gas: allow labeling of CFI instructions

When runtime patching code (like e.g. done by the Linux kernel) there
may be cases where the set of stack frame alterations differs between
unpatched and patched code. Consequently the corresponding unwind data
needs patching too. Locating the right places within an FDE, however,
is rather cumbersome without a way to insert labels in the resulting
section. Hence this patch introduces a new directive, .cfi_label. Note
that with the way CFI data gets emitted currently (at the end of the
assembly process) this can't support local FB- and dollar-labels.

gas/
2015-01-12  Jan Beulich  <jbeulich@suse.com>

	* gas/dw2gencfi.c (cfi_add_label, dot_cfi_label): New.
	(cfi_pseudo_table): Add "cfi_label".
	(output_cfi_insn): Handle CFI_label.
	(select_cie_for_fde): Als terminate CIE when encountering
	CFI_label.
	* dw2gencfi.h (cfi_add_label): Declare.
	(struct cfi_insn_data): New member "sym_name".
	(CFI_label): New.
	* read.c (read_symbol_name): Drop "static".
	* read.h (read_symbol_name): Declare.

gas/testsuite/
2015-01-12  Jan Beulich  <jbeulich@suse.com>

	gas/cfi/cfi-label.d, gas/cfi/cfi-label.s: New.
	gas/cfi/cfi.exp: Run new tests.

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 2e3b2e9c13a7079035853e23f6c161c17c215a9f..78501edc333b0e25cb0ccff93911d17c5b78cc06 100644 (file)
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,16 @@
+2015-01-12  Jan Beulich  <jbeulich@suse.com>
+
+       * gas/dw2gencfi.c (cfi_add_label, dot_cfi_label): New.
+       (cfi_pseudo_table): Add "cfi_label".
+       (output_cfi_insn): Handle CFI_label.
+       (select_cie_for_fde): Als terminate CIE when encountering
+       CFI_label.
+       * dw2gencfi.h (cfi_add_label): Declare.
+       (struct cfi_insn_data): New member "sym_name".
+       (CFI_label): New.
+       * read.c (read_symbol_name): Drop "static".
+       * read.h (read_symbol_name): Declare.
+
 2015-01-12  Jan Beulich  <jbeulich@suse.com>
 
        * gas/config/tc-arm.c (do_neon_shl_imm): Check immediate range.

diff --git a/gas/dw2gencfi.c b/gas/dw2gencfi.c
index 939c41a22391fb604e0981ded5ba9e127873d94e..6a80d0b0f19dbdd6d3678d65d1da7999857235cf 100644 (file)
--- a/gas/dw2gencfi.c
+++ b/gas/dw2gencfi.c
@@ -440,6 +440,19 @@ cfi_add_advance_loc (symbolS *label)
   frchain_now->frch_cfi_data->last_address = label;
 }
 
+/* Add a CFI insn to label the current position in the CFI segment.  */
+
+void
+cfi_add_label (const char *name)
+{
+  unsigned int len = strlen (name) + 1;
+  struct cfi_insn_data *insn = alloc_cfi_insn_data ();
+
+  insn->insn = CFI_label;
+  obstack_grow (&notes, name, len);
+  insn->u.sym_name = (char *) obstack_finish (&notes);
+}
+
 /* Add a DW_CFA_offset record to the CFI data.  */
 
 void
@@ -550,6 +563,7 @@ static void dot_cfi_endproc (int);
 static void dot_cfi_personality (int);
 static void dot_cfi_lsda (int);
 static void dot_cfi_val_encoded_addr (int);
+static void dot_cfi_label (int);
 
 const pseudo_typeS cfi_pseudo_table[] =
   {
@@ -575,6 +589,7 @@ const pseudo_typeS cfi_pseudo_table[] =
     { "cfi_personality", dot_cfi_personality, 0 },
     { "cfi_lsda", dot_cfi_lsda, 0 },
     { "cfi_val_encoded_addr", dot_cfi_val_encoded_addr, 0 },
+    { "cfi_label", dot_cfi_label, 0 },
     { NULL, NULL, 0 }
   };
 
@@ -1016,6 +1031,25 @@ dot_cfi_val_encoded_addr (int ignored ATTRIBUTE_UNUSED)
   demand_empty_rest_of_line ();
 }
 
