LoongArch: BPF: Don't override subprog's return value

The verifier test `calls: div by 0 in subprog` triggers a panic at the
ld.bu instruction. The ld.bu insn is trying to load byte from memory
addr

LoongArch: BPF: Don't override subprog's return value

The verifier test `calls: div by 0 in subprog` triggers a panic at the
ld.bu instruction. The ld.bu insn is trying to load byte from memory
address returned by the subprog. The subprog actually set the correct
address at the a5 register (dedicated register for BPF return values).
But at commit 73c359d1d356 ("LoongArch: BPF: Sign-extend return values")
we also sign extended a5 to the a0 register (return value in LoongArch).
For function call insn, we later propagate the a0 register back to a5
register. This is right for native calls but wrong for bpf2bpf calls
which expect zero-extended return value in a5 register. So only move a0
to a5 for native calls (i.e. non-BPF_PSEUDO_CALL).

Cc: [email protected]
Fixes: 73c359d1d356 ("LoongArch: BPF: Sign-extend return values")
Signed-off-by: Hengqi Chen <[email protected]>
Signed-off-by: Huacai Chen <[email protected]>

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LoongArch: BPF: Use move_addr() for BPF_PSEUDO_FUNC

Vincent reported that running XDP synproxy program on LoongArch results
in the following error:

JIT doesn't support bpf-to-bpf calls

With dm

LoongArch: BPF: Use move_addr() for BPF_PSEUDO_FUNC

Vincent reported that running XDP synproxy program on LoongArch results
in the following error:

JIT doesn't support bpf-to-bpf calls

With dmesg:

multi-func JIT bug 1391 != 1390

The root cause is that verifier will refill the imm with the correct
addresses of bpf_calls for BPF_PSEUDO_FUNC instructions and then run
the last pass of JIT. So we generate different JIT code for the same
instruction in two passes (one for placeholder and the other for the
real address). Let's use move_addr() instead.

See commit 64f50f6575721ef0 ("LoongArch, bpf: Use 4 instructions for
function address in JIT") for a similar fix.

Cc: [email protected]
Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper")
Fixes: bb035ef0cc91 ("LoongArch: BPF: Support mixing bpf2bpf and tailcalls")
Reported-by: Vincent Li <[email protected]>
Tested-by: Vincent Li <[email protected]>
Closes: https://lore.kernel.org/loongarch/CAK3+h2yfM9FTNiXvEQBkvtuoJrvzmN4c_NZsFXqEk4Cj1tsBNA@mail.gmail.com/T/#u
Signed-off-by: Hengqi Chen <[email protected]>
Signed-off-by: Huacai Chen <[email protected]>

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LoongArch: BPF: Fix off-by-one error in build_prologue()

Vincent reported that running BPF progs with tailcalls on LoongArch
causes kernel hard lockup. Debugging the issues shows that the JITed
imag

LoongArch: BPF: Fix off-by-one error in build_prologue()

Vincent reported that running BPF progs with tailcalls on LoongArch
causes kernel hard lockup. Debugging the issues shows that the JITed
image missing a jirl instruction at the end of the epilogue.

There are two passes in JIT compiling, the first pass set the flags and
the second pass generates JIT code based on those flags. With BPF progs
mixing bpf2bpf and tailcalls, build_prologue() generates N insns in the
first pass and then generates N+1 insns in the second pass. This makes
epilogue_offset off by one and we will jump to some unexpected insn and
cause lockup. Fix this by inserting a nop insn.

Cc: [email protected]
Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support")
Fixes: bb035ef0cc91 ("LoongArch: BPF: Support mixing bpf2bpf and tailcalls")
Reported-by: Vincent Li <[email protected]>
Tested-by: Vincent Li <[email protected]>
Closes: https://lore.kernel.org/loongarch/CAK3+h2w6WESdBN3UCr3WKHByD7D6Q_Ve1EDAjotVrnx6Or_c8g@mail.gmail.com/
Closes: https://lore.kernel.org/bpf/CAK3+h2woEjG_N=-XzqEGaAeCmgu2eTCUc7p6bP4u8Q+DFHm-7g@mail.gmail.com/
Signed-off-by: Hengqi Chen <[email protected]>
Signed-off-by: Huacai Chen <[email protected]>

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