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/*******************************************************************************
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2011-08-05 08:25:00 -04:00
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2013-07-10 09:26:01 -04:00
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Copyright(C) Jonas 'Sortie' Termansen 2011.
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2011-08-05 08:25:00 -04:00
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2013-07-10 09:26:01 -04:00
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This file is part of Sortix.
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2011-08-05 08:25:00 -04:00
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2013-07-10 09:26:01 -04:00
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Sortix is free software: you can redistribute it and/or modify it under the
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terms of the GNU General Public License as published by the Free Software
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Foundation, either version 3 of the License, or (at your option) any later
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version.
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Sortix is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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details.
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You should have received a copy of the GNU General Public License along with
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Sortix. If not, see <http://www.gnu.org/licenses/>.
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2011-08-05 08:25:00 -04:00
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2013-07-10 09:26:01 -04:00
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x86/base.s
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Bootstraps the kernel and passes over control from the boot-loader to the
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kernel main function.
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*******************************************************************************/
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.section .text
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.global beginkernel
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.type beginkernel, @function
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beginkernel:
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Fixed the horrible 'nofoo' bug!
When compiled with gcc 4.6.1, 32-bit Sortix would triple fault during
early boot: When the TLB is being flushed, somehow a garbage value had
sneaked into Sortix::Memory::currentdir, and a non-page aligned (and
garbage) page directory is loaded. (Triple fault, here we come!)
However, adding a volatile addr_t foo after the currentdir variable
actually caused the system to boot correctly - the garbage was written
into that variable instead. To debug the problem, I set the foo value
to 0: as long as !foo (hence the name nofoo) everything was alright.
After closer examination I found that the initrd open code wrote to a
pointer supplied by kernel.cpp. The element pointed to was on the
stack. Worse, its address was the same as currentdir (now foo).
Indeed, the stack had gone into the kernel's data segment!
Turns out that this gcc configuration stores variables in the data
segment in the reverse order they are defined in, whereas previous
compilers did the opposite. The hack used to set up the stack during
early boot relied on this (now obviously incorrect) fact.
In effect, the stack was initialized to the end of the stack, not
the start of it: completely ignoring all the nice stack space
allocated in kernel.cpp.
I did not see that one coming.
2011-12-24 21:33:12 -05:00
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# Initialize the stack pointer. The magic value is from kernel.cpp.
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movl $stack, %esp
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addl $65536, %esp # 64 KiB, see kernel.cpp
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# Reset EFLAGS.
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# pushl $0
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# popf
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# Push the pointer to the Multiboot information structure.
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push %ebx
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# Push the magic value.
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push %eax
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## Disable interrupts.
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cli
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call KernelInit
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.size beginkernel, . - beginkernel
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.global HaltKernel
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HaltKernel:
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cli
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hlt
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jmp HaltKernel
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.size HaltKernel, . - HaltKernel
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.global WaitForInterrupt
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.type WaitForInterrupt, @function # void WaitForInterrupt();
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WaitForInterrupt:
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hlt
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ret
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.size WaitForInterrupt, . - WaitForInterrupt
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