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Fixed two very nasty bugs in the x86 memory management code.

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1) The PML2 was not initialized to zeroes, thus leaving some bits behind that
caused the fork code to go crazy, forking the unforkable, and mapping addresses
that never, ever, should have been mapped, leaving behind a trail of page faults
and general protection faults on some computers, while other computers worked
because the uninitalized memory just wasn't uninitialized enough. Yep, this was
a schrödinbug!

2) Fixed a time bomb. The kernel heap was accidentally put such that whenever a
few megabytes were allocated, it would begin overwriting the physical page stack
causing unthinkable events to unfold and would probably be even more obscure to
debug than 1).

Oh, and some string errors fixed and removed RunApplication from kernel.cpp,
funny thing that even linked in the first place. Guess, the optimizer actually
did work for once. :)
This commit is contained in:
Jonas 'Sortie' Termansen 2011-10-20 03:40:37 +02:00
parent 52b8913bb6
commit b0df5186e6
4 changed files with 13 additions and 8 deletions
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2
sortix/kernel.cpp
View file

@ -226,7 +226,7 @@ namespace Sortix
// Initialize the scheduler.
Scheduler::Init();
Thread::Entry initstart = RunApplication;
Thread::Entry initstart = NULL;
// Create an address space for the first process.
addr_t addrspace = Memory::Fork();

2
sortix/memorymanagement.h
View file

@ -60,7 +60,7 @@ namespace Sortix
#if defined(PLATFORM_X86)
const addr_t HEAPLOWER = 0x80000000UL;
const addr_t HEAPUPPER = 0xFF800000UL;
const addr_t HEAPUPPER = 0xFF400000UL;
#elif defined(PLATFORM_X64)
const addr_t HEAPLOWER = 0xFFFF800000000000UL;
const addr_t HEAPUPPER = 0xFFFFFE8000000000UL;

15
sortix/x86-family/memorymanagement.cpp
View file

@ -129,6 +129,11 @@ namespace Sortix
if ( !page ) { Panic("out of memory allocating boot PMLs"); }
pml->entry[i] = page | flags;
// Invalidate the new PML and reset it to zeroes.
addr_t pmladdr = (addr_t) (PMLS[TOPPMLLEVEL-1] + i);
InvalidatePage(pmladdr);
Maxsi::Memory::Set((void*) pmladdr, 0, sizeof(PML));
}
}
}
@ -318,8 +323,8 @@ namespace Sortix
else if ( userspace && !(entry & PML_USERSPACE) )
{
PanicF("attempted to map physical page %p to virtual page "
"%p with userspace permissions, but the virtual page"
"wasn't in an userspace PML[%zu]. This is a bug in the"
"%p with userspace permissions, but the virtual page "
"wasn't in an userspace PML[%zu]. This is a bug in the "
"code calling this function", physical, mapto, i-1);
}
@ -362,8 +367,8 @@ namespace Sortix
}
else if ( userspace && !(entry & PML_USERSPACE) )
{
PanicF("attempted to unmap virtual page %p it wasn't in an"
"userspace PML[%zu]. This is a bug in the code"
PanicF("attempted to unmap virtual page %p it wasn't in an "
"userspace PML[%zu]. This is a bug in the code "
"calling this function", mapto, i-1);
}
@ -437,7 +442,7 @@ namespace Sortix
addr_t entry = (PMLS[level] + pmloffset)->entry[pos];
// If the entry should be forked, fork it!
if ( likely(entry & PML_FORK) )
if ( (entry & PML_FORK) && (entry & PML_PRESENT) )
{
// Pop the physical address of somewhere unused.
addr_t phys = Page::Get();

2
sortix/x86/memorymanagement.cpp
View file

@ -49,7 +49,7 @@ namespace Sortix
PML* const IDENPML1 = (PML* const) 0x04000UL;
// Initialize the memory structures with zeroes.
Maxsi::Memory::Set(BOOTPML1, 0, 0x6000UL);
Maxsi::Memory::Set((PML* const) 0x01000UL, 0, 0x6000UL);
// Identity map the first 4 MiB.
addr_t flags = PML_PRESENT | PML_WRITABLE;