Can't find .text section of certain functions while doing libgcc extraction for FPU

Is it possible for functions to just be stubs and have no code whatsoever.

For shared libraries, yes. You can, for example, generate place-holder libraries and expect the system executing the program to provide a library with the same name but with specific implementations of the functions. The placeholder provides to the compiler the name of the depending libraries.

However I do not know how libgcc.a is being used.

That said, the disassembly on my end returned :

$ armv7a-hardfloat-linux-gnueabi-objdump -d libgcc.a | grep -i __aeabi_f2d -A50

00000304 <__aeabi_f2d>:

304:    e1b02080     lsls    r2, r0, #1

308:    e1a011c2     asr    r1, r2, #3

30c:    e1a01061     rrx    r1, r1

310:    e1a00e02     lsl    r0, r2, #28

314:    121234ff     andsne    r3, r2, #-16777216    ; 0xff000000

318:    133304ff     teqne    r3, #-16777216    ; 0xff000000

31c:    1221130e     eorne    r1, r1, #939524096    ; 0x38000000

320:    112fff1e     bxne    lr

324:    e3320000     teq    r2, #0

328:    133304ff     teqne    r3, #-16777216    ; 0xff000000

32c:    012fff1e     bxeq    lr

330:    e92d4030     push    {r4, r5, lr}

334:    e3a04d0e     mov    r4, #896    ; 0x380

338:    e2015102     and    r5, r1, #-2147483648    ; 0x80000000

33c:    e3c11102     bic    r1, r1, #-2147483648    ; 0x80000000

340:    eaffff83     b    154 <__adddf3+0x148>

00000344 <__aeabi_ul2d>:

...

I have the source of __aeabi_f2d, but the source of __aeabi_l2f was giving me problems. It was just a stub. However, I've solved this problem now by making a very simple application, building it with gcc using the appropriate flags, and then seeing the disassembly. I don't know why I wasn't able to extract sources by dissembling libgcc.a. The thing about the place-holder libraries is kinda new for me. Thanks for that

Well, libgcc.a is an AR archive, containing multiple libraries and object files at once. For example, if you do :

$ ar t libgcc.a

This will print a listing of all the object files contained in your version of libgcc.a

The libgcc.a that my system use during cross-compiling contains an object file named _arm_addsubsf3.o, which defines :

$ armv7a-hardfloat-linux-gnueabi-nm -a _arm_addsubsf3.o 00000000 n .ARM.attributes

00000000 b .bss

00000000 d .data

00000000 N .debug_abbrev

00000000 N .debug_aranges

00000000 N .debug_info

00000000 N .debug_line

00000000 n .note.GNU-stack

00000000 t .text

0000000c T __addsf3

0000000c T __aeabi_fadd

00000000 T __aeabi_frsub

00000008 T __aeabi_fsub

000001a4 T __aeabi_i2f

000001d4 T __aeabi_l2f

0000019c T __aeabi_ui2f

000001c4 T __aeabi_ul2f

000001d4 T __floatdisf

000001a4 T __floatsisf

000001c4 T __floatundisf

0000019c T __floatunsisf

00000008 T __subsf3

The disassembly of __aeabi_l2f returned :

$ LANG=C armv7a-hardfloat-linux-gnueabi-objdump -d _arm_addsubsf3.o

_arm_addsubsf3.o:     file format elf32-littlearm

Disassembly of section .text:

...

000001d4 <__aeabi_l2f>:

1d4:    e1902001     orrs    r2, r0, r1

1d8:    012fff1e     bxeq    lr

1dc:    e2113102     ands    r3, r1, #-2147483648    ; 0x80000000

1e0:    5a000001     bpl    1ec <__aeabi_l2f+0x18>

1e4:    e2700000     rsbs    r0, r0, #0

1e8:    e2e11000     rsc    r1, r1, #0

1ec:    e1b0c001     movs    ip, r1

1f0:    01a0c000     moveq    ip, r0

1f4:    01a01000     moveq    r1, r0

1f8:    03a00000     moveq    r0, #0

1fc:    e383345b     orr    r3, r3, #1526726656    ; 0x5b000000

200:    02433201     subeq    r3, r3, #268435456    ; 0x10000000

204:    e2433502     sub    r3, r3, #8388608    ; 0x800000

208:    e16f2f1c     clz    r2, ip

20c:    e2522008     subs    r2, r2, #8

210:    e0433b82     sub    r3, r3, r2, lsl #23

214:    ba000006     blt    234 <__aeabi_l2f+0x60>

218:    e0833211     add    r3, r3, r1, lsl r2

21c:    e1a0c210     lsl    ip, r0, r2

220:    e2622020     rsb    r2, r2, #32

224:    e35c0102     cmp    ip, #-2147483648    ; 0x80000000

228:    e0a30230     adc    r0, r3, r0, lsr r2

22c:    03c00001     biceq    r0, r0, #1

230:    e12fff1e     bx    lr

234:    e2822020     add    r2, r2, #32

238:    e1a0c211     lsl    ip, r1, r2

23c:    e2622020     rsb    r2, r2, #32

240:    e190008c     orrs    r0, r0, ip, lsl #1

244:    e0a30231     adc    r0, r3, r1, lsr r2

248:    01c00fac     biceq    r0, r0, ip, lsr #31

24c:    e12fff1e     bx    lr

This libgcc.a was generated during the compilation of GCC by crossdev, on a Gentoo system.

Hi bwasim,

as myy says, the file which would be linked from libgcc.a is not _floatdisf.o nor _arm_floatdisf.o, but _arm_addsubsf3.o is linked.

The __aeabi_l2f is defined in the _arm_addsubsf3.o.
To know which library files had been linked is to compile a source file with "-Wl,-Map=output.map" option.

Best regards,
Yasuhiko Koumoto.