[binutils-gdb] gas: gcfg: fix handling of non-local direct jmps in gcfg

[binutils-gdb] gas: gcfg: fix handling of non-local direct jmps in gcfg

[Indu Bhagat]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=e67388a6a475ab1ddaac596f9995789363f1f10c

commit e67388a6a475ab1ddaac596f9995789363f1f10c
Author: Indu Bhagat <indu.bhagat@oracle.com>
Date:   Thu Mar 28 11:57:23 2024 -0700

    gas: gcfg: fix handling of non-local direct jmps in gcfg
    
    The ginsn infrastructure in GAS includes the ability to create a GCFG
    (ginsn CFG).  A GCFG is currently used for SCFI passes.
    
    This patch fixes the following invalid assumptions / code blocks:
     - The function ginsn_direct_local_jump_p () was erroneously _not_
       checking whether the symbol is locally defined (i.e., within the
       scope of the code block for which GCFG is desired).  Fix the code
       to do so.
     - Similarly, the GCFG creation code, in gcfg_build () itself had an
       assumption that a GINSN_TYPE_JUMP to a non-local symbol will not be
       seen.  The latter can indeed be seen, and in fact, needs to be treated
       the same way as an exit from the function in terms of control-flow.
    
    gas/
            * ginsn.c (ginsn_direct_local_jump_p): Check if the symbol
            is local to the code block or function being assembled.
            (add_bb_at_ginsn): Remove buggy assumption.
            (frch_ginsn_data_append): Direct jmps do not disqualify a stream
            of ginsns from GCFG creation.
    
    gas/testsuite/
            * gas/scfi/x86_64/scfi-cfg-3.d: New test.
            * gas/scfi/x86_64/scfi-cfg-3.l: New test.
            * gas/scfi/x86_64/scfi-cfg-3.s: New test.
            * gas/scfi/x86_64/scfi-x86-64.exp: Add new test.

Diff:
---
 gas/ginsn.c                                   | 47 ++++++++++++++++-----------
 gas/testsuite/gas/scfi/x86_64/scfi-cfg-3.d    | 32 ++++++++++++++++++
 gas/testsuite/gas/scfi/x86_64/scfi-cfg-3.l    |  2 ++
 gas/testsuite/gas/scfi/x86_64/scfi-cfg-3.s    | 40 +++++++++++++++++++++++
 gas/testsuite/gas/scfi/x86_64/scfi-x86-64.exp |  2 ++
 5 files changed, 104 insertions(+), 19 deletions(-)

diff --git a/gas/ginsn.c b/gas/ginsn.c
index 661f51d23c5..492e161876b 100644
--- a/gas/ginsn.c
+++ b/gas/ginsn.c
@@ -444,16 +444,26 @@ ginsn_indirect_jump_p (ginsnS *ginsn)
   return ret_p;
 }
 
+/* Return whether the GINSN is an unconditional jump to a label which is
+   defined locally in the scope of the block of insns, which are currently
+   being processed for GCFG creation.  */
+
 static bool
 ginsn_direct_local_jump_p (ginsnS *ginsn)
 {
-  bool ret_p = false;
+  bool local_p = false;
+  const symbolS *taken_label;
+
   if (!ginsn)
-    return ret_p;
+    return local_p;
 
-  ret_p |= (ginsn->type == GINSN_TYPE_JUMP
-	    && ginsn->src[0].type == GINSN_SRC_SYMBOL);
-  return ret_p;
+  if (ginsn->type == GINSN_TYPE_JUMP
+      && ginsn->src[0].type == GINSN_SRC_SYMBOL)
+    {
+      taken_label = ginsn->src[0].sym;
+      local_p = (label_ginsn_map_find (taken_label) != NULL);
+    }
+  return local_p;
 }
 
 static char *
@@ -785,16 +795,13 @@ add_bb_at_ginsn (const symbolS *func, gcfgS *gcfg, ginsnS *ginsn, gbbS *prev_bb,
 	  || ginsn->type == GINSN_TYPE_JUMP_COND
 	  || ginsn->type == GINSN_TYPE_RETURN)
 	{
-	  /* Indirect Jumps or direct jumps to symbols non-local to the
-	     function must not be seen here.  The caller must have already
-	     checked for that.  */
+	  /* Indirect jumps must not be seen here.  The caller must have
+	     already checked for that.  */
 	  gas_assert (!ginsn_indirect_jump_p (ginsn));
-	  if (ginsn->type == GINSN_TYPE_JUMP)
-	    gas_assert (ginsn_direct_local_jump_p (ginsn));
 
-	  /* Direct Jumps.  May include conditional or unconditional change of
-	     flow.  What is important for CFG creation is that the target be
-	     local to function.  */
+	  /* Handle direct jumps.  For unconditional direct jumps, where the
+	     target is not local to the function, treat them later as similar
+	     to an exit from function (in the else block).  */
 	  if (ginsn->type == GINSN_TYPE_JUMP_COND
 	      || ginsn_direct_local_jump_p (ginsn))
 	    {
@@ -822,10 +829,14 @@ add_bb_at_ginsn (const symbolS *func, gcfgS *gcfg, ginsnS *ginsn, gbbS *prev_bb,
 	      /* Add the bb for the fall through path.  */
 	      find_or_make_bb (func, gcfg, ginsn->next, prev_bb, errp);
 	    }
-	 else if (ginsn->type == GINSN_TYPE_RETURN)
+	 else
 	   {
-	     /* We'll come back to the ginsns following GINSN_TYPE_RETURN
-		from another path if they are indeed reachable code.  */
+	     gas_assert (ginsn->type == GINSN_TYPE_RETURN
+			 || (ginsn->type == GINSN_TYPE_JUMP
+			     && !ginsn_direct_local_jump_p (ginsn)));
+	     /* We'll come back to the ginsns following GINSN_TYPE_RETURN or
+		other (non-local) unconditional jmps from another path if they
+		are indeed reachable code.  */
 	     break;
 	   }
 
