Fix snapshot load on macOS arm64 (W^X + relocation decode + exec-link quoting)#1788
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Fix snapshot load on macOS arm64 (W^X + relocation decode + exec-link quoting)#1788dg1sbg wants to merge 3 commits into
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On Apple Silicon, snapshot_load fixes up the loaded code's data in place in MAP_JIT (W^X) memory; the bare stores fault with SIGBUS (KERN_PROTECTION_FAILURE). Wrap the three load-side write sites in JITDataReadWriteMaybeExecute() / JITDataReadExecute() (same pattern as the other JIT-literal write sites): - the code-literals memcpy, - the fixup_objects walk (walk_temporary_root_objects<fixup_objects_t>), - the fixup_internals walk. (The save path fixes up a RW copy of the buffer, so it never hit this.) This unblocks snapshot load past the W^X SIGBUS. The remaining failure -- the position-independent function-pointer relocation decode (decodeEntryPoint / fixedAddress) -- is separate, pre-existing sc598 relocation work. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
…ath quoting Make snapshot save/load/executable work on macOS arm64 (SLAD-SNAPSHOT and SLAD-EXECUTABLE now pass): 1. Relocation decode: the entry-point decode validated the resolved address by comparing its first byte against a saved firstByte and ABORTED on mismatch (decodeEntryPointForCompiledCode) / warned (fixedAddress). But a function's first instruction is frequently a relocatable instruction (e.g. ADRP) whose encoded immediate bytes legitimately differ between the save-time and load-time JIT (different load addresses => different page offsets). The offset/symbol-based decode is correct (verified: snapshot loads and returns the right value); drop the firstByte equality check, which was a false positive on every relocated first insn. 2. Executable link: save-lisp-and-die :executable builds a clang++ command run via system() (a shell); the -Wl,-force_load,<libdir>/libiclasp.a path was unquoted, so a build dir containing a space (e.g. a Dropbox path) split the arg and the link failed. Quote the output, sectcreate, and force_load paths. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
…e -L
The executable link command (run via system()) carried only the RELATIVE
-Lboehmprecise/lib from BUILD_LINKFLAGS, so -lclasp resolved only when
save-lisp-and-die :executable ran with CWD=build/; from any other directory the
link failed ("library not found for -lclasp"). Add an absolute, quoted
-L"<_LibDir>" (as the Linux branch already does). The runtime rpath is already
absolute, so the produced executable both links and runs from any CWD.
Verified: created and ran a standalone executable from /tmp (returns the right
value); SLAD-EXECUTABLE now passes from the repo root, not just build/.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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1, the snapshot load change, appears to be duplicating the similar change in #1768. |
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Makes snapshot load work on macOS arm64. With #1787 (which fixes the save unwinding),
SLAD-SNAPSHOTandSLAD-EXECUTABLEboth pass; full regression suite 1957/11 (the 11 are pre-existing, orthogonal).Three independent fixes, all in
snapshotSaveLoad.cc:1. W^X faults during in-place fixup (commit 1)
snapshot_loadfixes up the loaded code in place in MAP_JIT (rwx, W^X) memory; on Apple Silicon a bare store into execute-mode JIT memory faults withSIGBUS/KERN_PROTECTION_FAILURE. Three sites now switch to write mode viaJITDataReadWriteMaybeExecute()/JITDataReadExecute()(same pattern as the existing JIT-literal write sites): the code-literalsmemcpy, and thefixup_objects/fixup_internalswalks. (The save path fixes up a RW copy, so it never hit this.)2. Relocation-decode false positive (commit 2)
The entry-point decode validated the resolved address by comparing its first byte against a saved
firstByte, and aborted on mismatch (decodeEntryPointForCompiledCode) / warned (fixedAddress). But a function's first instruction is frequently a relocatable instruction (e.g. ADRP), whose encoded page-offset immediate legitimately differs between the save-time and load-time JIT (different load addresses). The offset/symbol-based decode is correct — verified: with the check made non-fatal the snapshot loads, runs, and returns the right value — so thefirstByteequality check is a false positive on every relocated first instruction. Dropped at both sites.3. Executable-link path quoting (commit 2)
save-lisp-and-die :executablebuilds aclang++command run viasystem()(a shell). The-Wl,-force_load,<libdir>/libiclasp.apath was unquoted, so a build/lib dir containing a space (e.g. a Dropbox path) split the arg and the link failed (no such file). The output,-sectcreatefile, and-force_loadpaths are now quoted.Verification (macOS arm64, native boehmprecise image)
SLAD-SNAPSHOTandSLAD-EXECUTABLEpass; full suite run frombuild/= 1957 passed / 11 failed (the 11 known pre-existing). No regressions.🤖 Generated with Claude Code