Commit 22f83974 authored by Eduard Zingerman's avatar Eduard Zingerman Committed by Alexei Starovoitov
Browse files

bpf: get_call_summary() utility function 



Refactor mark_fastcall_pattern_for_call() to extract a utility
function get_call_summary(). For a helper or kfunc call this function
fills the following information: {num_params, is_void, fastcall}.

This function would be used in the next patch in order to get number
of parameters of a helper or kfunc call.

Signed-off-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250304195024.2478889-3-eddyz87@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 80ca3f1d

kernel/bpf/verifier.c

+57 −64
Original line number Diff line number Diff line
@@ -17019,27 +17019,6 @@ static int visit_func_call_insn(int t, struct bpf_insn *insns, 
/* Bitmask with 1s for all caller saved registers */

#define ALL_CALLER_SAVED_REGS ((1u << CALLER_SAVED_REGS) - 1)









/* Return a bitmask specifying which caller saved registers are









 * clobbered by a call to a helper *as if* this helper follows









 * bpf_fastcall contract:









 * - includes R0 if function is non-void;









 * - includes R1-R5 if corresponding parameter has is described









 *   in the function prototype.









 */









static u32 helper_fastcall_clobber_mask(const struct bpf_func_proto *fn)









{









	u32 mask;









	int i;

















	mask = 0;









	if (fn->ret_type != RET_VOID)









		mask |= BIT(BPF_REG_0);









	for (i = 0; i < ARRAY_SIZE(fn->arg_type); ++i)









		if (fn->arg_type[i] != ARG_DONTCARE)









			mask |= BIT(BPF_REG_1 + i);









	return mask;









}

















/* True if do_misc_fixups() replaces calls to helper number 'imm',









 * replacement patch is presumed to follow bpf_fastcall contract









 * (see mark_fastcall_pattern_for_call() below).








@@ -17056,24 +17035,54 @@ static bool verifier_inlines_helper_call(struct bpf_verifier_env *env, s32 imm)







	}









}

















/* Same as helper_fastcall_clobber_mask() but for kfuncs, see comment above */









static u32 kfunc_fastcall_clobber_mask(struct bpf_kfunc_call_arg_meta *meta)









struct call_summary {









	u8 num_params;









	bool is_void;









	bool fastcall;









};

















/* If @call is a kfunc or helper call, fills @cs and returns true,









 * otherwise returns false.









 */









static bool get_call_summary(struct bpf_verifier_env *env, struct bpf_insn *call,









			     struct call_summary *cs)









{









	u32 vlen, i, mask;









	struct bpf_kfunc_call_arg_meta meta;









	const struct bpf_func_proto *fn;









	int i;

















	vlen = btf_type_vlen(meta->func_proto);









	mask = 0;









	if (!btf_type_is_void(btf_type_by_id(meta->btf, meta->func_proto->type)))









		mask |= BIT(BPF_REG_0);









	for (i = 0; i < vlen; ++i)









		mask |= BIT(BPF_REG_1 + i);









	return mask;









	if (bpf_helper_call(call)) {

















		if (get_helper_proto(env, call->imm, &fn) < 0)









			/* error would be reported later */









			return false;









		cs->fastcall = fn->allow_fastcall &&









			       (verifier_inlines_helper_call(env, call->imm) ||









				bpf_jit_inlines_helper_call(call->imm));









		cs->is_void = fn->ret_type == RET_VOID;









		cs->num_params = 0;









		for (i = 0; i < ARRAY_SIZE(fn->arg_type); ++i) {









			if (fn->arg_type[i] == ARG_DONTCARE)









				break;









			cs->num_params++;









		}









		return true;









	}

















/* Same as verifier_inlines_helper_call() but for kfuncs, see comment above */









static bool is_fastcall_kfunc_call(struct bpf_kfunc_call_arg_meta *meta)









{









	return meta->kfunc_flags & KF_FASTCALL;









	if (bpf_pseudo_kfunc_call(call)) {









		int err;

















		err = fetch_kfunc_meta(env, call, &meta, NULL);









		if (err < 0)









			/* error would be reported later */









			return false;









		cs->num_params = btf_type_vlen(meta.func_proto);









		cs->fastcall = meta.kfunc_flags & KF_FASTCALL;









		cs->is_void = btf_type_is_void(btf_type_by_id(meta.btf, meta.func_proto->type));









		return true;









	}

















	return false;









}

















/* LLVM define a bpf_fastcall function attribute.








@@ -17156,39 +17165,23 @@ static void mark_fastcall_pattern_for_call(struct bpf_verifier_env *env,







{









	struct bpf_insn *insns = env->prog->insnsi, *stx, *ldx;









	struct bpf_insn *call = &env->prog->insnsi[insn_idx];









	const struct bpf_func_proto *fn;









	u32 clobbered_regs_mask = ALL_CALLER_SAVED_REGS;









	u32 clobbered_regs_mask;









	struct call_summary cs;









	u32 expected_regs_mask;









	bool can_be_inlined = false;









	s16 off;









	int i;

















	if (bpf_helper_call(call)) {









		if (get_helper_proto(env, call->imm, &fn) < 0)









			/* error would be reported later */









			return;









		clobbered_regs_mask = helper_fastcall_clobber_mask(fn);









		can_be_inlined = fn->allow_fastcall &&









				 (verifier_inlines_helper_call(env, call->imm) ||









				  bpf_jit_inlines_helper_call(call->imm));









	}

















	if (bpf_pseudo_kfunc_call(call)) {









		struct bpf_kfunc_call_arg_meta meta;









		int err;

















		err = fetch_kfunc_meta(env, call, &meta, NULL);









		if (err < 0)









			/* error would be reported later */









			return;

















		clobbered_regs_mask = kfunc_fastcall_clobber_mask(&meta);









		can_be_inlined = is_fastcall_kfunc_call(&meta);









	}

















	if (clobbered_regs_mask == ALL_CALLER_SAVED_REGS)









	if (!get_call_summary(env, call, &cs))









		return;

















	/* A bitmask specifying which caller saved registers are clobbered









	 * by a call to a helper/kfunc *as if* this helper/kfunc follows









	 * bpf_fastcall contract:









	 * - includes R0 if function is non-void;









	 * - includes R1-R5 if corresponding parameter has is described









	 *   in the function prototype.









	 */









	clobbered_regs_mask = GENMASK(cs.num_params, cs.is_void ? 1 : 0);









	/* e.g. if helper call clobbers r{0,1}, expect r{2,3,4,5} in the pattern */









	expected_regs_mask = ~clobbered_regs_mask & ALL_CALLER_SAVED_REGS;
















@@ -17246,7 +17239,7 @@ static void mark_fastcall_pattern_for_call(struct bpf_verifier_env *env,







	 * don't set 'fastcall_spills_num' for call B so that remove_fastcall_spills_fills()









	 * does not remove spill/fill pair {4,6}.









	 */









	if (can_be_inlined)









	if (cs.fastcall)









		env->insn_aux_data[insn_idx].fastcall_spills_num = i - 1;









	else









		subprog->keep_fastcall_stack = 1;