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Re: [Patch/RFA]: Patch to fix R_ARM_THM_JUMP24 relocation truncated bug
On Fri, 2010-01-15 at 11:04 +1030, Alan Modra wrote:
> On Thu, Jan 14, 2010 at 02:01:11PM +0000, Matthew Gretton-Dann wrote:
> > HOWTO (R_ARM_THM_JUMP24, /* type */
> > 1, /* rightshift */
> > 2, /* size (0 = byte, 1 = short, 2 = long) */
> > - 24, /* bitsize */
> > + 25, /* bitsize */
> > TRUE, /* pc_relative */
> > 0, /* bitpos */
> > complain_overflow_signed,/* complain_on_overflow */
>
> This is odd. Normally, bitsize determines the allowed field value
> after the rightshift has been applied. Hmm, I see elf32-arm.c does
> it's own checking for these relocs and gets it wrong. It would be
> better to leave bitsize as 24 and remove the right shift on the
> reloc_signed_max calculation. You'd then need to adjust the
> R_ARM_THM_JUMP24 howto.
Thank you for your comments. Please find attached an updated patch for
review and further comments.
As well as removing the right shift on the reloc_signed_max calculation
I reviewed the bitsize for the affected relocations - R_ARM_THM_JUMP24,
R_ARM_THM_CALL, R_ARM_THM_XPC22. This resulted in leaving the bitsize
for R_ARM_THM_JUMP24 and R_ARM_THM_XPC22 alone (at 24 and 22
respectively), whilst the bitsize for R_ARM_THM_CALL is now 24 (instead
of 25).
Suggested new ChangeLog entries look like:
bfd/ChangeLog:
2010-01-18 Matthew Gretton-Dann <matthew.gretton-dann@arm.com>
* elf32-arm.c (elf32_arm_howto_table_1): Correct bitsize of
R_ARM_THM_CALL entry.
(elf32_arm_final_link_relocate): Correct calculation of
reloc_signed_max when doing a R_ARM_THM_CALL, R_ARM_THM_XPC22,
or R_ARM_THM_JUMP24 relocation.
ld/testsuite/ChangeLog:
2010-01-18 Matthew Gretton-Dann <matthew.gretton-dann@arm.com>
* ld-arm/jump-reloc-veneers-long.d: New test.
* ld-arm/jump-reloc-veneers-short1.d: Likewise.
* ld-arm/jump-reloc-veneers-short2.d: Likewise.
* ld-arm/jump-reloc-veneers.s: Likewise.
* ld-arm/arm-elf.exp (armelftests): Run them.
Thanks,
Matt
--
Matthew Gretton-Dann
Principal Engineer - Tools, PD Software
ARM Limited
Index: bfd/elf32-arm.c
===================================================================
RCS file: /cvs/src/src/bfd/elf32-arm.c,v
retrieving revision 1.218
diff -u -r1.218 elf32-arm.c
--- bfd/elf32-arm.c 28 Dec 2009 18:55:16 -0000 1.218
+++ bfd/elf32-arm.c 18 Jan 2010 11:58:22 -0000
@@ -222,7 +222,7 @@
HOWTO (R_ARM_THM_CALL, /* type */
1, /* rightshift */
2, /* size (0 = byte, 1 = short, 2 = long) */
- 25, /* bitsize */
+ 24, /* bitsize */
TRUE, /* pc_relative */
0, /* bitpos */
complain_overflow_signed,/* complain_on_overflow */
@@ -7552,7 +7552,7 @@
bitsize = howto->bitsize;
if (!thumb2)
bitsize -= 2;
- reloc_signed_max = ((1 << (bitsize - 1)) - 1) >> howto->rightshift;
+ reloc_signed_max = ((1 << (bitsize - 1)) - 1);
reloc_signed_min = ~reloc_signed_max;
/* Assumes two's complement. */
Index: ld/testsuite/ld-arm/arm-elf.exp
===================================================================
RCS file: /cvs/src/src/ld/testsuite/ld-arm/arm-elf.exp,v
retrieving revision 1.68
diff -u -r1.68 arm-elf.exp
--- ld/testsuite/ld-arm/arm-elf.exp 13 Jan 2010 19:01:10 -0000 1.68
