/*
* Copyright (c) 2012 Apple Inc. All rights reserved.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. The rights granted to you under the License
* may not be used to create, or enable the creation or redistribution of,
* unlawful or unlicensed copies of an Apple operating system, or to
* circumvent, violate, or enable the circumvention or violation of, any
* terms of an Apple operating system software license agreement.
*
* Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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* Please see the License for the specific language governing rights and
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*/
#if ALTERNATE_DEBUGGER
/*
*
* The alternate debugger feature is enabled by setting the boot arg "alternate_debugger_init"
* to the size of memory that should be set aside for the debugger. The boot arg
* "alternate_debugger_init_pages" is used to allocate more vmpages that the alternate debugger
* may use to do additional VA->PA mappings. The boot-arg "alternate_debugger_pause_for_load_at_boot"
* will halt the system so that the debugger can be loaded early in the boot cycle -- once the
* alternate debugger code is loaded, a register must be set to a 1 to continue the boot process.
*
* Here's an example:
* nvram boot-arg="alternate_debugger_init=0x800000 alternate_debugger_init_pages=0x8000 alternate_debugger_pause_for_load_at_boot=1"
*
* The low memory global lgAltDebugger will contain the address of the allocated memory for
* the alternate debugger. On arm64, the address of this low memory global is 0xffffff8000002048.
*
* At any point after the low memory global is non-zero, Astris may be used to halt the cpu
* and load the alternate debugger:
*
* If no alternate debugger is given, but alternate_debugger_init has been specified, and the
* kernel debugger is entered, the string ">MT<" is printed and normal processing continues.
*
* Anytime the alternate debugger is entered, the osversion string is modified to start with "ALT"
* so that panic reports can clearly indicated that some kernel poking may have occurred, and
* the panic should be weighted accordingly.
*
*/
#include <arm64/alternate_debugger.h>
#include <kern/kalloc.h>
#include <arm64/lowglobals.h>
#include <arm/caches_internal.h>
#include <kern/cpu_data.h>
#include <arm/pmap.h>
#include <pexpert/pexpert.h>
#include <vm/vm_map_xnu.h>
#include <vm/vm_kern_xnu.h>
#include <libkern/version.h>
void kprintf(const char *fmt, ...);
static mach_vm_address_t alt_code;
static mach_vm_size_t alt_size;
static mach_vm_address_t alt_pages;
static mach_vm_size_t alt_pages_size;
typedef void (*t_putc_fn)(char c);
typedef void (*t_call_altdbg_fn)(mach_vm_size_t size, mach_vm_address_t pages, mach_vm_size_t pages_size, t_putc_fn putc_address );
// used as a temporary alternate debugger until another is loaded
extern void alternate_debugger_just_return(__unused mach_vm_size_t size, __unused mach_vm_address_t pages, __unused mach_vm_size_t pages_size, t_putc_fn putc_address);
extern void *alternate_debugger_just_return_end;
// public entry to the alternate debugger
void
alternate_debugger_enter(void)
{
if (alt_code != 0) {
disable_preemption();
printf("########## Going to call ALTERNATE DEBUGGER\n");
// make sure it isn't in the cache
assert((alt_size & 0xFFFFFFFF00000000) == 0);
flush_dcache(alt_code, (unsigned int)alt_size, 0);
// set the code to execute
pmap_protect(kernel_map->pmap, alt_code, alt_code + alt_size, VM_PROT_READ | VM_PROT_EXECUTE);
// black-spot the OS version for any panic reports that occur because of entering the alternate debugger
if (*osversion) {
memcpy(osversion, "ALT", 3); // Version set, stomp on the begining of it
} else {
strncpy(osversion, "ALT - Version Not Set Yet", OSVERSIZE);
}
kprintf("########## Calling ALTERNATE DEBUGGER (size %lld, pages 0x%llx, pages_size 0x%llx, putc %p\n", alt_size, alt_pages, alt_pages_size, &consdebug_putc_unbuffered);
((t_call_altdbg_fn)alt_code)(alt_size, alt_pages, alt_pages_size, &consdebug_putc_unbuffered);
kprintf("########## Returned from calling ALTERNATE DEBUGGER\n");
enable_preemption();
}
}
// public entry to check boot args and init accordingly
void
alternate_debugger_init(void)
{
// use the alternate debugger
if (PE_parse_boot_argn("alternate_debugger_init", (void*)&alt_size, sizeof(alt_size))) {
vm_offset_t alt_va = 0;
kprintf("########## ALTERNATE_DEBUGGER\n");
PE_parse_boot_argn("alternate_debugger_init_pages", (void*)&alt_pages_size, sizeof(alt_pages_size));
alt_size = vm_map_round_page(alt_size,
VM_MAP_PAGE_MASK(kernel_map));
alt_pages_size = vm_map_round_page(alt_pages_size,
VM_MAP_PAGE_MASK(kernel_map));
kern_return_t kr = KERN_SUCCESS;
kr = kmem_alloc_contig(kernel_map, &alt_va, alt_size,
VM_MAP_PAGE_MASK(kernel_map), 0, 0,
KMA_NOPAGEWAIT | KMA_KOBJECT | KMA_LOMEM | KMA_PERMANENT,
VM_KERN_MEMORY_DIAG);
if (kr != KERN_SUCCESS) {
kprintf("########## ALTERNATE_DEBUGGER FAILED kmem_alloc_contig with %d\n", kr);
alt_va = 0;
} else {
if (alt_pages_size) {
alt_pages = (vm_offset_t)zalloc_permanent(alt_pages_size, ZALIGN_PTR);
}
}
kprintf("########## Initializing ALTERNATE DEBUGGER : [alloc size 0x%llx @0x%lx] [pages_size 0x%llx @0x%llx] -- lowmem pointer at %p\n",
alt_size, alt_va, alt_pages_size, alt_pages, &lowGlo.lgAltDebugger );
if (alt_va) {
uintptr_t just_return_size = (uintptr_t)&alternate_debugger_just_return_end - (uintptr_t)&alternate_debugger_just_return;
assert(just_return_size <= alt_size); // alt_size is page-rounded, just_return_size should be much less than a page.
// install a simple return vector
memcpy((void*)alt_va, (const void *)&alternate_debugger_just_return, just_return_size);
// code is ready, enable the pointers to it
lowGlo.lgAltDebugger = alt_code = alt_va;
#if 1
// DEBUG for BRING-UP testing
unsigned int alt_init_test;
if (PE_parse_boot_argn("alternate_debugger_pause_for_load_at_boot", &alt_init_test, sizeof(alt_init_test))) {
// debug!!
kprintf("########## Waiting for ALTERNATE DEBUGGER to load (in file %s).... to continue, set register to 1", __FILE__ );
volatile int ii = 0;
while (!ii) {
;
}
kprintf("\n");
alternate_debugger_enter();
}
#endif
}
}
}
#endif /* ALTERNATE_DEBUGGER */