Create kernel stack with correct size and set up a guard page #335
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The last page of stack memory was not used before because we initialized the stack pointer with the start address of the inclusive end page of the stack. This commit fixes this by initializing the stack pointer with the exact configured address, aligned to a 16-byte boundary.
Also: Add a convenience function for allocating page-aligned mappings.
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The last page of stack memory was not used before (see #294 ) because we initialized the stack pointer with the start address of the inclusive end page of the stack. This PR fixes this by initializing the stack pointer with the exact configured address, aligned to a 16-byte boundary. To verify that this works, I added a new
min_stacktest that tries booting with a kernel stack size of just 3000 bytes.We also claimed in the docs that we set up a guard page for the kernel stack, but never actually did this. This PR fixes that issue too by allocating an extra page when creating the virtual kernel stack mapping. We then leave the first page of that allocation unmapped so that a page fault will occur when the kernel overflows its stack.
To ensure that user-configured addresses have the correct alignment, I also added an alignment check to the
mapping_addrfunction. There is also a new convenience function for allocating page-aligned virtual regions.Fixes #294