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Better mm comments.

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This commit is contained in:
Jonas 'Sortie' Termansen 2011-10-22 15:17:58 +02:00
parent b0df5186e6
commit 4e8c2dfc33
1 changed files with 13 additions and 3 deletions
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16
sortix/x86-family/memorymanagement.cpp
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@ -74,7 +74,7 @@ namespace Sortix
// Check that we can use this kind of RAM. // Check that we can use this kind of RAM.
if ( mmap->type != 1 ) { continue; } if ( mmap->type != 1 ) { continue; }
// The kernels code may split this memory area into multiple pieces. // The kernel's code may split this memory area into multiple pieces.
addr_t base = (addr_t) mmap->addr; addr_t base = (addr_t) mmap->addr;
size_t length = mmap->len; size_t length = mmap->len;
@ -219,7 +219,7 @@ namespace Sortix
addr_t previous = currentdir; addr_t previous = currentdir;
// Swtich and flush the TLB. // Switch and flush the TLB.
asm volatile("mov %0, %%cr3":: "r"(addrspace)); asm volatile("mov %0, %%cr3":: "r"(addrspace));
currentdir = addrspace; currentdir = addrspace;
@ -293,6 +293,7 @@ namespace Sortix
const addr_t userflags = userspace ? (PML_USERSPACE | PML_FORK) : 0; const addr_t userflags = userspace ? (PML_USERSPACE | PML_FORK) : 0;
const addr_t flags = userflags | PML_PRESENT | PML_WRITABLE; const addr_t flags = userflags | PML_PRESENT | PML_WRITABLE;
// Translate the virtual address into PML indexes.
const size_t MASK = (1<<TRANSBITS)-1; const size_t MASK = (1<<TRANSBITS)-1;
size_t pmlchildid[TOPPMLLEVEL + 1]; size_t pmlchildid[TOPPMLLEVEL + 1];
for ( size_t i = 1; i <= TOPPMLLEVEL; i++ ) for ( size_t i = 1; i <= TOPPMLLEVEL; i++ )
@ -300,6 +301,7 @@ namespace Sortix
pmlchildid[i] = (mapto >> (12+(i-1)*TRANSBITS)) & MASK; pmlchildid[i] = (mapto >> (12+(i-1)*TRANSBITS)) & MASK;
} }
// For each PML level, make sure it exists, and that we may use it.
size_t offset = 0; size_t offset = 0;
for ( size_t i = TOPPMLLEVEL; i > 1; i-- ) for ( size_t i = TOPPMLLEVEL; i > 1; i-- )
{ {
@ -328,9 +330,11 @@ namespace Sortix
"code calling this function", physical, mapto, i-1); "code calling this function", physical, mapto, i-1);
} }
// Find the index of the next PML in the fractal mapped memory.
offset = offset * ENTRIES + childid; offset = offset * ENTRIES + childid;
} }
// Actually map the physical page to the virtual page.
(PMLS[1] + offset)->entry[pmlchildid[1]] = physical | flags; (PMLS[1] + offset)->entry[pmlchildid[1]] = physical | flags;
if ( invalidate ) if ( invalidate )
@ -344,6 +348,7 @@ namespace Sortix
template <bool userspace, bool invalidate> template <bool userspace, bool invalidate>
addr_t Unmap(addr_t mapto) addr_t Unmap(addr_t mapto)
{ {
// Translate the virtual address into PML indexes.
const size_t MASK = (1<<TRANSBITS)-1; const size_t MASK = (1<<TRANSBITS)-1;
size_t pmlchildid[TOPPMLLEVEL + 1]; size_t pmlchildid[TOPPMLLEVEL + 1];
for ( size_t i = 1; i <= TOPPMLLEVEL; i++ ) for ( size_t i = 1; i <= TOPPMLLEVEL; i++ )
@ -351,6 +356,8 @@ namespace Sortix
pmlchildid[i] = (mapto >> (12+(i-1)*TRANSBITS)) & MASK; pmlchildid[i] = (mapto >> (12+(i-1)*TRANSBITS)) & MASK;
} }
// For each PML level, make sure it exists, and that it belongs to
// user-space.
size_t offset = 0; size_t offset = 0;
for ( size_t i = TOPPMLLEVEL; i > 1; i-- ) for ( size_t i = TOPPMLLEVEL; i > 1; i-- )
{ {
@ -372,6 +379,7 @@ namespace Sortix
"calling this function", mapto, i-1); "calling this function", mapto, i-1);
} }
// Find the index of the next PML in the fractal mapped memory.
offset = offset * ENTRIES + childid; offset = offset * ENTRIES + childid;
} }
@ -410,8 +418,9 @@ namespace Sortix
return Unmap<true, false>(mapto); return Unmap<true, false>(mapto);
} }
// Create an exact copy of the current address space.
// TODO: Copying every frame is endlessly useless in many uses. It'd be // TODO: Copying every frame is endlessly useless in many uses. It'd be
// nice to upgrade this to a copy-on-demand algorithm. // nice to upgrade this to a copy-on-write algorithm.
addr_t Fork() addr_t Fork()
{ {
addr_t newtoppmladdr = Page::Get(); addr_t newtoppmladdr = Page::Get();
@ -428,6 +437,7 @@ namespace Sortix
MapKernel(newtoppmladdr, (addr_t) (FORKPML + level)); MapKernel(newtoppmladdr, (addr_t) (FORKPML + level));
InvalidatePage((addr_t) (FORKPML + level)); InvalidatePage((addr_t) (FORKPML + level));
// Recurse over the PMLs and fork what should be forked.
while ( positionstack[TOPPMLLEVEL] < ENTRIES ) while ( positionstack[TOPPMLLEVEL] < ENTRIES )
{ {
const size_t pos = positionstack[level]; const size_t pos = positionstack[level];