6.11-stable review patch. If anyone has any objections, please let me know.
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From: Leon Hwang hffilwlqm@gmail.com
[ Upstream commit 66ff4d61dc124eafe9efaeaef696a09b7f236da2 ]
This patch fixes a tailcall issue caused by abusing the tailcall in bpf2bpf feature on arm64 like the way of "bpf, x64: Fix tailcall hierarchy".
On arm64, when a tail call happens, it uses tail_call_cnt_ptr to increment tail_call_cnt, too.
At the prologue of main prog, it has to initialize tail_call_cnt and prepare tail_call_cnt_ptr.
At the prologue of subprog, it pushes x26 register twice, and does not initialize tail_call_cnt.
At the epilogue, it pops x26 twice, no matter whether it is main prog or subprog.
Fixes: d4609a5d8c70 ("bpf, arm64: Keep tail call count across bpf2bpf calls") Acked-by: Puranjay Mohan puranjay@kernel.org Signed-off-by: Leon Hwang hffilwlqm@gmail.com Link: https://lore.kernel.org/r/20240714123902.32305-3-hffilwlqm@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/net/bpf_jit_comp.c | 57 +++++++++++++++++++++++++---------- 1 file changed, 41 insertions(+), 16 deletions(-)
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index dd0bb069df4bb..59e05a7aea56a 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -26,7 +26,7 @@
#define TMP_REG_1 (MAX_BPF_JIT_REG + 0) #define TMP_REG_2 (MAX_BPF_JIT_REG + 1) -#define TCALL_CNT (MAX_BPF_JIT_REG + 2) +#define TCCNT_PTR (MAX_BPF_JIT_REG + 2) #define TMP_REG_3 (MAX_BPF_JIT_REG + 3) #define FP_BOTTOM (MAX_BPF_JIT_REG + 4) #define ARENA_VM_START (MAX_BPF_JIT_REG + 5) @@ -63,8 +63,8 @@ static const int bpf2a64[] = { [TMP_REG_1] = A64_R(10), [TMP_REG_2] = A64_R(11), [TMP_REG_3] = A64_R(12), - /* tail_call_cnt */ - [TCALL_CNT] = A64_R(26), + /* tail_call_cnt_ptr */ + [TCCNT_PTR] = A64_R(26), /* temporary register for blinding constants */ [BPF_REG_AX] = A64_R(9), [FP_BOTTOM] = A64_R(27), @@ -282,13 +282,35 @@ static bool is_lsi_offset(int offset, int scale) * mov x29, sp * stp x19, x20, [sp, #-16]! * stp x21, x22, [sp, #-16]! - * stp x25, x26, [sp, #-16]! + * stp x26, x25, [sp, #-16]! + * stp x26, x25, [sp, #-16]! * stp x27, x28, [sp, #-16]! * mov x25, sp * mov tcc, #0 * // PROLOGUE_OFFSET */
+static void prepare_bpf_tail_call_cnt(struct jit_ctx *ctx) +{ + const struct bpf_prog *prog = ctx->prog; + const bool is_main_prog = !bpf_is_subprog(prog); + const u8 ptr = bpf2a64[TCCNT_PTR]; + const u8 fp = bpf2a64[BPF_REG_FP]; + const u8 tcc = ptr; + + emit(A64_PUSH(ptr, fp, A64_SP), ctx); + if (is_main_prog) { + /* Initialize tail_call_cnt. */ + emit(A64_MOVZ(1, tcc, 0, 0), ctx); + emit(A64_PUSH(tcc, fp, A64_SP), ctx); + emit(A64_MOV(1, ptr, A64_SP), ctx); + } else { + emit(A64_PUSH(ptr, fp, A64_SP), ctx); + emit(A64_NOP, ctx); + emit(A64_NOP, ctx); + } +} + #define BTI_INSNS (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) ? 1 : 0) #define PAC_INSNS (IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL) ? 1 : 0)
@@ -296,7 +318,7 @@ static bool is_lsi_offset(int offset, int scale) #define POKE_OFFSET (BTI_INSNS + 1)
/* Tail call offset to jump into */ -#define PROLOGUE_OFFSET (BTI_INSNS + 2 + PAC_INSNS + 8) +#define PROLOGUE_OFFSET (BTI_INSNS + 2 + PAC_INSNS + 10)
