[PATCH v4 1/2] fs: semihosting: Fixup smh_read against overflow

[Andrew Goodbody]

The sys call SYS_READ was being used in a way that did not allow for
file sizes > 2^31. Fixing this required changing the signature of the
function to allow file sizes up to 2^32 - 2 and also being able to
return errors that could be tested for.

Signed-off-by: Andrew Goodbody <andrew.goodbody at linaro.org>
---
 common/spl/spl_semihosting.c        |  7 ++++---
 drivers/serial/serial_semihosting.c |  6 ++++--
 fs/semihostingfs.c                  |  9 +++++----
 include/semihosting.h               |  8 ++++----
 lib/semihosting.c                   | 22 ++++++++++++++++++----
 5 files changed, 35 insertions(+), 17 deletions(-)

diff --git a/common/spl/spl_semihosting.c b/common/spl/spl_semihosting.c
index f36863fe48d25859ee9af67a67140893b6e9e262..cff6f5351e265136b3effe483fd5d641fdd109f8 100644
--- a/common/spl/spl_semihosting.c
+++ b/common/spl/spl_semihosting.c
@@ -13,13 +13,14 @@ static ulong smh_fit_read(struct spl_load_info *load, ulong file_offset,
 			  ulong size, void *buf)
 {
 	long fd = *(long *)load->priv;
-	ulong ret;
+	long ret;
+	size_t bytes_read;
 
 	if (smh_seek(fd, file_offset))
 		return 0;
 
-	ret = smh_read(fd, buf, size);
-	return ret < 0 ? 0 : ret;
+	ret = smh_read(fd, buf, size, &bytes_read);
+	return ret < 0 ? 0 : bytes_read;
 }
 
 static int spl_smh_load_image(struct spl_image_info *spl_image,
diff --git a/drivers/serial/serial_semihosting.c b/drivers/serial/serial_semihosting.c
index 56a5ec72428afdd97eccad739a46189380ba3e76..017b1f8eda84f5c25e09be7e970d0ebfdbf2ace0 100644
--- a/drivers/serial/serial_semihosting.c
+++ b/drivers/serial/serial_semihosting.c
@@ -25,11 +25,12 @@ static int smh_serial_getc(struct udevice *dev)
 {
 	char ch = 0;
 	struct smh_serial_priv *priv = dev_get_priv(dev);
+	size_t bytes_read;
 
 	if (priv->infd < 0)
 		return smh_getc();
 
-	smh_read(priv->infd, &ch, sizeof(ch));
+	smh_read(priv->infd, &ch, sizeof(ch), &bytes_read);
 	return ch;
 }
 
@@ -140,11 +141,12 @@ static void smh_serial_setbrg(void)
 static int smh_serial_getc(void)
 {
 	char ch = 0;
+	size_t bytes_read;
 
 	if (infd < 0)
 		return smh_getc();
 
-	smh_read(infd, &ch, sizeof(ch));
+	smh_read(infd, &ch, sizeof(ch), &bytes_read);
 	return ch;
 }
 
diff --git a/fs/semihostingfs.c b/fs/semihostingfs.c
index 77e39ca407e4d240a1fd573497c5b6b908816454..15f58d578b65f7dbbadce19093546f5bdb46c0c3 100644
--- a/fs/semihostingfs.c
+++ b/fs/semihostingfs.c
@@ -23,7 +23,8 @@ int smh_fs_set_blk_dev(struct blk_desc *rbdd, struct disk_partition *info)
 static int smh_fs_read_at(const char *filename, loff_t pos, void *buffer,
 			  loff_t maxsize, loff_t *actread)
 {
-	long fd, size, ret;
+	long fd, ret;
+	size_t size;
 
 	fd = smh_open(filename, MODE_READ | MODE_BINARY);
 	if (fd < 0)
@@ -43,10 +44,10 @@ static int smh_fs_read_at(const char *filename, loff_t pos, void *buffer,
 		maxsize = size;
 	}
 
-	size = smh_read(fd, buffer, maxsize);
+	ret = smh_read(fd, buffer, maxsize, &size);
 	smh_close(fd);
-	if (size < 0)
-		return size;
+	if (ret < 0)
+		return ret;
 
 	*actread = size;
 	return 0;
diff --git a/include/semihosting.h b/include/semihosting.h
index 4e844cbad87bb1ae6bb365f87f3e7a8aeea445f4..42832d86c711ff04e91b6b739c80629253f6d30a 100644
--- a/include/semihosting.h
+++ b/include/semihosting.h
@@ -95,12 +95,12 @@ long smh_open(const char *fname, enum smh_open_mode mode);
  * @fd: A file descriptor returned from smh_open()
  * @memp: Pointer to a buffer of memory of at least @len bytes
  * @len: The number of bytes to read
+ * @read_len: Pointer which will be updated with actual bytes read on success,
+ *  with 0 indicating %EOF
  *
- * Return:
- * * The number of bytes read on success, with 0 indicating %EOF
- * * A negative error on failure
+ * Return: 0 on success or negative error on failure
  */
-long smh_read(long fd, void *memp, size_t len);
+long smh_read(long fd, void *memp, size_t len, size_t *read_len);
 
 /**
  * smh_write() - Write data to a file
diff --git a/lib/semihosting.c b/lib/semihosting.c
index 9be5bffd30124777c4f8110065e6cca5640312ac..e49b16b0aa34ab04b6c8949a3e7cab539fdbef82 100644
--- a/lib/semihosting.c
+++ b/lib/semihosting.c
@@ -93,9 +93,9 @@ struct smh_rdwr_s {
 	size_t len;
 };
 
-long smh_read(long fd, void *memp, size_t len)
+long smh_read(long fd, void *memp, size_t len, size_t *read_len)
 {
-	long ret;
+	size_t ret;
 	struct smh_rdwr_s read;
 
 	debug("%s: fd %ld, memp %p, len %zu\n", __func__, fd, memp, len);
@@ -105,9 +105,23 @@ long smh_read(long fd, void *memp, size_t len)
 	read.len = len;
 
 	ret = smh_trap(SYSREAD, &read);
-	if (ret < 0)
+	if (!ret) {
+		/* Success */
+		*read_len = len;
+		return 0;
+	} else if (ret == len) {
+		/* EOF */
+		*read_len = 0;
+		return 0;
+	} else if ((long)ret == -1) {
+		*read_len = 0;
 		return smh_errno();
-	return len - ret;
+	} else {
+		/* Partial success */
+		*read_len = len - ret;
+		return 0;
+	}
+
 }
 
 long smh_write(long fd, const void *memp, size_t len, ulong *written)

-- 
2.47.3