https://sourceware.org/bugzilla/show_bug.cgi?id=28474
Bug ID: 28474
Summary: R_ARM_THM_JUMP24 incorrect link result if symbol
duplicated
Product: binutils
Version: 2.35.1
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: ld
Assignee: unassigned at sourceware dot org
Reporter: sen2403 at hotmail dot com
Target Milestone: ---
Created attachment 13726
--> https://sourceware.org/bugzilla/attachment.cgi?id=13726&action=edit
simple code to reproduce this issue
Hello Sir,
I am link a program with a symbol file which defined the address of
functions/global variables already put in flash.
And, there are some duplicated function name existing in symbol file and the c
file part of the program. The linker have selected the function in the c file
part of the program.
However, the linker selects the function/global variables defined in the symbol
file after enabling LTO.
Moreover, the link result of R_ARM_THM_JUMP24 is also incorrect. Without the
LTO, the veneer jump to a function from THUMB mode to THUMB mode. With the LTO,
the veneer jump to a function from THUMB mode to ARM mode which is not expected
result.
I have wrote a simple code to reproduce this problem. You can change the
toolchain path and reproduce it by enabling/disabling the LTO option in the
makefile and check the result as shown below.
PS: I'm not sure whether this is a linker issue or not. I can do more
experiments to provide information if any suggestions. Thank you very much.
Toolchain: 10-2020-q4-major from
https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm/downloads
Please find the simple code from the attachment.
Following are the results of simple code.
(Correct) The veneer stay in THUMB mode if LTO is disabled.
Disassembly of section .text:
00001000 <dummy>:
1000: f04f 0004 mov.w r0, #4
1004: f04f 0105 mov.w r1, #5
1008: f000 b806 b.w 1018 <__foo_veneer>
100c: 4770 bx lr
0000100e <main>:
100e: b508 push {r3, lr}
1010: f7ff fff6 bl 1000 <dummy>
1014: 2000 movs r0, #0
1016: bd08 pop {r3, pc}
00001018 <__foo_veneer>:
1018: b401 push {r0}
101a: 4802 ldr r0, [pc, #8] ; (1024
<__foo_veneer+0xc>)
101c: 4684 mov ip, r0
101e: bc01 pop {r0}
1020: 4760 bx ip
1022: bf00 nop
1024: 10009ed1 .word 0x10009ed1
(Incorrect) The veneer switch to ARM mode if LTO is enabled.
Disassembly of section .text:
00001000 <dummy>:
1000: f04f 0004 mov.w r0, #4
1004: f04f 0105 mov.w r1, #5
1008: f000 b806 b.w 1018 <__foo_veneer>
100c: 4770 bx lr
0000100e <main>:
100e: b510 push {r4, lr}
1010: 2000 movs r0, #0
1012: f7ff fff5 bl 1000 <dummy>
1016: bd10 pop {r4, pc}
00001018 <__foo_veneer>:
1018: 4778 bx pc
101a: e7fd b.n 1018 <__foo_veneer>
101c: e51ff004 ldr pc, [pc, #-4] ; 1020
<__foo_veneer+0x8>
1020: 10009ed0 .word 0x10009ed0
1024: 00000000 .word 0x00000000
(Correct) After removing foo.o from C_OBJS in Makefile, the veneer stay in
THUMB mode as expected when LTO is enabled.
Disassembly of section .text:
00001000 <dummy>:
1000: f04f 0004 mov.w r0, #4
1004: f04f 0105 mov.w r1, #5
1008: f000 b806 b.w 1018 <__foo_veneer>
100c: 4770 bx lr
0000100e <main>:
100e: b510 push {r4, lr}
1010: 2000 movs r0, #0
1012: f7ff fff5 bl 1000 <dummy>
1016: bd10 pop {r4, pc}
00001018 <__foo_veneer>:
1018: b401 push {r0}
101a: 4802 ldr r0, [pc, #8] ; (1024
<__foo_veneer+0xc>)
101c: 4684 mov ip, r0
101e: bc01 pop {r0}
1020: 4760 bx ip
1022: bf00 nop
1024: 10009ed1 .word 0x10009ed1
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