blocklevel: smart_write: Fix unaligned writes to ECC partitions

Currently trying to clear a gard record results in errors:

    $ ./opal-gard -pef part create /sys0/node0/proc1
    $ ./opal-gard -pef part list
     ID       | Error    | Type       | Path
    ---------------------------------------------------------
     00000001 | 00000000 | Manual     | /Sys0/Node0/Proc1
    =========================================================
    $ ./opal-gard -pef part clear 00000001
    Clearing gard record 0x00000001...done
    ECC: uncorrectable error: ffffff00ffffffff ff
    libflash ecc invalid
    $

A little wrapper around hexdump(1) helps show where the error lies by grouping
output in blocks of nine such that the last byte is the ECC byte:

    $ declare -f ecchd
    ecchd ()
    {
        hexdump -e '"%08_ax""\t"' -e '9/1 "%02x ""\t""|"' -e '9/1 "%_p""|\n"' "$@"
    }

A clean GARD partition displays as:

    $ ecchd part
    0002c000        ff ff ff ff ff ff ff ff 00      |.........|
    *
    00030ffb        ff ff ff ff ff                  |.....|
    $

Dumping the corrupt partition shows:

    $ ecchd part
    0002c000        ff ff ff ff ff ff ff ff 00      |.........|
    *
    0002c024        ff ff ff ff ff ff ff ff ff      |.........|
    0002c02d        ff ff ff 00 ff ff ff ff ff      |.........|
    *
    0002c051        ff ff ff 00 ff ff ff ff 00      |.........|
    0002c05a        ff ff ff ff ff ff ff ff 00      |.........|
    *
    00030ffb        ff ff ff ff ff                  |.....|
    $

blocklevel_smart_write() turned out to not be quite as smart as it thought it
was in that any unaligned write to ECC protected partitions aligned the
calculated ECC values to the start of the write buffer and not relative to the
start of the partition.

Fixes: 29d1e6f ("libflash/blocklevel: add a smart write function which wraps up eraseing and writing")
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>

external/gard/test/results/11-clear-first.out

@@ -0,0 +1,13 @@
+Clearing the entire gard partition...done
+ ID       | Error    | Type       | Path
+---------------------------------------------------------
+ 00000001 | 00000000 | Manual     | /Sys0/Node0/Proc0
+ 00000002 | 00000000 | Manual     | /Sys0/Node0/Proc1
+=========================================================
+Clearing gard record 0x00000001...done
+ ID       | Error    | Type       | Path
+---------------------------------------------------------
+ 00000002 | 00000000 | Manual     | /Sys0/Node0/Proc1
+=========================================================
+Clearing gard record 0x00000002...done
+No GARD entries to display

external/gard/test/tests/11-clear-first

@@ -0,0 +1,26 @@
+#!/bin/sh
+
+set -e
+
+DATA=$(mktemp)
+
+cleanup() {
+	rm -f $DATA
+}
+
+trap cleanup EXIT
+
+dd if=/dev/zero of=$DATA bs=$((0x1000)) count=5 2>/dev/null
+
+run_binary "./opal-gard" "-p -e -f $DATA clear all"
+run_binary "./opal-gard" "-p -e -f $DATA create /sys0/node0/proc0"
+run_binary "./opal-gard" "-p -e -f $DATA create /sys0/node0/proc1"
+run_binary "./opal-gard" "-p -e -f $DATA list"
+run_binary "./opal-gard" "-p -e -f $DATA clear 00000001"
+run_binary "./opal-gard" "-p -e -f $DATA list"
+run_binary "./opal-gard" "-p -e -f $DATA clear 00000002"
+run_binary "./opal-gard" "-p -e -f $DATA list"
+
+diff_with_result
+
+pass_test

libflash/blocklevel.c

@@ -513,7 +513,7 @@ int blocklevel_smart_write(struct blocklevel_device *bl, uint64_t pos, const voi
 	void *erase_buf = NULL;
 	uint32_t erase_size;
 
-	const void *write_buf = buf;
+	const void *write_buf;
 	uint64_t write_len;
 	uint64_t write_pos;
 
@@ -543,27 +543,46 @@ int blocklevel_smart_write(struct blocklevel_device *bl, uint64_t pos, const voi
 	}
 
 	if (ecc_protection) {
+		uint64_t ecc_pos, ecc_align, ecc_diff, ecc_len;
+
 		FL_DBG("%s: region has ECC\n", __func__);
 
-		len = ecc_buffer_size(len);
+		ecc_pos = with_ecc_pos(ecc_start, pos);
+		ecc_align = ecc_buffer_align(ecc_start, ecc_pos);
+		ecc_diff = ecc_pos - ecc_align;
+		ecc_len = ecc_buffer_size(len + ecc_diff);
 
-		ecc_buf = malloc(len);
+		ecc_buf = malloc(ecc_len);
 		if (!ecc_buf) {
 			errno = ENOMEM;
 			return FLASH_ERR_MALLOC_FAILED;
 		}
 
-		if (memcpy_to_ecc(ecc_buf, buf, ecc_buffer_size_minus_ecc(len))) {
+		if (ecc_diff) {
+			rc = blocklevel_read(bl, ecc_align, ecc_buf, ecc_diff);
+			if (rc) {
+				errno = EBADF;
+				rc = FLASH_ERR_ECC_INVALID;
+				goto out;
+			}
+		}
+
+		rc = memcpy_to_ecc_unaligned(ecc_buf, buf, len, ecc_diff);
+		if (rc) {
 			free(ecc_buf);
 			errno = EBADF;
 			return FLASH_ERR_ECC_INVALID;
 		}
+
 		write_buf = ecc_buf;
+		write_len = ecc_len;
+		write_pos = ecc_pos;
+	} else {
+		write_buf = buf;
+		write_len = len;
+		write_pos = pos;
 	}
 
-	write_pos = pos;
-	write_len = len;
-
 	erase_buf = malloc(erase_size);
 	if (!erase_buf) {
 		errno = ENOMEM;