Commit ee7c3ec3 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/ebpf32: Use standard function call for functions within 32M distance 



If the target of a function call is within 32 Mbytes distance, use a
standard function call with 'bl' instead of the 'lis/ori/mtlr/blrl'
sequence.

In the first pass, no memory has been allocated yet and the code
position is not known yet (image pointer is NULL). This pass is there
to calculate the amount of memory to allocate for the EBPF code, so
assume the 4 instructions sequence is required, so that enough memory
is allocated.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/74944a1e3e5cfecc141e440a6ccd37920e186b70.1618227846.git.christophe.leroy@csgroup.eu
parent e7de0023

arch/powerpc/include/asm/ppc-opcode.h

+1 −0
Original line number Diff line number Diff line
@@ -265,6 +265,7 @@ 
#define PPC_INST_ORI			0x60000000

#define PPC_INST_ORIS			0x64000000

#define PPC_INST_BRANCH			0x48000000

#define PPC_INST_BL			0x48000001

#define PPC_INST_BRANCH_COND		0x40800000



/* Prefixes */

arch/powerpc/net/bpf_jit.h

+3 −0
Original line number Diff line number Diff line
@@ -26,6 +26,9 @@ 
/* Long jump; (unconditional 'branch') */

#define PPC_JMP(dest)		EMIT(PPC_INST_BRANCH |			      \

				     (((dest) - (ctx->idx * 4)) & 0x03fffffc))

/* blr; (unconditional 'branch' with link) to absolute address */

#define PPC_BL_ABS(dest)	EMIT(PPC_INST_BL |			      \

				     (((dest) - (unsigned long)(image + ctx->idx)) & 0x03fffffc))

/* "cond" here covers BO:BI fields. */

#define PPC_BCC_SHORT(cond, dest)	EMIT(PPC_INST_BRANCH_COND |	      \

					     (((cond) & 0x3ff) << 16) |	      \

arch/powerpc/net/bpf_jit_comp32.c

+11 −5
Original line number Diff line number Diff line
@@ -187,12 +187,18 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx) 


void bpf_jit_emit_func_call_rel(u32 *image, struct codegen_context *ctx, u64 func)

{

	s32 rel = (s32)func - (s32)(image + ctx->idx);



	if (image && rel < 0x2000000 && rel >= -0x2000000) {

		PPC_BL_ABS(func);

	} else {

		/* Load function address into r0 */

		EMIT(PPC_RAW_LIS(__REG_R0, IMM_H(func)));

		EMIT(PPC_RAW_ORI(__REG_R0, __REG_R0, IMM_L(func)));

		EMIT(PPC_RAW_MTLR(__REG_R0));

		EMIT(PPC_RAW_BLRL());

	}

}



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

{