spi_flash: fix stale read issue for memory mapped partition

On flash program operation (either erase or write), if corresponding address has
cache mapping present then cache is explicitly flushed (for both pro and app cpu)

Closes https://github.com/espressif/esp-idf/issues/2146

components/spi_flash/cache_utils.h

@@ -48,12 +48,10 @@ void spi_flash_disable_interrupts_caches_and_other_cpu_no_os();
 // This function is implied to be called when other CPU is not running or running code from IRAM.
 void spi_flash_enable_interrupts_caches_no_os();
 
-// Mark the pages containing a flash region as having been
-// erased or written to. This means the flash cache needs
-// to be evicted before these pages can be flash_mmap()ed again,
-// as they may contain stale data
-//
+// Flushes cache if address range has corresponding valid cache mappings
+// Recommended to use post flash program operation (erase or write)
 // Only call this while holding spi_flash_op_lock()
-void spi_flash_mark_modified_region(uint32_t start_addr, uint32_t length);
+// Returns true if cache was flushed, false otherwise
+bool spi_flash_check_and_flush_cache(uint32_t start_addr, uint32_t length);
 
 #endif //ESP_SPI_FLASH_CACHE_UTILS_H

components/spi_flash/flash_mmap.c

@@ -47,19 +47,6 @@
 #define VADDR1_FIRST_USABLE_ADDR 0x400D0000
 #define PRO_IRAM0_FIRST_USABLE_PAGE ((VADDR1_FIRST_USABLE_ADDR - VADDR1_START_ADDR) / SPI_FLASH_MMU_PAGE_SIZE + 64)
 
-/* Ensure pages in a region haven't been marked as written via
-   spi_flash_mark_modified_region(). If the page has
-   been written, flush the entire flash cache before returning.
-
-   This ensures stale cache entries are never read after fresh calls
-   to spi_flash_mmap(), while keeping the number of cache flushes to a
-   minimum.
-
-   Returns true if cache was flushed.
-*/
-
-static bool spi_flash_ensure_unmodified_region(size_t start_addr, size_t length);
-
 typedef struct mmap_entry_{
     uint32_t handle;
     int page;
@@ -144,7 +131,7 @@ esp_err_t IRAM_ATTR spi_flash_mmap_pages(const int *pages, size_t page_count, sp
                          const void** out_ptr, spi_flash_mmap_handle_t* out_handle)
 {
     esp_err_t ret;
-    bool did_flush, need_flush = false;
+    bool need_flush = false;
     if (!page_count) {
         return ESP_ERR_INVALID_ARG;
     }
@@ -163,12 +150,6 @@ esp_err_t IRAM_ATTR spi_flash_mmap_pages(const int *pages, size_t page_count, sp
 
     spi_flash_disable_interrupts_caches_and_other_cpu();
 
-    did_flush = 0;
-    for (int i = 0; i < page_count; i++) {
-        if (spi_flash_ensure_unmodified_region(pages[i]*SPI_FLASH_MMU_PAGE_SIZE, SPI_FLASH_MMU_PAGE_SIZE)) {
-            did_flush = 1;
-        }
-    }
     spi_flash_mmap_init();
     // figure out the memory region where we should look for pages
     int region_begin;   // first page to check
@@ -243,7 +224,7 @@ esp_err_t IRAM_ATTR spi_flash_mmap_pages(const int *pages, size_t page_count, sp
        Working on a long term fix that doesn't require invalidating
        entire cache.
     */
-    if (!did_flush && need_flush) {
+    if (need_flush) {
 #if CONFIG_SPIRAM_SUPPORT
         esp_spiram_writeback_cache();
 #endif
@@ -338,71 +319,6 @@ uint32_t IRAM_ATTR spi_flash_mmap_get_free_pages(spi_flash_mmap_memory_t memory)
     return count;
 }
 
