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#include "io.h"
#include "psr.h"
#include "memory.h"
#include "translation_table_descriptors.h"
#include "ramfs.h"
#include "strings.h"
void demo_paging_support(void)
{
uint32_t ID_MMFR0;
// get contents of coprocessor register to check for paging support
asm("mrc p15, 0, %0, c0, c1, 4" : "=r" (ID_MMFR0));
char *paging;
switch(ID_MMFR0 & 0xf) /* lowest 4 bits indicate VMSA support */
{
case 0 : paging = "no paging"; break;
case 1 : paging = "implementation defined paging"; break;
case 2 : paging = "VMSAv6, with cache and TLB type registers"; break;
case 3 : paging = "VMSAv7, with support for remapping and access flag"; break;
case 4 : paging = "VMSAv7 with PXN bit supported"; break;
case 5 : paging = "VMSAv7, PXN and long format descriptors. EPAE is supported."; break;
default : paging = "?_? unknown paging ?_?";
}
puts(paging);
}
void demo_current_mode(void)
{
// get content of current program status register to check the current
// processor mode (should be system, as we set it in boot.S)
PSR_t CPSR = read_CPSR();
char *mode_name;
switch(CPSR.fields.PSR_MODE_4_0)
{
case MODE_USER : mode_name = "User (PL0)"; break;
case MODE_FIQ : mode_name = "FIQ (PL1)"; break;
case MODE_IRQ : mode_name = "IRQ (PL1)"; break;
case MODE_SUPERVISOR : mode_name = "Supervisor (PL1)"; break;
case MODE_MONITOR : mode_name = "Monitor (PL1)"; break;
case MODE_ABORT : mode_name = "Abort (PL1)"; break;
case MODE_HYPERVISOR : mode_name = "Hyp (PL2)"; break;
case MODE_UNDEFINED : mode_name = "Undefined (PL1)"; break;
case MODE_SYSTEM : mode_name = "System (PL1)"; break;
default : mode_name = "Unknown mode"; break;
}
prints("current mode: ");
puts(mode_name);
}
#define TRANSLATION_TABLE \
((short_section_descriptor_t volatile*) TRANSLATION_TABLE_BASE)
extern char
_binary_ramfs_img_start,
_binary_ramfs_img_end,
_binary_ramfs_img_size;
void demo_setup_PL0(void)
{
// find PL_0_test.img im ramfs
struct ramfile PL_0_test_img;
if (find_file(&_binary_ramfs_img_start, "PL_0_test.img",
&PL_0_test_img))
{
puts("PL_0_test.img not found :(");
asm volatile ("wfi");
}
short_section_descriptor_t volatile *PL0_section_entry =
&TRANSLATION_TABLE[PL0_SECTION_NUMBER];
short_section_descriptor_t PL0_section = *PL0_section_entry;
// set up address of PL0 section
PL0_section.SECTION_BASE_ADDRESS_31_20 =
UNPRIVILEGED_MEMORY_START >> 20;
// make the selected section available for PL0
PL0_section.ACCESS_PERMISSIONS_2 =
AP_2_0_MODEL_RW_ALL >> 2;
PL0_section.ACCESS_PERMISSIONS_1_0 =
AP_2_0_MODEL_RW_ALL & 0b011;
*PL0_section_entry = PL0_section;
// invalidate main Translation Lookup Buffer (just in case)
asm("mcr p15, 0, %0, c8, c7, 0\n\r"
"isb" :: "r" (0) : "memory");
// check that translation works... by copying a string using one
// mapping and reading it using other :D
char message[] = "mapped sections for PL0 code";
memcpy((void*) UNPRIVILEGED_MEMORY_START, message, sizeof(message));
puts((char*) VIRTUAL_PL0_MEMORY_START);
// now paste a userspace program to that section
memcpy((void*) VIRTUAL_PL0_MEMORY_START,
PL_0_test_img.file_contents, PL_0_test_img.file_size);
puts("copied PL0 code to it's section");
}
void demo_go_unprivileged(void)
{
uint32_t PL0_regs[14] = {0};
PL0_regs[13] = VIRTUAL_PL0_MEMORY_START; // the new pc
PSR_t new_SPSR = read_CPSR();
new_SPSR.fields.PSR_MODE_4_0 = MODE_USER;
write_SPSR(new_SPSR);
puts("All ready, jumping to PL0 code");
asm volatile("cps %[sysmode]\n\r"
"mov sp, %[stackaddr]\n\r"
"cps %[supmode]\n\r"
"ldm %[contextaddr], {r0 - r12, pc} ^" ::
[sysmode]"I" (MODE_SYSTEM),
[supmode]"I" (MODE_SUPERVISOR),
[stackaddr]"r" ((PL0_SECTION_NUMBER + 1) << 20),
[contextaddr]"r" (PL0_regs) : "memory");
__builtin_unreachable();
}
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