38 lines
1.2 KiB
C
38 lines
1.2 KiB
C
// User-level page fault handler support.
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// Rather than register the C page fault handler directly with the
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// kernel as the page fault handler, we register the assembly language
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// wrapper in pfentry.S, which in turns calls the registered C
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// function.
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#include <inc/lib.h>
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// Assembly language pgfault entrypoint defined in lib/pfentry.S.
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extern void _pgfault_upcall(void);
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// Pointer to currently installed C-language pgfault handler.
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void (*_pgfault_handler)(struct UTrapframe *utf);
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//
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// Set the page fault handler function.
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// If there isn't one yet, _pgfault_handler will be 0.
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// The first time we register a handler, we need to
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// allocate an exception stack (one page of memory with its top
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// at UXSTACKTOP), and tell the kernel to call the assembly-language
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// _pgfault_upcall routine when a page fault occurs.
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//
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void
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set_pgfault_handler(void (*handler)(struct UTrapframe *utf))
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{
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int r;
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if (_pgfault_handler == 0) {
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if(sys_page_alloc(0, (void*) UXSTACKTOP - PGSIZE, PTE_U | PTE_P | PTE_W) < 0)
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panic("set_pgfault_handler");
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sys_env_set_pgfault_upcall(0, _pgfault_upcall);
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}
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// Save handler pointer for assembly to call.
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_pgfault_handler = handler;
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}
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