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-rw-r--r--tools/lib/bpf/usdt.c87
1 files changed, 67 insertions, 20 deletions
diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
index 5f085736c6c4..d1524f6f54ae 100644
--- a/tools/lib/bpf/usdt.c
+++ b/tools/lib/bpf/usdt.c
@@ -20,7 +20,6 @@
#include "libbpf_common.h"
#include "libbpf_internal.h"
#include "hashmap.h"
-#include "str_error.h"
/* libbpf's USDT support consists of BPF-side state/code and user-space
* state/code working together in concert. BPF-side parts are defined in
@@ -59,7 +58,7 @@
*
* STAP_PROBE3(my_usdt_provider, my_usdt_probe_name, 123, x, &y);
*
- * USDT is identified by it's <provider-name>:<probe-name> pair of names. Each
+ * USDT is identified by its <provider-name>:<probe-name> pair of names. Each
* individual USDT has a fixed number of arguments (3 in the above example)
* and specifies values of each argument as if it was a function call.
*
@@ -81,7 +80,7 @@
* NOP instruction that kernel can replace with an interrupt instruction to
* trigger instrumentation code (BPF program for all that we care about).
*
- * Semaphore above is and optional feature. It records an address of a 2-byte
+ * Semaphore above is an optional feature. It records an address of a 2-byte
* refcount variable (normally in '.probes' ELF section) used for signaling if
* there is anything that is attached to USDT. This is useful for user
* applications if, for example, they need to prepare some arguments that are
@@ -121,7 +120,7 @@
* a uprobe BPF program (which for kernel, at least currently, is just a kprobe
* program, so BPF_PROG_TYPE_KPROBE program type). With the only difference
* that uprobe is usually attached at the function entry, while USDT will
- * normally will be somewhere inside the function. But it should always be
+ * normally be somewhere inside the function. But it should always be
* pointing to NOP instruction, which makes such uprobes the fastest uprobe
* kind.
*
@@ -151,7 +150,7 @@
* libbpf sets to spec ID during attach time, or, if kernel is too old to
* support BPF cookie, through IP-to-spec-ID map that libbpf maintains in such
* case. The latter means that some modes of operation can't be supported
- * without BPF cookie. Such mode is attaching to shared library "generically",
+ * without BPF cookie. Such a mode is attaching to shared library "generically",
* without specifying target process. In such case, it's impossible to
* calculate absolute IP addresses for IP-to-spec-ID map, and thus such mode
* is not supported without BPF cookie support.
@@ -185,7 +184,7 @@
* as even if USDT spec string is the same, USDT cookie value can be
* different. It was deemed excessive to try to deduplicate across independent
* USDT attachments by taking into account USDT spec string *and* USDT cookie
- * value, which would complicated spec ID accounting significantly for little
+ * value, which would complicate spec ID accounting significantly for little
* gain.
*/
@@ -200,12 +199,23 @@ enum usdt_arg_type {
USDT_ARG_CONST,
USDT_ARG_REG,
USDT_ARG_REG_DEREF,
+ USDT_ARG_SIB,
};
/* should match exactly struct __bpf_usdt_arg_spec from usdt.bpf.h */
struct usdt_arg_spec {
__u64 val_off;
- enum usdt_arg_type arg_type;
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ enum usdt_arg_type arg_type: 8;
+ __u16 idx_reg_off: 12;
+ __u16 scale_bitshift: 4;
+ __u8 __reserved: 8; /* keep reg_off offset stable */
+#else
+ __u8 __reserved: 8; /* keep reg_off offset stable */
+ __u16 idx_reg_off: 12;
+ __u16 scale_bitshift: 4;
+ enum usdt_arg_type arg_type: 8;
+#endif
short reg_off;
