1+ #include "paging.h"
2+ #include "printf.h"
3+ #include "kmisc.h"
4+ #include "misc.h"
5+
6+ // Functions used by the kernel & drivers
7+
8+ // TODO: This might all go out the window in favor of conditionally-compiling misc.c functions; I haven't decided yet.
9+
10+ extern uint32_t memoryNextAvailableAddress ;
11+ extern uint32_t pagedMemoryAvailable ;
12+
13+ // TODO: Change this to a more robust scheme (?)
14+ ALLOCATION_ARRAY kallocationArray = { 0 };
15+ unsigned int knextAllocationSlot = 0 ;
16+
17+ // Very, very basic support for freeing memory:
18+ ALLOCATION_ARRAY kfreeMemoryArray = { 0 };
19+ unsigned int knextFreeMemorySlot = 0 ;
20+
21+ #ifdef DEBUG_MEM
22+ #define noFileName "FILENAME NOT SET";
23+ char * dbgMemFilename = noFileName ;
24+ int dbgMemLineNumber = 0 ;
25+ char * dbgFreeFilename = noFileName ;
26+ int dbgFreeLineNumber = 0 ;
27+ #endif
28+
29+ inline void addAllocationToKFreeMemoryArray (int allocationIndex )
30+ {
31+ // Try to add this memory to the free memory array
32+ if (knextFreeMemorySlot == MAX_ALLOCATIONS )
33+ {
34+ kprintf ("NSLFM" );
35+ return ;
36+ }
37+
38+ kfreeMemoryArray .address [knextFreeMemorySlot ] = kallocationArray .address [allocationIndex ];
39+ kfreeMemoryArray .size [knextFreeMemorySlot ] = kallocationArray .size [allocationIndex ];
40+ kfreeMemoryArray .inUse [knextFreeMemorySlot ++ ] = true;
41+ }
42+
43+ // Allocate some kernel memory. Mostly this is meant to be used by drivers.
44+ // This will be mapped into every tasks page space and will be allocated contiguously
45+ // TODO: Is it better to have this crazy scheme with the two functions, or just modify malloc to make sure
46+ // it never reuses user-space memory when called from the kernel?
47+
48+ void * kmalloc (size_t size )
49+ {
50+ if (knextAllocationSlot >= MAX_ALLOCATIONS )
51+ {
52+ kprintf ("Maximum memory allocations exceeded!\n" );
53+ return NULL ;
54+ }
55+
56+ #ifdef DEBUG_MEM
57+ kallocationArray .lineNumber [knextAllocationSlot ] = dbgMemLineNumber ;
58+ strncpy (kallocationArray .filename [knextAllocationSlot ], dbgMemFilename , MAX_DEBUG_FILENAME_LENGTH );
59+ dbgMemFilename = noFileName ;
60+ dbgMemLineNumber = 0 ;
61+ #endif
62+
63+ // See if there's freed memory available to reallocate (first fit algorithm; memory will end up wasted)
64+ for (size_t i = 0 ; i < knextFreeMemorySlot ; ++ i )
65+ {
66+ if (kfreeMemoryArray .size [i ] >= size )
67+ {
68+ // We found a piece of free memory we can reuse
69+
70+ // Keep track of the memory in our allocations array
71+ kallocationArray .address [knextAllocationSlot ] = kfreeMemoryArray .address [i ];
72+ kallocationArray .size [knextAllocationSlot ] = kfreeMemoryArray .size [i ];
73+ kallocationArray .inUse [knextAllocationSlot ] = true;
74+
75+ // We want to keep kfreeMemoryArray from fragmenting, so we'll copy
76+ // last used free memory entry of the array to the i position and decrease
77+ // the used portion of the array by one
78+ -- knextFreeMemorySlot ;
79+ if (knextFreeMemorySlot )
80+ {
81+ kfreeMemoryArray .address [i ] = kfreeMemoryArray .address [knextFreeMemorySlot ];
82+ kfreeMemoryArray .size [i ] = kfreeMemoryArray .size [knextFreeMemorySlot ];
83+ }
84+ // The last entry is no longer in use
85+ kfreeMemoryArray .inUse [knextFreeMemorySlot ] = false;
86+
87+ #ifdef DEBUG_MEM
