[rpms/gdb] gdb-17.2-rebase-f44: Backport "Save/restore file offset while reading notes in core file"

[Keith Seitz <keiths@redhat.com>]

            A new commit has been pushed.

            Repo   : rpms/gdb
            Branch : gdb-17.2-rebase-f44
            Commit : 0a3a5ea5a61b8887aa3b78ca7bc2908a0dc8abc1
            Author : Keith Seitz <keiths@redhat.com>
            Date   : 2021-03-31T14:49:14-07:00
            Stats  : +99/-2 in 5 file(s)
            URL    : https://src.fedoraproject.org/rpms/gdb/c/0a3a5ea5a61b8887aa3b78ca7bc2908a0dc8abc1?branch=gdb-17.2-rebase-f44

            Log:
            Backport "Save/restore file offset while reading notes in core file"
 (Keith Seitz, RHBZ 1931344)

Resolves: RHBZ 1931344

---
diff --git a/_gdb.spec.Patch.include b/_gdb.spec.Patch.include
index f0b8ff4..30023ab 100644
--- a/_gdb.spec.Patch.include
+++ b/_gdb.spec.Patch.include
@@ -424,3 +424,7 @@ Patch104: testing-custom-inputrc.patch
 # (Tom de Vries)
 Patch105: process_psymtab_comp_unit-type-unit.patch
 
+# Backport "Save/restore file offset while reading notes in core file"
+# (Keith Seitz, RHBZ 1931344)
+Patch106: gdb-rhbz1931344-bfd_seek-elf_read_notes.patch
+

diff --git a/_gdb.spec.patch.include b/_gdb.spec.patch.include
index df14ff4..1b966ef 100644
--- a/_gdb.spec.patch.include
+++ b/_gdb.spec.patch.include
@@ -103,3 +103,4 @@
 %patch103 -p1
 %patch104 -p1
 %patch105 -p1
+%patch106 -p1

diff --git a/_patch_order b/_patch_order
index b4d313e..85a4a81 100644
--- a/_patch_order
+++ b/_patch_order
@@ -103,3 +103,4 @@ gdb-rhbz1909902-frame_id_p-assert-2.patch
 gdb-rhbz1941080-fix-gdbserver-hang.patch
 testing-custom-inputrc.patch
 process_psymtab_comp_unit-type-unit.patch
+gdb-rhbz1931344-bfd_seek-elf_read_notes.patch

