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Re: [committed, PATCH] PR ld/20117: Don't convert R_386_GOT32 relocation

From: "H.J. Lu" <hjl dot tools at gmail dot com>
To: Binutils <binutils at sourceware dot org>
Date: Fri, 20 May 2016 09:44:49 -0700
Subject: Re: [committed, PATCH] PR ld/20117: Don't convert R_386_GOT32 relocation
Authentication-results: sourceware.org; auth=none
References: <20160519195835 dot GA12937 at intel dot com>

On Thu, May 19, 2016 at 12:58 PM, H.J. Lu <hongjiu.lu@intel.com> wrote:
> Don't convert R_386_GOT32 since we can't tell if it is applied
> to "mov $foo@GOT, %reg" which isn't a load via GOT.
>
> Checked into master.  Will backport it to 2.26 branch.
>
>
> H.J.
> --
> bfd/
>
>         PR ld/20117
>         * elf32-i386.c (elf_i386_convert_load_reloc): Don't check
>         R_386_GOT32X.
>         (elf_i386_convert_load): Don't convert R_386_GOT32.
>
> ld/
>
>         PR ld/20117
>         * testsuite/ld-i386/i386.exp: Run pr20117.
>         * testsuite/ld-i386/pr19609-1i.d: Updated.
>         * testsuite/ld-i386/pr20117.d: New file.
>         * testsuite/ld-i386/pr20117.s: Likewise.


This is what I checked into 2.26 branch.

-- 
H.J.

From c10d012d18caf2a39d7348a43eae7d8d5a940cdc Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Fri, 20 May 2016 09:41:50 -0700
Subject: [PATCH] Don't convert R_386_GOT32 relocation

Don't convert R_386_GOT32 since we can't tell if it is applied
to "mov $foo@GOT, %reg" which isn't a load via GOT.

bfd/

	Backport from master
	* elf32-i386.c (elf_i386_check_relocs): Don't check R_386_GOT32
	when setting need_convert_load.

	PR ld/20117
	* elf32-i386.c (elf_i386_convert_load): Don't convert
	R_386_GOT32.

ld/

	Backport from master
	PR ld/20117
	* testsuite/ld-i386/i386.exp: Run pr20117.
	* testsuite/ld-i386/pr20117.d: New file.
	* testsuite/ld-i386/pr20117.s: Likewise.
---
 bfd/ChangeLog                  | 14 ++++++++++++++
 bfd/elf32-i386.c               | 27 ++++++++++-----------------
 ld/ChangeLog                   | 10 ++++++++++
 ld/testsuite/ld-i386/i386.exp  |  1 +
 ld/testsuite/ld-i386/pr20117.d | 12 ++++++++++++
 ld/testsuite/ld-i386/pr20117.s |  7 +++++++
 6 files changed, 54 insertions(+), 17 deletions(-)
 create mode 100644 ld/testsuite/ld-i386/pr20117.d
 create mode 100644 ld/testsuite/ld-i386/pr20117.s

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index f56dca3..fbb8753 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,17 @@
+2016-05-20  H.J. Lu  <hongjiu.lu@intel.com>
+
+	Backport from master
+	2016-05-20  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* elf32-i386.c (elf_i386_check_relocs): Don't check R_386_GOT32
+	when setting need_convert_load.
+
+	2016-05-19  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/20117
+	* elf32-i386.c (elf_i386_convert_load): Don't convert
+	R_386_GOT32.
+
 2016-05-18  Christophe Monat  <christophe.monat@st.com>
 
 	Backport from master
diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c
index 79f339e..a3a241f 100644
--- a/bfd/elf32-i386.c
+++ b/bfd/elf32-i386.c
@@ -1962,7 +1962,7 @@ do_size:
 	    return FALSE;
 	}
 
-      if ((r_type == R_386_GOT32 || r_type == R_386_GOT32X)
+      if (r_type == R_386_GOT32X
 	  && (h == NULL || h->type != STT_GNU_IFUNC))
 	sec->need_convert_load = 1;
     }
@@ -2816,14 +2816,16 @@ elf_i386_convert_load (bfd *abfd, asection *sec,
       unsigned int nop;
       bfd_vma nop_offset;
 
-      if (r_type != R_386_GOT32 && r_type != R_386_GOT32X)
+      /* Don't convert R_386_GOT32 since we can't tell if it is applied
+	 to "mov $foo@GOT, %reg" which isn't a load via GOT.  */
+      if (r_type != R_386_GOT32X)
 	continue;
 
       roff = irel->r_offset;
       if (roff < 2)
 	continue;
 
-      /* Addend for R_386_GOT32 and R_386_GOT32X relocations must be 0.  */
+      /* Addend for R_386_GOT32X relocation must be 0.  */
       addend = bfd_get_32 (abfd, contents + roff);
       if (addend != 0)
 	continue;
@@ -2831,13 +2833,11 @@ elf_i386_convert_load (bfd *abfd, asection *sec,
       modrm = bfd_get_8 (abfd, contents + roff - 1);
       baseless = (modrm & 0xc7) == 0x5;
 
