From: Jan Beulich <jbeulich@suse.com>
Date: Fri, 14 Mar 2025 09:32:20 +0000 (+0100)
Subject: gas: permit LEB128 operands for .cfi_escape
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=9f42fb05256ad5731baf307dcdd321dd5d6b0828;p=thirdparty%2Fbinutils-gdb.git

gas: permit LEB128 operands for .cfi_escape

Many DW_CFA_* and DW_OP_* take LEB128 operands. Having to hand-encode
such when needing to resort to .cfi_escape isn't very helpful.
---

diff --git a/gas/doc/as.texi b/gas/doc/as.texi
index afe1737f4ce..edb498ac2f3 100644
--- a/gas/doc/as.texi
+++ b/gas/doc/as.texi
@@ -5176,7 +5176,18 @@ SPARC register window has been saved.
 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
 Allows the user to add arbitrary bytes to the unwind info.  One
 might use this to add OS-specific CFI opcodes, or generic CFI
-opcodes that GAS does not yet support.
+opcodes that GAS does not yet support.  To emit multi-byte data one may
+also use extended kind-of-expression forms:
+
+@itemize @bullet
+
+@item @code{sleb128(@var{expression})}
+to emit a SLEB128 item,
+
+@item @code{uleb128(@var{expression})}
+to emit a ULEB128 item.
+
+@end itemize
 
 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
 The current value of @var{register} is @var{label}.  The value of @var{label}
diff --git a/gas/dw2gencfi.c b/gas/dw2gencfi.c
index 310cb56a34e..45d2830f3db 100644
--- a/gas/dw2gencfi.c
+++ b/gas/dw2gencfi.c
@@ -941,7 +941,7 @@ dot_cfi (int arg)
 static void
 dot_cfi_escape (int ignored ATTRIBUTE_UNUSED)
 {
-  struct cfi_escape_data *head, **tail, *e;
+  struct cfi_escape_data *head, **tail;
   struct cfi_insn_data *insn;
 
   if (frchain_now->frch_cfi_data == NULL)
@@ -960,8 +960,39 @@ dot_cfi_escape (int ignored ATTRIBUTE_UNUSED)
   tail = &head;
   do
     {
-      e = notes_alloc (sizeof (*e));
-      e->reloc = do_parse_cons_expression (&e->exp, 1);
+      struct cfi_escape_data *e = notes_alloc (sizeof (*e));
+      char *id, *ilp_save = input_line_pointer;
+      char c = get_symbol_name (&id);
+
+      if (strcmp (id, "sleb128") == 0)
+	e->type = CFI_ESC_sleb128;
+      else if (strcmp (id, "uleb128") == 0)
+	e->type = CFI_ESC_uleb128;
+      else
+	e->type = CFI_ESC_byte;
+
+      c = restore_line_pointer (c);
+
+      if (e->type != CFI_ESC_byte)
+	{
+	  if (is_whitespace (c))
+	    c = *++input_line_pointer;
+	  if (c != '(')
+	    {
+	      input_line_pointer = ilp_save;
+	      e->type = CFI_ESC_byte;
+	    }
+	}
+
+      if (e->type == CFI_ESC_sleb128 || e->type == CFI_ESC_uleb128)
+	{
+	  /* We're still at the opening parenthesis.  Leave it to expression()
+	     to parse it and find the matching closing one.  */
+	  expression (&e->exp);
+	}
+      else
+	e->reloc = do_parse_cons_expression (&e->exp, 1);
+
       *tail = e;
       tail = &e->next;
     }
@@ -1778,7 +1809,12 @@ output_cfi_insn (struct cfi_insn_data *insn)
       {
 	struct cfi_escape_data *e;
 	for (e = insn->u.esc; e ; e = e->next)
-	  emit_expr_with_reloc (&e->exp, 1, e->reloc);
+	  {
+	    if (e->type == CFI_ESC_sleb128 || e->type == CFI_ESC_uleb128)
+	      emit_leb128_expr (&e->exp, e->type == CFI_ESC_sleb128);
+	    else
+	      emit_expr_with_reloc (&e->exp, 1, e->reloc);
+	  }
 	break;
       }
 
diff --git a/gas/dw2gencfi.h b/gas/dw2gencfi.h
index e9eec434573..c741f8f33ef 100644
--- a/gas/dw2gencfi.h
+++ b/gas/dw2gencfi.h
@@ -97,6 +97,11 @@ struct cfi_escape_data
 {
   struct cfi_escape_data *next;
   expressionS exp;
+  enum {
+    CFI_ESC_byte,
+    CFI_ESC_sleb128,
+    CFI_ESC_uleb128,
+  } type;
   TC_PARSE_CONS_RETURN_TYPE reloc;
 };
 
