From 38daaa32f8ba6570b566a6fad3a1fa8d99c22c90 Mon Sep 17 00:00:00 2001
From: Yasumasa Suenaga <yasuenag@gmail.com>
Date: Thu, 29 Jan 2026 10:21:47 +0900
Subject: [PATCH] Add new function to handle vDSO

---
 .../linux/native/libsaproc/ps_core.c          | 54 +++++++++++--------
 1 file changed, 33 insertions(+), 21 deletions(-)

diff --git a/src/jdk.hotspot.agent/linux/native/libsaproc/ps_core.c b/src/jdk.hotspot.agent/linux/native/libsaproc/ps_core.c
index fbf09ecf840..ade0eafdcaa 100644
--- a/src/jdk.hotspot.agent/linux/native/libsaproc/ps_core.c
+++ b/src/jdk.hotspot.agent/linux/native/libsaproc/ps_core.c
@@ -602,6 +602,38 @@ static uintptr_t calc_prelinked_load_address(struct ps_prochandle* ph, int lib_f
   return load_addr;
 }
 
+// Override vDSO path to kernel directory (/lib/modules/<version>/vdso) if possible.
+// Then lib_name would be overwritten that path.
+// Otherwise copy vDSO memory in coredump to temporal memory generated by memfd_create().
+// Returns FD for vDSO (should be closed by caller).
+static int handle_vdso(struct ps_prochandle* ph, char* lib_name, size_t lib_name_len) {
+  int lib_fd;
+  struct utsname uts;
+  uname(&uts);
+
+  // Check vDSO binary first (for referring debuginfo if possible).
+  char *vdso_path = (char*)malloc(lib_name_len);
+  snprintf(vdso_path, lib_name_len, "/lib/modules/%s/vdso/vdso64.so", uts.release);
+  if (access(vdso_path, F_OK) == 0) {
+    print_debug("replace vDSO: %s -> %s\n", lib_name, vdso_path);
+    strncpy(lib_name, vdso_path, lib_name_len);
+    lib_fd = pathmap_open(lib_name);
+  } else {
+    // Copy vDSO memory segment from core to temporal memory
+    // if vDSO binary is not available.
+    lib_fd = memfd_create("[vdso] in core", 0);
+    off64_t ofs = ph->core->vdso_offset;
+    if (sendfile64(lib_fd, ph->core->core_fd, &ofs, ph->core->vdso_size) == -1) {
+      print_debug("can't copy vDSO (%d)\n", errno);
+      close(lib_fd);
+      lib_fd = -1;
+    }
+  }
+
+  free(vdso_path);
+  return lib_fd;
+}
+
 // read shared library info from runtime linker's data structures.
 // This work is done by librtlb_db in Solaris
 static bool read_shared_lib_info(struct ps_prochandle* ph) {
@@ -699,27 +731,7 @@ static bool read_shared_lib_info(struct ps_prochandle* ph) {
       if (lib_name[0] != '\0') { // ignore empty lib names
          if (strcmp("linux-vdso.so.1", lib_name) == 0 ||
              strcmp("linux-vdso64.so.1", lib_name) == 0) {
-            struct utsname uts;
-            uname(&uts);
-
-            // Check vDSO binary first (for referring debuginfo if possible).
-            char vdso_path[PATH_MAX];
-            snprintf(vdso_path, sizeof(vdso_path), "/lib/modules/%s/vdso/vdso64.so", uts.release);
-            if (access(vdso_path, F_OK) == 0) {
-               print_debug("replace vDSO: %s -> %s\n", lib_name, vdso_path);
-               strcpy(lib_name, vdso_path);
-               lib_fd = pathmap_open(lib_name);
-            } else {
-               // Copy vDSO memory segment from core to temporal memory
-               // if vDSO binary is not available.
-               lib_fd = memfd_create("[vdso] in core", 0);
-               off64_t ofs = ph->core->vdso_offset;
-               if (sendfile64(lib_fd, ph->core->core_fd, &ofs, ph->core->vdso_size) == -1) {
-                  print_debug("can't copy vDSO (%d)\n", errno);
-                  close(lib_fd);
-                  lib_fd = -1;
-               }
-            }
+           lib_fd = handle_vdso(ph, lib_name, sizeof(lib_name));
          } else {
            lib_fd = pathmap_open(lib_name);
          }