diff options
| -rw-r--r-- | tools/lib/bpf/libbpf.c | 63 |
1 files changed, 22 insertions, 41 deletions
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index ed3cf0911b98..0781fae58a06 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -11192,43 +11192,6 @@ static int perf_event_uprobe_open_legacy(const char *probe_name, bool retprobe, return pfd; } -/* uprobes deal in relative offsets; subtract the base address associated with - * the mapped binary. See Documentation/trace/uprobetracer.rst for more - * details. - */ -static long elf_find_relative_offset(const char *filename, Elf *elf, long addr) -{ - size_t n; - int i; - - if (elf_getphdrnum(elf, &n)) { - pr_warn("elf: failed to find program headers for '%s': %s\n", filename, - elf_errmsg(-1)); - return -ENOENT; - } - - for (i = 0; i < n; i++) { - int seg_start, seg_end, seg_offset; - GElf_Phdr phdr; - - if (!gelf_getphdr(elf, i, &phdr)) { - pr_warn("elf: failed to get program header %d from '%s': %s\n", i, filename, - elf_errmsg(-1)); - return -ENOENT; - } - if (phdr.p_type != PT_LOAD || !(phdr.p_flags & PF_X)) - continue; - - seg_start = phdr.p_vaddr; - seg_end = seg_start + phdr.p_memsz; - seg_offset = phdr.p_offset; - if (addr >= seg_start && addr < seg_end) - return addr - seg_start + seg_offset; - } - pr_warn("elf: failed to find prog header containing 0x%lx in '%s'\n", addr, filename); - return -ENOENT; -} - /* Return next ELF section of sh_type after scn, or first of that type if scn is NULL. */ static Elf_Scn *elf_find_next_scn_by_type(Elf *elf, int sh_type, Elf_Scn *scn) { @@ -11315,6 +11278,8 @@ static long elf_find_func_offset(const char *binary_path, const char *name) for (idx = 0; idx < nr_syms; idx++) { int curr_bind; GElf_Sym sym; + Elf_Scn *sym_scn; + GElf_Shdr sym_sh; if (!gelf_getsym(symbols, idx, &sym)) continue; @@ -11352,12 +11317,28 @@ static long elf_find_func_offset(const char *binary_path, const char *name) continue; } } - ret = sym.st_value; + + /* Transform symbol's virtual address (absolute for + * binaries and relative for shared libs) into file + * offset, which is what kernel is expecting for + * uprobe/uretprobe attachment. + * See Documentation/trace/uprobetracer.rst for more + * details. + * This is done by looking up symbol's containing + * section's header and using it's virtual address + * (sh_addr) and corresponding file offset (sh_offset) + * to transform sym.st_value (virtual address) into + * desired final file offset. + */ + sym_scn = elf_getscn(elf, sym.st_shndx); + if (!sym_scn) + continue; + if (!gelf_getshdr(sym_scn, &sym_sh)) + continue; + + ret = sym.st_value - sym_sh.sh_addr + sym_sh.sh_offset; last_bind = curr_bind; } - /* For binaries that are not shared libraries, we need relative offset */ - if (ret > 0 && !is_shared_lib) - ret = elf_find_relative_offset(binary_path, elf, ret); if (ret > 0) break; } |