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adds a little bit of memory protection

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This commit is contained in:
Nathan Singer
2025-06-13 12:53:35 -04:00
parent 45c167568c
commit 779680987f
2 changed files with 20 additions and 18 deletions
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37
kernel/arch/pmm/pmm.c
View File

@ -1,6 +1,7 @@
#include <stdint.h> #include <stdint.h>
#include <stdbool.h> #include <stdbool.h>
#include <string.h> #include <string.h>
#include <stdlib.h>
#ifdef __TESTING__ #ifdef __TESTING__
#include <stdio.h> #include <stdio.h>
@ -41,29 +42,29 @@ struct pmm_mem_info {
struct pmm_mem_info main_mem; struct pmm_mem_info main_mem;
void pmm_set(int bit); void pmm_set(uint32_t bit);
void pmm_unset(int bit); void pmm_unset(uint32_t bit);
bool pmm_test(int bit); bool pmm_test(uint32_t bit);
int pmm_first_free(void); int pmm_first_free(void);
void pmm_init(void); void pmm_init(void);
void* pmm_alloc_block(void); void* pmm_alloc_block(void);
void pmm_free_block(void* p); void pmm_free_block(void* p);
void __pmm_set(int bit, struct pmm_mem_info* mem_block) void __pmm_set(uint32_t bit, struct pmm_mem_info* mem_block)
{ {
(mem_block->bitmap)[bit / 32] |= (1 << (bit % 32)); (mem_block->bitmap)[bit / 32] |= (1 << (bit % 32));
mem_block->used_blocks++; mem_block->used_blocks++;
mem_block->free_blocks--; mem_block->free_blocks--;
} }
void __pmm_unset(int bit, struct pmm_mem_info* mem_block) void __pmm_unset(uint32_t bit, struct pmm_mem_info* mem_block)
{ {
(mem_block->bitmap)[bit / 32] &= ~(1 << (bit % 32)); (mem_block->bitmap)[bit / 32] &= ~(1 << (bit % 32));
mem_block->used_blocks--; mem_block->used_blocks--;
mem_block->free_blocks++; mem_block->free_blocks++;
} }
bool __pmm_test(int bit, struct pmm_mem_info* mem_block) bool __pmm_test(uint32_t bit, struct pmm_mem_info* mem_block)
{ {
return (mem_block->bitmap)[bit / 32] & (1 << (bit % 32)); return (mem_block->bitmap)[bit / 32] & (1 << (bit % 32));
} }
@ -84,7 +85,7 @@ int __pmm_first_free(struct pmm_mem_info* mem_block)
void __pmm_add_mem_block(uint32_t addr, int32_t len, struct pmm_mem_info* mem_block) void __pmm_add_mem_block(uint32_t addr, int32_t len, struct pmm_mem_info* mem_block)
{ {
mem_block->startaddr = addr; // main_mem isn't properly being set like this... TODO mem_block->startaddr = addr;
mem_block->len = len; mem_block->len = len;
mem_block->bitmap = 0; mem_block->bitmap = 0;
} }
@ -125,12 +126,20 @@ void* __pmm_alloc_block(struct pmm_mem_info* mem_block)
void __pmm_free_block(void* p, struct pmm_mem_info* mem_block) void __pmm_free_block(void* p, struct pmm_mem_info* mem_block)
{ {
uint64_t* addr = (uint64_t*) &p; uint64_t* addr = (uint64_t*) &p;
int idx = ((*addr) - mem_block->startaddr) / PMM_PAGE_SIZE; uint32_t idx = ((*addr) - mem_block->startaddr) / PMM_PAGE_SIZE;
// TODO this might still be a little flaky
// should we be able to free any pointer? or just ones that we've given out?
if (idx == 0)
panic("Trying to free reserved memory!");
if (pmm_test(idx) == 0)
panic("Trying to free a block that was already free!");
__pmm_unset(idx, mem_block); __pmm_unset(idx, mem_block);
} }
void pmm_set(int bit) void pmm_set(uint32_t bit)
{ {
/** /**
* Here we want to calculate if the bit is over the length * Here we want to calculate if the bit is over the length
@ -145,13 +154,13 @@ void pmm_set(int bit)
__pmm_set(bit, &main_mem); __pmm_set(bit, &main_mem);
} }
void pmm_unset(int bit) void pmm_unset(uint32_t bit)
{ {
// TODO: same as above // TODO: same as above
__pmm_unset(bit, &main_mem); __pmm_unset(bit, &main_mem);
} }
bool pmm_test(int bit) bool pmm_test(uint32_t bit)
{ {
// TODO: same as above // TODO: same as above
return __pmm_test(bit, &main_mem); return __pmm_test(bit, &main_mem);
@ -175,18 +184,12 @@ void pmm_init(void)
void* pmm_alloc_block(void) void* pmm_alloc_block(void)
{ {
#ifdef __TESTING__
printf("PMM: Alloc'd a block!\n");
#endif
return __pmm_alloc_block(&main_mem); return __pmm_alloc_block(&main_mem);
} }
void pmm_free_block(void* p) void pmm_free_block(void* p)
{ {
__pmm_free_block(p, &main_mem); __pmm_free_block(p, &main_mem);
#ifdef __TESTING__
puts("PMM: Free'd a block!");
#endif
} }
void pmm_add_mem_block(uint32_t addr, uint32_t len) void pmm_add_mem_block(uint32_t addr, uint32_t len)

1
kernel/kmain.c
View File

@ -68,7 +68,6 @@ void _main(multiboot_info_t* mbd, uint32_t magic)
print_main_mem(); print_main_mem();
pmm_free_block(a); pmm_free_block(a);
print_main_mem(); print_main_mem();