Matthieu Longo <matthieu.lo...@arm.com> writes: > This patch series is only a refactoring of the existing implementation of > PAuth and returned-address signing. The existing behavior is preserved.
The series LGTM, thanks. OK for trunk if there are no objections before Monday. Richard > > 1. aarch64: store signing key and signing method in DWARF _Unwind_FrameState > > _Unwind_FrameState already contains several CIE and FDE information (see the > attributes below the comment "The information we care about from the CIE/FDE" > in libgcc/unwind-dw2.h). > The patch aims at moving the information from DWARF CIE (signing key stored > in the augmentation string) and FDE (the used signing method) into > _Unwind_FrameState along the already-stored CIE and FDE information. > Note: those information have to be saved in frame_state_reg_info instead of > _Unwind_FrameState as they need to be savable by DW_CFA_remember_state and > restorable by DW_CFA_restore_state, that both rely on the attribute "prev". > Those new information in _Unwind_FrameState simplifies the look-up of the > signing key when the return address is demangled. It also allows future > signing methods to be easily added. > _Unwind_FrameState is not a part of the public API of libunwind, so the > change is backward compatible. > > A new architecture-specific handler MD_ARCH_EXTENSION_FRAME_INIT allows to > reset values in the frame state and unwind context if needed by the > architecture extension before changing the frame state to the caller context. > A new architecture-specific handler MD_ARCH_EXTENSION_CIE_AUG_HANDLER > isolates the architecture-specific augmentation strings in AArch64 backend, > and allows others architectures to reuse augmentation strings that would have > clashed with AArch64 DWARF extensions. > aarch64_demangle_return_addr, DW_CFA_AARCH64_negate_ra_state and > DW_CFA_val_expression cases in libgcc/unwind-dw2-execute_cfa.h were > documented to clarify where the value of the RA state register is stored (FS > and CONTEXT respectively). > > 2. aarch64: skip copy of RA state register into target context > > The RA state register is local to a frame, so it should not be copied to the > target frame during the context installation. > This patch adds a new backend handler that check whether a register needs to > be skipped or not before its installation. > > 3. libgcc: hide CIE and FDE data for DWARF architecture extensions behind a > handler. > > This patch provides a new handler MD_ARCH_FRAME_STATE_T to hide an > architecture-specific structure containing CIE and FDE data related to DWARF > architecture extensions. > Hiding the architecture-specific attributes behind a handler has the > following benefits: > 1. isolating those data from the generic ones in _Unwind_FrameState > 2. avoiding casts to custom types. > 3. preserving typing information when debugging with GDB, and so > facilitating their printing. > > This approach required to add a new header md-unwind-def.h included at the > top of libgcc/unwind-dw2.h, and redirecting to the corresponding architecture > header via a symbolic link. > An obvious drawback is the increase in complexity with macros, and headers. > It also caused a split of architecture definitions between md-unwind-def.h > (types definitions used in unwind-dw2.h) and md-unwind.h (local types > definitions and handlers implementations). > The naming of md-unwind.h with .h extension is a bit misleading as the file > is only included in the middle of unwind-dw2.c. Changing this naming would > require modification of others backends, which I prefered to abstain from. > Overall the benefits are worth the added complexity from my perspective. > > 4. libgcc: update configure (regenerated by autoreconf) > > Regenerate the build files. > Note: This patch should be squashed with the previous one before merging. > > ### Diff between revisions 1 & 2 > > 1: code style formatting + remove resetting of the local frame register in > the context as recommended by Richard Sandiford. > 2: add a new handler as recommended by Richard Sandiford to skip the local > frame registers before installation in the target context. > 3: code style formatting. > 4: no change. > > ## Testing > > Those changes were testing by covering the 3 following cases: > - backtracing. > - exception handling in a C++ program. > - gcc/testsuite/gcc.target/aarch64/pr104689.c: pac-ret with unusual DWARF [1] > > Regression tested on aarch64-unknown-linux-gnu, and no regression found. > > [1]: https://gcc.gnu.org/pipermail/gcc-patches/2022-May/594414.html > > Ok for master? I don't have commit access so I need someone to commit on my > behalf. > > Regards, > Matthieu. > > Matthieu Longo (4): > aarch64: store signing key and signing method in DWARF > _Unwind_FrameState > aarch64: skip copy of RA state register into target context > libgcc: hide CIE and FDE data for DWARF architecture extensions behind > a handler. > libgcc: update configure (regenerated by autoreconf) > > libgcc/Makefile.in | 6 +- > libgcc/config.host | 13 +- > libgcc/config/aarch64/aarch64-unwind-def.h | 41 ++++++ > libgcc/config/aarch64/aarch64-unwind.h | 152 +++++++++++++++++---- > libgcc/config/no-unwind.h | 3 +- > libgcc/configure | 2 + > libgcc/configure.ac | 1 + > libgcc/unwind-dw2-execute_cfa.h | 26 ++-- > libgcc/unwind-dw2.c | 24 +++- > libgcc/unwind-dw2.h | 19 ++- > 10 files changed, 235 insertions(+), 52 deletions(-) > create mode 100644 libgcc/config/aarch64/aarch64-unwind-def.h
