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riscv, bpf: Fix broken BPF tail calls 

commit f1003b787c upstream.

The BPF JIT incorrectly clobbered the a0 register, and did not flag
usage of s5 register when BPF stack was being used.

Fixes: 2353ecc6f9 ("bpf, riscv: add BPF JIT for RV64G")
Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191216091343.23260-2-bjorn.topel@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Björn Töpel 2019-12-16 10:13:35 +01:00 committed by Greg Kroah-Hartman
parent f3107a3c9b
commit 5b0e9b563c
1 changed files with 11 additions and 2 deletions
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13
arch/riscv/net/bpf_jit_comp.c
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@ -120,6 +120,11 @@ static bool seen_reg(int reg, struct rv_jit_context *ctx)
return false;
}
static void mark_fp(struct rv_jit_context *ctx)
{
__set_bit(RV_CTX_F_SEEN_S5, &ctx->flags);
}
static void mark_call(struct rv_jit_context *ctx)
{
__set_bit(RV_CTX_F_SEEN_CALL, &ctx->flags);
@ -596,7 +601,8 @@ static void __build_epilogue(u8 reg, struct rv_jit_context *ctx)
emit(rv_addi(RV_REG_SP, RV_REG_SP, stack_adjust), ctx);
/* Set return value. */
emit(rv_addi(RV_REG_A0, RV_REG_A5, 0), ctx);
if (reg == RV_REG_RA)
emit(rv_addi(RV_REG_A0, RV_REG_A5, 0), ctx);
emit(rv_jalr(RV_REG_ZERO, reg, 0), ctx);
}
@ -1426,6 +1432,10 @@ static void build_prologue(struct rv_jit_context *ctx)
{
int stack_adjust = 0, store_offset, bpf_stack_adjust;
bpf_stack_adjust = round_up(ctx->prog->aux->stack_depth, 16);
if (bpf_stack_adjust)
mark_fp(ctx);
if (seen_reg(RV_REG_RA, ctx))
stack_adjust += 8;
stack_adjust += 8; /* RV_REG_FP */
@ -1443,7 +1453,6 @@ static void build_prologue(struct rv_jit_context *ctx)
stack_adjust += 8;
stack_adjust = round_up(stack_adjust, 16);
bpf_stack_adjust = round_up(ctx->prog->aux->stack_depth, 16);
stack_adjust += bpf_stack_adjust;
store_offset = stack_adjust - 8;