[PATCH 09/14] libdw, libdwfl: Save original path of ELF file

[Omar Sandoval <osandov@osandov.com>]

From: Omar Sandoval <osandov@fb.com>

libdw and libdwfl currently save the path of the directory containing
the ELF file to use when searching for alt and dwo files.  To search for
dwp files, we need the file name too.  Add an elfpath field to Dwarf,
and set the debugdir field from it.  Also update libdwfl to set elfpath
and debugdir.

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 libdw/ChangeLog                | 11 ++++++++++-
 libdw/dwarf_begin_elf.c        | 34 ++++++++++++++++++++--------------
 libdw/dwarf_end.c              |  3 ++-
 libdw/libdwP.h                 | 12 ++++++++++--
 libdwfl/ChangeLog              |  9 +++++++++
 libdwfl/dwfl_module.c          |  2 +-
 libdwfl/dwfl_module_getdwarf.c | 11 +++++++----
 libdwfl/libdwflP.h             |  2 +-
 libdwfl/offline.c              |  4 ++--
 9 files changed, 62 insertions(+), 26 deletions(-)

diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 1d229094..f491587f 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -20,7 +20,7 @@
 	instead of dbg parameter, which is now unused.
 	* libdwP.h (Dwarf_Macro_Op_Table): Replace is_64bit with address_size
 	and offset_size.  Add dbg.
-	(Dwarf): Add cu_index and tu_index.
+	(Dwarf): Add cu_index and tu_index.  Add elfpath.
 	(Dwarf_CU): Add dwp_row.
 	(Dwarf_Package_Index): New type.
 	(DW_SECT_TYPES): New macro.
@@ -28,6 +28,9 @@
 	(dwarf_cu_dwp_section_info): New INTDECL.
 	Add IDX_debug_cu_index and IDX_debug_tu_index.  Add
 	DWARF_E_UNKNOWN_SECTION.
+	(__libdw_debugdir): Replace declaration with...
+	(__libdw_elfpath): New declaration.
+	(__libdw_set_debugdir): New declaration.
 	* dwarf_begin_elf.c (dwarf_scnnames): Add IDX_debug_cu_index and
 	IDX_debug_tu_index.
 	(scn_to_string_section_idx): Ditto.
@@ -35,8 +38,14 @@
 	.zdebug_cu_index, and .zdebug_tu_index.
 	(check_section): Change .dwo suffix matching to account for
 	.debug_cu_index and .debug_tu_index.
+	(__libdw_debugdir): Replace with..
+	(__libdw_elfpath): New function.
+	(__libdw_set_debugdir): New function.
+	(valid_p): Call __libdw_elfpath and __libdw_set_debugdir instead of
+	__libdw_debugdir.
 	* Makefile.am (libdw_a_SOURCES): Add dwarf_cu_dwp_section_info.c.
 	* dwarf_end.c (dwarf_end): Free dwarf->cu_index and dwarf->tu_index.
+	Free dwarf->elfpath.
 	* dwarf_error.c (errmsgs): Add DWARF_E_UNKNOWN_SECTION.
 	* libdw.h (dwarf_cu_dwp_section_info): New declaration.
 	* libdw.map (ELFUTILS_0.190): Add dwarf_cu_dwp_section_info.
diff --git a/libdw/dwarf_begin_elf.c b/libdw/dwarf_begin_elf.c
index 7936d343..323a91d0 100644
--- a/libdw/dwarf_begin_elf.c
+++ b/libdw/dwarf_begin_elf.c
@@ -272,24 +272,27 @@ check_section (Dwarf *result, size_t shstrndx, Elf_Scn *scn, bool inscngrp)
   return result;
 }
 
-
-/* Helper function to set debugdir field.  We want to cache the dir
-   where we found this Dwarf ELF file to locate alt and dwo files.  */
 char *
-__libdw_debugdir (int fd)
+__libdw_elfpath (int fd)
 {
   /* strlen ("/proc/self/fd/") = 14 + strlen (<MAXINT>) = 10 + 1 = 25.  */
   char devfdpath[25];
   sprintf (devfdpath, "/proc/self/fd/%u", fd);
-  char *fdpath = realpath (devfdpath, NULL);
-  char *fddir;
-  if (fdpath != NULL && fdpath[0] == '/'
-      && (fddir = strrchr (fdpath, '/')) != NULL)
-    {
-      *++fddir = '\0';
-      return fdpath;
-    }
-  return NULL;
+  return realpath (devfdpath, NULL);
+}
+
+
+void
+__libdw_set_debugdir (Dwarf *dbg)
+{
+  if (dbg->elfpath == NULL || dbg->elfpath[0] != '/')
+    return;
+  size_t dirlen = strrchr (dbg->elfpath, '/') - dbg->elfpath + 1;
+  dbg->debugdir = malloc (dirlen + 1);
+  if (dbg->debugdir == NULL)
+    return;
+  memcpy (dbg->debugdir, dbg->elfpath, dirlen);
+  dbg->debugdir[dirlen] = '\0';
 }
 
 
@@ -421,7 +424,10 @@ valid_p (Dwarf *result)
     }
 
   if (result != NULL)
-    result->debugdir = __libdw_debugdir (result->elf->fildes);
+    {
+      result->elfpath = __libdw_elfpath (result->elf->fildes);
+      __libdw_set_debugdir(result);
+    }
 
   return result;
 }
diff --git a/libdw/dwarf_end.c b/libdw/dwarf_end.c
index 18a419ce..b7f817d9 100644
--- a/libdw/dwarf_end.c
+++ b/libdw/dwarf_end.c
@@ -147,7 +147,8 @@ dwarf_end (Dwarf *dwarf)
 	  close (dwarf->alt_fd);
 	}
 
