Run Time linker and relocation of multiple local labels

[Peter Dufault]

I’m porting a large vxWorks application and I’m trying to download “ld -r” files as you can on vxWorks using the run-time loader.  At least on ARM I can’t get it to work, it uses the first local address it sees for all occurrences.

Example: Label .LC2 is used in two places, once for the “r” in an fopen() and later for a format string.  In both cases the address used is 0x419f14, the address of “r”.

First is the readelf output, then the disassembly, then debugging output from the RTL.

FIRST OCCURRENCE OF .LC2 used as “r” in fopen()
readelf:
00000020  0000152f R_ARM_THM_MOVW_ABS_NC  00000008   .LC1
00000024  00001530 R_ARM_THM_MOVT_ABS     00000008   .LC1
0000002a  0000162f R_ARM_THM_MOVW_ABS_NC  0000002c   .LC2
0000002e  00001630 R_ARM_THM_MOVT_ABS     0000002c   .LC2
00000034  0000450a R_ARM_THM_CALL         00000000   fopen

Disassemble:
    if ((fd = fopen(string, "r")) == (0)) {
  2a:   f240 0100   movw    r1, #0
  2e:   f2c0 0100   movt    r1, #0
  32:   6878        ldr r0, [r7, #4]
  34:   f7ff fffe   bl  0 <fopen>

RTL:
rtl: THM_MOVT_ABS/THM_MOVW_ABS_NC 0x341f2c0 @ 0x4196dc in bad
rtl: rel: sym:.LC2(22)=00419f14 type:47 off:0000002a
rtl: THM_MOVT_ABS/THM_MOVW_ABS_NC 0x7114f649 @ 0x4196e2 in bad
rtl: rel: sym:.LC2(22)=00419f14 type:48 off:0000002e
rtl: THM_MOVT_ABS/THM_MOVW_ABS_NC 0x141f2c0 @ 0x4196e6 in bad
rtl: rel: sym:fopen(69)=000d33c1 type:10 off:00000034

SECOND OCCURRENCE of .LC2 used for the printf format string:

readelf:
000007a8  00002c2f R_ARM_THM_MOVW_ABS_NC  0000013c   .LC2
000007ac  00002c30 R_ARM_THM_MOVT_ABS     0000013c   .LC2
000007b0  0000330a R_ARM_THM_CALL         00000000   printf

Disassemble:
 7a6:   68f9        ldr r1, [r7, #12]
 7a8:   f240 0000   movw    r0, #0
 7ac:   f2c0 0000   movt    r0, #0
 7b0:   f7ff fffe   bl  0 <printf>

RTL:
rtl: rel: sym:.LC2(44)=00419f14 type:47 off:000007a8
rtl: THM_MOVT_ABS/THM_MOVW_ABS_NC 0x7014f649 @ 0x419e60 in /opt/flatland/arch/arm-stubs-vxstubs/bin/sys-bad
rtl: rel: sym:.LC2(44)=00419f14 type:48 off:000007ac
rtl: THM_MOVT_ABS/THM_MOVW_ABS_NC 0x41f2c0 @ 0x419e64 in /opt/flatland/arch/arm-stubs-vxstubs/bin/sys-bad
rtl: rel: sym:printf(51)=000daac9 type:10 off:000007b0

Peter
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Peter Dufault
HD Associates, Inc.      Software and System Engineering

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