diff --git a/gdb-rhbz1931344-bfd_seek-elf_read_notes.patch b/gdb-rhbz1931344-bfd_seek-elf_read_notes.patch
new file mode 100644
index 0000000..e212dc6
--- /dev/null
+++ b/gdb-rhbz1931344-bfd_seek-elf_read_notes.patch
@@ -0,0 +1,87 @@
+From FEDORA_PATCHES Mon Sep 17 00:00:00 2001
+From: Keith Seitz <keiths@redhat.com>
+Date: Thu, 25 Mar 2021 10:31:48 -0700
+Subject: gdb-rhbz1931344-bfd_seek-elf_read_notes.patch
+
+;; Backport "Save/restore file offset while reading notes in core file"
+;; (Keith Seitz, RHBZ 1931344)
+
+A recent bug (RH BZ 1931344) has exposed a bug in the core file
+build-ID support that I introduced a while ago. It is pretty
+easy to demonstate the problem following a simplified procedure
+outlined in that bug:
+
+[shell1]
+shell1$ /usr/libexec/qemu-kvm
+
+[shell2]
+shell2$ pkill -SEGV -x qemu-kvm
+
+[shell1]
+Segmentation fault (core dumped)
+
+Load this core file into GDB without specifying an executable
+(an unfortunate Fedora/RHEL-ism), and GDB will inform the user
+to install debuginfo for the "missing" executable:
+
+$ gdb -nx -q core.12345
+...
+Missing separate debuginfo for the main executable file
+Try: dnf --enablerepo='*debug*' install /usr/lib/debug/.build-id/e2/e9c66d3117fb2bbb5b2be122f04f2664e5df54
+Core was generated by `/usr/libexec/qemu-kvm'.
+Program terminated with signal SIGSEGV, Segmentation fault.
+...
+
+The suggested build-ID is actaully for gmp not qemu-kvm. The problem
+lies in _bfd_elf_core_find_build_id, where we loop over program headers
+looking for note segments:
+
+  /* Read in program headers and parse notes.  */
+  for (i = 0; i < i_ehdr.e_phnum; ++i, ++i_phdr)
+    {
+      Elf_External_Phdr x_phdr;
+
+      if (bfd_bread (&x_phdr, sizeof (x_phdr), abfd) != sizeof (x_phdr))
+        goto fail;
+      elf_swap_phdr_in (abfd, &x_phdr, i_phdr);
+
+      if (i_phdr->p_type == PT_NOTE && i_phdr->p_filesz > 0)
+        {
+          elf_read_notes (abfd, offset + i_phdr->p_offset,
+                          i_phdr->p_filesz, i_phdr->p_align);
+
+          if (abfd->build_id != NULL)
+            return TRUE;
+        }
+
+elf_read_notes uses bfd_seek to forward the stream to the location of
+the note segment. When control returns to _bfd_elf_core_fild_build_id,
+the stream is no longer in the location looking at program headers, and
+all subsequent reads will read from the wrong file offset.
+
+To fix this, this patch marks the stream location and ensures
+that it is restored after elf_read_notes is called.
+
+bfd/ChangeLog
+2021-03-26  Keith Seitz  <keiths@redhat.com>
+
+	* elfcore.h (_bfd_elf_core_find_build_id): Seek file
+	offset of program headers after calling elf_read_notes.
+
+diff --git a/bfd/elfcore.h b/bfd/elfcore.h
+--- a/bfd/elfcore.h
++++ b/bfd/elfcore.h
+@@ -410,6 +410,13 @@ NAME(_bfd_elf, core_find_build_id)
+ 	{
+ 	  elf_read_notes (abfd, offset + i_phdr->p_offset,
+ 			  i_phdr->p_filesz, i_phdr->p_align);
++
++	  /* Make sure ABFD returns to processing the program headers.  */
++	  if (bfd_seek (abfd, (file_ptr) (offset + i_ehdr.e_phoff
++					  + (i + 1) * sizeof (x_phdr)),
++			SEEK_SET) != 0)
++	    goto fail;
++
+ 	  if (abfd->build_id != NULL)
+ 	    return TRUE;
+ 	}

diff --git a/gdb.spec b/gdb.spec
index 37e5670..088f650 100644
--- a/gdb.spec
+++ b/gdb.spec
@@ -37,7 +37,7 @@ Version: 10.1
 
 # The release always contains a leading reserved number, start it at 1.
 # `upstream' is not a part of `name' to stay fully rpm dependencies compatible for the testing.
-Release: 17%{?dist}
+Release: 18%{?dist}
 
 License: GPLv3+ and GPLv3+ with exceptions and GPLv2+ and GPLv2+ with exceptions and GPL+ and LGPLv2+ and LGPLv3+ and BSD and Public Domain and GFDL
 # Do not provide URL for snapshots as the file lasts there only for 2 days.
@@ -1190,7 +1190,11 @@ fi
 %endif
 
 %changelog
-* Wed Mar 31 2021 Jonathan Wakely <jwakely@redhat.com>
+* Wed Mar 31 2021 Keith Seitz <keiths@redhat.com> - 10.1-18
+- Backport "Save/restore file offset while reading notes in core file"
+  (Keith Seitz, RHBZ 1931344)
+
+* Wed Mar 31 2021 Jonathan Wakely <jwakely@redhat.com> - 10.1-17
 - Rebuilt for removed libstdc++ symbols (#1937698)
 
 * Tue Mar 23 2021 Kevin Buettner <kevinb@redhat.com>