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| author | Kartik Agaram <vc@akkartik.com> | 2018-07-07 23:38:59 -0700 |
|---|---|---|
| committer | Kartik Agaram <vc@akkartik.com> | 2018-07-07 23:38:59 -0700 |
| commit | b0f89e4f9b204fa28fc02f6335dbf654d7a4dcf1 (patch) | |
| tree | 1ea228d87a93e0bfda06792ec9015327f6cc0ed8 | |
| parent | c90fa6534ecbdf3e61f19ce2b7cabbc2957ef202 (diff) | |
| download | mu-b0f89e4f9b204fa28fc02f6335dbf654d7a4dcf1.tar.gz | |
4326 - new example: read() from stdin
Currently only runs in emulated mode. Likely a paging issue, writing data to code page. I'm not checking the return value.
| -rw-r--r-- | subx/019syscalls.cc | 5 | ||||
| -rwxr-xr-x | subx/ex4 | bin | 0 -> 113 bytes | |||
| -rw-r--r-- | subx/ex4.subx | 23 |
3 files changed, 28 insertions, 0 deletions
diff --git a/subx/019syscalls.cc b/subx/019syscalls.cc index 96c11ee0..b83b92db 100644 --- a/subx/019syscalls.cc +++ b/subx/019syscalls.cc @@ -14,6 +14,11 @@ case 0xcd: { // int imm8 (software interrupt) void process_int80() { switch (Reg[EAX].u) { case 1: + cerr << "result: " << NUM(Mem.at(0x08048000)) << '\n'; exit(Reg[EBX].u); + break; + case 3: + read(/*file descriptor*/Reg[EBX].u, /*memory buffer*/&Mem.at(Reg[ECX].u), /*size*/Reg[EDX].u); + break; } } diff --git a/subx/ex4 b/subx/ex4 new file mode 100755 index 00000000..8fd70fbb --- /dev/null +++ b/subx/ex4 Binary files differdiff --git a/subx/ex4.subx b/subx/ex4.subx new file mode 100644 index 00000000..98b9f55a --- /dev/null +++ b/subx/ex4.subx @@ -0,0 +1,23 @@ +## read a character from stdin + +# opcode ModR/M SIB displacement immediate +# instruction mod, reg, Reg/Mem bits scale, index, base +# 1-3 bytes 0/1 byte 0/1 byte 0/1/2/4 bytes 0/1/2/4 bytes +# 0: e_entry = 0x08048054 + ## read(1, x, 1) + # fd = 1 + bb 1/imm32 # copy 1 to EBX + # set location to write to + b9 00 80 04 08 # copy 0x08040000 to ECX + # size = 1 character + ba 1/imm32 # copy 1 to EDX + # syscall = read + b8 3/imm32 # copy 3 to EAX + # call + cd 128/imm8 # int 80h + + ## exit(EBX) + b8 1/imm32 # copy 1 to EAX + cd 128/imm8 # int 80h + +# vim:ft=subx:nowrap |