I want redefine malloc symbol to own_malloc, so that I can know memory alloc details and print alloc-size.But I found it don't work when I excuting order:
arm-none-eabi-objcopy --redefine-sym malloc=own_malloc test.o
the test source:
#include <stdlib.h>
extern "C" void test();
void test(){
void* ptr = ::malloc(16);
free(ptr);
}
I exec objdump to look the symbol table
arm-none-eabi-objdump -t test.o
I fount there was not malloc/free symbol in symbols table.
SYMBOL TABLE:
00000000 l df *ABS* 00000000 test.cxx
00000000 l d .text 00000000 .text
00000000 l d .data 00000000 .data
00000000 l d .bss 00000000 .bss
00000000 l d .gnu.debuglto_.debug_info 00000000 .gnu.debuglto_.debug_info
00000000 l d .gnu.debuglto_.debug_abbrev 00000000 .gnu.debuglto_.debug_abbrev
00000000 l d .gnu.debuglto_.debug_line 00000000 .gnu.debuglto_.debug_line
00000000 l d .gnu.debuglto_.debug_str 00000000 .gnu.debuglto_.debug_str
00000000 l d .gnu.lto_.profile.7c13183f5b427e41 00000000 .gnu.lto_.profile.7c13183f5b427e41
00000000 l d .gnu.lto_.icf.7c13183f5b427e41 00000000 .gnu.lto_.icf.7c13183f5b427e41
00000000 l d .gnu.lto_.ipa_sra.7c13183f5b427e41 00000000 .gnu.lto_.ipa_sra.7c13183f5b427e41
00000000 l d .gnu.lto_.inline.7c13183f5b427e41 00000000 .gnu.lto_.inline.7c13183f5b427e41
00000000 l d .gnu.lto_.jmpfuncs.7c13183f5b427e41 00000000 .gnu.lto_.jmpfuncs.7c13183f5b427e41
00000000 l d .gnu.lto_.pureconst.7c13183f5b427e41 00000000 .gnu.lto_.pureconst.7c13183f5b427e41
00000000 l d .gnu.lto_.lto.7c13183f5b427e41 00000000 .gnu.lto_.lto.7c13183f5b427e41
00000000 l d .gnu.lto_test.0.7c13183f5b427e41 00000000 .gnu.lto_test.0.7c13183f5b427e41
00000000 l d .gnu.lto_.symbol_nodes.7c13183f5b427e41 00000000 .gnu.lto_.symbol_nodes.7c13183f5b427e41
00000000 l d .gnu.lto_.refs.7c13183f5b427e41 00000000 .gnu.lto_.refs.7c13183f5b427e41
00000000 l d .gnu.lto_.decls.7c13183f5b427e41 00000000 .gnu.lto_.decls.7c13183f5b427e41
00000000 l d .gnu.lto_.symtab.7c13183f5b427e41 00000000 .gnu.lto_.symtab.7c13183f5b427e41
00000000 l d .gnu.lto_.ext_symtab.7c13183f5b427e41 00000000 .gnu.lto_.ext_symtab.7c13183f5b427e41
00000000 l d .gnu.lto_.opts 00000000 .gnu.lto_.opts
00000000 l d .comment 00000000 .comment
00000000 l d .ARM.attributes 00000000 .ARM.attributes
00000000 w .gnu.debuglto_.debug_info 00000000 .hidden test.cxx.cee7ff5d
00000001 O *COM* 00000001 __gnu_lto_slim
I used the following compilation parameters:
arm-none-eabi-g++ -c -fno-common -nostdinc++ -Wall -Wshadow -Wundef -fno-exceptions -fcheck-new -fno-rtti -std=c++17 -pipe -Os -fno-strict-aliasing -fomit-frame-pointer -flto -fuse-linker-plugin -fno-builtin -ffunction-sections -fdata-sections -g -march=armv8-m.main+dsp -mtune=cortex-m33 -mthumb -mfpu=fpv5-sp-d16 -mfloat-abi=hard _ -Wno-cpp --std=c++17 -Werror test.cxx -o test.o
So how can I redefine malloc and free to own_malloc and own_free with lto flag ?
