Hi Thomas,
Thomas Schwinge wrote:
Here is a patch to fix a ``misunderstanding'' between the kernel (bflt
loader) and GDB; noticed on m68k / coldfire uClinux.
Lacking specific directives in the linker script, the linker *may* decide
to put .text and .data into the same segment:
Section to Segment mapping:
Segment Sections...
00 .text .data .eh_frame_hdr .eh_frame .bss
01 .eh_frame_hdr
The bflt loader in the kernel will, however, add a small extra data table
just before .data's content (cf. handling of MAX_SHARED_LIBS in
binfmt_flat.c:load_flat_file).
Now, if .text and .data are in the same segment, directly following each
other in the binary file, but have that extra data table added in the
run-time memory layout, GDB will get very confused when trying to access
items in the now-moved .data section. Without any kernel (loader) / GDB
changes, the solution is to tell the linker to always put .text and .data
into separate segments, which GDB will handle gracefully then.
Section to Segment mapping:
Segment Sections...
00 .text
01 .data .eh_frame_hdr .eh_frame .bss
Tested on m68k-uclinux (where the problem occurred) and arm-uclinuxeabi
(no regressions).
Applied to the elf2flt CVS.
Thanks
Greg
2010-02-27 Thomas Schwinge <tho...@codesourcery.com>
* elf2flt.ld.in: Explicitly put .text and .data into separate segments.
Index: elf2flt.ld.in
===================================================================
RCS file: /var/cvs/elf2flt/elf2flt.ld.in,v
retrieving revision 1.3
diff -u -p -r1.3 elf2flt.ld.in
--- elf2flt.ld.in 7 May 2009 06:14:27 -0000 1.3
+++ elf2flt.ld.in 27 Feb 2010 17:17:05 -0000
@@ -5,6 +5,11 @@ MEMORY {
flatmem : ORIGIN = 0x0, LENGTH = 0xfffffff
}
+PHDRS {
+ text PT_LOAD ;
+ data PT_LOAD ;
+}
+
SECTIONS {
.text 0x0 : {
@@ -38,7 +43,7 @@ W_RODAT *(.gnu.linkonce.r*)
. = ALIGN(0x20) ;
@symbol_pre...@_etext = . ;
- } > flatmem
+ } > flatmem :text
.data : {
. = ALIGN(0x4) ;
@@ -130,7 +135,7 @@ TOR: @symbol_pre...@__dtor_end__ = .;
KEEP (*(.fini_array))
KEEP (*(SORT(.fini_array.*)))
PROVIDE (@symbol_pre...@__fini_array_end = .);
- } > flatmem
+ } > flatmem :data
.eh_frame_hdr : { *(.eh_frame_hdr) } > flatmem
.eh_frame : { KEEP(*(.eh_frame)) } > flatmem
Regards,
Thomas
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Greg Ungerer -- Principal Engineer EMAIL: g...@snapgear.com
SnapGear Group, McAfee PHONE: +61 7 3435 2888
8 Gardner Close FAX: +61 7 3217 5323
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