diff options
Diffstat (limited to 'subx/012elf.cc')
| -rw-r--r-- | subx/012elf.cc | 28 |
1 files changed, 19 insertions, 9 deletions
diff --git a/subx/012elf.cc b/subx/012elf.cc index 0f058504..d0a3fbd2 100644 --- a/subx/012elf.cc +++ b/subx/012elf.cc @@ -66,6 +66,7 @@ void load_elf_contents(uint8_t* elf_contents, size_t size, int argc, char* argv[ assert(overlap.find(STACK_SEGMENT) == overlap.end()); Mem.push_back(vma(STACK_SEGMENT)); assert(overlap.find(AFTER_STACK) == overlap.end()); + // The stack grows downward. Reg[ESP].u = AFTER_STACK; Reg[EBP].u = 0; EIP = e_entry; @@ -129,15 +130,24 @@ void load_segment_from_program_header(uint8_t* elf_contents, int segment_index, } :(before "End Includes") -// Very primitive/fixed/insecure ELF segments for now: just consecutive VMAs. -// code: 0x09000000 -> 0x09ffffff -// data/heap: 0x0a000000 -> 0x0affffff -// stack: 0x0b000ffc -> 0x0b000000 (downward) -const int CODE_SEGMENT = 0x09000000; -const int DATA_SEGMENT = 0x0a000000; // keep sync'd with `Heap.limit` in allocate.subx -const int STACK_SEGMENT = 0x0b000000; -const int AFTER_STACK = 0x0c000000; -const int ARGV_DATA_SEGMENT = 0x0c000000; +// Very primitive/fixed/insecure ELF segments for now. +// code: 0x09000000 -> 0x09ffffff (specified in ELF binary) +// data: 0x0a000000 -> 0x0affffff (specified in ELF binary) +// --- heap gets mmap'd somewhere here --- +// stack: 0x7dffffff -> 0x7d000000 (downward; not in ELF binary) +// argv hack: 0x7f000000 -> 0x7fffffff (not in ELF binary) +// +// For now we avoid addresses with the most significant bit set; SubX doesn't +// support unsigned comparison yet (https://github.com/akkartik/mu/issues/30) +// Once we do, we can go up to 0xc0000000; higher addresses are reserved for +// the Linux kernel. +const int CODE_SEGMENT = 0x09000000; +const int DATA_SEGMENT = 0x0a000000; +const int STACK_SEGMENT = 0x7d000000; +const int AFTER_STACK = 0x7e000000; +const int ARGV_DATA_SEGMENT = 0x7f000000; +// When updating the above memory map, don't forget to update `mmap`'s +// implementation in the 'syscalls' layer. :(before "End Dump Info for Instruction") //? dump_stack(); // slow :(code) |