27 lines
829 B
Text
27 lines
829 B
Text
on application entry:
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there is a 1MiB - 8KiB area mapped writable and not
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executable with guard pages on either side, and rsp is
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set to the top of that. all other registers are set to 0.
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for all system calls:
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rax, rdi, rsi, rdx are in/out paramters.
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rbx, rbp, rsp, r12-r15 are preserved.
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rcx, rflags, r8-r11 are clobbered.
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encode color:
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rax in: 0
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edi in: r + g * 256 + b * 65536
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eax out: encoded color
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get framebuffer:
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rax in: 1
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rax out: pointer to framebuffer
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rdi out: width + height * 2 ** 32
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esi out: pitch
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framebuffer is always 32 bpp. use the encode color syscall
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to encode colors. pitch is in dwords, not in bytes.
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draw framebuffer:
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rax in: 2
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this draws changes to the framebuffer gotten by the get framebuffer
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system call. (currently, the entire thing is copied, not just changes.)
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