[WIP] Implement mmap/munmap

[d3m3vilurr]

No description provided.

[Rinnegatamante]

Does this make malloc to use mmap when heap finished? If so, depending on the case, it can break already existing homebrews. (Eg: an homebrew using vita2d that allocs a lot of textures will result in running out of available memblocks making mmap fail despite having still free memory. The viceversa case would apply too, you run out of newlib heap and keep alloc-ing memblocks with malloc until you run out of memblocks and then vita2d becomes completely unusable to alloc new textures).

[d3m3vilurr]

hm. maybe yes (main flow is alloc small block ->alloc large block->alloc with mmap->extend heap memblock, but i just readed very roughly). and it related mmap_threshold and default value for this is 128k.
you can change these settings values(M_TRIM_THRESHOLD, M_TOP_PAD, M_MMAP_THRESHOLD, M_MMAP_MAX) with mallopt`
(this is the reason why my test result is 96MB (default heap size is 32MB + mmap_max is 64)

and I'm not sure that this patch occurs breaking of homebrews if that apps were had quite right memory handling.

[d3m3vilurr]

@Rinnegatamante split malloc part to #46 to easy reviewing

[Rinnegatamante]

I'm quite sure mmap can't be replaced in all cases with sceKernelAllocMemBlock. Speaking about dynarec: mmap's generally used in that case but on Vita we need sceKernelAllocMemBlockForVM:
ioq3 armv7 dynarec: https://github.com/ioquake/ioq3/blob/master/code/qcommon/vm_armv7l.c#L628
vitaQuakeIII armv7 dynarec: https://github.com/Rinnegatamante/vitaQuakeIII/blob/master/code/qcommon/vm_armv7l.c#L619

@frangarcj may know more about this.

[d3m3vilurr]

well... we don't need to replace all of sceKernelAllocMemBlock cases.
mmap/munmmap are just one of posix spec functions.
technically, this functions don't need to care about dynarec as same reason.

more detail explain, maybe dynarec requires PROT_EXEC flag, and it's reason why you need sceKernelAllocMemBlockForVM instead sceKernelAllocMemBlock
it mean, you can patch mmap for PROT_EXEC, but maybe we need to introduce another chunk structure for detecting allocation method.
in this time, mmap function doesn't support the PROT_EXEC | PROT_WRITE

PS. same reason, ioq3 repo is wrong.

---

sorry ioq3's code is right. that code called mprotect with PROT_READ|PROT_EXEC

[d3m3vilurr]

added mark WIP.
we can detect alloc function using sceKernelGetMemBlockInfoByAddr
I'll update this patch to support RX memory block.
but I don't know good approach yet to implement mprotect to switch perm between WX and RX without any kernel plugin.

I didn't test yet, but imo, sceKernelOpenVMDomain and sceKernelCloseVMDomain will open all vm area.