flash_storage: add key-value flash storage support

soc/runtime/flash_storage.c

@@ -0,0 +1,173 @@
+/*
+ * Yann Sionneau <ys@m-labs.hk>, 2015
+ */
+
+#include <spiflash.h>
+#include <string.h>
+#include <generated/flash_geometry.h>
+#include <generated/mem.h>
+#include <system.h>
+#include "flash_storage.h"
+
+#define STORAGE_ADDRESS ((char *)(FLASH_BOOT_ADDRESS + 128*1024))
+#define STORAGE_SIZE    SECTOR_SIZE
+#define END_MARKER      (0xFFFFFFFF)
+
+#define min(a, b) (a>b?b:a)
+#define max(a, b) (a>b?a:b)
+
+#define goto_next_record(buff,addr) do { \
+        unsigned int key_size = strlen(&buff[addr])+1; \
+        if (key_size % 4) \
+            key_size += 4 - (key_size % 4); \
+        unsigned int *buflen_p = (unsigned int *)&buff[addr + key_size]; \
+        unsigned int buflen = *buflen_p; \
+        if (buflen % 4) \
+            buflen += 4 - (buflen % 4); \
+        addr += key_size + sizeof(int) + buflen; \
+    } while (0);
+
+union seek {
+    unsigned int integer;
+    char bytes[4];
+};
+
+char sector_buff[STORAGE_SIZE];
+
+static void write_at_offset(char *key, void *buffer, int buflen, unsigned int sector_offset);
+static char key_exists(char *buff, char *key, char *end);
+static char check_for_duplicates(char *buff);
+static unsigned int try_to_flush_duplicates(void);
+
+static char key_exists(char *buff, char *key, char *end)
+{
+    unsigned int addr;
+
+    for(addr = 0; &buff[addr] < end && *(unsigned int*)&buff[addr] != END_MARKER;) {
+        if(strcmp(&buff[addr], key) == 0)
+            return 1;
+        goto_next_record(buff, addr);
+    }
+    return 0;
+}
+
+static char check_for_duplicates(char *buff)
+{
+    unsigned int addr;
+    char *key_name;
+
+    for(addr = 0; addr < STORAGE_SIZE && *(unsigned int *)&buff[addr] != END_MARKER;) {
+        key_name = &buff[addr];
+        goto_next_record(buff, addr);
+        if(key_exists(&buff[addr], key_name, &buff[STORAGE_SIZE]))
+            return 1;
+    }
+
+    return 0;
+}
+
+static unsigned int try_to_flush_duplicates(void)
+{
+    unsigned int addr, i, key_size, buflen;
+    char *key_name, *last_duplicate;
+    union seek *seeker = (union seek *)sector_buff;
+
+    memcpy(sector_buff, STORAGE_ADDRESS, STORAGE_SIZE);
+    if(check_for_duplicates(sector_buff)) {
+        erase_flash_sector((unsigned int)STORAGE_ADDRESS);
+        flush_cpu_dcache();
+        for(addr = 0; addr < STORAGE_SIZE && seeker[addr >> 2].integer != END_MARKER;) {
+            key_name = &sector_buff[addr];
+            key_size = strlen(key_name)+1;
+            if(key_size % 4)
+                key_size += 4 - (key_size % 4);
+            if(!key_exists((char *)STORAGE_ADDRESS, key_name, STORAGE_ADDRESS+STORAGE_SIZE)) {
+                last_duplicate = key_name;
+                for(i = addr; i < STORAGE_SIZE;) {
+                    goto_next_record(sector_buff, i);
+                    if(strcmp(&sector_buff[i], key_name) == 0)
+                        last_duplicate = &sector_buff[i];
+                }
+                buflen = *(unsigned int *)&last_duplicate[key_size];
+                write(key_name, &last_duplicate[key_size+sizeof(int)], buflen);
+            }
+            goto_next_record(sector_buff, addr);
+        }
+        return 0;
+    } else
+        return 1;
+}
+
+static void write_at_offset(char *key, void *buffer, int buflen, unsigned int sector_offset)
+{
+    int key_len = strlen(key) + 1;
+    int key_len_alignment = 0, buflen_alignment = 0;
+    unsigned char padding[3] = {0, 0, 0};
+
+    if(key_len % 4)
+        key_len_alignment = 4 - (key_len % 4);
+
+    if(buflen % 4)
+        buflen_alignment = 4 - (buflen % 4);
+
+    write_to_flash(sector_offset, (unsigned char *)key, key_len);
+    write_to_flash(sector_offset+key_len, padding, key_len_alignment);
+    write_to_flash(sector_offset+key_len+key_len_alignment, (unsigned char *)&buflen, sizeof(buflen));
+    write_to_flash(sector_offset+key_len+key_len_alignment+sizeof(buflen), buffer, buflen);
+    write_to_flash(sector_offset+key_len+key_len_alignment+sizeof(buflen)+buflen, padding, buflen_alignment);
+}
+
+
+void write(char *key, void *buffer, unsigned int buflen)
+{
+    char *addr;
+    unsigned int key_size = strlen(key)+1;
+    unsigned int record_size = key_size + sizeof(int) + buflen;
+
+    for(addr = STORAGE_ADDRESS; addr < STORAGE_ADDRESS + STORAGE_SIZE - record_size; addr += 4) {
+        if(*(unsigned int *)addr == END_MARKER) {
+            write_at_offset(key, buffer, buflen, (unsigned int)addr);
+            flush_cpu_dcache();
+            break;
+        }
+    }
+    if(addr >= STORAGE_ADDRESS + STORAGE_SIZE - record_size) { // Flash is full? Try to flush duplicates.
+        if(try_to_flush_duplicates())
+            return; // No duplicates found, cannot write the new key-value record: sector is full.
+
+        // Now retrying to write, hoping enough flash was freed.
+        for(addr = STORAGE_ADDRESS; addr < STORAGE_ADDRESS + STORAGE_SIZE - record_size; addr += 4) {
+            if(*(unsigned int *)addr == END_MARKER) {
+                write_at_offset(key, buffer, buflen, (unsigned int)addr);
+                flush_cpu_dcache();
+                break;
+            }
+        }
+    }
+}
+
+unsigned int read(char *key, void *buffer, unsigned int buflen, unsigned int *remain)
+{
+    unsigned int read_length = 0;
+    char *addr;
+
+    for(addr = STORAGE_ADDRESS; addr < (STORAGE_ADDRESS + STORAGE_SIZE) && (*addr != END_MARKER);) {
+        unsigned int key_len, value_len;
+        char *key_addr = addr;
+        key_len = strlen(addr) + 1;
+        if(key_len % 4)
+            key_len += 4 - (key_len % 4);
+        addr += key_len;
+        value_len = *(unsigned int *)addr;
+        addr += sizeof(value_len);
+        if(strcmp(key_addr, key) == 0) {
+            memcpy(buffer, addr, min(value_len, buflen));
+            read_length = min(value_len, buflen);
+            *remain = max(0, (int)value_len - (int)buflen);
+        }
+        addr += value_len;
+        if((int)addr % 4)
+            addr += 4 - ((int)addr % 4);
+    }
+    return read_length;
+}

soc/runtime/flash_storage.h

@@ -0,0 +1,11 @@
+/*
+ * Yann Sionneau <ys@m-labs.hk>, 2015
+ */
+
+#ifndef __FLASH_STORAGE_H
+#define __FLASH_STORAGE_H
+
+void write(char *key, void *buffer, unsigned int buflen);
+unsigned int read(char *key, void *buffer, unsigned int buflen, unsigned int *remain);
+
+#endif /* __FLASH_STORAGE_H */