6.5-stable review patch. If anyone has any objections, please let me know.
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From: Björn Töpel bjorn@rivosinc.com
[ Upstream commit 7112cd26e606c7ba51f9cc5c1905f06039f6f379 ]
The RISC-V BPF uses a5 for BPF return values, which are zero-extended, whereas the RISC-V ABI uses a0 which is sign-extended. In other words, a5 and a0 can differ, and are used in different context.
The BPF trampoline are used for both BPF programs, and regular kernel functions.
Make sure that the RISC-V BPF trampoline saves, and restores both a0 and a5.
Fixes: 49b5e77ae3e2 ("riscv, bpf: Add bpf trampoline support for RV64") Signed-off-by: Björn Töpel bjorn@rivosinc.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/20231004120706.52848-3-bjorn@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/net/bpf_jit_comp64.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c index 3a3631bae05c1..3b4cb713e3684 100644 --- a/arch/riscv/net/bpf_jit_comp64.c +++ b/arch/riscv/net/bpf_jit_comp64.c @@ -757,8 +757,10 @@ static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_of if (ret) return ret;
- if (save_ret) - emit_sd(RV_REG_FP, -retval_off, regmap[BPF_REG_0], ctx); + if (save_ret) { + emit_sd(RV_REG_FP, -retval_off, RV_REG_A0, ctx); + emit_sd(RV_REG_FP, -(retval_off - 8), regmap[BPF_REG_0], ctx); + }
/* update branch with beqz */ if (ctx->insns) { @@ -844,7 +846,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET); if (save_ret) { - stack_size += 8; + stack_size += 16; /* Save both A5 (BPF R0) and A0 */ retval_off = stack_size; }
@@ -931,6 +933,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, if (ret) goto out; emit_sd(RV_REG_FP, -retval_off, RV_REG_A0, ctx); + emit_sd(RV_REG_FP, -(retval_off - 8), regmap[BPF_REG_0], ctx); im->ip_after_call = ctx->insns + ctx->ninsns; /* 2 nops reserved for auipc+jalr pair */ emit(rv_nop(), ctx); @@ -962,8 +965,10 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, if (flags & BPF_TRAMP_F_RESTORE_REGS) restore_args(nregs, args_off, ctx);
- if (save_ret) + if (save_ret) { emit_ld(RV_REG_A0, -retval_off, RV_REG_FP, ctx); + emit_ld(regmap[BPF_REG_0], -(retval_off - 8), RV_REG_FP, ctx); + }
emit_ld(RV_REG_S1, -sreg_off, RV_REG_FP, ctx);