ARM: net: bpf: avoid 'bx' instruction on non-Thumb capable CPUs

commit e9062481824384f00299971f923fecf6b3668001 upstream.

Avoid the 'bx' instruction on CPUs that have no support for Thumb and
thus do not implement this instruction by moving the generation of this
opcode to a separate function that selects between:

	bx	reg

and

	mov	pc, reg

according to the capabilities of the CPU.

Fixes: 39c13c204bb1 ("arm: eBPF JIT compiler")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index c199990e12b620fe40f34215abf2d577e6f90c70..4efb3743a89e05f2dd3bb0e48e92abf6c0d74d25 100644 (file)
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -285,16 +285,20 @@ static inline void emit_mov_i(const u8 rd, u32 val, struct jit_ctx *ctx)
                emit_mov_i_no8m(rd, val, ctx);
 }
 
-static inline void emit_blx_r(u8 tgt_reg, struct jit_ctx *ctx)
+static void emit_bx_r(u8 tgt_reg, struct jit_ctx *ctx)
 {
-       ctx->seen |= SEEN_CALL;
-#if __LINUX_ARM_ARCH__ < 5
-       emit(ARM_MOV_R(ARM_LR, ARM_PC), ctx);
-
        if (elf_hwcap & HWCAP_THUMB)
                emit(ARM_BX(tgt_reg), ctx);
        else
                emit(ARM_MOV_R(ARM_PC, tgt_reg), ctx);
+}
+
+static inline void emit_blx_r(u8 tgt_reg, struct jit_ctx *ctx)
+{
+       ctx->seen |= SEEN_CALL;
+#if __LINUX_ARM_ARCH__ < 5
+       emit(ARM_MOV_R(ARM_LR, ARM_PC), ctx);
+       emit_bx_r(tgt_reg, ctx);
 #else
        emit(ARM_BLX_R(tgt_reg), ctx);
 #endif
@@ -997,7 +1001,7 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
        emit_a32_mov_i(tmp2[1], off, false, ctx);
        emit(ARM_LDR_R(tmp[1], tmp[1], tmp2[1]), ctx);
        emit(ARM_ADD_I(tmp[1], tmp[1], ctx->prologue_bytes), ctx);
-       emit(ARM_BX(tmp[1]), ctx);
+       emit_bx_r(tmp[1], ctx);
 
        /* out: */
        if (out_offset == -1)
@@ -1166,7 +1170,7 @@ static void build_epilogue(struct jit_ctx *ctx)
        emit(ARM_POP(reg_set), ctx);
        /* Return back to the callee function */
        if (!(ctx->seen & SEEN_CALL))
-               emit(ARM_BX(ARM_LR), ctx);
+               emit_bx_r(ARM_LR, ctx);
 #endif
 }