[PATCH,AIX] Enable Stack Unwinding on AIX

[PATCH,AIX] Enable Stack Unwinding on AIX

[REIX, Tony]

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Description:
 * This patch enables the stack unwinding on AIX.

Tests:
 * Fedora25/x86_64 + GCC v7.1.0 : Configure/Build: SUCCESS
   - build made by means of a .spec file based on Fedora gcc-7.0.1-0.12 .spec file
     ../configure --enable-bootstrap --enable-languages=c,c++,objc,obj-c++,fortran,go,lto --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared --enable-threads=posix --enable-checking=release --enable-multilib --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-linker-build-id --with-gcc-major-version-only --with-linker-hash-style=gnu --enable-plugin --enable-initfini-array --with-isl --enable-libmpx --enable-offload-targets=nvptx-none --without-cuda-driver --enable-gnu-indirect-function --with-tune=generic --with-arch_32=i686 --build=x86_64-redhat-linux

ChangeLog:
  * libgcc/config/rs6000/aix-unwind.h : Implements stack unwinding on AIX.

Regards,

Tony Reix
Bull - ATOS
IBM Coop Architect & Technical Leader
Office : +33 (0) 4 76 29 72 67
1 rue de Provence - 38432 Échirolles - France
www.atos.net

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--- ./libgcc/config/rs6000/aix-unwind.h	2017-01-02 01:20:05 -0600
+++ ./libgcc/config/rs6000/aix-unwind.h	2017-04-28 10:03:16 -0500
@@ -64,7 +64,8 @@
 #endif
 
 /* Now on to MD_FALLBACK_FRAME_STATE_FOR.
-   32bit AIX 5.2, 5.3 and 7.1 only at this stage.  */
+   32bit AIX 5.2, 5.3, 6.1, 7.X and
+   64bit AIX 6.1, 7.X only at this stage.  */
 
 #include <stdlib.h>
 #include <stddef.h>
@@ -73,10 +74,10 @@
 
 #ifdef __64BIT__
 
-/* 64bit fallback not implemented yet, so MD_FALLBACK_FRAME_STATE_FOR not
-   defined.  Arrange just for the code below to compile.  */
 typedef struct __context64 mstate_t;
 
+#define MD_FALLBACK_FRAME_STATE_FOR ppc_aix_fallback_frame_state
+
 #else
 
 typedef struct mstsave mstate_t;
@@ -128,10 +129,26 @@ ucontext_for (struct _Unwind_Context *co
 {
   const unsigned int * ra = context->ra;
 
-  /* AIX 5.2, 5.3 and 7.1, threaded or not, share common patterns
+  /* AIX 5.2, 5.3, 6.1 and 7.X, threaded or not, share common patterns
      and feature variants depending on the configured kernel (unix_mp
      or unix_64).  */
 
+#ifdef __64BIT__
+  if (*(ra - 5) == 0x4c00012c     /* isync             */
+      && *(ra - 4) == 0xe8ec0000  /* ld      r7,0(r12) */
+      && *(ra - 3) == 0xe84c0008  /* ld      r2,8(r12) */
+      && *(ra - 2) == 0x7ce903a6  /* mtctr   r7        */
+      && *(ra - 1) == 0x4e800421  /* bctrl             */
+      && *(ra - 0) == 0x7de27b78) /* mr      r2,r15   <-- context->ra */
+    {
+      /* unix_64 */
+      if (*(ra - 6) == 0x7d000164)  /* mtmsrd  r8 */
+        {
+          /* AIX 6.1, 7.1 and 7.2 */
+          return (ucontext_t *)(context->cfa + 0x70);
+        }
+    }
+#else
   if (*(ra - 5) == 0x4c00012c     /* isync             */
       && *(ra - 4) == 0x80ec0000  /* lwz     r7,0(r12) */
       && *(ra - 3) == 0x804c0004  /* lwz     r2,4(r12) */
@@ -152,10 +169,14 @@ ucontext_for (struct _Unwind_Context *co
 	    case 0x835a0570:  /* lwz r26,1392(r26) */
 	      return (ucontext_t *)(context->cfa + 0x40);
 
-	      /* AIX 7.1 */
+	      /* AIX 6.1 and 7.1 */
 	    case 0x2c1a0000:  /* cmpwi   r26,0 */
 	      return (ucontext_t *)(context->cfa + 0x40);
-		
+
+	      /* AIX 7.2 */
+	    case 0x3800000a:  /* li   r0,A */
+	      return (ucontext_t *)(context->cfa + 0x40);
+
 	    default:
 	      return 0;
 	    }
@@ -174,7 +195,7 @@ ucontext_for (struct _Unwind_Context *co
 	  return &frame->ucontext;
 	}
     }
-
+#endif
   return 0;
 }
 

Re: [PATCH,AIX] Enable Stack Unwinding on AIX

[David Edelsohn]

On Tue, May 16, 2017 at 9:50 AM, REIX, Tony <tony.reix@atos.net> wrote:
> Tests:
>
> The change has been tested in 32bit and 64bit on AIX 6.1, 7.1 & 7.2 by using the libbacktrace (with XCOFF support) within a signal handler context (we used a specific back.c program).
> And it has been tested with Go tests on AIX for sure (recover tests on SIGSEGV do not work without this change).
>
> ChangeLog:
>
> * config/rs6000/aix-unwind.h (ppc_aix_fallback_frame_state): Add 64 bit support for AIX 6.1 and 7.X and 32 bit support for AIX 7.2.

If ppc_aix_fallback_frame_state is used for both 32 bit and 64 bit,
there is no need to define it twice.  Just move the
MD_FALLBACK_FRAME_STATE_FOR macro definition outside the #ifdef.  This
also needs a separate ChangeLog comment.

The function that you modified is "ucontext_for".  Please use that
name in the ChangeLog entry.

Will you need someone to apply the patch for you?

Thanks, David

Re: [PATCH,AIX] Enable Stack Unwinding on AIX

[David Edelsohn]

Please do not email my IBM Notes address with patches.  Please copy
this Gmail address for patch submissions.

>   * libgcc/config/rs6000/aix-unwind.h : Implements stack unwinding on AIX.

This ChangeLog entry clearly is wrong because aix-unwind.h already
implements ppc_aix_fallback_frame_state.  The ChangeLog entry should
reference the exact function being modified and a useful comment about
how it is modified, e.g.,

* config/rs6000/aix-unwind.h (ppc_aix_fallback_frame_state): Add 64
bit support Add 32 bit support for AIX 6.1 and 7.2.

The ChangeLog file is in libgcc, so the file reference is wrong
because it should not use libgcc in the path.

How was this tested?

Thanks, David