[src/trunk]: src/external/gpl3/gdb/dist/gdb PR toolchain/56268

[rin <rin%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/d7b7489b753c
branches:  trunk
changeset: 368157:d7b7489b753c
user:      rin <rin%NetBSD.org@localhost>
date:      Sun Jun 26 08:28:07 2022 +0000

description:
PR toolchain/56268

For NetBSD/m68k, program header is erroneously readable from core dump,
although a page containing it is missing. This spoils relocation for
the main executable, and debugging with core dumps becomes impossible,
as described in the PR.

In order to avoid this failure, add consistency check for program header;
for NetBSD, 1st entry of program header refers program header itself. If
this is not the case, we should be reading random garbage from core dump.

Yes, this is a kind of the hackest hack. But, unable to debug with core
dump is critical. Therefore, I commit this workaround temporarily until
the real cause is found and fixed.

Note that this is not a recent regression for GDB nor kernel, as
mentioned in the PR. These from netbsd-8 and -9 fail in the same way
without this hack.

diffstat:

 external/gpl3/gdb/dist/gdb/solib-svr4.c |  34 +++++++++++++++++++++++++++++++++
 1 files changed, 34 insertions(+), 0 deletions(-)

diffs (44 lines):

diff -r f563f2058dfc -r d7b7489b753c external/gpl3/gdb/dist/gdb/solib-svr4.c
--- a/external/gpl3/gdb/dist/gdb/solib-svr4.c   Sun Jun 26 06:25:09 2022 +0000
+++ b/external/gpl3/gdb/dist/gdb/solib-svr4.c   Sun Jun 26 08:28:07 2022 +0000
@@ -541,6 +541,40 @@
   if (target_read_memory (sect_addr, buf.data (), sect_size))
     return {};
 
+#if defined(__NetBSD__) && defined(__m68k__)
+  /*
+   * XXX PR toolchain/56268
+   *
+   * For NetBSD/m68k, program header is erroneously readable from core dump,
+   * although a page containing it is missing. This spoils relocation for
+   * the main executable, and debugging with core dumps becomes impossible,
+   * as described in toolchain/56268.
+   *
+   * In order to avoid this failure, we carry out consistency check for
+   * program header; for NetBSD, 1st entry of program header refers program
+   * header itself. If this is not the case, we should be reading random
+   * garbage from core dump.
+   */
+  if (type == -1 && arch_size == 32)
+    {
+      Elf32_External_Phdr phdr;
+      int p_type, p_filesz, p_memsz;
+
+      if (target_read_memory (at_phdr, (gdb_byte *)&phdr, sizeof (phdr)))
+        return {};
+
+      p_type = extract_unsigned_integer ((gdb_byte *) phdr.p_type, 4,
+                                        byte_order);
+      p_filesz = extract_unsigned_integer ((gdb_byte *)phdr.p_filesz, 4,
+                                          byte_order);
+      p_memsz = extract_unsigned_integer ((gdb_byte *)phdr.p_memsz, 4,
+                                         byte_order);
+
+      if (p_type != PT_PHDR || p_filesz != sect_size || p_memsz != sect_size)
+       return {};
+    }
+#endif
+
   if (p_arch_size)
     *p_arch_size = arch_size;
   if (base_addr)