casaroli commented on code in PR #21354:
URL: https://github.com/apache/nuttx/pull/21354#discussion_r4467817014
##########
drivers/misc/dev_mem.c:
##########
@@ -96,21 +97,20 @@ static ssize_t devmem_read(FAR struct file *filep, FAR char
*buffer,
size_t buflen)
{
FAR struct memory_region_s *region = filep->f_inode->i_private;
- uintptr_t src = filep->f_pos;
uintptr_t start;
uintptr_t end;
ssize_t len;
int i;
for (i = 0; region[i].start != 0 && region[i].end != 0; i++)
{
- start = MAX(src, region[i].start);
+ start = region[i].start + filep->f_pos;
Review Comment:
Run on qemu-armv8a:nsh with CONFIG_DEV_MEM=y. On master, lseek() to an
address in .text, .data or .bss then read() returns that memory, and a
sequential read returns all three regions (374328 bytes). With this PR each of
those read() calls returns -EINVAL and the sequential read stops after .text
(303104 bytes), so .data and .bss cannot be read. mmap() still uses absolute
addresses. Correction to my earlier comment: write(0) then read(0) giving
different memory is also in master.
Fix: keep `f_pos` as the absolute address, as in master and in mmap(), and
only add the SEEK_END case if you need it.
##########
drivers/misc/dev_mem.c:
##########
@@ -66,6 +66,7 @@ static ssize_t devmem_read(FAR struct file *filep, FAR char
*buffer,
size_t buflen);
static ssize_t devmem_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen);
+static off_t devmem_seek(FAR struct file *filep, off_t offset, int whence);
Review Comment:
With CONFIG_DEV_MEM=y this file does not compile on qemu-armv8a:nsh, on this
head or on master: `struct file` is an incomplete type because <nuttx/fs/fs.h>
is not included. So the `dd` test in the PR body does not build on this tree.
Fix: add <nuttx/fs/fs.h>, <nuttx/mm/map.h>, <errno.h> and <string.h> here;
with these it builds and runs.
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