feat(exceptions): implement basic exception handlers (Phase 1.2.4)#63
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feat(exceptions): implement basic exception handlers (Phase 1.2.4)#63
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Upgrade Phase-1 exception stubs from minimal vector-name stubs to full diagnostic handlers that report all available fault context over serial. Assembly changes (boot/src/main.rs global_asm!): - Add isr_stub_ec macro for vectors that receive a CPU-pushed error code. Pops the error code into RSI before capturing RSP → ExceptionFrame. - isr_stub updated: RSI=0, RDX=RSP (→ ExceptionFrame). - __exception_common now calls exception_handler(vector, error_code, frame). - Vectors 8,10-14,17,21,29,30 switched to isr_stub_ec per Intel SDM §6.13. exception_handler() (was exception_halt): - arg1 RDI: vector number - arg2 RSI: error code (0 for non-error-code vectors) - arg3 RDX: pointer to ExceptionFrame [RIP, CS, RFLAGS, old_RSP, SS] - Prints: vector name, error code (for applicable vectors), faulting RIP, RFLAGS, old RSP, and CR2 (faulting virtual address) for #PF (vector 14). Adds ExceptionFrame struct documenting the 5-quadword CPU-pushed layout. Closes #9. QEMU boot verification passes.
tests/boot_tests.rs — 35 tests covering: - GDT: bit-pattern correctness for null/code/data descriptors (P, DPL, S, L, D/B, G, executable, writable bits per Intel SDM Vol 3A §3.4.5) - GDT: selector alignment (index × 8, TI=0, RPL=0) - IDT: 64-bit gate attribute bytes (0x8E interrupt, 0x8F trap) - IDT: handler address splitting into offset_low/mid/high fields; round-trip reconstruction; edge cases (0, u64::MAX) - IDT: 256 entries × 16 bytes = 4096 bytes - Exception vectors: which 10 push CPU error codes (Intel SDM Vol 3A §6.13); no-error-code vectors; hardware IRQs (32-255) never push one - ExceptionFrame: 5 quadwords, sequential 8-byte field offsets - Stack constants: 64 KiB total, 4 KiB guard, 60 KiB usable, 16 KiB bootstrap — all page-aligned lib/boot-info/src/lib.rs — 22 tests covering: - BOOT_INFO_MAGIC and BOOT_INFO_VERSION constant stability (ABI contract) - KernelBootInfo::is_valid(): passes for new(), fails for corrupt magic/version - Default field values: acpi_rsdp=0, has_framebuffer=false, empty map - Bootloader name null-termination - KernelMemoryDescriptor::size_bytes() arithmetic - KernelMemoryDescriptor::is_usable() for all usable and reserved types - KernelMemoryMap::entries() slice length matches count field - KernelFramebuffer::zeroed() pixel format and field values - Pixel format constants are distinct - Struct sizes: KernelMemoryDescriptor=32B, KernelFramebuffer=32B
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Summary
Implements Phase 1.2.4: Basic Exception Handlers, closing issue #9.
Upgrades the Phase-1 exception stubs from one-liner vector-name printers to full diagnostic handlers that surface all CPU-provided fault context over serial.
Assembly stub redesign
Two
global_asm!macro variants replace the previous singleisr_stub:isr_stub v[RIP, CS, RFLAGS, old_RSP, SS]isr_stub_ec v[error_code, RIP, CS, RFLAGS, old_RSP, SS]Both stubs pass three arguments to
__exception_common:pop rsi)ExceptionFrame(RSP after error code is consumed)exception_handler() output
For any CPU exception, the handler now prints:
ExceptionFrame struct
Documents the 5-quadword layout the CPU always pushes in 64-bit mode:
[RIP, CS, RFLAGS, old_RSP, SS]Test plan
cargo build— clean, no errorscargo fmt— no formatting changesbash scripts/verify-boot.sh—[PASS] Boot verification PASSED[OK] IDT loaded (32 exception handlers with error codes + RIP + CR2, interrupts disabled)Serial output (QEMU)
Closes #9