-      /* The cached dir we found the Dwarf ELF file in.  */
+      /* The cached path and dir we found the Dwarf ELF file in.  */
+      free (dwarf->elfpath);
       free (dwarf->debugdir);
 
       /* Free the context descriptor.  */
diff --git a/libdw/libdwP.h b/libdw/libdwP.h
index 13ca58ce..214d1711 100644
--- a/libdw/libdwP.h
+++ b/libdw/libdwP.h
@@ -169,6 +169,10 @@ struct Dwarf
   /* The underlying ELF file.  */
   Elf *elf;
 
+  /* The (absolute) path to the ELF file, if known.  To help locating
+     dwp files.  */
+  char *elfpath;
+
   /* The (absolute) path to the ELF dir, if known.  To help locating
      alt and dwo files.  */
   char *debugdir;
@@ -1385,9 +1389,13 @@ __libdw_link_skel_split (Dwarf_CU *skel, Dwarf_CU *split)
 int __libdw_addrx (Dwarf_CU *cu, Dwarf_Word idx, Dwarf_Addr *addr);
 
 
-/* Helper function to set debugdir field in Dwarf, used from dwarf_begin_elf
+/* Helper function to set elfpath field in Dwarf, used from dwarf_begin_elf
    and libdwfl process_file.  */
-char * __libdw_debugdir (int fd);
+char * __libdw_elfpath (int fd);
+
+/* Helper function to set debugdir field in Dwarf after elfpath field has been
+   set.  */
+void __libdw_set_debugdir (Dwarf *dbg);
 
 
 /* Given the directory of a debug file, an absolute or relative dir
diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 54d85921..abbf0dfe 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,12 @@
+2023-09-27  Omar Sandoval  <osandov@fb.com>
+	* dwfl_module.c (__libdwfl_module_free): Free mod->elfpath instead of
+	mod->elfdir.
+	* dwfl_module_getdwarf.c (load_dw): Set mod->dw->elfpath and call
+	__libdw_set_debugdir instead of setting mod->dw->debugdir.
+	* libdwflP.h (Dwfl_Module): Replace elfdir with elfpath.
+	* offline.c (process_elf): Call __libdw_elfpath and set mod->elfpath
+	instead of mod->elfdir.
+
 2023-04-24  John Gallagher  <john@gllghr.com>
 
 	* gzip.c: Fix memory leak in unzip()
diff --git a/libdwfl/dwfl_module.c b/libdwfl/dwfl_module.c
index 221d726d..c4d872d4 100644
--- a/libdwfl/dwfl_module.c
+++ b/libdwfl/dwfl_module.c
@@ -119,7 +119,7 @@ __libdwfl_module_free (Dwfl_Module *mod)
     free (mod->reloc_info);
 
   free (mod->name);
-  free (mod->elfdir);
+  free (mod->elfpath);
   free (mod);
 }
 
diff --git a/libdwfl/dwfl_module_getdwarf.c b/libdwfl/dwfl_module_getdwarf.c
index 9ba499bb..6f98c02b 100644
--- a/libdwfl/dwfl_module_getdwarf.c
+++ b/libdwfl/dwfl_module_getdwarf.c
@@ -1362,11 +1362,14 @@ load_dw (Dwfl_Module *mod, struct dwfl_file *debugfile)
     }
 
   /* We might have already closed the fd when we asked dwarf_begin_elf to
-     create an Dwarf.  Help out a little in case we need to find an alt or
-     dwo file later.  */
-  if (mod->dw->debugdir == NULL && mod->elfdir != NULL
+     create an Dwarf.  Help out a little in case we need to find an alt,
+     dwo, or dwp file later.  */
+  if (mod->dw->elfpath == NULL && mod->elfpath != NULL
       && debugfile == &mod->main)
-    mod->dw->debugdir = strdup (mod->elfdir);
+    {
+      mod->dw->elfpath = strdup (mod->elfpath);
+      __libdw_set_debugdir (mod->dw);
+    }
 
   /* Until we have iterated through all CU's, we might do lazy lookups.  */
   mod->lazycu = 1;
diff --git a/libdwfl/libdwflP.h b/libdwfl/libdwflP.h
index cdc528d0..b3dfea1d 100644
--- a/libdwfl/libdwflP.h
+++ b/libdwfl/libdwflP.h
@@ -186,7 +186,7 @@ struct Dwfl_Module
   Elf_Data *symxndxdata;	/* Data in the extended section index table. */
   Elf_Data *aux_symxndxdata;	/* Data in the extended auxiliary table. */
 
-  char *elfdir;			/* The dir where we found the main Elf.  */
+  char *elfpath;		/* The path where we found the main Elf.  */
 
   Dwarf *dw;			/* libdw handle for its debugging info.  */
   Dwarf *alt;			/* Dwarf used for dwarf_setalt, or NULL.  */
diff --git a/libdwfl/offline.c b/libdwfl/offline.c
index e090b42b..50abe8c3 100644
--- a/libdwfl/offline.c
+++ b/libdwfl/offline.c
@@ -151,9 +151,9 @@ process_elf (Dwfl *dwfl, const char *name, const char *file_name, int fd,
       /* Don't keep the file descriptor around.  */
       if (mod->main.fd != -1 && elf_cntl (mod->main.elf, ELF_C_FDREAD) == 0)
 	{
-	  /* Grab the dir path in case we want to report this file as
+	  /* Grab the path in case we want to report this file as
 	     Dwarf later.  */
-	  mod->elfdir = __libdw_debugdir (mod->main.fd);
+	  mod->elfpath = __libdw_elfpath (mod->main.fd);
 	  close (mod->main.fd);
 	  mod->main.fd = -1;
 	}
-- 
2.41.0