Alan-Jowett / sonde / 25947942070

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github

Committed by web-flow

Commit Message

fix(bpf): tag pointers loaded from context via ContextPointerField (#929)

* fix(bpf): tag pointers loaded from context via ContextPointerField (#928)

The BPF interpreter treated all values loaded from context via LDX as
plain scalars, which meant C-compiled programs using the standard
`ctx->input_data` / `ctx->input_end` pattern failed with
`NonDereferenceableAccess` when dereferencing the loaded pointers.

Add `ContextPointerField` — a descriptor that tells the interpreter
which u64 fields within the context buffer hold pointers and what
memory region they refer to.  During `LD_DW_REG` from a context
(or writable-memory) region, the interpreter computes the effective
context offset and, if it matches a declared field, tags the loaded
value with the described region instead of returning a scalar.

The offset match uses `effective_address - ctx_base` so it works
regardless of whether the source register points at the context base
or has been adjusted via pointer arithmetic.

Update the decoder execution path (`decoder.rs`) to declare context
pointer fields for `input_data` (offset 0) and `input_end`
(offset 8), enabling C-compiled decoder programs to work correctly.

Closes #928

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* style: apply cargo fmt

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix: use Context tag for decoder data region, add ctx_ptrs doc

- Change decoder data_region from RegionTag::Memory to
  RegionTag::Context so writes through ctx->input_data are silently
  ignored, matching the read_only_ctx=true semantics.
- Add ctx_ptrs to the # Arguments doc section of execute_program.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* test: strengthen adjusted-base test to dereference loaded pointer

The test now loads input_end via the adjusted base register, then
dereferences `input_end - 1` to read the last blob byte.  This
proves the adjusted-base context pointer ... (continued)

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3 existing lines in 1 file now uncovered.

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