Re: Start of relro segment adjustment

["H.J. Lu" <hjl.tools@gmail.com>]

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On Wed, Apr 1, 2015 at 2:11 AM, Alan Modra <amodra@gmail.com> wrote:
> Adjusting the start of the relro segment in order to make it end
> exactly on a page boundary runs into difficulties when sections in the
> relro segment are aligned;  Adjusting the start by (next_page - end)
> sometimes results in more than that adjustment occurring at the end,
> overrunning the page boundary.  So when that occurs we try a new lower
> start position by masking the adjusted start with the maximum section
> alignment.  However, we didn't consider that this masked start address
> may in fact be before the initial relro base, which is silly since
> that can only increase padding at the relro end.
>
> I've also moved some calculations closer to where they are used, and
> comments closer to the relevant statements.
>
>         * ldlang.c (lang_size_sections): When alignment of sections
>         results in relro base adjustment being too large, don't go lower
>         than the initial value.
>         * ldexp.c (fold_binary <DATA_SEGMENT_RELRO_END>): Comment.
>         * scripttempl/elf.sc (DATA_SEGMENT_ALIGN): Omit SEGMENT_SIZE
>         alignment when SEGMENT_SIZE is the same as MAXPAGESIZE.
>

Thanks.

I checked in this testcase.


-- 
H.J.

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From 875b5b9d147d37c99a189aa95354f9bebdd64ef5 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Wed, 1 Apr 2015 04:24:05 -0700
Subject: [PATCH] Add a testcase for PR ld/18176

	PR ld/18176
	* ld-x86-64/pr18176.d: New file.
	* ld-x86-64/pr18176.s: Likewise.
	* ld-x86-64/pr18176.t: Likewise.
	* ld-x86-64/x86-64.exp: Run pr18176.
---
 ld/ChangeLog                      |  1 +
 ld/testsuite/ChangeLog            |  8 ++++++
 ld/testsuite/ld-x86-64/pr18176.d  |  9 +++++++
 ld/testsuite/ld-x86-64/pr18176.s  | 52 +++++++++++++++++++++++++++++++++++++++
 ld/testsuite/ld-x86-64/pr18176.t  | 39 +++++++++++++++++++++++++++++
 ld/testsuite/ld-x86-64/x86-64.exp |  1 +
 6 files changed, 110 insertions(+)
 create mode 100644 ld/testsuite/ld-x86-64/pr18176.d
 create mode 100644 ld/testsuite/ld-x86-64/pr18176.s
 create mode 100644 ld/testsuite/ld-x86-64/pr18176.t

diff --git a/ld/ChangeLog b/ld/ChangeLog
index 718cdb6..6082e28 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -5,6 +5,7 @@
 
