cnt);
if (err) {
pr_warn("usdt: failed to get memory segments in PID %d for shared library '%s': %d\n",
pid, path, err);
@@ -707,7 +710,7 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *
}
}
- seg = find_elf_seg(lib_segs, lib_seg_cnt, usdt_rel_ip, true /* relative */);
+ seg = find_vma_seg(vma_segs, vma_seg_cnt, usdt_rel_ip);
if (!seg) {
err = -ESRCH;
pr_warn("usdt: failed to find shared lib memory segment for '%s:%s' in '%s' at relative IP 0x%lx\n",
@@ -715,7 +718,7 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *
goto err_out;
}
- usdt_abs_ip = seg->start + (usdt_rel_ip - seg->offset);
+ usdt_abs_ip = seg->start - seg->offset + usdt_rel_ip;
}
pr_debug("usdt: probe for '%s:%s' in %s '%s': addr 0x%lx base 0x%lx (resolved abs_ip 0x%lx rel_ip 0x%lx) args '%s' in segment [0x%lx, 0x%lx) at offset 0x%lx\n",
@@ -723,7 +726,7 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *
note.loc_addr, note.base_addr, usdt_abs_ip, usdt_rel_ip, note.args,
seg ? seg->start : 0, seg ? seg->end : 0, seg ? seg->offset : 0);
- /* Adjust semaphore address to be a relative offset */
+ /* Adjust semaphore address to be a file offset */
if (note.sema_addr) {
if (!man->has_sema_refcnt) {
pr_warn("usdt: kernel doesn't support USDT semaphore refcounting for '%s:%s' in '%s'\n",
@@ -732,7 +735,7 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *
goto err_out;
}
- seg = find_elf_seg(segs, seg_cnt, note.sema_addr, false /* relative */);
+ seg = find_elf_seg(segs, seg_cnt, note.sema_addr);
if (!seg) {
err = -ESRCH;
pr_warn("usdt: failed to find ELF loadable segment with semaphore of '%s:%s' in '%s' at 0x%lx\n",
@@ -747,7 +750,7 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *
goto err_out;
}
- usdt_sema_off = note.sema_addr - (seg->start - seg->offset);
+ usdt_sema_off = note.sema_addr - seg->start + seg->offset;
pr_debug("usdt: sema for '%s:%s' in %s '%s': addr 0x%lx base 0x%lx (resolved 0x%lx) in segment [0x%lx, 0x%lx] at offset 0x%lx\n",
usdt_provider, usdt_name, ehdr.e_type == ET_EXEC ? "exec" : "lib ",
@@ -770,7 +773,7 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *
target->rel_ip = usdt_rel_ip;
target->sema_off = usdt_sema_off;
- /* notes->args references strings from Elf itself, so they can
+ /* notes.args references strings from Elf itself, so they can
* be referenced safely until elf_end() call
*/
target->spec_str = note.args;
@@ -788,7 +791,7 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *
err_out:
free(segs);
- free(lib_segs);
+ free(vma_segs);
if (err < 0)
free(targets);
return err;
@@ -1089,8 +1092,8 @@ err_out:
/* Parse out USDT ELF note from '.note.stapsdt' section.
* Logic inspired by perf's code.
*/
-static int parse_usdt_note(Elf *elf, const char *path, long base_addr,
- GElf_Nhdr *nhdr, const char *data, size_t name_off, size_t desc_off,
+static int parse_usdt_note(Elf *elf, const char *path, GElf_Nhdr *nhdr,
+ const char *data, size_t name_off, size_t desc_off,
struct usdt_note *note)
{
const char *provider, *name, *args;
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