+static void
+dot_cfi_label (int ignored ATTRIBUTE_UNUSED)
+{
+  char *name = read_symbol_name ();
+
+  if (name == NULL)
+    return;
+
+  /* If the last address was not at the current PC, advance to current.  */
+  if (symbol_get_frag (frchain_now->frch_cfi_data->last_address) != frag_now
+      || S_GET_VALUE (frchain_now->frch_cfi_data->last_address)
+        != frag_now_fix ())
+    cfi_add_advance_loc (symbol_temp_new_now ());
+
+  cfi_add_label (name);
+
+  demand_empty_rest_of_line ();
+}
+
 /* By default emit .eh_frame only, not .debug_frame.  */
 #define CFI_EMIT_eh_frame      (1 << 0)
 #define CFI_EMIT_debug_frame   (1 << 1)
@@ -1386,6 +1420,10 @@ output_cfi_insn (struct cfi_insn_data *insn)
       }
       break;
 
+    case CFI_label:
+      colon (insn->u.sym_name);
+      break;
+
     default:
       abort ();
     }
@@ -1761,7 +1799,8 @@ select_cie_for_fde (struct fde_entry *fde, bfd_boolean eh_frame,
     if (i->insn == DW_CFA_advance_loc
        || i->insn == DW_CFA_remember_state
        || i->insn == CFI_escape
-       || i->insn == CFI_val_encoded_addr)
+       || i->insn == CFI_val_encoded_addr
+       || i->insn == CFI_label)
       break;
 
   cie->last = i;

diff --git a/gas/dw2gencfi.h b/gas/dw2gencfi.h
index e80b19e5e174e8047170f2e369c6e027e086f68c..6e2c50e5143d6ff57790be6fd2158dd7d20487c9 100644 (file)
--- a/gas/dw2gencfi.h
+++ b/gas/dw2gencfi.h
@@ -37,6 +37,7 @@ extern void cfi_new_fde (struct symbol *);
 extern void cfi_end_fde (struct symbol *);
 extern void cfi_set_return_column (unsigned);
 extern void cfi_add_advance_loc (struct symbol *);
+extern void cfi_add_label (const char *);
 
 extern void cfi_add_CFA_offset (unsigned, offsetT);
 extern void cfi_add_CFA_def_cfa (unsigned, offsetT);
@@ -94,6 +95,8 @@ struct cfi_insn_data
       unsigned reg, encoding;
       expressionS exp;
     } ea;
+
+    const char *sym_name;
   } u;
 };
 
@@ -128,5 +131,6 @@ extern struct fde_entry *all_fde_data;
 #define CFI_escape             0x103
 #define CFI_signal_frame       0x104
 #define CFI_val_encoded_addr   0x105
+#define CFI_label              0x106
 
 #endif /* DW2GENCFI_H */

diff --git a/gas/read.c b/gas/read.c
index 7dfc20a737116c5968d1bf457c0c6e6a569055dc..b2d50272d7fde8ba2af87a29c905c8dd245e08ae 100644 (file)
--- a/gas/read.c
+++ b/gas/read.c
@@ -1600,7 +1600,7 @@ s_altmacro (int on)
    If a symbol name could not be read, the routine issues an error
    messages, skips to the end of the line and returns NULL.  */
 
-static char *
+char *
 read_symbol_name (void)
 {
   char * name;

diff --git a/gas/read.h b/gas/read.h
index 32d376727b69c6abb412a68d7c1e03eda726ebb9..d7ac6ce26abbd4e59a61f3913a03d93f64ab926a 100644 (file)
--- a/gas/read.h
+++ b/gas/read.h
@@ -127,6 +127,7 @@ extern void pseudo_set (symbolS * symbolP);
 extern void read_a_source_file (char *name);
 extern void read_begin (void);
 extern void read_print_statistics (FILE *);
+extern char *read_symbol_name (void);
 extern int sizeof_leb128 (valueT, int sign);
 extern void stabs_generate_asm_file (void);
 extern void stabs_generate_asm_lineno (void);

diff --git a/gas/testsuite/ChangeLog b/gas/testsuite/ChangeLog
index ef359a1ba57a528b9045c8c4881009564d6501df..54d9c6e8ed7707fde83b9a69636214df9945fcf8 100644 (file)
--- a/gas/testsuite/ChangeLog
+++ b/gas/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2015-01-12  Jan Beulich  <jbeulich@suse.com>
+
+       gas/cfi/cfi-label.d, gas/cfi/cfi-label.s: New.
+       gas/cfi/cfi.exp: Run new tests.
+
 2015-01-12  Jan Beulich  <jbeulich@suse.com>
 
