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Properly detect memory using atags and add it to the memory-management subsystem

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This commit is contained in:
Aaron Lindsay 2012-09-25 22:44:19 -04:00
parent d6e3899fc1
commit afba079256
8 changed files with 171 additions and 24 deletions
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48
include/atags.h Normal file
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@ -0,0 +1,48 @@
#ifndef ATAGS_H
#define ATAGS_H
#include <types.h>
#define ATAG_NONE 0x00000000
#define ATAG_CORE 0x54410001
#define ATAG_MEM 0x54410002
#define ATAG_VIDEOTEXT 0x54410003
#define ATAG_RAMDISK 0x54410004
#define ATAG_INITRD2 0x54420005
#define ATAG_SERIAL 0x54410006
#define ATAG_REVISION 0x54410007
#define ATAG_VIDEOLFB 0x54410008
#define ATAG_CMDLINE 0x54410009
struct atag_core {
uint32 flags; /* bit 0 = read-only */
uint32 pagesize; /* systems page size (usually 4k) */
uint32 rootdev; /* root device number */
};
struct atag_mem {
uint32 size; /* size of the area */
uint32 start; /* physical start address */
};
struct atag {
uint32 size; /* Size of tag in words (includes entire struct) */
uint32 tag;
union {
struct atag_core core;
struct atag_mem mem;
// struct atag_videotext videotext;
// struct atag_ramdisk ramdisk;
// struct atag_initrd2 initrd2;
// struct atag_serialnr serialnr;
// struct atag_revision revision;
// struct atag_videolfb videolfb;
// struct atag_cmdline cmdline;
} data;
};
#define atags_first_mem_region(atag) _atags_mem_region(atag, 1)
#define atags_next_mem_region(atag) _atags_mem_region(atag, 0)
int _atags_mem_region(struct atag **mem_header, int initialize);
#endif /* ATAGS_H */

3
include/mmu.h
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@ -1,8 +1,9 @@
#ifndef MMU_H
#define MMU_H
extern unsigned int *kernel_start_phys, *kernel_start_virt, *kernel_end_phys, *kernel_end_virt;
#include <types.h>
void mmu_reinit();
void declare_memory_region(void *lower, void *upper);
#endif /* MMU_H */

1
include/types.h Normal file
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@ -0,0 +1 @@
typedef unsigned int uint32;

1
kernel/Makefile.inc
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@ -1,5 +1,6 @@
KERNEL_PREFIX = kernel
KOBJS += $(KERNEL_PREFIX)/atags.o
KOBJS += $(KERNEL_PREFIX)/console.o
KOBJS += $(KERNEL_PREFIX)/font.o
KOBJS += $(KERNEL_PREFIX)/framebuffer.o

42
kernel/atags.c Normal file
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@ -0,0 +1,42 @@
#include <atags.h>
extern uint32 atags_ptr;
int atag_valid(struct atag *a) {
switch (a->tag) {
case ATAG_NONE:
return a->size == 2;
case ATAG_CORE:
return a->size == 2 || a->size == 5;
case ATAG_MEM:
case ATAG_INITRD2:
case ATAG_SERIAL:
return a->size == 4;
case ATAG_VIDEOTEXT:
case ATAG_RAMDISK:
return a->size == 5;
case ATAG_REVISION:
return a->size == 3;
case ATAG_VIDEOLFB:
return a->size == 8;
case ATAG_CMDLINE:
return a->size >= 3;
default:
return 0;
}
}
int _atags_mem_region(struct atag **mem_header, int initialize) {
if (initialize)
*mem_header = (struct atag *)atags_ptr;
else
*mem_header = (struct atag *)((uint32 *)*mem_header + (*mem_header)->size);
while (atag_valid(*mem_header) && (*mem_header)->tag != ATAG_NONE && (*mem_header)->tag != ATAG_MEM) {
*mem_header = (struct atag *)((uint32 *)*mem_header + (*mem_header)->size);
}
if (!atag_valid(*mem_header) || (*mem_header)->tag == ATAG_NONE)
return -1;
return 0;
}