 2015-04-01  Alan Modra  <amodra@gmail.com>
 
+	PR ld/18176
 	* ldlang.c (lang_size_sections): When alignment of sections
 	results in relro base adjustment being too large, don't go lower
 	than the initial value.
diff --git a/ld/testsuite/ChangeLog b/ld/testsuite/ChangeLog
index 47bb489..b35ab3f 100644
--- a/ld/testsuite/ChangeLog
+++ b/ld/testsuite/ChangeLog
@@ -1,3 +1,11 @@
+2015-04-01  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/18176
+	* ld-x86-64/pr18176.d: New file.
+	* ld-x86-64/pr18176.s: Likewise.
+	* ld-x86-64/pr18176.t: Likewise.
+	* ld-x86-64/x86-64.exp: Run pr18176.
+
 2015-03-31  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* ld-bootstrap/bootstrap.exp (extralibs): Add -lz.
diff --git a/ld/testsuite/ld-x86-64/pr18176.d b/ld/testsuite/ld-x86-64/pr18176.d
new file mode 100644
index 0000000..3a08539
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/pr18176.d
@@ -0,0 +1,9 @@
+#name: PR ld/18176
+#as: --64
+#ld: -melf_x86_64 -shared -z relro -T pr18176.t -z max-page-size=0x200000 -z common-page-size=0x1000
+#readelf: -l --wide
+#target: x86_64-*-linux*
+
+#...
+  GNU_RELRO      0x04bd07 0x000000000024bd07 0x000000000024bd07 0x0022f9 0x0022f9 R   0x1
+#pass
diff --git a/ld/testsuite/ld-x86-64/pr18176.s b/ld/testsuite/ld-x86-64/pr18176.s
new file mode 100644
index 0000000..405355f
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/pr18176.s
@@ -0,0 +1,52 @@
+	.section .init,"ax",@progbits
+	.p2align 2
+	.space 0x1a
+	.section .text,"ax",@progbits
+	.p2align 4
+	.space 0x3ab96
+	.section .fini,"ax",@progbits
+	.p2align 2
+	.space 0x9
+	.section .foo_hdr,"a",@progbits
+	.p2align 2
+	.space 0xd14
+	.section .foo,"a",@progbits
+	.p2align 3
+	.space 0x4d5c
+	.section .rodata,"a",@progbits
+	.p2align 6
+	.space 0xa54d
+	.section .xxx,"a",@progbits
+	.space 0xf43
+	.section .yyy,"aw",@progbits
+	.space 0x1
+	.section .init_array,"aw",@init_array
+	.p2align 3
+	.space 0x10
+	.section .fini_array,"aw",@fini_array
+	.p2align 3
+	.space 0x8
+	.section	.tdata,"awT",%progbits
+	.p2align 3
+	.space 0x4
+	.section	.tbss,"awT",%nobits
+	.p2align 3
+	.space 0x40
+	.section	.data.rel.ro,"aw",%progbits
+	.p2align 6
+	.space 0x1b60
+	.section .jcr,"aw",@progbits
+	.p2align 3
+	.space 0x8
+	.section .bar,"aw",@progbits
+	.p2align 3
+	.space 0x640
+	.section	.data,"aw",%progbits
+	.p2align 5
+	.space 0x70
+	.section	.bss,"aw",%nobits
+	.p2align 6
+	.space 0x8a0
+	.section	BUS_ERROR_MAP,"aw",%progbits
+	.p2align 3
+	.space 0x230
diff --git a/ld/testsuite/ld-x86-64/pr18176.t b/ld/testsuite/ld-x86-64/pr18176.t
new file mode 100644
index 0000000..480c0cd
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/pr18176.t
@@ -0,0 +1,39 @@
+SECTIONS
+{
+  /* Read-only sections, merged into text segment: */
+  . = SEGMENT_START("text-segment", 0) + SIZEOF_HEADERS;
+  .hash           : { *(.hash) }
+  .gnu.hash       : { *(.gnu.hash) }
+  .dynsym         : { *(.dynsym) }
+  .dynstr         : { *(.dynstr) }
+  .init           : { *(.init) }
+  .text           : { *(.text) }
+  .fini           : { *(.fini) }
+  .rodata         : { *(.rodata) }
+  .foo_hdr : { *(.foo_hdr) }
+  .foo : { *(.foo) }
+  .xxx : { *(.xxx) }
+  . = ALIGN (CONSTANT (MAXPAGESIZE)) - ((CONSTANT (MAXPAGESIZE) - .) & (CONSTANT (MAXPAGESIZE) - 1)); . = DATA_SEGMENT_ALIGN (CONSTANT (MAXPAGESIZE), CONSTANT (COMMONPAGESIZE));
+  .yyy : { *(.yyy) }
+  .tdata	  : { *(.tdata) }
+  .tbss		  : { *(.tbss) }
+  .init_array     : { *(.init_array) }
+  .fini_array     : { *(.fini_array) }
+  .jcr            : { *(.jcr) }
+  .data.rel.ro : { *(.data.rel.ro.local* .gnu.linkonce.d.rel.ro.local.*) *(.data.rel.ro .data.rel.ro.* .gnu.linkonce.d.rel.ro.*) }
+  .dynamic        : { *(.dynamic) }
+  .bar            : { *(.bar) }
+  . = DATA_SEGMENT_RELRO_END (SIZEOF (.got.plt) >= 24 ? 24 : 0, .);
+  .got.plt        : { *(.got.plt) }
+  .data           : { *(.data) }
+  __bss_start = .;
+  .bss            :
+  {
+   *(.bss)
+   . = ALIGN(. != 0 ? 64 / 8 : 1);
+  }
+  . = ALIGN(64 / 8);
+  _end = .; PROVIDE (end = .);
+  . = DATA_SEGMENT_END (.);
+  /DISCARD/ : { *(.*) }
+}
diff --git a/ld/testsuite/ld-x86-64/x86-64.exp b/ld/testsuite/ld-x86-64/x86-64.exp
index 7bceb7f..98514ed 100644
--- a/ld/testsuite/ld-x86-64/x86-64.exp
+++ b/ld/testsuite/ld-x86-64/x86-64.exp
@@ -318,6 +318,7 @@ run_dump_test "mov1d"
 run_dump_test "pr17935-1"
 run_dump_test "pr17935-2"
 run_dump_test "pr18160"
+run_dump_test "pr18176"
 
 # Must be native with the C compiler
 if { [isnative] && [which $CC] != 0 } {
-- 
2.1.0