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armv7-a elf file load / kernel build
hello, I find that in the kernel build mode for armv7-a arch, the apps (elf file) contains R_ARM_THM_JUMP24 relocation sections, take the nsh file for example, and by default CONFIG_ARM_THUMB is false. so while loading elf file, the libs>libc>machine>arm>armv7-a>arch_elf.c>up_relocate function will report an error “ERROR: Unsupported relocation: ...”.
parts of the relocation section info of nsh are like this: Relocation section '.rel.text' at offset 0xd3a7c contains 2895 entries: Offset Info Type Sym.Value Sym. Name 00000014 0005ca1e R_ARM_THM_JUMP24 0000017d __aeabi_ldiv0 00000020 00056d0a R_ARM_THM_CALL 00000071 __udivmoddi4 000003d8 0006231e R_ARM_THM_JUMP24 0000017d __aeabi_idiv0 00000438 00001a2b R_ARM_MOVW_ABS_NC 000003f8 sig_trampoline 0000043c 00001a2c R_ARM_MOVT_ABS 000003f8 sig_trampoline
and the compiler option for nsh are like this: CC: nsh_consolemain.c arm-none-eabi-gcc -c -Wstrict-prototypes -Wno-attributes -Wno-unknown-pragmas -Wno-psabi -fno-common -pipe -fomit-frame-pointer -fno-common -Wall -Wshadow -Wundef -ffunction-sections -fdata-sections -g -mcpu=cortex-a9 -mfloat-abi=hard -mfpu=neon-vfpv3 -mlittle-endian -isystem /home/cloud/nuttx-12.4.0/apps/import/include -isystem /home/cloud/nuttx-12.4.0/apps/import/include -D__NuttX__ -DNDEBUG -I "/home/cloud/nuttx-12.4.0/apps/include" nsh_consolemain.c -o nsh_consolemain.c.home.cloud.nuttx-12.4.0.apps.nshlib.o
so the options like -mthumb -mthumb-interwork are not set.
but why there are some THUMB type relocaiton sections? who can help explan this, thanks very much. defconfig.txt
well, it seems that the reason is the linker option.
below is the linker options: arm-none-eabi-ld -r -e main -T /home/cloud/nuttx-12.4.0/nuttx/binfmt/libelf/gnu-elf.ld -r -e _start -Bstatic -T/home/cloud/nuttx-12.4.0/apps/import/scripts/gnu-elf.ld -L/home/cloud/nuttx-12.4.0/apps/import/libs -L "/opt/gcc-arm-none-eabi-10.3-2021.10/bin/../lib/gcc/arm-none-eabi/10.3.1/../../../../arm-none-eabi/lib/thumb/v7-a+simd/hard" -L "/opt/gcc-arm-none-eabi-10.3-2021.10/bin/../lib/gcc/arm-none-eabi/10.3.1/thumb/v7-a+simd/hard" /home/cloud/nuttx-12.4.0/apps/import/startup/crt0.o elf_main.c.home.cloud.nuttx-12.4.0.apps.examples.elf.o --start-group -lmm -lc -lproxies -lxx -lm -lgcc /home/cloud/nuttx-12.4.0/apps/libapps.a /opt/gcc-arm-none-eabi-10.3-2021.10/bin/../lib/gcc/arm-none-eabi/10.3.1/thumb/v7-a+simd/hard/libgcc.a --end-group -o /home/cloud/nuttx-12.4.0/apps/bin/elf
according to the apps/import/Make.defs Line:87, the output for the command "arm-none-eabi-gcc -mcpu=cortex-a9 -mfloat-abi=hard -mfpu=neon-vfpv3 -mlittle-endian --print-file-name=libgcc.a" is:
/opt/gcc-arm-none-eabi-10.3-2021.10/bin/../lib/gcc/arm-none-eabi/10.3.1/thumb/v7-a+simd/hard/libgcc.a
so. how the output comes? anyone can help explain this? thanks a lot.
Hi @xyluo555 did you get it working? Try to do "git grep thumb" or similar, it could help you to find some examples. @xiaoxiang781216 @lupyuen any suggestion?
Yes, the CONFIG_ARM_THUMB should be enabled. But I haven't figure out why ld select "/opt/gcc-arm-none-eabi-10.3-2021.10/bin/../lib/gcc/arm-none-eabi/10.3.1/thumb/v7-a+simd/hard" as the library path. actually, as is defined in apps/import/Make.def, while the command "arm-none-eabi-gcc -mcpu=cortex-a9 -mfloat-abi=hard -mfpu=neon-vfpv3 -mlittle-endian --print-file-name=libgcc.a" is executed, the output is "/opt/gcc-arm-none-eabi-10.3-2021.10/bin/../lib/gcc/arm-none-eabi/10.3.1/thumb/v7-a+simd/hard/libgcc.a".
Yes, sometimes the linker does something very strange, it is not too smart.
BTW, did you get NuttX working on ZYNQ7000 ? If so, please consider submitting support to mainline ;-)
sorry, the porting is on going. there seems to be a bug, as shown in issue #12618 . currently, the console is ok and kernel & apps images are build separately. but there are more work to be finished.
/opt/gcc-arm-none-eabi-10.3-2021.10/bin/../lib/gcc/arm-none-eabi/10.3.1/thumb/v7-a+simd/hard/libgcc.a
so. how the output comes? anyone can help explain this? thanks a lot.
@xyluo555 I think gcc is configured to do this by default. For armv7-a, both ARM and THUMB programs will link to libraries in the thumb directory. See the output of this command, all the options seem to be mapped to thumb: arm-none-eabi-gcc --print-multi-lib
Also see this file in the gcc tree. Use "blame" to read the history of the file for more details.
