commit be82bb5f9dfecd854c53eda321d1914f28f19790

Author: Mark Wielaard <mark@klomp.org>

Date:   Sat Dec 9 23:01:29 2017 +0100

    Fix gnu debug alt file resolving.

    https://bugs.kde.org/show_bug.cgi?id=387773

    The path to the alt file is relative to the actual debug file.

    Make sure that we got the real file, not a (build-id) symlink.

    Also handle the case where a debug or alt file is an absolute path.

diff --git a/coregrind/m_debuginfo/readelf.c b/coregrind/m_debuginfo/readelf.c

index e612250..c19ff21 100644

--- a/coregrind/m_debuginfo/readelf.c

+++ b/coregrind/m_debuginfo/readelf.c

@@ -33,6 +33,7 @@

 #include "pub_core_basics.h"

 #include "pub_core_vki.h"

+#include "pub_core_vkiscnums.h"

 #include "pub_core_debuginfo.h"

 #include "pub_core_libcbase.h"

 #include "pub_core_libcprint.h"

@@ -40,6 +41,7 @@

 #include "pub_core_machine.h"      /* VG_ELF_CLASS */

 #include "pub_core_options.h"

 #include "pub_core_oset.h"

+#include "pub_core_syscall.h"

 #include "pub_core_tooliface.h"    /* VG_(needs) */

 #include "pub_core_xarray.h"

 #include "priv_misc.h"             /* dinfo_zalloc/free/strdup */

@@ -1323,6 +1325,12 @@ DiImage* find_debug_file( struct _DebugInfo* di,

                      + (extrapath ? VG_(strlen)(extrapath) : 0)

                      + (serverpath ? VG_(strlen)(serverpath) : 0));

+      if (debugname[0] == '/') {

+         VG_(sprintf)(debugpath, "%s", debugname);

+         dimg = open_debug_file(debugpath, buildid, crc, rel_ok, NULL);

+         if (dimg != NULL) goto dimg_ok;

+      }

+

       VG_(sprintf)(debugpath, "%s/%s", objdir, debugname);

       dimg = open_debug_file(debugpath, buildid, crc, rel_ok, NULL);

       if (dimg != NULL) goto dimg_ok;

@@ -1527,6 +1535,56 @@ static Bool check_compression(ElfXX_Shdr* h, DiSlice* s) {

     return True;

 }

+/* Helper function to get the readlink path. Returns a copy of path if the

+   file wasn't a symbolic link. Returns NULL on error. Unless NULL is

+   returned the result needs to be released with dinfo_free.

+*/

+static HChar* readlink_path (const HChar *path)

+{

+   SizeT bufsiz = VG_(strlen)(path);

+   HChar *buf = ML_(dinfo_strdup)("readlink_path.strdup", path);

+   UInt   tries = 6;

+

+   while (tries > 0) {

+      SysRes res;

+#if defined(VGP_arm64_linux)

+      res = VG_(do_syscall4)(__NR_readlinkat, VKI_AT_FDCWD,

+                                              (UWord)path, (UWord)buf, bufsiz);

+#elif defined(VGO_linux) || defined(VGO_darwin)

+      res = VG_(do_syscall3)(__NR_readlink, (UWord)path, (UWord)buf, bufsiz);

+#elif defined(VGO_solaris)

+      res = VG_(do_syscall4)(__NR_readlinkat, VKI_AT_FDCWD, (UWord)path,

+                             (UWord)buf, bufsiz);

+#else

+#       error Unknown OS

+#endif

+      if (sr_isError(res)) {

+         if (sr_Err(res) == VKI_EINVAL)

+            return buf; // It wasn't a symbolic link, return the strdup result.

+         ML_(dinfo_free)(buf);

+         return NULL;

+      }

+

+      SSizeT r = sr_Res(res);

+      if (r < 0) break;

+      if (r == bufsiz) {  // buffer too small; increase and retry

+         bufsiz *= 2 + 16;

+         buf = ML_(dinfo_realloc)("readlink_path.realloc", buf, bufsiz);

+         tries--;

+         continue;

+      }

+      buf[r] = '\0';

+      break;

+   }

+

+   if (tries == 0) { // We tried, but weird long path?

+      ML_(dinfo_free)(buf);

+      return NULL;

+   }

+

+  return buf;

+}

+

 /* The central function for reading ELF debug info.  For the

    object/exe specified by the DebugInfo, find ELF sections, then read

    the symbols, line number info, file name info, CFA (stack-unwind

@@ -2926,8 +2984,12 @@ Bool ML_(read_elf_debug_info) ( struct _DebugInfo* di )

                                 (debugaltlink_escn.szB - buildid_offset)

                                 * 2 + 1);

-         /* The altfile might be relative to the debug file or main file. */

+         /* The altfile might be relative to the debug file or main file.

+	    Make sure that we got the real file, not a symlink.  */

          HChar *dbgname = di->fsm.dbgname ? di->fsm.dbgname : di->fsm.filename;

+         HChar* rdbgname = readlink_path (dbgname);

+         if (rdbgname == NULL)

+            rdbgname = ML_(dinfo_strdup)("rdbgname", dbgname);

          for (j = 0; j < debugaltlink_escn.szB - buildid_offset; j++)

             VG_(sprintf)(

@@ -2937,9 +2999,11 @@ Bool ML_(read_elf_debug_info) ( struct _DebugInfo* di )

                                         + buildid_offset + j));

          /* See if we can find a matching debug file */

-         aimg = find_debug_file( di, dbgname, altbuildid,

+         aimg = find_debug_file( di, rdbgname, altbuildid,

                                  altfile_str_m, 0, True );

+         ML_(dinfo_free)(rdbgname);

+

          if (altfile_str_m)

             ML_(dinfo_free)(altfile_str_m);

          ML_(dinfo_free)(altbuildid);

diff --git a/coregrind/m_debuginfo/readelf.c b/coregrind/m_debuginfo/readelf.c

index c19ff212b..70c28e629 100644

--- a/coregrind/m_debuginfo/readelf.c

+++ b/coregrind/m_debuginfo/readelf.c

@@ -1582,6 +1582,24 @@ static HChar* readlink_path (const HChar *path)

       return NULL;

    }

+  if (buf[0] == '/')

+    return buf;

+

+  /* Relative path, add link dir.  */

+  HChar *linkdirptr;

+  SizeT linkdir_len = VG_(strlen)(path);

+  if ((linkdirptr = VG_(strrchr)(path, '/')) != NULL)

+    linkdir_len -= VG_(strlen)(linkdirptr + 1);

+

+  SizeT buflen = VG_(strlen)(buf);

+  SizeT needed = linkdir_len + buflen + 1;

+  if (bufsiz < needed)

+    buf = ML_(dinfo_realloc)("readlink_path.linkdir", buf, needed);

+

+  VG_(memmove)(buf + linkdir_len, buf, buflen);

+  VG_(memcpy)(buf, path, linkdir_len);

+  buf[needed - 1] = '\0';

+

   return buf;

 }