[committed] MIPS: Don't infer IRIX OS ABI from generic section names

["Maciej W. Rozycki" <macro at codesourcery dot com>]

Hi,

 The recent addition of the `.MIPS.abiflags' section triggered a nasty 
problem early on in mips-linux-gnu regression testing:

[...]
_start () at .../gdb/testsuite/gdb.asm/asmsrc1.s:14
14              gdbasm_startup
(gdb) continue
Continuing.

Breakpoint 1, main () at .../gdb/testsuite/gdb.asm/asmsrc1.s:42
42              gdbasm_several_nops
(gdb) f
#0  main () at .../gdb/testsuite/gdb.asm/asmsrc1.s:42
42              gdbasm_several_nops
(gdb) PASS: gdb.asm/asm-source.exp: f at main
n
warning: Remote failure reply: E01
ptrace: Input/output error.
input_interrupt, count = 1 c = 36 ('$')
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: next over macro (timeout)
s
Ignoring packet error, continuing...
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: step into foo2 (timeout)
info target
Ignoring packet error, continuing...
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: info target (timeout)
info symbol 0x0
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: info symbol (timeout)
list
Ignoring packet error, continuing...
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: list (timeout)
search A routine for foo2 to call
Ignoring packet error, continuing...
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: search (timeout)
f
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: f in foo2 (timeout)
n
Ignoring packet error, continuing...
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: n in foo2 (timeout)
bt 10
Ignoring packet error, continuing...
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: bt ALL in foo2 (timeout)
bt 2
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: bt 2 in foo2 (timeout)
s
Ignoring packet error, continuing...
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: s 2 (timeout)
n
Ignoring packet error, continuing...
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: n 2 (timeout)
bt 3
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: bt 3 in foo3 (timeout)
info source
Ignoring packet error, continuing...
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: info source asmsrc1.s (timeout)
finish
Ignoring packet error, continuing...
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: finish from foo3 (timeout)
info source
Ignoring packet error, continuing...
FAIL: gdb.asm/asm-source.exp: info source asmsrc2.s (timeout)
info sources
Ignoring packet error, continuing...
Ignoring packet error, continuing...
Ignoring packet error, continuing...
Ignoring packet error, continuing...
Ignoring packet error, continuing...
Ignoring packet error, continuing...
Ignoring packet error, continuing...
Ignoring packet error, continuing...
[And then so on, ad infinitum.]

At this point the test suite is irrecoverable, for some reason the harness 
does not want to terminate this test case, so testing never progresses any 
further.

 I think we have 3 bugs here:

1. GDB/gdbserver fails with the `n' (`next') command.

2. GDB does not handle the `E01' error reply from a failed `vCont' packet.

3. The harness does not timeout and recover.

I'll be handling issue #1 here only, leaving the other two open.

 The problem here is we've got assembly source that does not have the 
usual ABI tag GDB normally infers the OS ABI from.  As a result it resorts 
to an old way of concluding that the OS ABI is IRIX if there are any 
sections whose names start with `.MIPS.' present in the executable.  As a 
result of setting this OS ABI, GDB concludes `ptrace(PTRACE_SINGLESTEP, 
...)' is available that I infer on IRIX is.  Consequently it does not 
internally install the software single-stepper `mips_software_single_step' 
and issues a `vCont;s...' packet instead.  In response to that `gdbserver' 
tries to issue the said `ptrace' request, that fails with EIO and the 
reply packet propagates the error.  But GDB ignores the error reply and 
insists the packet has succeeded.

 This is not a new problem, it just used not to trigger in my testing 
because gdb.asm/asm-source.exp is only run for the default multilib and I 
only ran testing with o32 being the default.  With the n64 ABI being the 
default there would already be a `.MIPS.options' section present in any 
Linux executable triggering the same problem.  A third section that is 
also present in SVR4 Linux executables these days (so again, not o32 PLT 
ones) is `.MIPS.stubs'.  This brings us with the obvious solution, that is 
excluding these generic section names from deciding on the OS ABI.

 I've checked a random IRIX executable I've had handy and it has plenty of 
other sections whose names start with `.MIPS.':

.MIPS.content.MIPS.stubs
.MIPS.content.data
.MIPS.content.fini
.MIPS.content.got
.MIPS.content.got_2
.MIPS.content.init
.MIPS.content.interp
.MIPS.content.lit4_2
.MIPS.content.lit8_1
.MIPS.content.lit8_2
.MIPS.content.rodata
.MIPS.content.sbss_1
.MIPS.content.sbss_2
.MIPS.content.sdata_1
.MIPS.content.sdata_2
.MIPS.content.srdata_1
.MIPS.content.srdata_2
.MIPS.content.text
.MIPS.content_MIPS_eh_region
.MIPS.content_MIPS_eh_region_supp
.MIPS.events.MIPS.stubs
.MIPS.events.fini
.MIPS.events.init
.MIPS.events.text
.MIPS.interfaces
.MIPS.options
.MIPS.stubs
.MIPS.symlib

so I think excluding these that are present in Linux executables won't 
hurt.

 This does not affect the case where the IRIX OS ABI is the default, e.g. 
GDB configured for the mips-sgi-irix6 target.  And if all else fails, then 
an automatically selected OS ABI can be overridden with `set osabi'.

 I have verified this change to work correctly in mips-linux-gnu 
regression testing and committed now.

2014-09-09  Maciej W. Rozycki  <macro@codesourcery.com>

	gdb/
	* mips-irix-tdep.c (mips_irix_elf_osabi_sniff_abi_tag_sections):
	Exclude `.MIPS.abiflags', `.MIPS.options' and `.MIPS.stubs' from
	the list of sections determining GDB_OSABI_IRIX.

  Maciej

gdb-mips-irix-abi-tag.diff
Index: gdb-fsf-trunk-quilt/gdb/mips-irix-tdep.c
===================================================================
--- gdb-fsf-trunk-quilt.orig/gdb/mips-irix-tdep.c	2014-08-23 01:11:20.000000000 +0100
+++ gdb-fsf-trunk-quilt/gdb/mips-irix-tdep.c	2014-09-09 05:24:53.037976725 +0100
@@ -38,12 +38,16 @@ mips_irix_elf_osabi_sniff_abi_tag_sectio
   name = bfd_get_section_name (abfd, sect);
   sectsize = bfd_section_size (abfd, sect);
 
-  if (strncmp (name, ".MIPS.", 6) == 0 && sectsize > 0)
-    {
-      /* The presence of a section named with a ".MIPS." prefix is
-         indicative of an IRIX binary.  */
-      *os_ident_ptr = GDB_OSABI_IRIX;
-    }
+  /* The presence of a section named with a ".MIPS." prefix is usually
+     indicative of an IRIX binary, however there are exceptions that
+     are present universally, so check for those names and avoid
+     switching away from the default OS ABI in the case of a match.  */
+  if (strncmp (name, ".MIPS.", 6) == 0
+      && strcmp (name, ".MIPS.abiflags") != 0
+      && strcmp (name, ".MIPS.options") != 0
+      && strcmp (name, ".MIPS.stubs") != 0
+      && sectsize > 0)
+    *os_ident_ptr = GDB_OSABI_IRIX;
 }
 
 static enum gdb_osabi