bpf: Comment on check_mem_size_reg

andreimatei · anakryiko · commit 745e03113065 · 2023-12-12T15:35:32.000-08:00
This patch adds a comment to check_mem_size_reg -- a function whose meaning is not very transparent. The function implicitly deals with two registers connected by convention, which is not obvious. Signed-off-by: Andrei Matei <andreimatei1@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20231210225149.67639-1-andreimatei1@gmail.com
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
@@ -7256,6 +7256,12 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
 	}
 }
 
+/* verify arguments to helpers or kfuncs consisting of a pointer and an access
+ * size.
+ *
+ * @regno is the register containing the access size. regno-1 is the register
+ * containing the pointer.
+ */
 static int check_mem_size_reg(struct bpf_verifier_env *env,
 			      struct bpf_reg_state *reg, u32 regno,
 			      bool zero_size_allowed,

Original file line number	Diff line number	Diff line change
`@@ -7256,6 +7256,12 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,`
`7256`	`7256`	`}`
`7257`	`7257`	`}`
`7258`	`7258`
	`7259`	`+/* verify arguments to helpers or kfuncs consisting of a pointer and an access`
	`7260`	`+ * size.`
	`7261`	`+ *`
	`7262`	`+ * @regno is the register containing the access size. regno-1 is the register`
	`7263`	`+ * containing the pointer.`
	`7264`	`+ */`
`7259`	`7265`	`static int check_mem_size_reg(struct bpf_verifier_env *env,`
`7260`	`7266`	`struct bpf_reg_state *reg, u32 regno,`
`7261`	`7267`	`bool zero_size_allowed,`