Re: [PATCH ver3] gdb: Add PowerPC support to gdb.dwarf2/frame-inlined-in-outer-frame.exp

[Carl Love <cel@us.ibm.com>]

Simon:

On Fri, 2021-12-03 at 21:13 -0500, Simon Marchi wrote:
> <snip>
> 
> Format like this:
> 
> #if defined (__powerpc64__)
> #  if _CALL_ELF == 2
> ...
> #  else
> ...
> #  endif
> #endif
> 
> Put the assembly statements at column 0, as they would be without the
> preprocessor conditionals.

I made the requested changes, above, to the patch.

> I guess I'll have to trust you because I know nothing about PowerPC
> assembly but... this is all really necessary for such a simple
> program?

Per Will Schmidt's commnets

   Yes..  Details as I paraphrase them are that 
   ElfV1 (Powerpc Big Endian) requires an opd (Official Procedure
   Descriptor) section that contains the function descriptors. 
   So, the assembly here is defining the abiversion, and the .opd
   section
   (with required alignment), and adding an entry for the _start
   function
   in that section.

   This requirement was eliminated in the ELF V2 ABI, as
   seen in the simpler #ifdef branch above.

   Thanks
   -Will

Yes unfortunately.  I would also add to what Will said that we need tp
explicitly specify which abi version ( directive .abiversion ) for the
assembler to use. Otherwise it will assume version 1 by default.

Please let me know if the patch is acceptable for mainline.  Thanks.

                    Carl 

---------------------------------------------------------------------
gdb: Add PowerPC support to gdb.dwarf2/frame-inlined-in-outer-frame

This patch adds an #elif defined for PowerPC to setup the exit_0 macro.
This patch addes the needed macro definitionald logic to handle both elfV1
and elfV2.

The patch has been successfully tested on both PowerPC BE, Powerpc LE and
X86_64 with no regressions.
---
 .../gdb.dwarf2/frame-inlined-in-outer-frame.S | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/gdb/testsuite/gdb.dwarf2/frame-inlined-in-outer-frame.S b/gdb/testsuite/gdb.dwarf2/frame-inlined-in-outer-frame.S
index 9fb6e7b7164..09fe75d8132 100644
--- a/gdb/testsuite/gdb.dwarf2/frame-inlined-in-outer-frame.S
+++ b/gdb/testsuite/gdb.dwarf2/frame-inlined-in-outer-frame.S
@@ -65,6 +65,16 @@
 	swi 0x0
 .endm
 
+#elif defined __powerpc64__
+
+# define RETURN_ADDRESS_REGNO 65
+
+.macro exit_0
+	li 0, __NR_exit  /* r0 - contains system call number */
+	li 3, 0          /* r3 - contains first argument for sys call */
+	sc
+.endm
+
 #else
 # error "Unsupported architecture"
 #endif
@@ -90,8 +100,28 @@
    16 }
 */
 
+#if defined __powerpc64__
+#  if _CALL_ELF == 2
+.abiversion 2   /* Tell gdb what ELF version to use. */
+.global _start
+_start:
+#  else
+.abiversion 1   /* Tell gdb what ELF version to use. */
+.align 2
+.global _start
+.section ".opd", "aw"
+.align 3
+_start:
+.quad ._start,.TOC.@tocbase,0
+.previous
+.type ._start,@function
+._start:
+#  endif
+#else
 .global _start
 _start:
+#endif
+
 .cfi_startproc
 
 /* State that the return address for this frame is undefined. */
-- 
2.30.2