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Remove pico_rand and use boot random instead
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Rejig everything to fit into scratch, so full 512k of SRAM is available for the user
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will-v-pi committed Jan 21, 2025
1 parent 4b3378b commit 3c13ca0
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Showing 4 changed files with 272 additions and 22 deletions.
15 changes: 3 additions & 12 deletions enc_bootloader/CMakeLists.txt
Original file line number Diff line number Diff line change
Expand Up @@ -35,13 +35,13 @@ if (NOT USE_PRECOMPILED)

target_link_libraries(enc_bootloader
pico_stdlib
pico_rand
)

# use stack guards, as AES variables are written near the stack
target_compile_definitions(enc_bootloader PRIVATE
PICO_USE_STACK_GUARDS=1
PICO_STACK_SIZE=0x200
PICO_NO_PROGRAM_INFO=1
# No heap is used
PICO_HEAP_SIZE=0
# These inits are not required
Expand All @@ -51,17 +51,8 @@ if (NOT USE_PRECOMPILED)
pico_minimize_runtime(enc_bootloader)

pico_set_binary_type(enc_bootloader no_flash)
set(USE_USB_DPRAM FALSE)
# create linker script to run from 0x20070000
file(READ ${PICO_LINKER_SCRIPT_PATH}/memmap_no_flash.ld LINKER_SCRIPT)
if (USE_USB_DPRAM)
string(REPLACE "RAM(rwx) : ORIGIN = 0x20000000, LENGTH = 512k" "RAM(rwx) : ORIGIN = 0x2007F000, LENGTH = 4k" LINKER_SCRIPT "${LINKER_SCRIPT}")
target_compile_definitions(enc_bootloader PRIVATE USE_USB_DPRAM=1)
else()
string(REPLACE "RAM(rwx) : ORIGIN = 0x20000000, LENGTH = 512k" "RAM(rwx) : ORIGIN = 0x2007F000, LENGTH = 4k" LINKER_SCRIPT "${LINKER_SCRIPT}")
endif()
file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/memmap_enc_bootloader.ld "${LINKER_SCRIPT}")
pico_set_linker_script(enc_bootloader ${CMAKE_CURRENT_BINARY_DIR}/memmap_enc_bootloader.ld)
set(USE_USB_DPRAM TRUE)
pico_set_linker_script(enc_bootloader ${CMAKE_CURRENT_LIST_DIR}/memmap_enc_bootloader.ld)
pico_add_dis_output(enc_bootloader)
else()
project(enc_bootloader C CXX ASM)
Expand Down
18 changes: 9 additions & 9 deletions enc_bootloader/enc_bootloader.c
Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,6 @@
#include "pico/stdlib.h"
#include "boot/picobin.h"
#include "pico/bootrom.h"
#include "pico/rand.h"
#include "hardware/structs/otp.h"
#if USE_USB_DPRAM
#include "hardware/structs/usb_dpram.h"
Expand All @@ -34,10 +33,12 @@ extern uint32_t lut_a_map[1];
extern uint32_t lut_b_map[1];
extern uint32_t rstate_sha[4],rstate_lfsr[2];

void __scratch_x("aes") resetrng() {
void resetrng() {
uint32_t f0,f1;
do f0=get_rand_32(); while(f0==0); // make sure we don't initialise the LFSR to zero
f1=get_rand_32();
uint32_t boot_random[4];
rom_get_boot_random(boot_random);
do f0=boot_random[0]; while(f0==0); // make sure we don't initialise the LFSR to zero
f1=boot_random[1];
rstate_sha[0]=f0&0xffffff00; // bottom byte must be zero (or 4) for SHA, representing "out of data"
rstate_sha[1]=f1;
rstate_sha[2]=0x41414141;
Expand All @@ -50,15 +51,15 @@ void __scratch_x("aes") resetrng() {
#endif
}

static void __scratch_x("aes") init_lut_map() {
static void init_lut_map() {
int i;
for(i=0;i<256;i++) lut_b[i]=gen_rand_sha()&0xff, lut_a[i]^=lut_b[i];
lut_a_map[0]=0;
lut_b_map[0]=0;
remap();
}

static void __scratch_x("aes") init_aes() {
static void init_aes() {
resetrng();
gen_lut_sbox();
init_lut_map();
Expand All @@ -67,8 +68,7 @@ static void __scratch_x("aes") init_aes() {
#if USE_USB_DPRAM
uint8_t* workarea = (uint8_t*)USBCTRL_DPRAM_BASE;
#else
// static __attribute__((aligned(4))) uint8_t workarea[4 * 1024];
uint8_t* workarea = (uint8_t*)SRAM_SCRATCH_Y_BASE;
uint8_t* workarea = (uint8_t*)0x20080200; // AES Code & workspace from 0x20080180 -> 0x20081600
#endif

