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dbcd7f5f |
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10-Dec-2022 |
Youling Tang <tangyouling@loongson.cn> |
LoongArch: BPF: Add BPF exception tables Inspired by commit 800834285361("bpf, arm64: Add BPF exception tables"), do similar to LoongArch to add BPF exception tables. When a tracing BPF program attempts to read memory without using the bpf_probe_read() helper, the verifier marks the load instruction with the BPF_PROBE_MEM flag. Since the LoongArch JIT does not currently recognize this flag it falls back to the interpreter. Add support for BPF_PROBE_MEM, by appending an exception table to the BPF program. If the load instruction causes a data abort, the fixup infrastructure finds the exception table and fixes up the fault, by clearing the destination register and jumping over the faulting instruction. To keep the compact exception table entry format, inspect the pc in fixup_exception(). A more generic solution would add a "handler" field to the table entry, like on x86, s390 and arm64, etc. Signed-off-by: Youling Tang <tangyouling@loongson.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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26bc8244 |
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10-Dec-2022 |
Youling Tang <tangyouling@loongson.cn> |
LoongArch: extable: Add `type` and `data` fields This is a LoongArch port of commit d6e2cc564775 ("arm64: extable: add `type` and `data` fields"). Subsequent patches will add specialized handlers for fixups, in addition to the simple PC fixup we have today. In preparation, this patch adds a new `type` field to struct exception_table_entry, and uses this to distinguish the fixup and other cases. A `data` field is also added so that subsequent patches can associate data specific to each exception site (e.g. register numbers). Handlers are named ex_handler_*() for consistency, following the example of x86. At the same time, get_ex_fixup() is split out into a helper so that it can be used by other ex_handler_*() functions in the subsequent patches. Signed-off-by: Youling Tang <tangyouling@loongson.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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3d36f429 |
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10-Dec-2022 |
Youling Tang <tangyouling@loongson.cn> |
LoongArch: Switch to relative exception tables Similar to other architectures such as arm64, x86, riscv and so on, use offsets relative to the exception table entry values rather than their absolute addresses for both the exception location and the fixup. However, LoongArch label difference because it will actually produce two relocations, a pair of R_LARCH_ADD32 and R_LARCH_SUB32. Take simple code below for example: $ cat test_ex_table.S .section .text 1: nop .section __ex_table,"a" .balign 4 .long (1b - .) .previous $ loongarch64-unknown-linux-gnu-gcc -c test_ex_table.S $ loongarch64-unknown-linux-gnu-readelf -Wr test_ex_table.o Relocation section '.rela__ex_table' at offset 0x100 contains 2 entries: Offset Info Type Symbol's Value Symbol's Name + Addend 0000000000000000 0000000600000032 R_LARCH_ADD32 0000000000000000 .L1^B1 + 0 0000000000000000 0000000500000037 R_LARCH_SUB32 0000000000000000 L0^A + 0 The modpost will complain the R_LARCH_SUB32 relocation, so we need to patch modpost.c to skip this relocation for .rela__ex_table section. Signed-off-by: Youling Tang <tangyouling@loongson.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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