-      if (r_type == R_386_GOT32X
-	  && baseless
+      if (baseless
 	  && bfd_link_pic (link_info))
 	{
 	  /* For PIC, disallow R_386_GOT32X without a base register
-	     since we don't know what the GOT base is.   Allow
-	     R_386_GOT32 for existing object files.  */
+	     since we don't know what the GOT base is.  */
 	  const char *name;
 
 	  if (r_symndx < symtab_hdr->sh_info)
@@ -2865,12 +2865,6 @@ elf_i386_convert_load (bfd *abfd, asection *sec,
       /* It is OK to convert mov to lea.  */
       if (opcode != 0x8b)
 	{
-	  /* Only convert R_386_GOT32X relocation for call, jmp or
-	     one of adc, add, and, cmp, or, sbb, sub, test, xor
-	     instructions.  */
-	  if (r_type != R_386_GOT32X)
-	    continue;
-
 	  /* It is OK to convert indirect branch to direct branch.  It
 	     is OK to convert adc, add, and, cmp, or, sbb, sub, test,
 	     xor only when PIC is false.   */
@@ -2878,8 +2872,8 @@ elf_i386_convert_load (bfd *abfd, asection *sec,
 	    continue;
 	}
 
-      /* Try to convert R_386_GOT32 and R_386_GOT32X.  Get the symbol
-	 referred to by the reloc.  */
+      /* Try to convert R_386_GOT32X.  Get the symbol referred to by
+         the reloc.  */
       if (r_symndx < symtab_hdr->sh_info)
 	{
 	  isym = bfd_sym_from_r_symndx (&htab->sym_cache,
@@ -2991,8 +2985,7 @@ convert_load:
 		{
 		  /* Convert "mov foo@GOT(%reg1), %reg2" to
 		     "lea foo@GOTOFF(%reg1), %reg2".  */
-		  if (r_type == R_386_GOT32X
-		      && (baseless || !bfd_link_pic (link_info)))
+		  if (baseless || !bfd_link_pic (link_info))
 		    {
 		      r_type = R_386_32;
 		      /* For R_386_32, convert
diff --git a/ld/ChangeLog b/ld/ChangeLog
index c8ce258..5a6b5bd 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,13 @@
+2016-05-20  H.J. Lu  <hongjiu.lu@intel.com>
+
+	Backport from master
+	2016-05-19  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/20117
+	* testsuite/ld-i386/i386.exp: Run pr20117.
+	* testsuite/ld-i386/pr20117.d: New file.
+	* testsuite/ld-i386/pr20117.s: Likewise.
+
 2016-05-18  Christophe Monat  <christophe.monat@st.com>
 
 	Backport from master
diff --git a/ld/testsuite/ld-i386/i386.exp b/ld/testsuite/ld-i386/i386.exp
index 1916c24..b1332ff 100644
--- a/ld/testsuite/ld-i386/i386.exp
+++ b/ld/testsuite/ld-i386/i386.exp
@@ -328,6 +328,7 @@ run_dump_test "load5b"
 run_dump_test "load6"
 run_dump_test "pr19175"
 run_dump_test "pr19615"
+run_dump_test "pr20117"
 
 if { !([istarget "i?86-*-linux*"]
        || [istarget "i?86-*-gnu*"]
diff --git a/ld/testsuite/ld-i386/pr20117.d b/ld/testsuite/ld-i386/pr20117.d
new file mode 100644
index 0000000..59c77ee
--- /dev/null
+++ b/ld/testsuite/ld-i386/pr20117.d
@@ -0,0 +1,12 @@
+#as: --32
+#ld: -melf_i386
+#objdump: -dw
+
+.*: +file format .*
+
+
+Disassembly of section .text:
+
+[a-f0-9]+ <_start>:
+[ 	]*[a-f0-9]+:	eb 8b                	jmp    [a-f0-9]+ <_start\-0x[a-f0-9]+>
+[ 	]*[a-f0-9]+:	bd ([0-9a-f]{2} ){4} *	mov    \$0x[a-f0-9]+\,%ebp
diff --git a/ld/testsuite/ld-i386/pr20117.s b/ld/testsuite/ld-i386/pr20117.s
new file mode 100644
index 0000000..de2dd28
--- /dev/null
+++ b/ld/testsuite/ld-i386/pr20117.s
@@ -0,0 +1,7 @@
+	.comm	DEBUGLEVEL,4,4
+	.text
+	.globl	_start
+	.type	_start, @function
+_start:
+	.byte 0xeb, 0x8b
+	movl      $DEBUGLEVEL@GOT, %ebp
-- 
2.5.5

References:
- [committed, PATCH] PR ld/20117: Don't convert R_386_GOT32 relocation
  - From: H.J. Lu

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