#include <stdint.h>
#include "serene/rt/fiber.h"
#include "serene/rt/mm/interface.h"
#include "serene/utils.h"
#include <sys/mman.h>

Include dependency graph for stack_posix.c:

Macros
#define	STACK_FLAGS MAP_PRIVATE \| MAP_ANONYMOUS \| MAP_NORESERVE \| MAP_STACK

Functions
srn_fiber_stack_t	srn_fiber_stack_alloc (size_t size)
	Allocate a stack of at least `size` usable bytes plus a guard page, or SRN_FIBER_DEFAULT_STACK_SIZE when `size` is 0.

void	srn_fiber_stack_free (srn_fiber_stack_t stack)

Macro Definition Documentation

◆ STACK_FLAGS

#define STACK_FLAGS MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE | MAP_STACK

Definition at line 30 of file stack_posix.c.

Function Documentation

◆ srn_fiber_stack_alloc()

srn_fiber_stack_t srn_fiber_stack_alloc ( size_t size )

nodiscard

Allocate a stack of at least size usable bytes plus a guard page, or SRN_FIBER_DEFAULT_STACK_SIZE when size is 0.

Platform specific.

Definition at line 34 of file stack_posix.c.

                                                     {
  const size_t os_page_size = srn_mm_get_os_page_size();
  const size_t desired_size = size ? size : (size_t)SRN_FIBER_DEFAULT_STACK_SIZE;
 
  // Round upto a multiple of PAGE size
  const size_t usable = (desired_size + os_page_size - 1) & ~(os_page_size - 1);
  // Add a page to act as a guard page
  const size_t total = usable + os_page_size;
 
  // Since stack grows downward, the starting point where mmap returns will
  // be the end of the stack for us. We could of used MAP_GROWSDOWN to
  // change the behaviour, but that causes the stack to grow, but we have
  // a fix stack.
  void *end = mmap(nullptr, total, PROT_READ | PROT_WRITE, STACK_FLAGS,
                   // according to the man page, for anonymous mode fd should be -1
                   -1,
                   // according to the man page, for anonymous mode offset should be 0
                   0);
 
  PANIC_IF(end == MAP_FAILED, "Failed to allocate the stack for the fiber subsystem");
 
  if (mprotect(end, os_page_size, PROT_NONE) == -1) {
    munmap(end, total);
    PANIC("Failed to allocate the guard page for the fiber subsystem");
  }
 
  const uintptr_t start = (uintptr_t)end + (uintptr_t)total;
  const uintptr_t limit = (uintptr_t)end + (uintptr_t)os_page_size;
 
  srn_fiber_stack_t stack = {.start = (void *)start, .limit = (void *)limit, .guard = end};
  return stack;
}

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◆ srn_fiber_stack_free()

void srn_fiber_stack_free ( srn_fiber_stack_t stack )

Definition at line 67 of file stack_posix.c.

                                                   {
  munmap(stack.guard, (uintptr_t)stack.start - (uintptr_t)stack.guard);
}