src/pkg/runtime/linux/mem.c

#include "runtime.h"
#include "defs.h"
#include "os.h"
#include "malloc.h"

void*
SysAlloc(uintptr n)
{
	void *p;

	mstats.sys += n;
	p = runtime_mmap(nil, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_PRIVATE, -1, 0);
	if(p < (void*)4096) {
		if(p == (void*)EACCES) {
			printf("mmap: access denied\n");
			printf("If you're running SELinux, enable execmem for this process.\n");
			exit(2);
		}
		printf("mmap: errno=%p\n", p);
		throw("mmap");
	}
	return p;
}

void
SysUnused(void *v, uintptr n)
{
	USED(v);
	USED(n);
	// TODO(rsc): call madvise MADV_DONTNEED
}

void
SysFree(void *v, uintptr n)
{
	mstats.sys -= n;
	runtime_munmap(v, n);
}

void
SysMemInit(void)
{
	// Code generators assume that references to addresses
	// on the first page will fault.  Map the page explicitly with
	// no permissions, to head off possible bugs like the system
	// allocating that page as the virtual address space fills.
	// Ignore any error, since other systems might be smart
	// enough to never allow anything there.
	runtime_mmap(nil, 4096, PROT_NONE, MAP_FIXED|MAP_ANON|MAP_PRIVATE, -1, 0);
}