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| author | Kartik K. Agaram <vc@akkartik.com> | 2021-04-28 22:22:55 -0700 |
|---|---|---|
| committer | Kartik K. Agaram <vc@akkartik.com> | 2021-04-28 22:22:55 -0700 |
| commit | 4541bfa59b37cd226187667951eebed0c5359c83 (patch) | |
| tree | 0e6f5cd801aa32ffe64ac126174ea34b4c9376d7 /mu-init.subx | |
| parent | dcb6a21a911d61c51d1f54c357b5c6fcb01dd7cc (diff) | |
| download | mu-4541bfa59b37cd226187667951eebed0c5359c83.tar.gz | |
extremely threadbare null-pointer protection
This protects us from reading null arrays, but not null structs. It also doesn't protect us from writes to address 0 itself. It is also incredibly unsafe. According to https://wiki.osdev.org/Memory_Map_(x86), address 0 contains the real-mode IVT. Am I sure it'll never ever get used after I switch to protected mode? I really need a page table, something minimal to protect the first 4KB of physical memory or something. I wonder what other languages/OSs do to protect against really large struct definitions.
Diffstat (limited to 'mu-init.subx')
| -rw-r--r-- | mu-init.subx | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/mu-init.subx b/mu-init.subx index b60249ba..5e7ae9bb 100644 --- a/mu-init.subx +++ b/mu-init.subx @@ -12,6 +12,12 @@ Entry: # initialize stack bd/copy-to-ebp 0/imm32 + # Clear memory location 0 to ensure that uninitialized arrays run afoul of + # the bounds checker. + # TODO: This is utterly bonkers, and does not actually protect us against + # all null pointer reads/writes. Create a real page table sometime. + b8/copy-to-eax 0/imm32 + c7 0/subop/copy *eax 0/imm32 #? (main 0 0 Primary-bus-secondary-drive) # always first run tests (run-tests) |