This is the strangest problem I have ever encountered. I am programming a chess engine and I have a function that returns a rank mask. For example, Consider this 64-bit bitboard.
00000000
00000000
00000000
00000000
00000100
00000000
00000000
00000000
The 1 in the middle is a piece.
Now my function should return
00000000
00000000
00000000
00000000
11111111
00000000
00000000
00000000
Very simple, just return a mask of the rank. Here is my code
uint64_t get_rank_mask(int sq)
{
return (0xFF<<(sq-(sq%8)));
}
Here is what the function returns when I pass 36, or the square e5
00000000
00000000
00000000
00000000
00000000
00000000
00000000
11111111
Hmm, strange it is. Let me make a small change in the code.
uint64_t get_rank_mask(int sq)
{
uint64_t mask = 0xFF;
mask<<=(sq-(sq%8));
return mask;
}
Here is the return value now
00000000
00000000
00000000
11111111
00000000
00000000
00000000
00000000
And magically, that is the intended result. I don't even know the difference between the two code samples. Can anyone explain this behaviour?
0xFF is an int. Assuming an int has 32 bits, shifting this value left by 32 will invoke undefined behavior.
In the second version, you are storing 0xFF in an unsigned integral type. This can be shifted any number of bits, and that operation is well defined. In your case, you are storing it in an unsigned int with 64 bits, and so shifting left by 32 gives the result you want.
A simple hello world program:
#include <stdio.h>
int main(void)
{
printf("Hello, world!\n");
return 0;
}
After dumpbin it with /HEADERS flag, i get those segments:
8 .bss
A0 .debug$S
62 .drectve
F .rdata
8B .text$mn
If compile the program with /TC, so that it's a C program, i get those segments after the same use of a dumpbin:
2000 .data
1000 .gfids
7000 .rdata
1000 .reloc
10000 .text
point is:
How do i get this similar kind of output:
# objdump -hrt hello.o
hello.o: file format elf32-i386
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 00000011 00000000 00000000 00000034 2**2
CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
1 .data 00000000 00000000 00000000 00000048 2**2
CONTENTS, ALLOC, LOAD, DATA
2 .bss 00000000 00000000 00000000 00000048 2**2
ALLOC
3 .rodata.str1.1 0000000d 00000000 00000000 00000048 2**0
CONTENTS, ALLOC, LOAD, READONLY, DATA
4 .comment 00000033 00000000 00000000 00000055 2**0
CONTENTS, READONLY
SYMBOL TABLE:
00000000 l df *ABS* 00000000 hello.c
00000000 l d .text 00000000
00000000 l d .data 00000000
00000000 l d .bss 00000000
00000000 l d .rodata.str1.1 00000000
00000000 l d .comment 00000000
00000000 g F .text 00000011 main
00000000 *UND* 00000000 puts
The stack frame pointer (EBP) should always point to where the previous stack frame was right but why is that not the case in my application! That would indicate something is really wrong..hard to believe!
I created multiple simple demo applications where the stack pointer always points to the previous stack frame but I can't make sense of why this is not the case in this application and it is happening when my application is just starting up!
The following is my call stack
0:000> k
# ChildEBP RetAddr
00 0018fee4 6381d1cd acn!CAcnApp::InitInstance+0x41 [c:\acn-project\acn\acn.cpp # 527]
01 0018fef4 00428575 MFC80U!AfxWinMain+0x48 [f:\dd\vctools\vc7libs\ship\atlmfc\src\mfc\winmain.cpp # 37]
02 0018ff88 765d336a acn!__tmainCRTStartup+0x150 [f:\dd\vctools\crt_bld\self_x86\crt\src\crtexe.c # 589]
03 0018ff94 76f59902 kernel32!BaseThreadInitThunk+0xe
04 0018ffd4 76f598d5 ntdll!__RtlUserThreadStart+0x70
05 0018ffec 00000000 ntdll!_RtlUserThreadStart+0x1b
0:000> dc 0018fee4
0018fee4 ffffffff 6381d1cd 00489498 00000001 .......c..H.....
0018fef4 00000000 00428575 00400000 00000000 ....u.B...#.....
0018ff04 01e53fd2 0000000a 87b8aee0 00000000 .?..............
