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PATCH: The current linker failed to generate working Linux kernel
On Wed, Aug 16, 2006 at 10:16:12AM -0700, H. J. Lu wrote:
> On Wed, Aug 16, 2006 at 06:00:17PM +0930, Alan Modra wrote:
> > On Tue, Aug 15, 2006 at 06:10:42PM -0700, H. J. Lu wrote:
> > > FYI, I opened a linker bug
> > >
> > > http://sources.redhat.com/bugzilla/show_bug.cgi?id=3052
> > >
> > > The current linker failed to generate working Linux 2.6 x86-64 kernel.
> > > There is a small testcase in the bug report.
> >
> > The kernel script is invalid because it moves dot backwards. Sigh.
> >
> > This patch moves the code the sets section lmas from lang_do_assignments
> > to lang_size_sections, which I think is a more natural place to do
> > this. I've also tweaked the lma code to fall back to lma == vma if dot
> > moves backwards, for compatibility with buggy ld scripts.
> >
>
> I don't think this fix is complete. Here is a patch with 2 testcases.
> The first one moves dot backwards similar to Linux kernel and the
> second doesn't. The issue here is
>
> .bar XXX : AT (YYY)
> . = LOADADDR(.bar) + ZZZ;
> .data : { *(.data) }
>
> For .bar, lma != vma. But we can't assume it is also true for .data.
>
Here is the updated patch with a fix.
H.J.
----
ld/
2006-08-16 H.J. Lu <hongjiu.lu@intel.com>
PR ld/3052
* ldlang.c (lang_size_sections_1): Don't change lma unless the
current vma overlaps the previous section.
ld/testsuite/
2006-08-16 H.J. Lu <hongjiu.lu@intel.com>
PR ld/3052
* ld-elf/loadaddr.s: New file.
* ld-elf/loadaddr1.d: Likewise.
* ld-elf/loadaddr1.t: Likewise.
* ld-elf/loadaddr2.d: Likewise.
* ld-elf/loadaddr2.t: Likewise.
--- ld/ldlang.c.loadaddr 2006-08-16 10:08:02.000000000 -0700
+++ ld/ldlang.c 2006-08-16 11:20:53.000000000 -0700
@@ -4405,30 +4405,19 @@ lang_size_sections_1
}
else if (r->last_os != NULL)
{
- bfd_vma lma;
asection *last;
last = r->last_os->output_section_statement.bfd_section;
- /* If dot moved backwards (which is invalid according
- to ld docs) then leave lma equal to vma. This
- keeps users of buggy ld scripts happy. */
- if (dot >= last->vma)
+ /* lvm should be the same as vma. But if the current vma
+ overlaps the previous section, then set the current lma
+ to that at the end of the previous section. The
+ previous section was probably an overlay. */
+ if ((dot >= last->vma
+ && dot < last->vma + last->size)
+ || (last->vma >= dot
+ && last->vma < dot + os->bfd_section->size))
{
- /* If the current vma overlaps the previous section,
- then set the current lma to that at the end of
- the previous section. The previous section was
- probably an overlay. */
- if ((dot >= last->vma
- && dot < last->vma + last->size)
- || (last->vma >= dot
- && last->vma < dot + os->bfd_section->size))
- lma = last->lma + last->size;
-
- /* Otherwise, keep the same lma to vma relationship
- as the previous section. */
- else
- lma = dot + last->lma - last->vma;
-
+ bfd_vma lma = last->lma + last->size;
if (os->section_alignment != -1)
lma = align_power (lma, os->section_alignment);
os->bfd_section->lma = lma;
--- ld/testsuite/ld-elf/loadaddr.s.loadaddr 2006-08-16 10:08:02.000000000 -0700
+++ ld/testsuite/ld-elf/loadaddr.s 2006-08-16 10:08:02.000000000 -0700
@@ -0,0 +1,16 @@
+ .text
+ .globl main
+ .globl start
+ .globl _start
+ .globl __start
+main:
+start:
+_start:
+__start:
+ .byte 0
+ .section .bar,"ax","progbits"
+ .byte 0
+ .section .foo,"aw","progbits"
+ .byte 0
+ .data
+ .byte 0
--- ld/testsuite/ld-elf/loadaddr1.d.loadaddr 2006-08-16 10:08:02.000000000 -0700
+++ ld/testsuite/ld-elf/loadaddr1.d 2006-08-16 10:08:02.000000000 -0700
@@ -0,0 +1,10 @@
+#source: loadaddr.s
+#ld: -T loadaddr1.t -z max-page-size=0x200000
+#readelf: -l --wide
+#target: *-*-linux*
+
+#...
+ LOAD +0x000000 0xf*80000000 0xf*80000000 0x100041 0x100041 RWE 0x200000
+ LOAD +0x200000 0xf*ff600000 0xf*80101000 0x0*1 0x0*1 R E 0x200000
+ LOAD +0x302000 0xf*80102000 0xf*80102000 0x0*1 0x0*1 RW 0x200000
+#pass
--- ld/testsuite/ld-elf/loadaddr1.t.loadaddr 2006-08-16 10:08:02.000000000 -0700
+++ ld/testsuite/ld-elf/loadaddr1.t 2006-08-16 10:08:02.000000000 -0700
@@ -0,0 +1,13 @@
+SECTIONS
+{
+ . = -0x7ff00000;
+ .text : {*(.text .text.*)}
+ . = ALIGN(64);
+ .foo : { *(.foo) }
+ .bar -0xa00000 : AT ((LOADADDR(.foo) + SIZEOF(.foo) + 4095) & ~(4095))
+ { *(.bar) }
+ . = LOADADDR(.bar) + 4096;
+ . = ALIGN(8192);
+ .data : { *(.data) }
+ /DISCARD/ : { *(.*) }
+}
--- ld/testsuite/ld-elf/loadaddr2.d.loadaddr 2006-08-16 10:08:02.000000000 -0700
+++ ld/testsuite/ld-elf/loadaddr2.d 2006-08-16 10:08:02.000000000 -0700
@@ -0,0 +1,10 @@
+#source: loadaddr.s
+#ld: -T loadaddr2.t -z max-page-size=0x200000
+#readelf: -l --wide
+#target: *-*-linux*
+
+#...
+ LOAD +0x000000 0xf*80000000 0xf*80000000 0x100041 0x100041 RWE 0x200000
+ LOAD +0x110000 0xf*80110000 0xf*80101000 0x0*1 0x0*1 R E 0x200000
+ LOAD +0x302000 0xf*80302000 0xf*80302000 0x0*1 0x0*1 RW 0x200000
+#pass
--- ld/testsuite/ld-elf/loadaddr2.t.loadaddr 2006-08-16 10:08:02.000000000 -0700
+++ ld/testsuite/ld-elf/loadaddr2.t 2006-08-16 10:08:02.000000000 -0700
@@ -0,0 +1,13 @@
+SECTIONS
+{
+ . = -0x7ff00000;
+ .text : {*(.text .text.*)}
+ . = ALIGN(64);
+ .foo : { *(.foo) }
+ .bar -0x7fef0000 : AT ((LOADADDR(.foo) + SIZEOF(.foo) + 4095) & ~(4095))
+ { *(.bar) }
+ . = LOADADDR(.bar) + 0x200000;
+ . = ALIGN(8192);
+ .data : { *(.data) }
+ /DISCARD/ : { *(.*) }
+}