+++ ld/testsuite/ld-arm/arm-elf.exp 18 Jan 2010 11:58:24 -0000
@@ -241,6 +241,24 @@
{"Relocation boundaries" "-defsym x=0 -defsym y=0 -defsym _start=0" "" {reloc-boundaries.s}
{{objdump -s reloc-boundaries.d}}
"reloc-boundaries"}
+ {"R_ARM_THM_JUMP24 Relocation veneers: Short 1"
+ "-defsym _start=0x8000 --section-start destsect=0x00009000"
+ "-march=armv7-a -mthumb"
+ {jump-reloc-veneers.s}
+ {{objdump -d jump-reloc-veneers-short1.d}}
+ "jump-reloc-veneers-short1"}
+ {"R_ARM_THM_JUMP24 Relocation veneers: Short 2"
+ "-defsym _start=0x8000 --section-start destsect=0x00900000"
+ "-march=armv7-a -mthumb"
+ {jump-reloc-veneers.s}
+ {{objdump -d jump-reloc-veneers-short2.d}}
+ "jump-reloc-veneers-short2"}
+ {"R_ARM_THM_JUMP24 Relocation veneers: Long"
+ "-defsym _start=0x8000 --section-start destsect=0x09000000"
+ "-march=armv7-a -mthumb"
+ {jump-reloc-veneers.s}
+ {{objdump -d jump-reloc-veneers-long.d}}
+ "jump-reloc-veneers-long"}
}
run_ld_link_tests $armelftests
Index: ld/testsuite/ld-arm/jump-reloc-veneers.s
===================================================================
diff -u /dev/null jump-reloc-veneers.s
--- /dev/null 2009-05-17 13:34:33.498340648 +0100
+++ ld/testsuite/ld-arm/jump-reloc-veneers.s 2010-01-08 10:58:48.054129000 +0000
@@ -0,0 +1,12 @@
+ .text
+ .syntax unified
+ .thumb_func
+ .global _start
+ .type _start,%function
+_start:
+ b.w dest
+
+ .section destsect, "x"
+ .thumb_func
+dest:
+ b dest
Index: ld/testsuite/ld-arm/jump-reloc-short1.d
===================================================================
diff -u /dev/null jump-reloc-veneers-short1.d
--- /dev/null 2009-05-17 13:34:33.498340648 +0100
+++ ld/testsuite/ld-arm/jump-reloc-veneers-short1.d 2010-01-08 11:23:43.572369000 +0000
@@ -0,0 +1,13 @@
+
+.*: file format.*
+
+
+Disassembly of section destsect:
+
+00009000 <[^>]*>:
+ 9000: e7fe b.n 9000 <dest>
+
+Disassembly of section .text:
+
+00008054 <[^>]*>:
+ 8054: f000 bfd4 b.w 9000 <dest>
Index: ld/testsuite/ld-arm/jump-reloc-short2.d
===================================================================
diff -u /dev/null jump-reloc-veneers-short2.d
--- /dev/null 2009-05-17 13:34:33.498340648 +0100
+++ ld/testsuite/ld-arm/jump-reloc-veneers-short2.d 2010-01-08 11:32:56.653566000 +0000
@@ -0,0 +1,13 @@
+
+.*: file format.*
+
+
+Disassembly of section destsect:
+
+00900000 <[^>]*>:
+ 900000: e7fe b.n 900000 <dest>
+
+Disassembly of section .text:
+
+00008054 <[^>]*>:
+ 8054: f0f7 9fd4 b.w 900000 <dest>
Index: ld/testsuite/ld-arm/jump-reloc-long.d
===================================================================
diff -u /dev/null jump-reloc-veneers-long.d
--- /dev/null 2009-05-17 13:34:33.498340648 +0100
+++ ld/testsuite/ld-arm/jump-reloc-veneers-long.d 2010-01-08 11:23:06.012845000 +0000
@@ -0,0 +1,21 @@
+
+.*: file format.*
+
+
+Disassembly of section destsect:
+
+09000000 <[^>]*>:
+ 9000000: e7fe b.n 9000000 <dest>
+
+Disassembly of section .text:
+
+00008058 <[^>]*>:
+ 8058: b802f000 .word 0xb802f000
+ 805c: 00000000 andeq r0, r0, r0
+
+00008060 <[^>]*>:
+ 8060: 4778 bx pc
+ 8062: 46c0 nop ; \(mov r8, r8\)
+ 8064: e59fc000 ldr ip, \[pc, #0\] ; 806c <__dest_veneer\+0xc>
+ 8068: e12fff1c bx ip
+ 806c: 09000001 .word 0x09000001