[PATCH v12 0/2] rust: Add safe pointer formatting support

[Ke Sun <sunke@kylinos.cn>]

This series fixes two issues with {:p} pointer formatting:
- The impl_fmt_adapter_forward! macro destructures self into a local
  variable, causing {:p} to print a stack address instead of the actual
  pointer
- Kernel address leak — {:p} prints raw pointer values, exposing kernel
  address space layout

---
Changes in v12:
- Split into 2 patches: fix {:p} printing stack addresses → route {:p}
  through HashedPtr
- Test cleanup: NoHashPointersGuard RAII guard replaces raw
  save/restore; mod expected consolidates 32/64-bit constants
- Impl delegation: &T, &mut T, *mut T all forward to *const T (matching
  core library conventions), replacing v11's blanket impl + macro
- Link to v11: https://lore.kernel.org/r/20260205-hashedptr-v11-1-bd0fec7fe6f1@kylinos.cn

Changes in v11:
- Fix inaccurate or inappropriate descriptions in comments
- Use as_char_ptr instead of as_ptr so that a *const u8 pointer is
  always passed to scnprintf on all architectures
- Per Tamir's suggestion, replace doctests with mod tests and adjust
  test content to make the tests more meaningful
- Remove the RawPtr wrapper type: it and HashedPtr use different
  formatting mechanisms (HashedPtr uses scnprintf and pad; RawPtr would
  call core's Pointer impl directly). This series focuses on fixing the
  issue that without it {:p} would output the pointer's stack address,
  and on using HashedPtr to safely format raw pointers and avoid leaking
  kernel address space layout information
- Link to v10: https://lore.kernel.org/r/20260121050059.2315091-1-sunke@kylinos.cn

Changes in v10:
- Merge all patches into a single patch
- Improve `kernel::fmt::Pointer` trait implementation
Link to v9: https://lore.kernel.org/r/20260119033006.1453006-1-sunke@kylinos.cn

Changes in v9: https://lore.kernel.org/r/20260119033006.1453006-1-sunke@kylinos.cn
- Refactor implementation to use Pointer trait and Adapter pattern
  instead of exporting ptr_to_hashval() from lib/vsprintf.c. Use
  scnprintf directly in Rust for pointer hashing, eliminating the
  need for C function export
- Move pointer wrapper types from rust/kernel/ptr.rs to
  rust/kernel/fmt.rs
- Split implementation into more granular patches: Pointer trait
  foundation, HashedPtr type, raw pointer default behavior, and
  RawPtr type
- Remove documentation patch, integrate examples into code doctests
- Simplify API and improve code organization following Display trait
  pattern
- Link to v8: https://lore.kernel.org/r/20260101081605.1300953-1-sunke@kylinos.cn

Changes in v8:
- Remove RestrictedPtr (%pK) support: only export ptr_to_hashval() with
  EXPORT_SYMBOL_NS_GPL using "RUST_INTERNAL" namespace, provide only two
  pointer wrapper types (HashedPtr, RawPtr) for %p and %px
- Change API from HashedPtr::from(ptr) to HashedPtr(ptr) for direct
  construction
- Link to v7: https://lore.kernel.org/r/20251229072157.3857053-1-sunke@kylinos.cn

Changes in v7:
- Refactor kptr_restrict handling: extract kptr_restrict_value() from
  restricted_pointer() in lib/vsprintf.c and export it for Rust use, and
  improve RestrictedPtr::fmt() implementation to directly handle
  kptr_restrict_value() return values (0, 1, 2, -1) for better code
  clarity
- Remove Debug derive from pointer wrapper types (HashedPtr,
  RestrictedPtr, RawPtr)
- Link to v6: https://lore.kernel.org/r/20251227033958.3713232-1-sunke@kylinos.cn

Changes in v6:
- Fix placeholder formatting to use `f.pad()` instead of `f.write_str()`
  in format_hashed_ptr(), ensuring width, alignment, and padding options
  are correctly applied to PTR_PLACEHOLDER
- Link to v5: https://lore.kernel.org/r/20251226140751.2215563-1-sunke@kylinos.cn

Changes in v5: https://lore.kernel.org/r/20251226140751.2215563-1-sunke@kylinos.cn
- Format use statements in rust/kernel/ptr.rs and rust/kernel/fmt.rs
  using kernel vertical style with alphabetical ordering
- Remove unnecessary SAFETY comment in rust/kernel/ptr.rs (addressed
  Clippy warning)
- Update type ordering to alphabetical (HashedPtr, RawPtr,
  RestrictedPtr) in fmt.rs macro invocation
- Link to v4: https://lore.kernel.org/r/20251225225709.3944255-1-sunke@kylinos.cn

Changes in v4:
- Use Pointer::fmt() instead of write!(f, "{:p}", ...) to preserve
  formatting options (width, alignment, padding characters)
- Improve code structure: reduce unsafe block scope, use early return
  pattern
- Add doctests with formatting option tests for all pointer wrapper
  types
- Enhance documentation with detailed formatting options section,
  including examples for width, alignment, and padding
- Fix RestrictedPtr example to use pr_info! instead of seq_print! in
  docs
- Link to v3: https://lore.kernel.org/r/20251224081315.729684-1-sunke@kylinos.cn

Changes in v3:
- Export ptr_to_hashval() from lib/vsprintf.c for Rust pointer hashing
- Add three pointer wrapper types (HashedPtr, RestrictedPtr, RawPtr) in
  rust/kernel/ptr.rs corresponding to %p, %pK, and %px
- Make raw pointers automatically use HashedPtr when formatted with {:p}
- Add documentation for pointer wrapper types
- Link to v2: https://lore.kernel.org/r/20251223033018.2814732-1-sunke@kylinos.cn

Changes in v2:
- Disabled {:p} raw pointer printing by default to prevent accidental
  information leaks
- Link to v1: https://lore.kernel.org/r/20251218032709.2184890-1-sunke@kylinos.cn

Signed-off-by: Ke Sun <sunke@kylinos.cn>

---
Ke Sun (2):
      rust: fmt: fix {:p} printing stack addresses
      rust: fmt: route {:p} through HashedPtr to prevent address leaks

 rust/kernel/fmt.rs | 178 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 176 insertions(+), 2 deletions(-)
---
base-commit: 50897c955902c93ae71c38698abb910525ebdc89
change-id: 20260512-hashedptr-22469b930113

Best regards,
-- 
Ke Sun <sunke@kylinos.cn>