0018ff14 00000000 7efde000 00000044 01e54012 .......~D....#..
0018ff24 01e53ff2 01e53fd4 00000000 00000000 .?...?..........
0018ff34 00000000 00000000 00000000 00000000 ................
0018ff44 00000000 00000000 00000000 00000000 ................
0018ff54 00000000 00000000 0018ff84 00428e5d ............].B.
0:000> dc 0018fef4
0018fef4 00000000 00428575 00400000 00000000 ....u.B...#.....
0018ff04 01e53fd2 0000000a 87b8aee0 00000000 .?..............
0018ff14 00000000 7efde000 00000044 01e54012 .......~D....#..
0018ff24 01e53ff2 01e53fd4 00000000 00000000 .?...?..........
0018ff34 00000000 00000000 00000000 00000000 ................
0018ff44 00000000 00000000 00000000 00000000 ................
0018ff54 00000000 00000000 0018ff84 00428e5d ............].B.
0018ff64 01e53fd2 00000000 00000000 0018ff0c .?..............
0:000> dc 0018ff88
0018ff88 0018ff94 765d336a 7efde000 0018ffd4 ....j3]v...~....
0018ff98 76f59902 7efde000 7d7a657d 00000000 ...v...~}ez}....
0018ffa8 00000000 7efde000 00000000 00000000 .......~........
0018ffb8 00000000 0018ffa0 00000000 ffffffff ................
0018ffc8 76f958c5 0b965c89 00000000 0018ffec .X.v.\..........
0018ffd8 76f598d5 0042873d 7efde000 00000000 ...v=.B....~....
0018ffe8 00000000 00000000 00000000 0042873d ............=.B.
0018fff8 7efde000 00000000 78746341 00000020 ...~....Actx ...
The control is in the first line of InitInstance() so it's like my application is drawing its first breath and the stack seems to be already corrupted? Well the app class constructor comes before this but I checked the call stack is in similar state there as well.
Notice the stack frame pointer (EFP) check for both 1st and 2nd frame fails but the stack is good beyond that.
My first question is that is there any explanation the call stack can be like this and this being Ok? In other words, can we say the call stack is definitely broken? The application does load and calls various dlls if that may play any part (don't know why it would though).
What could be the suspect in this case since the application has only barely started!?
Update (code)
Here is constructor which is very simple. And as for InitInstance(), that function is very long but my breakpoint is on first line so its code is never executed when call stack is like that.
CAcnApp::CAcnApp()
{
m_bServMode = FALSE;
m_bFactory = FALSE;
m_bDownload = FALSE;
m_pEngine = NULL;
m_hWiztomMod = NULL;
m_pServer = new CAcnServer;
}
Second update
I posted a follow up question to share extra information after further investigation and that does qualify as separate question due to differences.
BTW, global or file global objects are created before the main function is called.
If an object's constructor has problems, you could see any number of defects occurring before main is called.
Review your object's constructors. You should be able to set a breakpoint in the object's constructor.
Edit 1: Memory allocation in constructor
Having a global object that has dynamic memory allocation may cause problems. The object requires that the dynamic memory allocation is initialized before the object is constructed. Try commenting out the dynamic memory allocation and see if the issue goes away.
A workaround is to create an "initialize" method that can be called after the main entry point is reached. The initialize method would perform dynamic memory allocation.
I would like to overwrite function (interupt handlers) with the weak attribute, but linker does not link my definition. Codes are shorted for better reading.
