This adds functionality to map pages dynamically into kernel virtual
memory. This allows implementing I/O remap for example, which is a useful
(future) feature.
Now, the first target is to support mapping user pages for the kernel.
Why? There are some userspace structures that might be needed when the
userspace process is not running. Semaphores are one such example. Signals
and the WDT timeout both need access to the user semaphore to work
properly. Even though for this only obtaining the kernel addressable
page pool virtual address is needed, for completeness a procedure is
provided to map several pages.
Add a new field to record the global on the basis of mm_backtrace.
When using alloc, the field is incremented by 1,
so that the memory usage can be dumped within the range
Signed-off-by: anjiahao <anjiahao@xiaomi.com>
This change introduce 2 items:
1. If the size of the space requested is 0, the behavior is implementation-defined:
either a null pointer shall be returned, or the behavior shall be as if the size
were some non-zero value, except that the behavior is undefined if the returned
pointer is used to access an object.
Change the behavior to be similar to Linux and Android and allocates an object
of a minimum size instead of returning null pointer.
https://pubs.opengroup.org/onlinepubs/9699919799/functions/malloc.htmlhttps://pubs.opengroup.org/onlinepubs/9699919799/functions/calloc.htmlhttps://pubs.opengroup.org/onlinepubs/9699919799/functions/realloc.html
2. The description of realloc() has been modified from previous versions of this
standard to align with the ISO/IEC 9899:1999 standard. Previous versions explicitly
permitted a call to realloc (p, 0) to free the space pointed to by p and return
a null pointer. While this behavior could be interpreted as permitted by this
version of the standard, the C language committee have indicated that this
interpretation is incorrect. Applications should assume that if realloc() returns
a null pointer, the space pointed to by p has not been freed. Since this could lead
to double-frees, implementations should also set errno if a null pointer actually
indicates a failure, and applications should only free the space if errno was changed.
Do not free memory of zero-length reallocation is requested
https://pubs.opengroup.org/onlinepubs/9699919799/functions/realloc.html
Co-authored-by: fangxinyong <fangxinyong@xiaomi.com>
Signed-off-by: Petro Karashchenko <petro.karashchenko@gmail.com>
Use double delim to fix windows native build and give an error:
makefile:132: *** target mode do not include“%”. stop.
In Windows environment DELIM := $(strip \) but \ has two role:
first: \ as directory, and second \ as Escape character, Reference:
https://github.com/apache/nuttx/pull/7572#discussion_r1028219229
Signed-off-by: chao an <anchao@xiaomi.com>
We don't want to get a NULL pointer after iob_pack on an IOB chain with
several iobs with length 0, it should return one IOB with length 0.
Otherwise each place calls iob_pack needs to check the result.
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
This way the mappings can be modified for any vm area, not only the
process that is running.
Why? This allows mapping pages to kernel dynamically, this functionality
will be presented later.