static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf, bool is_exception_cb, u64 arena_vm_start) @@ -308,7 +330,6 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf, const u8 r8 = bpf2a64[BPF_REG_8]; const u8 r9 = bpf2a64[BPF_REG_9]; const u8 fp = bpf2a64[BPF_REG_FP]; - const u8 tcc = bpf2a64[TCALL_CNT]; const u8 fpb = bpf2a64[FP_BOTTOM]; const u8 arena_vm_base = bpf2a64[ARENA_VM_START]; const int idx0 = ctx->idx; @@ -359,7 +380,7 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf, /* Save callee-saved registers */ emit(A64_PUSH(r6, r7, A64_SP), ctx); emit(A64_PUSH(r8, r9, A64_SP), ctx); - emit(A64_PUSH(fp, tcc, A64_SP), ctx); + prepare_bpf_tail_call_cnt(ctx); emit(A64_PUSH(fpb, A64_R(28), A64_SP), ctx); } else { /* @@ -372,18 +393,15 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf, * callee-saved registers. The exception callback will not push * anything and re-use the main program's stack. * - * 10 registers are on the stack + * 12 registers are on the stack */ - emit(A64_SUB_I(1, A64_SP, A64_FP, 80), ctx); + emit(A64_SUB_I(1, A64_SP, A64_FP, 96), ctx); }
/* Set up BPF prog stack base register */ emit(A64_MOV(1, fp, A64_SP), ctx);
if (!ebpf_from_cbpf && is_main_prog) { - /* Initialize tail_call_cnt */ - emit(A64_MOVZ(1, tcc, 0, 0), ctx); - cur_offset = ctx->idx - idx0; if (cur_offset != PROLOGUE_OFFSET) { pr_err_once("PROLOGUE_OFFSET = %d, expected %d!\n", @@ -432,7 +450,8 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
const u8 tmp = bpf2a64[TMP_REG_1]; const u8 prg = bpf2a64[TMP_REG_2]; - const u8 tcc = bpf2a64[TCALL_CNT]; + const u8 tcc = bpf2a64[TMP_REG_3]; + const u8 ptr = bpf2a64[TCCNT_PTR]; const int idx0 = ctx->idx; #define cur_offset (ctx->idx - idx0) #define jmp_offset (out_offset - (cur_offset)) @@ -449,11 +468,12 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx) emit(A64_B_(A64_COND_CS, jmp_offset), ctx);
/* - * if (tail_call_cnt >= MAX_TAIL_CALL_CNT) + * if ((*tail_call_cnt_ptr) >= MAX_TAIL_CALL_CNT) * goto out; - * tail_call_cnt++; + * (*tail_call_cnt_ptr)++; */ emit_a64_mov_i64(tmp, MAX_TAIL_CALL_CNT, ctx); + emit(A64_LDR64I(tcc, ptr, 0), ctx); emit(A64_CMP(1, tcc, tmp), ctx); emit(A64_B_(A64_COND_CS, jmp_offset), ctx); emit(A64_ADD_I(1, tcc, tcc, 1), ctx); @@ -469,6 +489,9 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx) emit(A64_LDR64(prg, tmp, prg), ctx); emit(A64_CBZ(1, prg, jmp_offset), ctx);
+ /* Update tail_call_cnt if the slot is populated. */ + emit(A64_STR64I(tcc, ptr, 0), ctx); + /* goto *(prog->bpf_func + prologue_offset); */ off = offsetof(struct bpf_prog, bpf_func); emit_a64_mov_i64(tmp, off, ctx); @@ -721,6 +744,7 @@ static void build_epilogue(struct jit_ctx *ctx, bool is_exception_cb) const u8 r8 = bpf2a64[BPF_REG_8]; const u8 r9 = bpf2a64[BPF_REG_9]; const u8 fp = bpf2a64[BPF_REG_FP]; + const u8 ptr = bpf2a64[TCCNT_PTR]; const u8 fpb = bpf2a64[FP_BOTTOM];
/* We're done with BPF stack */ @@ -738,7 +762,8 @@ static void build_epilogue(struct jit_ctx *ctx, bool is_exception_cb) /* Restore x27 and x28 */ emit(A64_POP(fpb, A64_R(28), A64_SP), ctx); /* Restore fs (x25) and x26 */ - emit(A64_POP(fp, A64_R(26), A64_SP), ctx); + emit(A64_POP(ptr, fp, A64_SP), ctx); + emit(A64_POP(ptr, fp, A64_SP), ctx);
/* Restore callee-saved register */ emit(A64_POP(r8, r9, A64_SP), ctx);