@@ -1083,9 +1094,7 @@ frch_ginsn_data_append (ginsnS *ginsn)
     {
       temp->id = ++id;
 
-      if (ginsn_indirect_jump_p (temp)
-	  || (ginsn->type == GINSN_TYPE_JUMP
-	      && !ginsn_direct_local_jump_p (temp)))
+      if (ginsn_indirect_jump_p (temp))
 	frchain_now->frch_ginsn_data->gcfg_apt_p = false;
 
       if (listing & LISTING_GINSN_SCFI)
diff --git a/gas/testsuite/gas/scfi/x86_64/scfi-cfg-3.d b/gas/testsuite/gas/scfi/x86_64/scfi-cfg-3.d
new file mode 100644
index 00000000000..c5a9838e527
--- /dev/null
+++ b/gas/testsuite/gas/scfi/x86_64/scfi-cfg-3.d
@@ -0,0 +1,32 @@
+#as: --scfi=experimental -W
+#as:
+#objdump: -Wf
+#name: Synthesize CFI in presence of control flow 3
+#...
+Contents of the .eh_frame section:
+
+00000000 0+0014 0+0000 CIE
+  Version:               1
+  Augmentation:          "zR"
+  Code alignment factor: 1
+  Data alignment factor: -8
+  Return address column: 16
+  Augmentation data:     1b
+  DW_CFA_def_cfa: r7 \(rsp\) ofs 8
+  DW_CFA_offset: r16 \(rip\) at cfa-8
+  DW_CFA_nop
+  DW_CFA_nop
+
+0+0018 0+0010 0+001c FDE cie=00000000 pc=0+0000..0+001e
+  DW_CFA_nop
+#...
+
+0+002c 0+0018 0+0030 FDE cie=00000000 pc=0+001e..0+0029
+  DW_CFA_advance_loc: 1 to 0+001f
+  DW_CFA_def_cfa_offset: 16
+  DW_CFA_offset: r6 \(rbp\) at cfa-16
+  DW_CFA_advance_loc: 3 to 0+0022
+  DW_CFA_def_cfa_register: r6 \(rbp\)
+  DW_CFA_nop
+
+#pass
diff --git a/gas/testsuite/gas/scfi/x86_64/scfi-cfg-3.l b/gas/testsuite/gas/scfi/x86_64/scfi-cfg-3.l
new file mode 100644
index 00000000000..23ca73422b5
--- /dev/null
+++ b/gas/testsuite/gas/scfi/x86_64/scfi-cfg-3.l
@@ -0,0 +1,2 @@
+.*Assembler messages:
+.*9: Warning: SCFI ignores most user-specified CFI directives
diff --git a/gas/testsuite/gas/scfi/x86_64/scfi-cfg-3.s b/gas/testsuite/gas/scfi/x86_64/scfi-cfg-3.s
new file mode 100644
index 00000000000..1c8f9b9e910
--- /dev/null
+++ b/gas/testsuite/gas/scfi/x86_64/scfi-cfg-3.s
@@ -0,0 +1,40 @@
+# Testcase with jmp to function instead of a call.
+# Also includes a jmp to label locally defined.
+# The CFG creation process is not expected to warn about
+# missing foo_handler_v1 or xstrdup.
+	.text
+	.globl  foo_handler
+	.type   foo_handler, @function
+foo_handler:
+	.cfi_startproc
+	movl    current_style(%rip), %eax
+	jmp     .L2
+.L2:
+	cmpl    $-1, %eax
+	je      .L5
+	testb   $4, %al
+	je      .L3
+	jmp     foo_handler_v1
+.L3:
+	xorl    %eax, %eax
+	ret
+.L5:
+	jmp     xstrdup
+	.cfi_endproc
+	.size   foo_handler, .-foo_handler
+
+# New function with unconditional jump to a label previously defined
+# in a different function.
+	.globl  bar
+	.type   bar, @function
+bar:
+	.cfi_startproc
+	pushq   %rbp
+	.cfi_def_cfa_offset 16
+	.cfi_offset %rbp, -16
+	movq    %rsp, %rbp
+	.cfi_def_cfa_register %rbp
+	movl    $0, %eax
+	jmp     .L2
+	.cfi_endproc
+	.size   bar, .-bar
diff --git a/gas/testsuite/gas/scfi/x86_64/scfi-x86-64.exp b/gas/testsuite/gas/scfi/x86_64/scfi-x86-64.exp
index 5324af386f8..c004d99b4ac 100644
--- a/gas/testsuite/gas/scfi/x86_64/scfi-x86-64.exp
+++ b/gas/testsuite/gas/scfi/x86_64/scfi-x86-64.exp
@@ -78,6 +78,8 @@ if  { ([istarget "x86_64-*-*"] && ![istarget "x86_64-*-linux*-gnux32"]) } then {
     run_list_test "scfi-cfg-1" "--scfi=experimental --warn"
     run_dump_test "scfi-cfg-2"
     run_list_test "scfi-cfg-2" "--scfi=experimental --warn"
+    run_dump_test "scfi-cfg-3"
+    run_list_test "scfi-cfg-3" "--scfi=experimental --warn"
     run_dump_test "scfi-asm-marker-1"
     run_list_test "scfi-asm-marker-1" "--scfi=experimental --warn"
     run_dump_test "scfi-asm-marker-2"