vectors.c
void NMI_Handler (void) __attribute__((weak));
void HardFault_Handler (void) __attribute__((weak));
__attribute__ ((section(".vectors"), used))
void (* const gVectors[])(void) =
{
NMI_Handler,
HardFault_Handler
};
void NMI_Handler (void) { while(1); }
void HardFault_Handler (void) { while(1); }
I redefine default definition in the file cpuexcept.cpp
extern "C" __attribute__((naked))
void NMI_Handler()
{
EXCEPT_ENTRY(CPUExcept);
}
extern "C" __attribute__((naked))
void HardFault_Handler()
{
EXCEPT_ENTRY(CPUExcept);
}
If I compile and dump it, output (library lib.a) is:
cpuexcept.oo: file format elf32-littlearm
rw-rw-rw- 0/0 4728 Jun 26 16:20 2012 cpuexcept.oo
architecture: arm, flags 0x00000011:
HAS_RELOC, HAS_SYMS
start address 0x00000000
private flags = 5000000: [Version5 EABI]
Sections:
Idx Name Size VMA LMA File off Algn Flags
0 .text 0000051c 00000000 00000000 00000034 2**2 CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
1 .data 00000000 00000000 00000000 00000550 2**0 CONTENTS, ALLOC, LOAD, DATA
2 .bss 00000000 00000000 00000000 00000550 2**0 ALLOC
3 .rodata 000001dc 00000000 00000000 00000550 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA
4 .comment 00000012 00000000 00000000 0000072c 2**0 CONTENTS, READONLY
5 .ARM.attributes 00000031 00000000 00000000 0000073e 2**0 CONTENTS, READONLY
SYMBOL TABLE:
00000000 l df *ABS* 00000000 cpuexcept.cpp
00000000 l d .text 00000000 .text
00000000 l d .data 00000000 .data
00000000 l d .bss 00000000 .bss
000004e0 g F .text 0000000a NMI_Handler
000004ec g F .text 0000000a HardFault_Handler
000004e0 <NMI_Handler>:
4e0: e92d 0ff0 stmdb sp!, {r4, r5, r6, r7, r8, r9, sl, fp}
4e4: 4668 mov r0, sp
4e6: f7ff fffe bl c0 <CPUExcept> 4e6: R_ARM_THM_CALL CPUExcept
4ea: bf00 nop
000004ec <HardFault_Handler>:
4ec: e92d 0ff0 stmdb sp!, {r4, r5, r6, r7, r8, r9, sl, fp}
4f0: 4668 mov r0, sp
4f2: f7ff fffe bl c0 <CPUExcept> 4f2: R_ARM_THM_CALL CPUExcept
4f6: bf00 nop
vectors.o: file format elf32-littlearm
rw-rw-rw- 0/0 4464 Jun 27 13:52 2012 vectors.o
architecture: arm, flags 0x00000011:
HAS_RELOC, HAS_SYMS
start address 0x00000000
private flags = 5000000: [Version5 EABI]
Sections:
Idx Name Size VMA LMA File off Algn Flags
0 .text 00000114 00000000 00000000 00000034 2**2 CONTENTS, ALLOC, LOAD, READONLY, CODE
1 .data 00000000 00000000 00000000 00000148 2**0 CONTENTS, ALLOC, LOAD, DATA
2 .bss 00000000 00000000 00000000 00000148 2**0 ALLOC
3 .vectors 00000130 00000000 00000000 00000148 2**2 CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
4 .comment 00000012 00000000 00000000 00000278 2**0 CONTENTS, READONLY
5 .ARM.attributes 00000031 00000000 00000000 0000028a 2**0 CONTENTS, READONLY
SYMBOL TABLE:
00000000 l df *ABS* 00000000 vectors.c
00000000 l d .text 00000000 .text
00000000 l d .data 00000000 .data
00000000 l d .bss 00000000 .bss
00000000 l d .vectors 00000000 .vectors
00000000 l d .comment 00000000 .comment
00000000 l d .ARM.attributes 00000000 .ARM.attributes
00000000 w F .text 00000002 NMI_Handler
00000004 w F .text 00000002 HardFault_Handler
00000000 <NMI_Handler>:
0: e7fe b.n 0 <NMI_Handler>
2: bf00 nop
00000004 <HardFault_Handler>:
4: e7fe b.n 4 <HardFault_Handler>
6: bf00 nop
Default function with the weak attribute is linked in to target application. My definition is linked correct, if I define function f() in cpuexcept.cpp and I use it in main function or if my definiton of handler is in other .c module.
I use arm-none-eabi-gcc 4.6.2 (YAGARTO) compiler in cygwin.
You could try to define your function like
void NMI_Handler(void)
and not as
void NMI_Handler()
As the weak definition is also void NMI_Handler (void) __attribute__((weak));
So the linker will not see any difference.