lib/cgptlib/cgptlib.c

/* Copyright 2013 The ChromiumOS Authors
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "2common.h"
#include "2sysincludes.h"
#include "cgptlib.h"
#include "cgptlib_internal.h"
#include "crc32.h"
#include "gpt.h"
#include "vboot_api.h"

int GptInit(GptData *gpt)
{
	int retval;

	gpt->modified = 0;
	gpt->current_kernel = CGPT_KERNEL_ENTRY_NOT_FOUND;
	gpt->current_priority = 999;

	retval = GptValidityCheck(gpt);
	if (GPT_SUCCESS != retval) {
		VB2_DEBUG("GptInit() failed validity check\n");
		return retval;
	}

	GptRepair(gpt);
	return GPT_SUCCESS;
}

GptEntry *GptNextKernelEntry(GptData *gpt)
{
	GptHeader *header = (GptHeader *)gpt->primary_header;
	GptEntry *entries = (GptEntry *)gpt->primary_entries;
	GptEntry *e;
	int new_kernel = CGPT_KERNEL_ENTRY_NOT_FOUND;
	int new_prio = 0;
	uint32_t i;

	/*
	 * If we already found a kernel, continue the scan at the current
	 * kernel's priority, in case there is another kernel with the same
	 * priority.
	 */
	if (gpt->current_kernel != CGPT_KERNEL_ENTRY_NOT_FOUND) {
		for (i = gpt->current_kernel + 1;
		     i < header->number_of_entries; i++) {
			e = entries + i;
			if (!IsKernelEntry(e))
				continue;
			VB2_DEBUG("GptNextKernelEntry looking at same prio "
				  "partition %d\n", i+1);
			VB2_DEBUG("GptNextKernelEntry s%d t%d p%d\n",
				  GetEntrySuccessful(e), GetEntryTries(e),
				  GetEntryPriority(e));
			if (!(GetEntrySuccessful(e) || GetEntryTries(e)))
				continue;
			if (GetEntryPriority(e) == gpt->current_priority) {
				gpt->current_kernel = i;
				VB2_DEBUG("GptNextKernelEntry likes it\n");
				return e;
			}
		}
	}

	/*
	 * We're still here, so scan for the remaining kernel with the highest
	 * priority less than the previous attempt.
	 */
	for (i = 0, e = entries; i < header->number_of_entries; i++, e++) {
		int current_prio = GetEntryPriority(e);
		if (!IsKernelEntry(e))
			continue;
		VB2_DEBUG("GptNextKernelEntry looking at new prio "
			  "partition %d\n", i+1);
		VB2_DEBUG("GptNextKernelEntry s%d t%d p%d\n",
			  GetEntrySuccessful(e), GetEntryTries(e),
			  GetEntryPriority(e));
		if (!(GetEntrySuccessful(e) || GetEntryTries(e)))
			continue;
		if (current_prio >= gpt->current_priority) {
			/* Already returned this kernel in a previous call */
			continue;
		}
		if (current_prio > new_prio) {
			new_kernel = i;
			new_prio = current_prio;
		}
	}

	/*
	 * Save what we found.  Note that if we didn't find a new kernel,
	 * new_prio will still be -1, so future calls to this function will
	 * also fail.
	 */
	gpt->current_kernel = new_kernel;
	gpt->current_priority = new_prio;

	if (CGPT_KERNEL_ENTRY_NOT_FOUND == new_kernel) {
		VB2_DEBUG("GptNextKernelEntry no more kernels\n");
		return NULL;
	}

	VB2_DEBUG("GptNextKernelEntry likes partition %d\n", new_kernel + 1);
	e = entries + new_kernel;
	return e;
}

/*
 * Func: GptUpdateKernelWithEntry
 * Desc: This function updates the given kernel entry according to the provided
 * update_type.
 */
int GptUpdateKernelWithEntry(GptData *gpt, GptEntry *e, uint32_t update_type)
{
	int modified = 0;

	if (!IsKernelEntry(e))
		return GPT_ERROR_INVALID_UPDATE_TYPE;

	switch (update_type) {
	case GPT_UPDATE_ENTRY_TRY: {
		/* Used up a try */
		int tries;
		if (GetEntrySuccessful(e)) {
			/*
			 * Successfully booted this partition, so tries field
			 * is ignored.
			 */
			return GPT_SUCCESS;
		}
		tries = GetEntryTries(e);
		if (tries > 1) {
			/* Still have tries left */
			modified = 1;
			SetEntryTries(e, tries - 1);
			break;
		}
		/* Out of tries, so drop through and mark partition bad. */
		VBOOT_FALLTHROUGH;
	}
	case GPT_UPDATE_ENTRY_BAD: {
		/* Giving up on this partition entirely. */
		if (!GetEntrySuccessful(e)) {
			/*
			 * Only clear tries and priority if the successful bit
			 * is not set.
			 */
			modified = 1;
			SetEntryTries(e, 0);
			SetEntryPriority(e, 0);
		}
		break;
	}
	case GPT_UPDATE_ENTRY_ACTIVE: {
		/*
		 * Used for fastboot mode. If kernel partition slot is marked
		 * active, its GPT entry is marked with S1,P2,T0.
		 */
		modified = 1;
		SetEntryTries(e, 0);
		SetEntryPriority(e, 2);
		SetEntrySuccessful(e, 1);
		break;
	}
	case GPT_UPDATE_ENTRY_INVALID: {
		/*
		 * Used for fastboot mode. If kernel partition slot is marked
		 * invalid, its GPT entry is marked with S0,P0,T0
		 */
		modified = 1;
		SetEntryTries(e, 0);
		SetEntryPriority(e, 0);
		SetEntrySuccessful(e, 0);
		break;
	}
	default:
		return GPT_ERROR_INVALID_UPDATE_TYPE;
	}

	if (modified) {
		GptModified(gpt);
	}

	return GPT_SUCCESS;
}

/*
 * Func: GptUpdateKernelEntry
 * Desc: This function updates current_kernel entry with provided
 * update_type. If current_kernel is not set, then it returns error.
 */
int GptUpdateKernelEntry(GptData *gpt, uint32_t update_type)
{
	GptEntry *entries = (GptEntry *)gpt->primary_entries;
	GptEntry *e = entries + gpt->current_kernel;

	if (gpt->current_kernel == CGPT_KERNEL_ENTRY_NOT_FOUND)
		return GPT_ERROR_INVALID_UPDATE_TYPE;

	return GptUpdateKernelWithEntry(gpt, e, update_type);
}

/*
 * Func: GptFindNthEntry
 * Desc: This function returns the nth instance of parition entry matching the
 * partition type guid from the gpt table. Instance value starts from 0. If the
 * entry is not found it returns NULL.
 */
GptEntry *GptFindNthEntry(GptData *gpt, const Guid *guid, unsigned int n)
{
	GptHeader *header = (GptHeader *)gpt->primary_header;
	GptEntry *entries = (GptEntry *)gpt->primary_entries;
	GptEntry *e;
	int i;

	for (i = 0, e = entries; i < header->number_of_entries; i++, e++) {
		if (!memcmp(&e->type, guid, sizeof(*guid))) {
			if (n == 0)
				return e;
			n--;
		}
	}

	return NULL;
}