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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>
Inspired by commit 2e77a62cb3a6("arm64: extable: add a dedicated uaccess
handler"), do similar to LoongArch to add a dedicated uaccess exception
handler to update registers in exception context and subsequently return
back into the function which faulted, so we remove the need for fixups
specialized to each faulting instruction.
Add gpr-num.h here because we need to map the same GPR names to integer
constants, so that we can use this to build meta-data for the exception
fixups.
The compiler treats gpr 0 as zero rather than $r0, so set it separately
to .L__gpr_num_zero, otherwise the following assembly error will occurs:
{standard input}: Assembler messages:
{standard input}:1074: Error: invalid operands (*UND* and *ABS* sections) for `<<'
{standard input}:1160: Error: invalid operands (*UND* and *ABS* sections) for `<<'
make[1]: *** [scripts/Makefile.build:249: fs/fcntl.o] Error 1
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This is a LoongArch port of commit d6e2cc5647 ("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>
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>
Add memory management support for LoongArch, including: cache and tlb
management, page fault handling and ioremap/mmap support.
Reviewed-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