15
kernel/mm.c
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@ -32,12 +32,13 @@ void mm_add_free_region(void *start, void *end) {
void *page;
//make sure both start and end address are aligned to the size of a page
if ((unsigned int)start & MM_PAGE_SIZE || (unsigned int)(end+1) & MM_PAGE_SIZE) {
print("Error: Supplied memory area(%x,%x) is not aligned to the page size (%d)\n", (unsigned int)start, (unsigned int)end, MM_PAGE_SIZE);
return;
}
if ((char *)end - (char *)start < MM_PAGE_SIZE<<1) {
print("Error: Supplied memory area(%x,%x) is not aligned to the page size (%d)\n", (unsigned int)start, (unsigned int)end, MM_PAGE_SIZE);
if ((unsigned int)start % MM_PAGE_SIZE != 0)
start = (char*)start + (MM_PAGE_SIZE - ((unsigned int)start % MM_PAGE_SIZE));
if (((unsigned int)end + 1) % MM_PAGE_SIZE != 0)
end = (char*)end - ((unsigned int)end + 1) % MM_PAGE_SIZE;
if ((char *)end + 1 - (char *)start < MM_PAGE_SIZE<<1) {
print("Error: Supplied memory area(%x,%x) is smaller than the page size (%d)\n", (unsigned int)start, (unsigned int)end, MM_PAGE_SIZE);
return;
}
@ -46,7 +47,7 @@ void mm_add_free_region(void *start, void *end) {
//TODO we're potentially losing memory here because we're calculating
//the number of page structs we need even for those pages that will contain only page structs
num_pages = ((char *)end - (char *)start) / MM_PAGE_SIZE;
num_pages = ((char *)end + 1 - (char *)start) / MM_PAGE_SIZE;
usable_pages = num_pages - num_pages * sizeof(struct page) / MM_PAGE_SIZE;
if (num_pages * sizeof(struct page) % MM_PAGE_SIZE)
usable_pages--;

