[PATCH bpf-next v1 08/18] bpf: Express ARG_CONST_SIZE_OR_ZERO as ARG_CONST_SIZE | SCALAR_MAYBE_ZERO

[Amery Hung <ameryhung@gmail.com>]

Add SCALAR_MAYBE_ZERO as an alias of PTR_MAYBE_NULL for scalar size
arguments, and define ARG_CONST_SIZE_OR_ZERO as ARG_CONST_SIZE |
SCALAR_MAYBE_ZERO instead of a distinct base type. This lets
check_func_arg() handle both with a single ARG_CONST_SIZE case, and the
redundant compatible_reg_types[] entry is dropped.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
---
 include/linux/bpf.h   |  4 +++-
 kernel/bpf/verifier.c | 12 ++----------
 2 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index d9542127dfdf..a7b3bb56c70b 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -748,6 +748,7 @@ extern const struct bpf_map_ops bpf_map_offload_ops;
 enum bpf_type_flag {
 	/* PTR may be NULL. */
 	PTR_MAYBE_NULL		= BIT(0 + BPF_BASE_TYPE_BITS),
+	SCALAR_MAYBE_ZERO	= PTR_MAYBE_NULL,
 
 	/* MEM is read-only. When applied on bpf_arg, it indicates the arg is
 	 * compatible with both mutable and immutable memory.
@@ -889,7 +890,6 @@ enum bpf_arg_type {
 	ARG_PTR_TO_ARENA,
 
 	ARG_CONST_SIZE,		/* number of bytes accessed from memory */
-	ARG_CONST_SIZE_OR_ZERO,	/* number of bytes accessed from memory or 0 */
 
 	ARG_PTR_TO_CTX,		/* pointer to context */
 	ARG_ANYTHING,		/* any (initialized) argument is ok */
@@ -922,6 +922,8 @@ enum bpf_arg_type {
 	ARG_PTR_TO_UNINIT_MEM		= MEM_UNINIT | MEM_WRITE | ARG_PTR_TO_MEM,
 	/* Pointer to valid memory of size known at compile time. */
 	ARG_PTR_TO_FIXED_SIZE_MEM	= MEM_FIXED_SIZE | ARG_PTR_TO_MEM,
+	/* Number of bytes accessed from memory, or 0. */
+	ARG_CONST_SIZE_OR_ZERO		= SCALAR_MAYBE_ZERO | ARG_CONST_SIZE,
 
 	/* This must be the last entry. Its purpose is to ensure the enum is
 	 * wide enough to hold the higher bits reserved for bpf_type_flag.
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index be5d93c0da81..5e09b95458ba 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7724,8 +7724,7 @@ static int process_iter_next_call(struct bpf_verifier_env *env, int insn_idx,
 
 static bool arg_type_is_mem_size(enum bpf_arg_type type)
 {
-	return type == ARG_CONST_SIZE ||
-	       type == ARG_CONST_SIZE_OR_ZERO;
+	return base_type(type) == ARG_CONST_SIZE;
 }
 
 static bool arg_type_is_raw_mem(enum bpf_arg_type type)
@@ -7872,7 +7871,6 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
 	[ARG_PTR_TO_MAP_KEY]		= &mem_types,
 	[ARG_PTR_TO_MAP_VALUE]		= &mem_types,
 	[ARG_CONST_SIZE]		= &scalar_types,
-	[ARG_CONST_SIZE_OR_ZERO]	= &scalar_types,
 	[ARG_CONST_ALLOC_SIZE_OR_ZERO]	= &scalar_types,
 	[ARG_CONST_MAP_PTR]		= &const_map_ptr_types,
 	[ARG_PTR_TO_CTX]		= &context_types,
@@ -8500,13 +8498,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		err = check_mem_size_reg(env, reg_state(env, regno - 1), reg,
 					 argno_from_reg(regno - 1), argno,
 					 fn->arg_type[arg - 1] & MEM_WRITE ? BPF_WRITE : BPF_READ,
-					 false, meta);
-		break;
-	case ARG_CONST_SIZE_OR_ZERO:
-		err = check_mem_size_reg(env, reg_state(env, regno - 1), reg,
-					 argno_from_reg(regno - 1), argno,
-					 fn->arg_type[arg - 1] & MEM_WRITE ? BPF_WRITE : BPF_READ,
-					 true, meta);
+					 arg_type & SCALAR_MAYBE_ZERO, meta);
 		break;
 	case ARG_PTR_TO_DYNPTR:
 		err = process_dynptr_func(env, reg, argno, insn_idx, arg_type, &meta->ref_obj,
-- 
2.52.0