Implementation of out-of-line static calls for PowerPC 64-bit ELF V2 ABI. Static calls patch an indirect branch into a direct branch at runtime. Out-of-line specifically has a caller directly call a trampoline, and the trampoline gets patched to directly call the target.
Previous versions here: V2: https://lore.kernel.org/all/20220926064316.765967-1-bg...@linux.ibm.com/ V1: https://lore.kernel.org/all/20220916062330.430468-1-bg...@linux.ibm.com/ Changed for V3: [general] * Rebased on top of https://lore.kernel.org/all/0df84a2eea551c1d000c34c36d0c1d23cbe26a97.1664289176.git.christophe.le...@csgroup.eu/ for removing the separate CONFIG_STRICT_KERNEL_RWX cases. Can rebase back onto next if necessary. * Some some minor refactoring/style fixes throughout [1/6] * Code patching rewritten again * This time it only adds support for what is needed: * int or long sized writes only * assumed within a cacheline (static call pointers are aligned for atomic updates, instructions are aligned anyway) * unconditional instruction syncing because non-instruction patching is not used in any performance sensitive paths * similarly, dword case is marked unlikely. ftrace activation is biggest performance concern, and it only uses non-prefixed instructions. * Should be zero difference on 32-bit, minor differences on 64-bit * Design doesn't need to be revisited unless specifically 1 or 2 byte patching is needed. Most such patches can be emulated by read-update-store of 4 bytes. Non-cacheline safe patches can be split similarly (they can't have atomicity requirements if they aren't aligned). [3/6] * Refactored to use patch_branch (thx Christophe) [5/6] * Required .localentry NAME, 1 directive guarded by toolchain version check * Removed #ifdef's from static call implementation. Added sign_extend_long to support this. * Fixed a bug in ppc_function_toc handling of lis case & made it more verbose to make such errors stand out more. New layout splits into calculating required values, and then applying them in two steps. [6/6] * Replaced SAVE_REGS/RESTORE_REGS macros with functions * Reduced global register usage of tests * Support running on 32-bit as well Benjamin Gray (6): powerpc/code-patching: Implement generic text patching function powerpc/module: Handle caller-saved TOC in module linker powerpc/module: Optimise nearby branches in ELF V2 ABI stub static_call: Move static call selftest to static_call_selftest.c powerpc/64: Add support for out-of-line static calls powerpc: Add tests for out-of-line static calls arch/powerpc/Kconfig | 26 ++- arch/powerpc/include/asm/code-patching.h | 30 +++ arch/powerpc/include/asm/static_call.h | 80 ++++++- arch/powerpc/kernel/Makefile | 4 +- arch/powerpc/kernel/module_64.c | 26 ++- arch/powerpc/kernel/static_call.c | 183 +++++++++++++++- arch/powerpc/kernel/static_call_test.c | 263 +++++++++++++++++++++++ arch/powerpc/kernel/static_call_test.h | 56 +++++ arch/powerpc/lib/code-patching.c | 73 +++++-- kernel/Makefile | 1 + kernel/static_call_inline.c | 43 ---- kernel/static_call_selftest.c | 41 ++++ 12 files changed, 753 insertions(+), 73 deletions(-) create mode 100644 arch/powerpc/kernel/static_call_test.c create mode 100644 arch/powerpc/kernel/static_call_test.h create mode 100644 kernel/static_call_selftest.c base-commit: 9a5e80596e50f1ab19fecb2d337e7ea3287ee083 -- 2.37.3