-/* 256-bit (up to 16MB of 64KB pages) bitset of all flash pages
-   that have been written to since last cache flush.
-
-   Before mmaping a page, need to flush caches if that page has been
-   written to.
-
-   Note: It's possible to do some additional performance tweaks to
-   this algorithm, as we actually only need to flush caches if a page
-   was first mmapped, then written to, then is about to be mmaped a
-   second time. This is a fair bit more complex though, so unless
-   there's an access pattern that this would significantly boost then
-   it's probably not worth it.
-*/
-static uint32_t written_pages[256/32];
-
-static bool update_written_pages(size_t start_addr, size_t length, bool mark);
-
-void IRAM_ATTR spi_flash_mark_modified_region(size_t start_addr, size_t length)
-{
-    update_written_pages(start_addr, length, true);
-}
-
-static IRAM_ATTR bool spi_flash_ensure_unmodified_region(size_t start_addr, size_t length)
-{
-    return update_written_pages(start_addr, length, false);
-}
-
-/* generic implementation for the previous two functions */
-static inline IRAM_ATTR bool update_written_pages(size_t start_addr, size_t length, bool mark)
-{
-    /* align start_addr & length to full MMU pages */
-    uint32_t page_start_addr = start_addr & ~(SPI_FLASH_MMU_PAGE_SIZE-1);
-    length += (start_addr - page_start_addr);
-    length = (length + SPI_FLASH_MMU_PAGE_SIZE - 1) & ~(SPI_FLASH_MMU_PAGE_SIZE-1);
-    for (uint32_t addr = page_start_addr; addr < page_start_addr + length; addr += SPI_FLASH_MMU_PAGE_SIZE) {
-        int page = addr / SPI_FLASH_MMU_PAGE_SIZE;
-        if (page >= 256) {
-            return false; /* invalid address */
-        }
-
-        int idx = page / 32;
-        uint32_t bit = 1 << (page % 32);
-
-        if (mark) {
-            written_pages[idx] |= bit;
-        } else if (written_pages[idx] & bit) {
-            /* it is tempting to write a version of this that only
-               flushes each CPU's cache as needed. However this is
-               tricky because mmaped memory can be used on un-pinned
-               cores, or the pointer passed between CPUs.
-            */
-#if CONFIG_SPIRAM_SUPPORT
-            esp_spiram_writeback_cache();
-#endif
-            Cache_Flush(0);
-#ifndef CONFIG_FREERTOS_UNICORE
-            Cache_Flush(1);
-#endif
-            bzero(written_pages, sizeof(written_pages));
-            return true;
-        }
-    }
-    return false;
-}
-
 uint32_t spi_flash_cache2phys(const void *cached)
 {
     intptr_t c = (intptr_t)cached;
@@ -464,3 +380,55 @@ const void *IRAM_ATTR spi_flash_phys2cache(uint32_t phys_offs, spi_flash_mmap_me
     spi_flash_enable_interrupts_caches_and_other_cpu();
     return NULL;
 }
+
+static bool IRAM_ATTR is_page_mapped_in_cache(uint32_t phys_page)
+{
+    int start[2], end[2];
+
+    /* SPI_FLASH_MMAP_DATA */
+    start[0] = 0;
+    end[0] = 64;
+
+    /* SPI_FLASH_MMAP_INST */
+    start[1] = PRO_IRAM0_FIRST_USABLE_PAGE;
+    end[1] = 256;
+
+    DPORT_INTERRUPT_DISABLE();
+    for (int j = 0; j < 2; j++) {
+        for (int i = start[j]; i < end[j]; i++) {
+            if (DPORT_SEQUENCE_REG_READ((uint32_t)&DPORT_PRO_FLASH_MMU_TABLE[i]) == phys_page) {
+                DPORT_INTERRUPT_RESTORE();
+                return true;
+            }
+        }
+    }
+    DPORT_INTERRUPT_RESTORE();
+    return false;
+}
+
+/* Validates if given flash address has corresponding cache mapping, if yes, flushes cache memories */
+IRAM_ATTR bool spi_flash_check_and_flush_cache(size_t start_addr, size_t length)
+{
+    /* align start_addr & length to full MMU pages */
+    uint32_t page_start_addr = start_addr & ~(SPI_FLASH_MMU_PAGE_SIZE-1);
+    length += (start_addr - page_start_addr);
+    length = (length + SPI_FLASH_MMU_PAGE_SIZE - 1) & ~(SPI_FLASH_MMU_PAGE_SIZE-1);
+    for (uint32_t addr = page_start_addr; addr < page_start_addr + length; addr += SPI_FLASH_MMU_PAGE_SIZE) {
+        uint32_t page = addr / SPI_FLASH_MMU_PAGE_SIZE;
+        if (page >= 256) {
+            return false; /* invalid address */
+        }
+
+        if (is_page_mapped_in_cache(page)) {
+#if CONFIG_SPIRAM_SUPPORT
+            esp_spiram_writeback_cache();
+#endif
+            Cache_Flush(0);
+#ifndef CONFIG_FREERTOS_UNICORE
+            Cache_Flush(1);
+#endif
+            return true;
+        }
+    }
+    return false;
+}

components/spi_flash/flash_ops.c

@@ -238,6 +238,11 @@ esp_err_t IRAM_ATTR spi_flash_erase_range(uint32_t start_addr, uint32_t size)
         }
     }
     COUNTER_STOP(erase);
+
+    spi_flash_guard_start();
+    spi_flash_check_and_flush_cache(start_addr, size);
+    spi_flash_guard_end();
+
     return spi_flash_translate_rc(rc);
 }
 
@@ -404,9 +409,9 @@ esp_err_t IRAM_ATTR spi_flash_write(size_t dst, const void *srcv, size_t size)
 out:
     COUNTER_STOP(write);
 
-    spi_flash_guard_op_lock();
-    spi_flash_mark_modified_region(dst, size);
-    spi_flash_guard_op_unlock();
+    spi_flash_guard_start();
+    spi_flash_check_and_flush_cache(dst, size);
+    spi_flash_guard_end();
 
     return spi_flash_translate_rc(rc);
 }
@@ -470,9 +475,9 @@ esp_err_t IRAM_ATTR spi_flash_write_encrypted(size_t dest_addr, const void *src,
     COUNTER_ADD_BYTES(write, size);
     COUNTER_STOP(write);
 
-    spi_flash_guard_op_lock();
-    spi_flash_mark_modified_region(dest_addr, size);
-    spi_flash_guard_op_unlock();
+    spi_flash_guard_start();
+    spi_flash_check_and_flush_cache(dest_addr, size);
+    spi_flash_guard_end();
 
     return spi_flash_translate_rc(rc);
 }

components/spi_flash/sim/flash_mock_util.c

@@ -11,9 +11,9 @@ void spi_flash_init(const char* chip_size, size_t block_size, size_t sector_size
     _spi_flash_init(chip_size, block_size, sector_size, page_size, partition_bin);
 }
 
-void spi_flash_mark_modified_region(size_t start_addr, size_t length)
+bool spi_flash_check_and_flush_cache(size_t start_addr, size_t length)
 {
-    return;
+    return true;
 }
 
 esp_rom_spiflash_result_t esp_rom_spiflash_unlock()