diff mbox series

[bpf,v3,1/3] bpf: add some comments to stack representation

Message ID 20231202230558.1648708-2-andreimatei1@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: fix accesses to uninit stack slots | expand

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netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf
netdev/ynl success SINGLE THREAD; Generated files up to date; no warnings/errors;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1178 this patch: 1178
netdev/cc_maintainers fail 11 maintainers not CCed: haoluo@google.com jolsa@kernel.org kpsingh@kernel.org martin.lau@linux.dev john.fastabend@gmail.com song@kernel.org daniel@iogearbox.net ast@kernel.org andrii@kernel.org sdf@google.com yonghong.song@linux.dev
netdev/build_clang success Errors and warnings before: 1143 this patch: 1143
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
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netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Andrei Matei Dec. 2, 2023, 11:05 p.m. UTC 
Signed-off-by: Andrei Matei <andreimatei1@gmail.com>
---
 include/linux/bpf_verifier.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

Comments

Andrii Nakryiko Dec. 4, 2023, 6:18 p.m. UTC | #1 
On Sat, Dec 2, 2023 at 3:06 PM Andrei Matei <andreimatei1@gmail.com> wrote:
>

Please add some commit message here, even if a single sentence one.



> Signed-off-by: Andrei Matei <andreimatei1@gmail.com>
> ---
>  include/linux/bpf_verifier.h | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index aa4d19d0bc94..ec3612c2b057 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -316,7 +316,17 @@ struct bpf_func_state {
>         /* The following fields should be last. See copy_func_state() */
>         int acquired_refs;
>         struct bpf_reference_state *refs;
> +       /* Size of the current stack, in bytes. The stack state is tracked below, in
> +        * `stack`. allocated_stack is always a multiple of BPF_REG_SIZE.
> +        */
>         int allocated_stack;
> +       /* The state of the stack. Each element of the array describes BPF_REG_SIZE
> +        * (i.e. 8) bytes worth of stack memory.
> +        * stack[0] represents bytes [*(r10-8)..*(r10-1)]
> +        * stack[1] represents bytes [*(r10-16)..*(r10-9)]
> +        * ...
> +        * stack[allocated_stack/8 - 1] represents [*(r10-allocated_size)..*(r10-allocated_size+7)]
> +        */
>         struct bpf_stack_state *stack;
>  };
>
> @@ -630,6 +640,10 @@ struct bpf_verifier_env {
>         int exception_callback_subprog;
>         bool explore_alu_limits;
>         bool allow_ptr_leaks;
> +       /* Allow access to uninitialized stack memory. Writes with fixed offset are
> +        * always allowed, so this refers to reads (with fixed or variable offset),
> +        * to writes with variable offset and to indirect (helper) accesses.
> +        */
>         bool allow_uninit_stack;
>         bool bpf_capable;
>         bool bypass_spec_v1;
> --
> 2.40.1
>
Eduard Zingerman Dec. 4, 2023, 6:25 p.m. UTC | #2 
On Sat, 2023-12-02 at 18:05 -0500, Andrei Matei wrote:
> Signed-off-by: Andrei Matei <andreimatei1@gmail.com>
> ---

[...]

>  	int allocated_stack;
> +	/* The state of the stack. Each element of the array describes BPF_REG_SIZE
> +	 * (i.e. 8) bytes worth of stack memory.
> +	 * stack[0] represents bytes [*(r10-8)..*(r10-1)]
> +	 * stack[1] represents bytes [*(r10-16)..*(r10-9)]
> +	 * ...
> +	 * stack[allocated_stack/8 - 1] represents [*(r10-allocated_size)..*(r10-allocated_size+7)]
> +	 */

Nit: this uses variable 'allocated_size' that does not seem defined.
Otherwise a nice comment, thanks.
diff mbox series

Patch

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index aa4d19d0bc94..ec3612c2b057 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -316,7 +316,17 @@  struct bpf_func_state {
 	/* The following fields should be last. See copy_func_state() */
 	int acquired_refs;
 	struct bpf_reference_state *refs;
+	/* Size of the current stack, in bytes. The stack state is tracked below, in
+	 * `stack`. allocated_stack is always a multiple of BPF_REG_SIZE.
+	 */
 	int allocated_stack;
+	/* The state of the stack. Each element of the array describes BPF_REG_SIZE
+	 * (i.e. 8) bytes worth of stack memory.
+	 * stack[0] represents bytes [*(r10-8)..*(r10-1)]
+	 * stack[1] represents bytes [*(r10-16)..*(r10-9)]
+	 * ...
+	 * stack[allocated_stack/8 - 1] represents [*(r10-allocated_size)..*(r10-allocated_size+7)]
+	 */
 	struct bpf_stack_state *stack;
 };
 
@@ -630,6 +640,10 @@  struct bpf_verifier_env {
 	int exception_callback_subprog;
 	bool explore_alu_limits;
 	bool allow_ptr_leaks;
+	/* Allow access to uninitialized stack memory. Writes with fixed offset are
+	 * always allowed, so this refers to reads (with fixed or variable offset),
+	 * to writes with variable offset and to indirect (helper) accesses.
+	 */
 	bool allow_uninit_stack;
 	bool bpf_capable;
 	bool bypass_spec_v1;