64
kernel/mmu.c
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@ -1,4 +1,6 @@
#include <print.h>
#include <types.h>
#include <mm.h>
#define SCTLR 15,0,1,0,0
#define TTBR0 15,0,2,0,0
@ -11,23 +13,29 @@
#define cp_write(var, ...) _cp_write(var, __VA_ARGS__)
#define TT_BASE_SIZE (1<<14) /* 16k */
#define TT_SECTION_SIZE (1<<20) /* 1mb */
unsigned int *kernel_start_phys, *kernel_start_virt, *kernel_end_phys, *kernel_end_virt;
uint32 *kernel_start_phys, *kernel_start_virt, *kernel_end_phys, *kernel_end_virt;
void print_mapping(void *addr) {
extern uint32 tt_base_virtual;
print("%x: %x\n", addr, *(uint32 *)(tt_base_virtual + (((uint32)addr)>>18)));
}
void mmu_reinit() {
extern unsigned int tt_base_virtual, tt_base_physical, start;
unsigned int curr_addr;
unsigned int *curr_tt_entry;
extern uint32 tt_base_virtual, tt_base_physical, start;
uint32 curr_addr;
uint32 *curr_tt_entry;
int virt_phys_offset;
virt_phys_offset = tt_base_virtual - tt_base_physical;
kernel_start_virt = &start;
kernel_start_phys = kernel_start_virt - virt_phys_offset/4;
kernel_end_virt = (unsigned int *)(tt_base_virtual + TT_BASE_SIZE);
kernel_end_phys = (unsigned int *)(tt_base_physical + TT_BASE_SIZE);
kernel_end_virt = (uint32 *)(tt_base_virtual + TT_BASE_SIZE);
kernel_end_phys = (uint32 *)(tt_base_physical + TT_BASE_SIZE);
//get the current translation table base address
curr_tt_entry = (unsigned int *)tt_base_virtual;
curr_tt_entry = (uint32 *)tt_base_virtual;
//do first loop iteration outside the loop, because we have to check against wrapping back around to know we're done
*curr_tt_entry = 0xc02; /* 0xc02 means read/write at any priviledge level, and that it's a section w/o PXN bit set */
@ -38,9 +46,9 @@ void mmu_reinit() {
//memory, make sure we keep those mappings correct, and we'll actually
//swap the twp mappings so all of memory is addressable.
for (curr_addr = 0x00100000; curr_addr != 0; curr_addr += 0x00100000) {
if ((unsigned int *)curr_addr >= kernel_start_phys && (unsigned int *)curr_addr < kernel_end_phys) {
if ((uint32 *)curr_addr >= kernel_start_phys && (uint32 *)curr_addr < kernel_end_phys) {
*curr_tt_entry = (curr_addr + virt_phys_offset) | 0xc02;
} else if ((unsigned int *)curr_addr >= kernel_start_virt && (unsigned int *)curr_addr < kernel_end_virt) {
} else if ((uint32 *)curr_addr >= kernel_start_virt && (uint32 *)curr_addr < kernel_end_virt) {
*curr_tt_entry = (curr_addr - virt_phys_offset) | 0xc02;
} else {
*curr_tt_entry = curr_addr | 0xc02;
@ -48,3 +56,41 @@ void mmu_reinit() {
curr_tt_entry++;
}
}
int mmu_region_contains(void *lower_a, void *upper_a, void *lower_b, void *upper_b) {
return lower_b >= lower_a && upper_b <= upper_a;
}
#define section_round_down(ptr) (((uint32)ptr) & ~(TT_SECTION_SIZE-1))
#define section_round_up(ptr) (((((uint32)ptr) & ~1) + (TT_SECTION_SIZE-1) ) & ~(TT_SECTION_SIZE-1))
/* Called one per physical memory region by bootup code. This function is
* responsible for only adding (via mm_add_free_region()) those parts of the
* memory region which are still available (i.e. aren't in the kernel and
* haven't been remapped anywhere else. */
void declare_memory_region(void *lower, void *upper) {
void *k_section_start_phys = (void *)section_round_down(kernel_start_phys);
void *k_section_end_phys = (void *)(section_round_up(kernel_end_phys) - 1);
void *k_section_start_virt = (void *)section_round_down(kernel_start_virt);
void *k_section_end_virt = (void *)(section_round_up(kernel_end_virt) - 1);
if (upper - lower < 1) {
print("Warning: declare_memory_region() called with lower=%x, upper=%x. Ignoring.\n", lower, upper);
return;
}
//TODO It's possible (though highly unlikely) that the kernel (virtual)
//is split across two different memory regions. We should probably
//handle this.
if (mmu_region_contains(lower, upper, k_section_start_phys, k_section_end_phys)) {
//Don't map any of the physical kernel's memory
declare_memory_region(lower, (void *) ((char *)k_section_start_phys - 1));
declare_memory_region((void *) ((char *)k_section_end_phys + 1), upper);
mm_add_free_region(kernel_end_virt, k_section_end_virt);
} else if (mmu_region_contains(lower, upper, k_section_start_virt, k_section_end_virt)) {
declare_memory_region(lower, (void *) ((char *)k_section_start_virt - 1));
declare_memory_region((void *) ((char *)k_section_end_virt + 1), upper);
} else {
mm_add_free_region(lower, upper);
}
}

21
kernel/start_kernel.c
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@ -1,3 +1,4 @@
#include <atags.h>
#include <mmu.h>
#include <mm.h>
#include <print.h>
@ -52,7 +53,8 @@ void test_memory() {
}
int main(void) {
char *lower;
char *lower, *upper;
struct atag *atags;
//setup MMU
mmu_reinit();
@ -61,12 +63,17 @@ int main(void) {
//setup memory
mm_init();
mm_add_free_region((void*)0x60000000, (void*)0x7FFFFFFF);
mm_add_free_region((void*)0x80000000, (void*)0x800FFFFF);
lower = (char*) &kernel_end_virt;
if ((unsigned int)lower % MM_PAGE_SIZE != 0)
lower += (MM_PAGE_SIZE - ((unsigned int)lower % MM_PAGE_SIZE));
mm_add_free_region((void*)lower, (void*)0x9FFFFFFF); //subtract the memory used by the kernel
if (atags_first_mem_region(&atags)) {
print("Error: atags must contain at least one memory region\n");
return -1;
}
do {
lower = (char *)atags->data.mem.start;
upper = lower + atags->data.mem.size - 1;
declare_memory_region(lower, upper);
} while (!atags_next_mem_region(&atags));
test_memory();