int main() {
Expand Down Expand Up @@ -127,7 +127,7 @@ int main() {

int rc = rom_chain_image(
workarea,
4 * 1024 - PICO_STACK_SIZE, // Don't use stack in workarea
4 * 1024,
data_start_addr,
data_size
);
Expand Down
259 changes: 259 additions & 0 deletions enc_bootloader/memmap_enc_bootloader.ld
Original file line number Diff line number Diff line change
@@ -0,0 +1,259 @@
/* Based on GCC ARM embedded samples.
Defines the following symbols for use by code:
__exidx_start
__exidx_end
__etext
__data_start__
__preinit_array_start
__preinit_array_end
__init_array_start
__init_array_end
__fini_array_start
__fini_array_end
__data_end__
__bss_start__
__bss_end__
__end__
end
__HeapLimit
__StackLimit
__StackTop
__stack (== StackTop)
*/

MEMORY
{
RAM_START(rwx) : ORIGIN = 0x20080000, LENGTH = 0x180
SCRATCH_X(rwx) : ORIGIN = 0x20080180, LENGTH = 0xE80
SCRATCH_Y(rwx) : ORIGIN = 0x20081000, LENGTH = 0x800
RAM(rwx) : ORIGIN = 0x20081800, LENGTH = 0x800
}

ENTRY(_entry_point)

SECTIONS
{
/* Note unlike RP2040, we start the image with a vector table even for
NO_FLASH builds. On Arm, the bootrom expects a VT at the start of the
image by default; on RISC-V, the default is to enter the image at its
lowest address, so an IMAGEDEF item is required to specify the
nondefault entry point. */

.start_text : {
__logical_binary_start = .;
/* Vectors require 512-byte alignment on v8-M when >48 IRQs are used,
so we would waste RAM if the vector table were not at the
start. */
KEEP (*(.vectors))
KEEP (*(.binary_info_header))
__binary_info_header_end = .;
KEEP (*(.embedded_block))
__embedded_block_end = .;
} > RAM_START

.text : {
__reset_start = .;
KEEP (*(.reset))
__reset_end = .;
*(.time_critical*)
*(.text*)
. = ALIGN(4);
*(.init)
*(.fini)
/* Pull all c'tors into .text */
*crtbegin.o(.ctors)
*crtbegin?.o(.ctors)
*(EXCLUDE_FILE(*crtend?.o *crtend.o) .ctors)
*(SORT(.ctors.*))
*(.ctors)
/* Followed by destructors */
*crtbegin.o(.dtors)
*crtbegin?.o(.dtors)
*(EXCLUDE_FILE(*crtend?.o *crtend.o) .dtors)
*(SORT(.dtors.*))
*(.dtors)

*(.eh_frame*)
} > RAM

.rodata : {
. = ALIGN(4);
*(.rodata*)
*(.srodata*)
. = ALIGN(4);
*(SORT_BY_ALIGNMENT(SORT_BY_NAME(.flashdata*)))
. = ALIGN(4);
} > RAM

.ARM.extab :
{
*(.ARM.extab* .gnu.linkonce.armextab.*)
} > RAM

__exidx_start = .;
.ARM.exidx :
{
*(.ARM.exidx* .gnu.linkonce.armexidx.*)
} > RAM
__exidx_end = .;

/* Machine inspectable binary information */
. = ALIGN(4);
__binary_info_start = .;
.binary_info :
{
KEEP(*(.binary_info.keep.*))
*(.binary_info.*)
} > RAM
__binary_info_end = .;
. = ALIGN(4);

.data : {
__data_start__ = .;
*(vtable)
*(.data*)
*(.sdata*)

. = ALIGN(4);
*(.after_data.*)
. = ALIGN(4);
/* preinit data */
PROVIDE_HIDDEN (__mutex_array_start = .);
KEEP(*(SORT(.mutex_array.*)))
KEEP(*(.mutex_array))
PROVIDE_HIDDEN (__mutex_array_end = .);

. = ALIGN(4);
/* preinit data */
PROVIDE_HIDDEN (__preinit_array_start = .);
KEEP(*(SORT(.preinit_array.*)))
KEEP(*(.preinit_array))
PROVIDE_HIDDEN (__preinit_array_end = .);

. = ALIGN(4);
/* init data */
PROVIDE_HIDDEN (__init_array_start = .);
KEEP(*(SORT(.init_array.*)))
KEEP(*(.init_array))
PROVIDE_HIDDEN (__init_array_end = .);

. = ALIGN(4);
/* finit data */
PROVIDE_HIDDEN (__fini_array_start = .);
*(SORT(.fini_array.*))
*(.fini_array)
PROVIDE_HIDDEN (__fini_array_end = .);

