[2/2] Make GDB resolve dlopen of memory mapped shared libraries
Commit Message
Introduced `check_proc_self_file` that checks if a path used by
inferior in dlopen is in the form of `/proc/self/...` and if so resolves
it to `/proc/[pid]/...`
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29586
---
gdb/solib-svr4.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 56 insertions(+), 2 deletions(-)
Comments
On Mon, Oct 17, 2022 at 9:39 PM Asaf Fisher via Gdb-patches <
gdb-patches@sourceware.org> wrote:
> Introduced `check_proc_self_file` that checks if a path used by
> inferior in dlopen is in the form of `/proc/self/...` and if so resolves
> it to `/proc/[pid]/...`
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29586
> ---
> gdb/solib-svr4.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 56 insertions(+), 2 deletions(-)
>
> diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
> index 7e83819a03d..231a4fb40e5 100644
> --- a/gdb/solib-svr4.c
> +++ b/gdb/solib-svr4.c
> @@ -34,6 +34,7 @@
> #include "regcache.h"
> #include "gdbthread.h"
> #include "observable.h"
> +#include "gdbsupport/pathstuff.h"
>
> #include "solist.h"
> #include "solib.h"
> @@ -46,6 +47,9 @@
> #include "gdb_bfd.h"
> #include "probe.h"
>
> Looks correct to me. I can confirm gdb.base/solib-proc-self.exp test added
> by [PATCH 1/2]
fails and hangs without this fix and passes after applying it. This patch
needs rebase.
@@ -34,6 +34,7 @@
#include "regcache.h"
#include "gdbthread.h"
#include "observable.h"
+#include "gdbsupport/pathstuff.h"
#include "solist.h"
#include "solib.h"
@@ -46,6 +47,9 @@
#include "gdb_bfd.h"
#include "probe.h"
+#define SLASH_SELF "/self"
+#define PROC_SELF "/proc" SLASH_SELF
+
static struct link_map_offsets *svr4_fetch_link_map_offsets (void);
static int svr4_have_link_map_offsets (void);
static void svr4_relocate_main_executable (void);
@@ -1187,6 +1191,54 @@ svr4_default_sos (svr4_info *info)
return newobj;
}
+/* Check and fix a cenerio where the so path that we extract has a path to
+ /proc/self e.g. /proc/self/fd/[fd_num] If inferior dlopen a path that has
+ /proc/self, GDB must not open it directly becuase the files in /proc/self are
+ unique for each process. Instead we resolve /proc/self to
+ /proc/[inferior_pid]. This change will give GDB the correct path */
+
+static size_t check_proc_self_file(char *so_name, char *normalized_so_name,
+ size_t out_normalized_so_name_len) {
+ /* We dont want a path with /../ yak. */
+ gdb::unique_xmalloc_ptr<char> normalized_path_obj = gdb_realpath(so_name);
+ gdb::string_view normalized_path = gdb::string_view(
+ normalized_path_obj.get(),
+ std::min(strlen(normalized_path_obj.get()), out_normalized_so_name_len));
+
+ /* Is the path really a /proc/self? */
+ if (0 != normalized_path.rfind(PROC_SELF, 0)) return 0;
+
+ /* Lets get the part of the path after /proc/self e.g. /proc/self/fd -> /fd */
+ size_t slash_self_index = normalized_path.rfind(SLASH_SELF);
+ if (std::string::npos == slash_self_index) return 0;
+ size_t after_self_index = slash_self_index + strlen(SLASH_SELF);
+ gdb::string_view after_self_path = normalized_path.substr(after_self_index);
+
+ /* Get inferior path */
+ int inferior_pid = inferior_ptid.pid();
+ std::string inferior_procfs_path = string_printf("/proc/%d", inferior_pid);
+
+ /* Check if there's enoght space in the out buffer for the normalized path. */
+ size_t normalized_so_name_length =
+ inferior_procfs_path.length() + after_self_path.length();
+ if (out_normalized_so_name_len < normalized_so_name_length) return 0;
+
+ /* Build the full path */
+ inferior_procfs_path.append(std::string(after_self_path));
+
+ warning(_("Detected loaded library (%s) from /proc/self.\nAttempting to "
+ "replace `self` with inferior's PID. -> %s"),
+ normalized_path.begin(), inferior_procfs_path.c_str());
+
+ auto out_length =
+ std::min(inferior_procfs_path.length(), out_normalized_so_name_len);
+
+ /* Copy the new path to the out buffer */
+ strncpy(normalized_so_name, inferior_procfs_path.c_str(), out_length);
+
+ return out_length;
+}
+
/* Read the whole inferior libraries chain starting at address LM.
Expect the first entry in the chain's previous entry to be PREV_LM.
Add the entries to the tail referenced by LINK_PTR_PTR. Ignore the
@@ -1246,8 +1298,10 @@ svr4_read_so_list (svr4_info *info, CORE_ADDR lm, CORE_ADDR prev_lm,
warning (_("Can't read pathname for load map."));
continue;
}
-
- strncpy (newobj->so_name, buffer.get (), SO_NAME_MAX_PATH_SIZE - 1);
+ /* Check if path is in /proc/self */
+ if (0 == check_proc_self_file(buffer.get(), newobj->so_name,
+ SO_NAME_MAX_PATH_SIZE - 1))
+ strncpy(newobj->so_name, buffer.get(), SO_NAME_MAX_PATH_SIZE - 1);
newobj->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
strcpy (newobj->so_original_name, newobj->so_name);