diff --git a/gas/gen-sframe.c b/gas/gen-sframe.c
index 15133cb698e..5b5e7b14b3a 100644
--- a/gas/gen-sframe.c
+++ b/gas/gen-sframe.c
@@ -1345,6 +1345,7 @@ sframe_xlate_do_escape_expr (const struct sframe_xlate_ctx *xlate_ctx,
 	  || i >= CFI_ESC_NUM_EXP
 	  || (i < 2
 	      && (e->exp.X_op != O_constant
+	 	  || e->type != CFI_ESC_byte
 		  || e->reloc != TC_PARSE_CONS_RETURN_NONE)))
 	goto warn_and_exit;
       items[i] = e->exp.X_add_number;
@@ -1409,6 +1410,7 @@ sframe_xlate_do_escape_val_offset (const struct sframe_xlate_ctx *xlate_ctx,
     {
       e = e->next;
       if (i >= CFI_ESC_NUM_EXP || e->exp.X_op != O_constant
+	  || e->type != CFI_ESC_byte
 	  || e->reloc != TC_PARSE_CONS_RETURN_NONE)
 	goto warn_and_exit;
       items[i] = e->exp.X_add_number;
@@ -1483,7 +1485,9 @@ sframe_xlate_do_cfi_escape (const struct sframe_xlate_ctx *xlate_ctx,
   if (!e)
     return SFRAME_XLATE_ERR_INVAL;
 
-  if (e->exp.X_op != O_constant || e->reloc != TC_PARSE_CONS_RETURN_NONE)
+  if (e->exp.X_op != O_constant
+      || e->type != CFI_ESC_byte
+      || e->reloc != TC_PARSE_CONS_RETURN_NONE)
     return SFRAME_XLATE_ERR_NOTREPRESENTED;
 
   firstop = e->exp.X_add_number;
@@ -1495,6 +1499,7 @@ sframe_xlate_do_cfi_escape (const struct sframe_xlate_ctx *xlate_ctx,
 	{
 	  e = e->next;
 	  if (e->exp.X_op != O_constant || e->exp.X_add_number != DW_CFA_nop
+	      || e->type != CFI_ESC_byte
 	      || e->reloc != TC_PARSE_CONS_RETURN_NONE)
 	    {
 	      warn_p = true;
diff --git a/gas/testsuite/gas/cfi/listing.l b/gas/testsuite/gas/cfi/listing.l
index b15c6ca605c..b30f1143020 100644
--- a/gas/testsuite/gas/cfi/listing.l
+++ b/gas/testsuite/gas/cfi/listing.l
@@ -20,8 +20,20 @@
 [ 	]*[0-9]*[ 	]+([0-9a-f]{4} [0 	]+)?\.cfi_endproc
 [ 	]*[0-9]*[ 	]*
 [ 	]*[0-9]*[ 	]+func2:
-[ 	]*[0-9]*[ 	]+[0-9a-f]{4} (1[048]00 ?0000|0000 ?001[048])[ 	]+\.cfi_startproc
+[ 	]*[0-9]*[ 	]+[0-9a-f]{4} ((1C|2[048])00 ?0000|0000 ?00(1C|2[048]))[ 	]+\.cfi_startproc
 [ 	]*[0-9]*[ 	]+(4[048]00 ?0000|0000 ?004[048]) *
 [ 	]*[0-9]*[ 	]+[0-9a-f]{4} .*[ 	]\.nop
+[ 	]*[0-9]*[ 	]+/\* DW_CFA_register reg127, reg129.  \*/
+[ 	]*[0-9]*[ 	]+[0-9a-f]{4} 4.09 ?7F81[ 	]+\.cfi_escape 0x09, uleb128\(127\), uleb128\(129\)
+[ 	]*[0-9]*[ 	]+01
+[ 	]*[0-9]*[ 	]+/\* DW_CFA_val_expression reg250, ...  \*/
+[ 	]*[0-9]*[ 	]+[0-9a-f]{4} 16FA ?01[ 	]+\.cfi_escape 0x16, uleb128\(250\)
+[ 	]*[0-9]*[ 	]+/\* ... <len>.  \*/
+[ 	]*[0-9]*[ 	]+[0-9a-f]{4} 03[ 	]+\.cfi_escape uleb128\(.LE0e - .LE0s\)
+[ 	]*[0-9]*[ 	]+\.cfi_label .LE0s
+[ 	]*[0-9]*[ 	]+/\* DW_OP_breg3.  \*/
+[ 	]*[0-9]*[ 	]+[0-9a-f]{4} 7380 ?78[ 	]+\.cfi_escape 0x73, sleb128\(-1024\)
+[ 	]*[0-9]*[ 	]+\.cfi_label .LE0e
+[ 	]*[0-9]*[ 	]+[0-9a-f]{4} .*[ 	]\.nop
 [ 	]*[0-9]*[ 	]+([0-9a-f]{4} [0 	]+)?\.cfi_endproc
 #pass
diff --git a/gas/testsuite/gas/cfi/listing.s b/gas/testsuite/gas/cfi/listing.s
index e091c54fa56..449ac8970ef 100644
--- a/gas/testsuite/gas/cfi/listing.s
+++ b/gas/testsuite/gas/cfi/listing.s
@@ -19,4 +19,15 @@ func:
 func2:
 	.cfi_startproc
 	.nop
+	/* DW_CFA_register reg127, reg129.  */
+	.cfi_escape 0x09, uleb128(127), uleb128(129)
+	/* DW_CFA_val_expression reg250, ...  */
+	.cfi_escape 0x16, uleb128(250)
+	/* ... <len>.  */
+	.cfi_escape uleb128(.LE0e - .LE0s)
+	.cfi_label .LE0s
+	/* DW_OP_breg3.  */
+	.cfi_escape 0x73, sleb128(-1024)
+	.cfi_label .LE0e
+	.nop
 	.cfi_endproc