88+ //printf("Reusing freed memory from slot %d, (reuse #%d)\n", i, ++reuses);
89+ #endif
90+ return (void * )kallocationArray .address [knextAllocationSlot ++ ];
91+ }
92+ }
93+
94+ uint32_t availableAddress = memoryNextAvailableAddress ;
95+
96+ #ifdef DEBUG_MEM
97+ printf ("Allocating new %d bytes\n" , size );
98+ #endif
99+
100+ //if(debugLevel)
101+ //printf("size: %d\nadrress: %d\n", size, memoryNextAvailableAddress);
102+
103+ /*terminal_writestring("Paged memory available: ");
104+ terminal_print_int(pagedMemoryAvailable);
105+ terminal_newline();*/
106+
107+ // see if we need to allocate a page
108+ if (size > pagedMemoryAvailable )
109+ {
110+ // TODO: Support dynamic page granularity, not just large pages
111+ unsigned int pagesToAllocate = size / FOUR_MEGABYTES ;
112+
113+ // check for remainder from division
114+ if (pagesToAllocate * FOUR_MEGABYTES < size )
115+ ++ pagesToAllocate ;
116+
117+ // Allocate the pages
118+ unsigned int pagesAllocated ;
119+ KPageAllocator (pagesToAllocate , & pagesAllocated , & availableAddress );
120+
121+ // We need to ensure the pages are in order
122+ if (!availableAddress || (pagesAllocated < pagesToAllocate ))
123+ {
124+ kprintf ("Returning NULL, %d pages allocated out of %d\n" , pagesAllocated , pagesToAllocate );
125+ // TODO: Free allocated pages
126+ return NULL ;
127+ }
128+
129+ // TODO: see if the page we allocated follows the previous page
130+ // for now, we'll just ignore the old allocated memory
131+ pagedMemoryAvailable = pagesAllocated * FOUR_MEGABYTES ;
132+
133+ memoryNextAvailableAddress = availableAddress ;
134+ }
135+
136+ pagedMemoryAvailable -= size ;
137+ availableAddress = memoryNextAvailableAddress ;
138+ memoryNextAvailableAddress += size ;
139+
140+ // Keep track of the memory in our allocations array
141+ kallocationArray .address [knextAllocationSlot ] = availableAddress ;
142+ kallocationArray .size [knextAllocationSlot ] = size ;
143+ kallocationArray .inUse [knextAllocationSlot ++ ] = true;
144+
145+ return (void * )availableAddress ;
146+ }
147+
148+ void kfree (void * ptr )
149+ {
150+ // Find this pointer in the allocation array
151+ for (size_t i = 0 ; i < knextAllocationSlot ; ++ i )
152+ {
153+ if (kallocationArray .address [i ] == (uint32_t )ptr )
154+ {
155+ if (kallocationArray .inUse [i ])
156+ {
157+ addAllocationToKFreeMemoryArray (i );
158+
159+ // We want to keep the allocation array from being fragmented, so we
160+ // copy the final entry in allocation array to the i position and
161+ // decrease the size of the allocation array
162+ -- knextAllocationSlot ;
163+ if (knextAllocationSlot )
164+ {
165+ kallocationArray .address [i ] = kallocationArray .address [knextAllocationSlot ];
166+ kallocationArray .size [i ] = kallocationArray .size [knextAllocationSlot ];
167+ }
168+
169+ kallocationArray .inUse [knextAllocationSlot ] = false;
170+ }
171+ else
172+ {
173+ kprintf ("free() called to free already-freed pointer, 0x%lX\n" , ptr );
174+ }
175+
176+ return ;
177+ }
178+ }
179+
180+ kprintf ("free() called with invalid pointer: 0x%lX" , ptr );
181+ #ifdef DEBUG_MEM
182+ printf (" from %s, line %d\n" , dbgFreeFilename , dbgFreeLineNumber );
183+ dbgFreeFilename = noFileName ;
184+ dbgFreeLineNumber = 0 ;
185+ //for (;;)
186+ // __halt();
187+ #else
188+ kprintf ("\n" );
189+ #endif
190+ }
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