bool arg_signed;
char arg_bitshift;
@@ -570,9 +580,8 @@ static struct elf_seg *find_vma_seg(struct elf_seg *segs, size_t seg_cnt, long o
return NULL;
}
-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_note(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);
@@ -626,7 +635,7 @@ 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, &nhdr, data->d_buf, name_off, desc_off, &note);
+ err = parse_usdt_note(&nhdr, data->d_buf, name_off, desc_off, &note);
if (err)
goto err_out;
@@ -661,7 +670,7 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *
* [0] https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation
*/
usdt_abs_ip = note.loc_addr;
- if (base_addr)
+ if (base_addr && note.base_addr)
usdt_abs_ip += base_addr - note.base_addr;
/* When attaching uprobes (which is what USDTs basically are)
@@ -1132,8 +1141,7 @@ 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, GElf_Nhdr *nhdr,
- const char *data, size_t name_off, size_t desc_off,
+static int parse_usdt_note(GElf_Nhdr *nhdr, const char *data, size_t name_off, size_t desc_off,
struct usdt_note *note)
{
const char *provider, *name, *args;
@@ -1283,11 +1291,51 @@ static int calc_pt_regs_off(const char *reg_name)
static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
{
- char reg_name[16];
- int len, reg_off;
- long off;
+ char reg_name[16] = {0}, idx_reg_name[16] = {0};
+ int len, reg_off, idx_reg_off, scale = 1;
+ long off = 0;
+
+ if (sscanf(arg_str, " %d @ %ld ( %%%15[^,] , %%%15[^,] , %d ) %n",
+ arg_sz, &off, reg_name, idx_reg_name, &scale, &len) == 5 ||
+ sscanf(arg_str, " %d @ ( %%%15[^,] , %%%15[^,] , %d ) %n",
+ arg_sz, reg_name, idx_reg_name, &scale, &len) == 4 ||
+ sscanf(arg_str, " %d @ %ld ( %%%15[^,] , %%%15[^)] ) %n",
+ arg_sz, &off, reg_name, idx_reg_name, &len) == 4 ||
+ sscanf(arg_str, " %d @ ( %%%15[^,] , %%%15[^)] ) %n",
+ arg_sz, reg_name, idx_reg_name, &len) == 3
+ ) {
+ /*
+ * Scale Index Base case:
+ * 1@-96(%rbp,%rax,8)
+ * 1@(%rbp,%rax,8)
+ * 1@-96(%rbp,%rax)
+ * 1@(%rbp,%rax)
+ */
+ arg->arg_type = USDT_ARG_SIB;
+ arg->val_off = off;
- if (sscanf(arg_str, " %d @ %ld ( %%%15[^)] ) %n", arg_sz, &off, reg_name, &len) == 3) {
+ reg_off = calc_pt_regs_off(reg_name);
+ if (reg_off < 0)
+ return reg_off;
+ arg->reg_off = reg_off;
+
+ idx_reg_off = calc_pt_regs_off(idx_reg_name);
+ if (idx_reg_off < 0)
+ return idx_reg_off;
+ arg->idx_reg_off = idx_reg_off;
+
+ /* validate scale factor and set fields directly */
+ switch (scale) {
+ case 1: arg->scale_bitshift = 0; break;
+ case 2: arg->scale_bitshift = 1; break;
+ case 4: arg->scale_bitshift = 2; break;
+ case 8: arg->scale_bitshift = 3; break;
+ default:
+ pr_warn("usdt: invalid SIB scale %d, expected 1, 2, 4, 8\n", scale);
+ return -EINVAL;
+ }
+ } else if (sscanf(arg_str, " %d @ %ld ( %%%15[^)] ) %n",
+ arg_sz, &off, reg_name, &len) == 3) {
/* Memory dereference case, e.g., -4@-20(%rbp) */
arg->arg_type = USDT_ARG_REG_DEREF;
arg->val_off = off;
@@ -1306,6 +1354,7 @@ static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec
} else if (sscanf(arg_str, " %d @ %%%15s %n", arg_sz, reg_name, &len) == 2) {
/* Register read case, e.g., -4@%eax */
arg->arg_type = USDT_ARG_REG;
+ /* register read has no memory offset */
arg->val_off = 0;
reg_off = calc_pt_regs_off(reg_name);
@@ -1327,8 +1376,6 @@ static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec
#elif defined(__s390x__)
-/* Do not support __s390__ for now, since user_pt_regs is broken with -m31. */
-
static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
{
unsigned int reg;
generated by cgit (git 2.34.1) at 2025-12-24 22:14:55 +0000