*(.jcr)
. = ALIGN(4);
} > RAM

.tdata : {
. = ALIGN(4);
*(.tdata .tdata.* .gnu.linkonce.td.*)
/* All data end */
__tdata_end = .;
} > RAM
PROVIDE(__data_end__ = .);

.uninitialized_data (NOLOAD): {
. = ALIGN(4);
*(.uninitialized_data*)
} > RAM
/* __etext is (for backwards compatibility) the name of the .data init source pointer (...) */
__etext = LOADADDR(.data);

.tbss (NOLOAD) : {
. = ALIGN(4);
__bss_start__ = .;
__tls_base = .;
*(.tbss .tbss.* .gnu.linkonce.tb.*)
*(.tcommon)

__tls_end = .;
} > RAM

.bss (NOLOAD) : {
. = ALIGN(4);
__tbss_end = .;

*(SORT_BY_ALIGNMENT(SORT_BY_NAME(.bss*)))
*(COMMON)
PROVIDE(__global_pointer$ = . + 2K);
*(.sbss*)
. = ALIGN(4);
__bss_end__ = .;
} > RAM

.heap (NOLOAD):
{
__end__ = .;
end = __end__;
KEEP(*(.heap*))
} > RAM
/* historically on GCC sbrk was growing past __HeapLimit to __StackLimit, however
to be more compatible, we now set __HeapLimit explicitly to where the end of the heap is */
__HeapLimit = ORIGIN(RAM) + LENGTH(RAM);

/* Start and end symbols must be word-aligned */
.scratch_x : {
__scratch_x_start__ = .;
*(.scratch_x.*)
. = ALIGN(4);
__scratch_x_end__ = .;
} > SCRATCH_X
__scratch_x_source__ = LOADADDR(.scratch_x);

.scratch_y : {
__scratch_y_start__ = .;
*(.scratch_y.*)
. = ALIGN(4);
__scratch_y_end__ = .;
} > SCRATCH_Y
__scratch_y_source__ = LOADADDR(.scratch_y);

/* .stack*_dummy section doesn't contains any symbols. It is only
* used for linker to calculate size of stack sections, and assign
* values to stack symbols later
*
* stack1 section may be empty/missing if platform_launch_core1 is not used */

/* by default we put core 0 stack at the end of scratch Y, so that if core 1
* stack is not used then all of SCRATCH_X is free.
*/
.stack1_dummy (NOLOAD):
{
*(.stack1*)
} > SCRATCH_X
.stack_dummy (NOLOAD):
{
KEEP(*(.stack*))
} > SCRATCH_Y

/* stack limit is poorly named, but historically is maximum heap ptr */
__StackLimit = ORIGIN(RAM) + LENGTH(RAM);
__StackOneTop = ORIGIN(SCRATCH_X) + LENGTH(SCRATCH_X);
__StackTop = ORIGIN(SCRATCH_Y) + LENGTH(SCRATCH_Y);
__StackOneBottom = __StackOneTop - SIZEOF(.stack1_dummy);
__StackBottom = __StackTop - SIZEOF(.stack_dummy);
PROVIDE(__stack = __StackTop);

/* picolibc and LLVM */
PROVIDE (__heap_start = __end__);
PROVIDE (__heap_end = __HeapLimit);
PROVIDE( __tls_align = MAX(ALIGNOF(.tdata), ALIGNOF(.tbss)) );
PROVIDE( __tls_size_align = (__tls_size + __tls_align - 1) & ~(__tls_align - 1));
PROVIDE( __arm32_tls_tcb_offset = MAX(8, __tls_align) );

/* llvm-libc */
PROVIDE (_end = __end__);
PROVIDE (__llvm_libc_heap_limit = __HeapLimit);

/* Check if data + heap + stack exceeds RAM limit */
ASSERT(__StackLimit >= __HeapLimit, "region RAM overflowed")

ASSERT( __binary_info_header_end - __logical_binary_start <= 1024, "Binary info must be in first 1024 bytes of the binary")
ASSERT( __embedded_block_end - __logical_binary_start <= 4096, "Embedded block must be in first 4096 bytes of the binary")

/* todo assert on extra code */
}
2 changes: 1 addition & 1 deletion main.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -4938,7 +4938,7 @@ bool encrypt_command::execute(device_map &devices) {
enc_elf->read_file(tmp);

// Bootloader size
auto bootloader_txt = enc_elf->get_section(".text");
auto bootloader_txt = enc_elf->get_section(".start_text");
uint32_t bootloader_size = 0x20082000 - bootloader_txt->virtual_address();

// Move bootloader down in physical space to start of SRAM (which will be start of flash once packaged)
Expand Down

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