        * gas/arm/neon-addressing-bad.s: Add test for invalid VSHL,

diff --git a/gas/testsuite/gas/cfi/cfi-label.d b/gas/testsuite/gas/cfi/cfi-label.d
new file mode 100644 (file)
index 0000000..e96c795
--- /dev/null
+++ b/gas/testsuite/gas/cfi/cfi-label.d
@@ -0,0 +1,43 @@
+#objdump: -tWf
+#name: .cfi_label directive
+
+.*\.o:     file format elf.*
+
+SYMBOL TABLE:
+0*00 l    d  \.text    0*00 \.text
+0*00 l    d  \.data    0*00 \.data
+0*00 l    d  \.bss     0*00 \.bss
+0*00 l     F \.text    0*04 cfilabel
+0*2f l       \.eh_frame        0*00 cfi2
+0*00 l    d  \.eh_frame        0*00 \.eh_frame
+0*2b g       \.eh_frame        0*00 cfi1
+
+
+Contents of the .eh_frame section:
+
+0*00 0*14 0*00 CIE
+  Version:               1
+  Augmentation:          "zR"
+  Code alignment factor: 1
+  Data alignment factor: -[48]
+  Return address column: (8|16)
+  Augmentation data:     1b
+
+  DW_CFA_def_cfa: r.* \([er]sp\) ofs [48]
+  DW_CFA_offset: r.* \([er]ip\) at cfa-[48]
+  DW_CFA_nop
+  DW_CFA_nop
+
+0*18 0*1[8c] 0*1c FDE cie=0*00 pc=0*00..0*04
+  DW_CFA_remember_state
+  DW_CFA_advance_loc: 1 to 0*01
+  DW_CFA_nop
+  DW_CFA_nop
+  DW_CFA_nop
+  DW_CFA_advance_loc: 1 to 0*02
+  DW_CFA_nop
+  DW_CFA_nop
+  DW_CFA_advance_loc: 1 to 0*03
+  DW_CFA_nop
+  DW_CFA_restore_state
+#pass

diff --git a/gas/testsuite/gas/cfi/cfi-label.s b/gas/testsuite/gas/cfi/cfi-label.s
new file mode 100644 (file)
index 0000000..f0297ab
--- /dev/null
+++ b/gas/testsuite/gas/cfi/cfi-label.s
@@ -0,0 +1,19 @@
+       .text
+cfilabel:
+       .cfi_startproc
+       .cfi_remember_state
+       nop
+       .globl cfi1
+       .cfi_label cfi1
+       .cfi_escape 0, 0, 0
+       nop
+       .cfi_label cfi2
+       .cfi_escape 0, 0
+       nop
+       .cfi_label .Lcfi3
+       .cfi_escape 0
+       .cfi_restore_state
+       ret
+       .cfi_endproc
+       .type cfilabel, STT_FUNC
+       .size cfilabel, . - cfilabel

diff --git a/gas/testsuite/gas/cfi/cfi.exp b/gas/testsuite/gas/cfi/cfi.exp
index 33ae13e9578a4babc1a8edd77a1be00e5c91df0b..be84941b7c137b7d5bbc53ba5563f0d7be4587ad 100644 (file)
--- a/gas/testsuite/gas/cfi/cfi.exp
+++ b/gas/testsuite/gas/cfi/cfi.exp
@@ -51,6 +51,10 @@ if  { [istarget "i*86-*-*"] || [istarget "x86_64-*-*"] } then {
        set ASFLAGS "$old_ASFLAGS"
     }
 
+    if { [is_elf_format] } then {
+       run_dump_test "cfi-label"
+    }
+
     if { [is_pecoff_format] } then {
        run_dump_test "reloc-pe-i386"
     }