Commit 9670f6d2 authored by Naveen N Rao's avatar Naveen N Rao Committed by Michael Ellerman
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powerpc64/bpf: Fold bpf_jit_emit_func_call_hlp() into bpf_jit_emit_func_call_rel() 



Commit 61688a82 ("powerpc/bpf: enable kfunc call") enhanced
bpf_jit_emit_func_call_hlp() to handle calls out to module region, where
bpf progs are generated. The only difference now between
bpf_jit_emit_func_call_hlp() and bpf_jit_emit_func_call_rel() is in
handling of the initial pass where target function address is not known.
Fold that logic into bpf_jit_emit_func_call_hlp() and rename it to
bpf_jit_emit_func_call_rel() to simplify bpf function call JIT code.

We don't actually need to load/restore TOC across a call out to a
different kernel helper or to a different bpf program since they all
work with the kernel TOC. We only need to do it if we have to call out
to a module function. So, guard TOC load/restore with appropriate
conditions.

Signed-off-by: default avatarNaveen N Rao <naveen@kernel.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241030070850.1361304-10-hbathini@linux.ibm.com
parent ed614465

arch/powerpc/net/bpf_jit_comp64.c

+17 −44
Original line number Diff line number Diff line
@@ -202,14 +202,22 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx) 
	EMIT(PPC_RAW_BLR());

}



static int

bpf_jit_emit_func_call_hlp(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func)

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

{

	unsigned long func_addr = func ? ppc_function_entry((void *)func) : 0;

	long reladdr;



	if (WARN_ON_ONCE(!kernel_text_address(func_addr)))

		return -EINVAL;

	/* bpf to bpf call, func is not known in the initial pass. Emit 5 nops as a placeholder */

	if (!func) {

		for (int i = 0; i < 5; i++)

			EMIT(PPC_RAW_NOP());

		/* elfv1 needs an additional instruction to load addr from descriptor */

		if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1))

			EMIT(PPC_RAW_NOP());

		EMIT(PPC_RAW_MTCTR(_R12));

		EMIT(PPC_RAW_BCTRL());

		return 0;

	}



#ifdef CONFIG_PPC_KERNEL_PCREL

	reladdr = func_addr - local_paca->kernelbase;
@@ -266,6 +274,7 @@ bpf_jit_emit_func_call_hlp(u32 *image, u32 *fimage, struct codegen_context *ctx, 
			 * We can clobber r2 since we get called through a

			 * function pointer (so caller will save/restore r2).

			 */

			if (is_module_text_address(func_addr))

				EMIT(PPC_RAW_LD(_R2, bpf_to_ppc(TMP_REG_2), 8));

		} else {

			PPC_LI64(_R12, func);
@@ -276,6 +285,7 @@ bpf_jit_emit_func_call_hlp(u32 *image, u32 *fimage, struct codegen_context *ctx, 
		 * Load r2 with kernel TOC as kernel TOC is used if function address falls

		 * within core kernel text.

		 */

		if (is_module_text_address(func_addr))

			EMIT(PPC_RAW_LD(_R2, _R13, offsetof(struct paca_struct, kernel_toc)));

	}

#endif
@@ -283,39 +293,6 @@ bpf_jit_emit_func_call_hlp(u32 *image, u32 *fimage, struct codegen_context *ctx, 
	return 0;

}



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

{

	unsigned int i, ctx_idx = ctx->idx;



	if (WARN_ON_ONCE(func && is_module_text_address(func)))

		return -EINVAL;



	/* skip past descriptor if elf v1 */

	func += FUNCTION_DESCR_SIZE;



	/* Load function address into r12 */

	PPC_LI64(_R12, func);



	/* For bpf-to-bpf function calls, the callee's address is unknown

	 * until the last extra pass. As seen above, we use PPC_LI64() to

	 * load the callee's address, but this may optimize the number of

	 * instructions required based on the nature of the address.

	 *

	 * Since we don't want the number of instructions emitted to increase,

	 * we pad the optimized PPC_LI64() call with NOPs to guarantee that

	 * we always have a five-instruction sequence, which is the maximum

	 * that PPC_LI64() can emit.

	 */

	if (!image)

		for (i = ctx->idx - ctx_idx; i < 5; i++)

			EMIT(PPC_RAW_NOP());



	EMIT(PPC_RAW_MTCTR(_R12));

	EMIT(PPC_RAW_BCTRL());



	return 0;

}



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

{

	/*
@@ -1102,11 +1079,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code 
			if (ret < 0)

				return ret;



			if (func_addr_fixed)

				ret = bpf_jit_emit_func_call_hlp(image, fimage, ctx, func_addr);

			else

			ret = bpf_jit_emit_func_call_rel(image, fimage, ctx, func_addr);



			if (ret)

				return ret;