[PATCH v3 06/15] gas: Skip SFrame FDE if CFI specifies non-FP/SP base register

[Jens Remus <jremus@linux.ibm.com>]

Do not generate SFrame FDE if DWARF CFI directives .cfi_def_cfa or
.cfi_def_cfa_register specify a CFA base register number other than
the architecture-specific stack-pointer (SP) or frame-pointer (FP)
register numbers.

This also causes the assembler to print a warning message, so that
skipping of the SFrame FDE does not occur silently.

Update the generic ld SFrame test case to be architecture independent.
Do not use CFI directive .cfi_def_cfa, as the specified CFA base
register number is not a valid SP/FP register number on all
architectures. An invalid SP/FP register number will now cause the
assembler to print a warning message and skip SFrame FDE generation.
Remove the offending CFI directive, that cannot be coded architecture-
independent, as the test case requires SFrame information to be
generated. This was reported by the Linaro-TCWG-CI for AArch64.

gas/
	* gen-sframe.c: Skip SFrame generation if CFI specifies
	non-FP/SP base register.

ld/testsuite/
	* ld-sframe/discard.s: Update generic SFrame test case to be
	architecture independent.

Reviewed-by: Andreas Krebbel <krebbel@linux.ibm.com>
Reviewed-by: Indu Bhagat <indu.bhagat@oracle.com>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---

Notes (jremus):
    Changes v2 -> v3:
    - Corrected formatting of ChangeLog in commit message.
    
    Changes v1 -> v2:
    - Update generic SFrame test case to be architecture independent to
      resolve generic ld SFrame test case failure reported by
      Linaro-TCWG-CI for AArch64. It would fail similar on s390x.
    
    Without this patch the assembler would erroneously generate bad SFrame
    information for the s390-specific SFrame error test cases 1 and 2, that
    get introduced by patch "s390: Initial support to generate .sframe from
    CFI directives in assembler".

 gas/gen-sframe.c                 | 13 +++++++++++--
 ld/testsuite/ld-sframe/discard.s |  1 -
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/gas/gen-sframe.c b/gas/gen-sframe.c
index d35baaac54b2..1269b2b77c54 100644
--- a/gas/gen-sframe.c
+++ b/gas/gen-sframe.c
@@ -986,7 +986,11 @@ sframe_xlate_do_def_cfa (struct sframe_xlate_ctx *xlate_ctx,
 			       get_dw_fde_start_addrS (xlate_ctx->dw_fde));
   }
   /* Define the current CFA rule to use the provided register and
-     offset.  */
+     offset.  However, if the register is not FP/SP, skip creating
+     SFrame stack trace info for the function.  */
+  if (cfi_insn->u.r != SFRAME_CFA_SP_REG
+      && cfi_insn->u.r != SFRAME_CFA_FP_REG)
+    return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented.  */
   sframe_fre_set_cfa_base_reg (cur_fre, cfi_insn->u.ri.reg);
   sframe_fre_set_cfa_offset (cur_fre, cfi_insn->u.ri.offset);
   cur_fre->merge_candidate = false;
@@ -1004,9 +1008,14 @@ sframe_xlate_do_def_cfa_register (struct sframe_xlate_ctx *xlate_ctx,
   struct sframe_row_entry *last_fre = xlate_ctx->last_fre;
   /* Get the scratchpad FRE.  This FRE will eventually get linked in.  */
   struct sframe_row_entry *cur_fre = xlate_ctx->cur_fre;
+
   gas_assert (cur_fre);
   /* Define the current CFA rule to use the provided register (but to
-     keep the old offset).  */
+     keep the old offset).  However, if the register is not FP/SP,
+     skip creating SFrame stack trace info for the function.  */
+  if (cfi_insn->u.r != SFRAME_CFA_SP_REG
+      && cfi_insn->u.r != SFRAME_CFA_FP_REG)
+    return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented.  */
   sframe_fre_set_cfa_base_reg (cur_fre, cfi_insn->u.ri.reg);
   sframe_fre_set_cfa_offset (cur_fre, last_fre->cfa_offset);
   cur_fre->merge_candidate = false;
diff --git a/ld/testsuite/ld-sframe/discard.s b/ld/testsuite/ld-sframe/discard.s
index a438b42bffa1..5591a50d486a 100644
--- a/ld/testsuite/ld-sframe/discard.s
+++ b/ld/testsuite/ld-sframe/discard.s
@@ -5,7 +5,6 @@
 foo:
 	.cfi_startproc
 	.cfi_def_cfa_offset 16
-	.cfi_def_cfa 7, 8
 	.cfi_endproc
 
 	.globl _start
-- 
2.40.1