1 files changed, 63 insertions, 6 deletions

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index c04ace8f4843..3dd23050a6c8 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -7,6 +7,7 @@
 
 #define pr_fmt(fmt) "bpf_jit: " fmt
 
+#include <linux/arm-smccc.h>
 #include <linux/bitfield.h>
 #include <linux/bpf.h>
 #include <linux/filter.h>
@@ -17,6 +18,7 @@
 #include <asm/asm-extable.h>
 #include <asm/byteorder.h>
 #include <asm/cacheflush.h>
+#include <asm/cpufeature.h>
 #include <asm/debug-monitors.h>
 #include <asm/insn.h>
 #include <asm/patching.h>
@@ -653,7 +655,51 @@ static void build_plt(struct jit_ctx *ctx)
 		plt->target = (u64)&dummy_tramp;
 }
 
-static void build_epilogue(struct jit_ctx *ctx)
+/* Clobbers BPF registers 1-4, aka x0-x3 */
+static void __maybe_unused build_bhb_mitigation(struct jit_ctx *ctx)
+{
+	const u8 r1 = bpf2a64[BPF_REG_1]; /* aka x0 */
+	u8 k = get_spectre_bhb_loop_value();
+
+	if (!IS_ENABLED(CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY) ||
+	    cpu_mitigations_off() || __nospectre_bhb ||
+	    arm64_get_spectre_v2_state() == SPECTRE_VULNERABLE)
+		return;
+
+	if (capable(CAP_SYS_ADMIN))
+		return;
+
+	if (supports_clearbhb(SCOPE_SYSTEM)) {
+		emit(aarch64_insn_gen_hint(AARCH64_INSN_HINT_CLEARBHB), ctx);
+		return;
+	}
+
+	if (k) {
+		emit_a64_mov_i64(r1, k, ctx);
+		emit(A64_B(1), ctx);
+		emit(A64_SUBS_I(true, r1, r1, 1), ctx);
+		emit(A64_B_(A64_COND_NE, -2), ctx);
+		emit(aarch64_insn_gen_dsb(AARCH64_INSN_MB_ISH), ctx);
+		emit(aarch64_insn_get_isb_value(), ctx);
+	}
+
+	if (is_spectre_bhb_fw_mitigated()) {
+		emit(A64_ORR_I(false, r1, AARCH64_INSN_REG_ZR,
+			       ARM_SMCCC_ARCH_WORKAROUND_3), ctx);
+		switch (arm_smccc_1_1_get_conduit()) {
+		case SMCCC_CONDUIT_HVC:
+			emit(aarch64_insn_get_hvc_value(), ctx);
+			break;
+		case SMCCC_CONDUIT_SMC:
+			emit(aarch64_insn_get_smc_value(), ctx);
+			break;
+		default:
+			pr_err_once("Firmware mitigation enabled with unknown conduit\n");
+		}
+	}
+}
+
+static void build_epilogue(struct jit_ctx *ctx, bool was_classic)
 {
 	const u8 r0 = bpf2a64[BPF_REG_0];
 	const u8 r6 = bpf2a64[BPF_REG_6];
@@ -675,10 +721,13 @@ static void build_epilogue(struct jit_ctx *ctx)
 	emit(A64_POP(r8, r9, A64_SP), ctx);
 	emit(A64_POP(r6, r7, A64_SP), ctx);
 
+	if (was_classic)
+		build_bhb_mitigation(ctx);
+
 	/* Restore FP/LR registers */
 	emit(A64_POP(A64_FP, A64_LR, A64_SP), ctx);
 
-	/* Set return value */
+	/* Move the return value from bpf:r0 (aka x7) to x0 */
 	emit(A64_MOV(1, A64_R(0), r0), ctx);
 
 	/* Authenticate lr */
@@ -1527,7 +1576,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 	}
 
 	ctx.epilogue_offset = ctx.idx;
-	build_epilogue(&ctx);
+	build_epilogue(&ctx, was_classic);
 	build_plt(&ctx);
 
 	extable_align = __alignof__(struct exception_table_entry);
@@ -1563,7 +1612,7 @@ skip_init_ctx:
 		goto out_off;
 	}
 
-	build_epilogue(&ctx);
+	build_epilogue(&ctx, was_classic);
 	build_plt(&ctx);
 
 	/* 3. Extra pass to validate JITed code. */
@@ -1893,7 +1942,11 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
 	emit(A64_STR64I(A64_R(20), A64_SP, regs_off + 8), ctx);
 
 	if (flags & BPF_TRAMP_F_CALL_ORIG) {
-		emit_addr_mov_i64(A64_R(0), (const u64)im, ctx);
+		/* for the first pass, assume the worst case */
+		if (!ctx->image)
+			ctx->idx += 4;
+		else
+			emit_a64_mov_i64(A64_R(0), (const u64)im, ctx);
 		emit_call((const u64)__bpf_tramp_enter, ctx);
 	}
 
@@ -1937,7 +1990,11 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
 
 	if (flags & BPF_TRAMP_F_CALL_ORIG) {
 		im->ip_epilogue = ctx->image + ctx->idx;
-		emit_addr_mov_i64(A64_R(0), (const u64)im, ctx);
+		/* for the first pass, assume the worst case */
+		if (!ctx->image)
+			ctx->idx += 4;
+		else
+			emit_a64_mov_i64(A64_R(0), (const u64)im, ctx);
 		emit_call((const u64)__bpf_tramp_exit, ctx);
 	}