Commit 20ccb004 authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Michael Ellerman
Browse files

powerpc/bpf: Use bctrl for making function calls 



blrl corrupts the link stack. Instead use bctrl when making function
calls from BPF programs.

Reported-by: default avatarAnton Blanchard <anton@ozlabs.org>
Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210609090024.1446800-1-naveen.n.rao@linux.vnet.ibm.com
parent b8ee3e6d

arch/powerpc/net/bpf_jit_comp32.c

+2 −2
Original line number Diff line number Diff line
@@ -195,8 +195,8 @@ void bpf_jit_emit_func_call_rel(u32 *image, struct codegen_context *ctx, u64 fun 
		/* Load function address into r0 */

		EMIT(PPC_RAW_LIS(_R0, IMM_H(func)));

		EMIT(PPC_RAW_ORI(_R0, _R0, IMM_L(func)));

		EMIT(PPC_RAW_MTLR(_R0));

		EMIT(PPC_RAW_BLRL());

		EMIT(PPC_RAW_MTCTR(_R0));

		EMIT(PPC_RAW_BCTRL());

	}

}

arch/powerpc/net/bpf_jit_comp64.c

+6 −6
Original line number Diff line number Diff line
@@ -153,8 +153,8 @@ static void bpf_jit_emit_func_call_hlp(u32 *image, struct codegen_context *ctx, 
	PPC_LI64(b2p[TMP_REG_2], func);

	/* Load actual entry point from function descriptor */

	PPC_BPF_LL(b2p[TMP_REG_1], b2p[TMP_REG_2], 0);

	/* ... and move it to LR */

	EMIT(PPC_RAW_MTLR(b2p[TMP_REG_1]));

	/* ... and move it to CTR */

	EMIT(PPC_RAW_MTCTR(b2p[TMP_REG_1]));

	/*

	 * Load TOC from function descriptor at offset 8.

	 * We can clobber r2 since we get called through a
@@ -165,9 +165,9 @@ static void bpf_jit_emit_func_call_hlp(u32 *image, struct codegen_context *ctx, 
#else

	/* We can clobber r12 */

	PPC_FUNC_ADDR(12, func);

	EMIT(PPC_RAW_MTLR(12));

	EMIT(PPC_RAW_MTCTR(12));

#endif

	EMIT(PPC_RAW_BLRL());

	EMIT(PPC_RAW_BCTRL());

}



void bpf_jit_emit_func_call_rel(u32 *image, struct codegen_context *ctx, u64 func)
@@ -202,8 +202,8 @@ void bpf_jit_emit_func_call_rel(u32 *image, struct codegen_context *ctx, u64 fun 
	PPC_BPF_LL(12, 12, 0);

#endif



	EMIT(PPC_RAW_MTLR(12));

	EMIT(PPC_RAW_BLRL());

	EMIT(PPC_RAW_MTCTR(12));

	EMIT(PPC_RAW_BCTRL());

}



static void bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 out)