The struct z_page_frame is marked __packed to avoid extra padding as
such padding may represent significant memory waste when lots of page
frames are used. However this is a bad strategy.
The code contained this somewhat dubious comment and code in
free_page_frame_list_put():
/* The structure is packed, which ensures that this is true */
void *node = pf;
sys_slist_append(&free_page_frame_list, node);
This is bad for many reasons:
- type checking is completely bypassed;
- if the sys_snode_t node member is no longer located at the front of
struct z_page_frame then the code will still compile and possibly run
but be broken with memory corruption as a likely outcome;
- the sys_slist_append() code is completely unaware of the packed
attribute which breaks architectures with alignment restrictions.
Let's improve code efficiency as well as memory usage by removing the
packed attribute and manually packing the flags in the unused virtual
address bits. This way the page frame array remains naturally aligned,
data access becomes optimal and the actual array size gets even smaller.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Introduce z_page_frame_set() and z_page_frame_clear() to manipulate
flags. Obtain the virtual address using the existing
z_page_frame_to_virt(). This will make changes to the page frame
structure easier.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
- modified parameter types to receive a const pointer when a
non-const pointer is not needed
- avoided redundant casts
Signed-off-by: Hess Nathan <nhess@baumer.com>
Add a closing comment to the endif with the configuration
information to which the endif belongs too.
To make the code more clearer if the configs need adaptions.
Signed-off-by: Simon Hein <Shein@baumer.com>
It is possible that address + size will overflow the available
address space and the pointer wraps around back to zero. Some
of these have been fixed in previous commits. This fixes
the remaining ones with regard to Z_PHYS_RAM_START/_END,
and Z_VIRT_RAM_START/_END.
Fixes#65542
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
z_free_page_count is only used in one file, so there is
no need to expose it, even to other part of kernel.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
This moves the k_* memory management functions from sys/ into
kernel/ includes, as there are kernel public APIs. The z_*
functions are further separated into the kernel internal
header directory.
Also made a quick change to doxygen to group sys_mem_* into
the OS Memory Management group so they will appear in doc.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
z_page_frame can't be packed on Xtensa due memory alignment
constraints. When this is struct is packed it is 5 bytes long it will
cause an memory alignment problem on Xtensa.
Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
In order to bring consistency in-tree, migrate all kernel code to the
new prefix <zephyr/...>. Note that the conversion has been scripted,
refer to zephyrproject-rtos#45388 for more details.
Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>
These functions are those that need be implemented by backing
store outside kernel. Promote them from z_* so these can be
included in documentation.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
These functions and data structures are those that need
to be implemented by eviction algorithm and application
outside kernel. Promote them from z_* so these can be
included in documentation.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Add a 'U' suffix to values when computing and comparing against
unsigned variables and other related fixes of the same MISRA rule (10.4)
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
This adds a new kconfig CONFIG_SRAM_OFFSET to specify the offset
from beginning of SRAM where the kernel begins. On x86 and
PC compatible platforms, the first 1MB of RAM is reserved and
Zephyr should not link anything there. However, this 1MB still
needs to be mapped by the MMU to access various platform related
information. CONFIG_SRAM_OFFSET serves similar function as
CONFIG_KERNEL_VM_OFFSET and is needed for proper phys/virt
address translations.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
The Z_BOOT_VIRT_TO_PHYS() and Z_BOOT_PHYS_TO_VIRT() address
translation macros are flipped in their calculations.
The calculation is supposed to be:
virt = phys + ((KERNEL_VM_BASE + KERNEL_VM_OFFSET) -
SRAM_BASE_ADDRESS)
So fix the them.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
The linker script defines `z_mapped_size` as follows:
```
z_mapped_size = z_mapped_end - z_mapped_start;
```
This is done with the belief that precomputed values at link time will
make the code smaller and faster.
On Aarch64, symbol values are relocated and loaded relative to the PC
as those are normally meant to be memory addresses.
Now if you have e.g. `CONFIG_SRAM_BASE_ADDRESS=0x2000000000` then
`z_mapped_size` might still have a reasonable value, say 0x59334.
But, when interpreted as an address, that's very very far from the PC
whose value is in the neighborhood of 0x2000000000. That overflows the
4GB relocation range:
```
kernel/libkernel.a(mmu.c.obj): in function `z_mem_manage_init':
kernel/mmu.c:527:(.text.z_mem_manage_init+0x1c):
relocation truncated to fit: R_AARCH64_ADR_PREL_PG_HI21
```
The solution is to define `Z_KERNEL_VIRT_SIZE` in terms of
`z_mapped_end - z_mapped_start` at the source code level. Given this
is used within loops that already start with `z_mapped_start` anyway,
the compiler is smart enough to combine the two occurrences and
dispense with a size counter, making the code effectively
slightly better for all while avoiding the Aarch64 relocation
overflow:
```
text data bss dec hex filename
1216 8 294936 296160 484e0 mmu.c.obj.arm64.before
1212 8 294936 296156 484dc mmu.c.obj.arm64.after
1110 8 9244 10362 287a mmu.c.obj.x86-64.before
1106 8 9244 10358 2876 mmu.c.obj.x86-64.after
```
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Some arches like x86 need all memory mapped so that they can
fetch information placed arbitrarily by firmware, like ACPI
tables.
Ensure that if this is the case, the kernel won't accidentally
clobber it by thinking the relevant virtual memory is unused.
Otherwise this has no effect on page frame management.
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
If we evict enough pages to completely fill the backing store,
through APIs like k_mem_map(), z_page_frame_evict(), or
z_mem_page_out(), this will produce a crash the next time we
try to handle a page fault.
The backing store now always reserves a free storage location
for actual page faults.
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
If we evict enough pages to completely fill the backing store,
through APIs like k_mem_map(), z_page_frame_evict(), or
z_mem_page_out(), this will produce a crash the next time we
try to handle a page fault.
The backing store now always reserves a free storage location
for actual page faults.
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
