28 lines
1.1 KiB
Markdown
28 lines
1.1 KiB
Markdown
# User applications
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This folder contains code designed to be "userspace" application. Unlike the
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kernel, which always stay in memory. Those apps here will more likely be loaded
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in RAM from storage, ran, then discarded so that another userspace program can
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be run.
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That doesn't mean that you can't include that code in your kernel though, but
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you will typically not want to do that.
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## Userspace convention
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We execute a userspace application by calling the address it's loaded into. This
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means: a userspace application is expected to return.
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Whatever calls the userspace app (usually, it will be the shell), should set
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HL to a pointer to unparsed arguments in string form, null terminated.
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The userspace application is expected to set A on return. 0 means success,
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non-zero means error.
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A userspace application can expect the `SP` pointer to be properly set. If it
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moves it, it should take care of returning it where it was before returning
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because otherwise, it will break the kernel.
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Apps in Collapse OS are design to be ROM-compatible, that is, they don't write
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to addresses that are part of the code's address space.
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