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x86: grant user mode access to newlib heap

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Newlib uses any RAM between _end and the bounds of physical
RAM for the _sbrk() heap. Set up a user-writable region
so that this works properly on x86.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
This commit is contained in:
Andrew Boie 2018-05-09 15:59:32 -07:00 • committed by Andrew Boie
commit fc76839b6b
2 changed files with 23 additions and 0 deletions
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1
include/arch/x86/linker.ld
View file

@ -306,6 +306,7 @@ SECTIONS
#include <linker/kobject.ld>
MMU_PAGE_ALIGN
__data_ram_end = .;
/* All unused memory also owned by the kernel for heaps */

22
lib/libc/newlib/libc-hooks.c
View file

@ -10,6 +10,7 @@
#include <sys/stat.h>
#include <linker/linker-defs.h>
#include <misc/util.h>
#include <init.h>
#define USED_RAM_END_ADDR POINTER_TO_UINT(&_end)
@ -157,3 +158,24 @@ void *_sbrk(int count)
}
}
FUNC_ALIAS(_sbrk, sbrk, void *);
#ifdef CONFIG_X86_MMU
static int newlib_mmu_prepare(struct device *unused)
{
ARG_UNUSED(unused);
/* Set up the newlib heap area as a globally user-writable region.
* We can't do this at build time with MMU_BOOT_REGION() as the _end
* pointer shifts significantly between build phases due to the
* introduction of page tables.
*/
_x86_mmu_set_flags(UINT_TO_POINTER(USED_RAM_END_ADDR), MAX_HEAP_SIZE,
MMU_ENTRY_PRESENT | MMU_ENTRY_WRITE |
MMU_ENTRY_USER,
MMU_PTE_P_MASK | MMU_PTE_RW_MASK | MMU_PTE_US_MASK);
return 0;
}
SYS_INIT(newlib_mmu_prepare, APPLICATION, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);
#endif /* CONFIG_X86_MMU */