[binutils-gdb] gas: Skip SFrame FDE if CFI specifies non-FP/SP base register

[Jens Remus]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=e24992c3341a1f8e69e74b74e7d1a813445dc0b7

commit e24992c3341a1f8e69e74b74e7d1a813445dc0b7
Author: Jens Remus <jremus@linux.ibm.com>
Date:   Thu Jul 4 10:34:12 2024 +0200

    gas: Skip SFrame FDE if CFI specifies non-FP/SP base register
    
    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.
    
    Signed-off-by: Jens Remus <jremus@linux.ibm.com>

Diff:
---
 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 116d1f48f78..52c2f3f4ff8 100644
--- a/gas/gen-sframe.c
+++ b/gas/gen-sframe.c
@@ -988,7 +988,11 @@ 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;
@@ -1006,9 +1010,14 @@ 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 a438b42bffa..5591a50d486 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