[flashrom-gerrit] [M] Change in flashrom[master]: flashrom: Check for flash access restricitons write_flash()

[Nikolai Artemiev (Code Review)]

Attention is currently required from: Edward O'Callaghan.

Hello Edward O'Callaghan,

I'd like you to do a code review.
Please visit

https://review.coreboot.org/c/flashrom/+/70516

to review the following change.

Change subject: flashrom: Check for flash access restricitons write_flash()
......................................................................

flashrom: Check for flash access restricitons write_flash()

Make write_flash() skip unwritable regions if
FLASHROM_FLAG_SKIP_UNREADABLE_REGIONS is true. If the flag is false
write operations that include an unwritable region will not write
anything and return an error.

BUG=b:260440773
BRANCH=none
TEST=flashrom -w on dedede (JSL)

Change-Id: Idacf0d5218da9d9929f4877fc7665fe608b87fe0
CoAuthored-by: Edward O'Callaghan 
Signed-off-by: Edward O'Callaghan 
Signed-off-by: Nikolai Artemiev 
---
M flashrom.c
1 file changed, 72 insertions(+), 3 deletions(-)

git pull ssh://review.coreboot.org:29418/flashrom refs/changes/16/70516/1

diff --git a/flashrom.c b/flashrom.c
index 76a2801..7a77845 100644
--- a/flashrom.c
+++ b/flashrom.c
@@ -932,10 +932,58 @@
    return NULL;
 }

-static int write_flash(struct flashctx *flash, const uint8_t *buf, unsigned int start, unsigned int len)
+/*
+ * write_flash - wrapper for flash->write() with additional high-level policy
+ *
+ * @param flash flash chip
+ * @param buf   buffer to write to flash
+ * @param start start address in flash
+ * @param len   number of bytes to write
+ * @return      0 on success,
+ *              -1 if any write fails.
+ *
+ * This wrapper simplifies most cases when the flash chip needs to be written
+ * since policy decisions such as non-fatal error handling is centralized.
+ */
+static int write_flash(struct flashctx *flash, const uint8_t *buf,
+		       unsigned int start, unsigned int len)
 {
-	write_func_t *write_func = lookup_write_func_ptr(flash->chip);
-	return write_func(flash, buf, start, len);
+	unsigned int write_len;
+	for (unsigned int addr = start; addr < start + len; addr += write_len) {
+		struct flash_region region;
+		get_flash_region(flash, addr, &region);
+
+		write_len = min(start + len, region.end) - addr;
+		const uint8_t *rbuf = buf + addr - start;
+
+		if (region.write_prot) {
+			if (flash->flags.skip_unwritable_regions) {
+				msg_gdbg("%s: cannot write inside %s region (%#08x..%#08x), skipping (%#08x..%#08x).\n",
+					 __func__, region.name, region.start, region.end - 1, addr, addr + write_len - 1);
+				continue;
+			} else {
+				msg_gerr("%s: cannot write inside %s region (%#08x..%#08x).\n",
+					 __func__, region.name, region.start, region.end - 1);
+				free(region.name);
+				return -1;
+			}
+		}
+
+		msg_gdbg("%s: %s region (%#08x..%#08x) is writable, writing range (%#08x..%#08x).\n",
+			 __func__, region.name, region.start, region.end - 1, addr, addr + write_len - 1);
+
+		write_func_t *write_func = lookup_write_func_ptr(flash->chip);
+		int ret = write_func(flash, rbuf, addr, write_len);
+		if (ret) {
+			msg_gerr("%s: failed to write (%#08x..%#08x).\n", __func__, addr, addr + write_len - 1);
+			free(region.name);
+			return -1;
+		}
+
+		free(region.name);
+	}
+
+	return 0;
 }

typedef int (probe_func_t)(struct flashctx *flash);