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foss-for-synopsys-dwc-arc-processors / linux

Helpful resources for users & developers of Linux kernel for ARC
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kernel modules can't be loaded if build with 2019.03-rc1 toolchain #9

Closed evgeniy-paltsev closed 5 years ago

evgeniy-paltsev commented 5 years ago

If we build kernel with 2019.03-rc1 toolchain we get errors on modules loading.

I.E:

insmod ./lib/modules/4.19.9/kernel/net/ipv6/ipv6.ko
ipv6: unknown relocation: 82
insmod: ERROR: could not insert module ./lib/modules/4.19.9/kernel/net/ipv6/ipv6.ko: Invalid module format

Everything works fine with previous toolchain (2018.09). This issue can be reproduced on different versions of kernel (I've tried 4.19.9, 4.20)

evgeniy-paltsev commented 5 years ago

CC @vineetgarc @abrodkin

evgeniy-paltsev commented 5 years ago

BTW, it's enough to build only modules with 2019.03-rc1 toolchain to reproduce this issue. (I.E. build modules with 2019.03-rc1, build the rest of the kernel with 2018.09)

evgeniy-paltsev commented 5 years ago

Ok, it's new R_ARC_S8H_PCREL type of relocation. We need to add support of this relocation type to the our module.c

claziss commented 5 years ago

No need to do such an operation for the time being. The following relocs have being introduced to support linker-time relaxation:

Enum ELF Reloc Type Description Details
80 R_ARC_S9H_PCREL PC-relative bits9 = ME ( ( ( ( S + A ) - P ) >> 1 ) ) )
81 R_ARC_S7H_PCREL PC-relative bits7 = (( S + A ) - P ) >> 1
82 R_ARC_S8H_PCREL PC-relative disp8h = (( S + A ) - P ) >> 1
83 R_ARC_S10H_PCREL PC-relative bits10 = (( S + A ) - P ) >> 1
84 R_ARC_S13H_PCREL PC-relative bits13 = ME ( ( ( ( S + A ) - P ) >> 1 ) ) )
85 R_ARC_ALIGN Alignment statement
86 R_ARC_ADD8 8-bit label addition word8 = S + A
87 R_ARC_ADD16 16-bit label addition word16 = S + A
88 R_ARC_SUB8 8-bit label subtraction word8 = S - A
89 R_ARC_SUB16 16-bit label subtraction word16 = S - A
90 R_ARC_SUB32 32-bit label subtraction word32 = S - A

A binutils patch will be added to make the tools to behave as "before" when the linker relaxation is not required.

evgeniy-paltsev commented 5 years ago

Kernel nodules loading works fine if we build modules with 2019.03-rc2 toolchain.