Import code for article1, 2, 3, 4

1 files changed, 269 insertions, 0 deletions

diff --git a/sos-code-article4/sos/physmem.c b/sos-code-article4/sos/physmem.c
new file mode 100644
index 0000000..99cffb7
--- /dev/null
+++ b/sos-code-article4/sos/physmem.c
@@ -0,0 +1,269 @@
+/* Copyright (C) 2004  David Decotigny
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; either version 2
+   of the License, or (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+   USA. 
+*/
+#include <sos/list.h>
+#include <sos/macros.h>
+#include <sos/assert.h>
+#include <sos/klibc.h>
+
+#include "physmem.h"
+
+/** A descriptor for a physical page in SOS */
+struct physical_page_descr
+{
+  /** The physical base address for the page */
+  sos_paddr_t paddr;
+
+  /** The reference count for this physical page. > 0 means that the
+     page is in the used list. */
+  sos_count_t ref_cnt;
+
+  /** The other pages on the list (used, free) */
+  struct physical_page_descr *prev, *next;
+};
+
+/** These are some markers present in the executable file (see sos.lds) */
+extern char __b_kernel, __e_kernel;
+
+/** The array of ppage descriptors will be located at this address */
+#define PAGE_DESCR_ARRAY_ADDR \
+  SOS_PAGE_ALIGN_SUP((sos_paddr_t) (& __e_kernel))
+static struct physical_page_descr * physical_page_descr_array;
+
+/** The list of physical pages currently available */
+static struct physical_page_descr *free_ppage;
+
+/** The list of physical pages currently in use */
+static struct physical_page_descr *used_ppage;
+
+/** We will store here the interval of valid physical addresses */
+static sos_paddr_t physmem_base, physmem_top;
+
+/** We store the number of pages used/free */
+static sos_count_t physmem_total_pages, physmem_used_pages;
+
+sos_ret_t sos_physmem_setup(sos_size_t ram_size,
+			    /* out */sos_paddr_t *kernel_core_base,
+			    /* out */sos_paddr_t *kernel_core_top)
+{
+  /* The iterator over the page descriptors */
+  struct physical_page_descr *ppage_descr;
+
+  /* The iterator over the physical addresses */
+  sos_paddr_t ppage_addr;
+
+  /* Make sure ram size is aligned on a page boundary */
+  ram_size = SOS_PAGE_ALIGN_INF(ram_size);/* Yes, we may lose at most a page */
+
+  /* Reset the used/free page lists before building them */
+  free_ppage = used_ppage = NULL;
+  physmem_total_pages = physmem_used_pages = 0;
+
+  /* Make sure that there is enough memory to store the array of page
+     descriptors */
+  *kernel_core_base = SOS_PAGE_ALIGN_INF((sos_paddr_t)(& __b_kernel));
+  *kernel_core_top
+    = PAGE_DESCR_ARRAY_ADDR
+      + SOS_PAGE_ALIGN_SUP( (ram_size >> SOS_PAGE_SHIFT)
+			    * sizeof(struct physical_page_descr));
+  if (*kernel_core_top > ram_size)
+    return -SOS_ENOMEM;
+
+  /* Page 0-4kB is not available in order to return address 0 as a
+     means to signal "no page available" */
+  physmem_base = SOS_PAGE_SIZE;
+  physmem_top  = ram_size;
+
+  /* Setup the page descriptor arrray */
+  physical_page_descr_array
+    = (struct physical_page_descr*)PAGE_DESCR_ARRAY_ADDR;
+
+  /* Scan the list of physical pages */
+  for (ppage_addr = 0,
+	 ppage_descr = physical_page_descr_array ;
+       ppage_addr < physmem_top ;
+       ppage_addr += SOS_PAGE_SIZE,
+	 ppage_descr ++)
+    {
+      enum { PPAGE_MARK_RESERVED, PPAGE_MARK_FREE,
+	     PPAGE_MARK_KERNEL, PPAGE_MARK_HWMAP } todo;
+
+      memset(ppage_descr, 0x0, sizeof(struct physical_page_descr));
+
+      /* Init the page descriptor for this page */
+      ppage_descr->paddr = ppage_addr;
+
+      /* Reserved : 0 ... base */
+      if (ppage_addr < physmem_base)
+	todo = PPAGE_MARK_RESERVED;
+
+      /* Free : base ... BIOS */
+      else if ((ppage_addr >= physmem_base)
+	       && (ppage_addr < BIOS_N_VIDEO_START))
+	todo = PPAGE_MARK_FREE;
+
+      /* Used : BIOS */
+      else if ((ppage_addr >= BIOS_N_VIDEO_START)
+	       && (ppage_addr < BIOS_N_VIDEO_END))
+	todo = PPAGE_MARK_HWMAP;
+
+      /* Free : BIOS ... kernel */
+      else if ((ppage_addr >= BIOS_N_VIDEO_END)
+	       && (ppage_addr < (sos_paddr_t) (& __b_kernel)))
+	todo = PPAGE_MARK_FREE;
+
+      /* Used : Kernel code/data/bss + physcal page descr array */
+      else if ((ppage_addr >= *kernel_core_base)
+		&& (ppage_addr < *kernel_core_top))
+	todo = PPAGE_MARK_KERNEL;
+
+      /* Free : first page of descr ... end of RAM */
+      else
+	todo = PPAGE_MARK_FREE;
+
+      /* Actually does the insertion in the used/free page lists */
+      physmem_total_pages ++;
+      switch (todo)
+	{
+	case PPAGE_MARK_FREE:
+	  ppage_descr->ref_cnt = 0;
+	  list_add_head(free_ppage, ppage_descr);
+	  break;
+
+	case PPAGE_MARK_KERNEL:
+	case PPAGE_MARK_HWMAP:
+	  ppage_descr->ref_cnt = 1;
+	  list_add_head(used_ppage, ppage_descr);
+	  physmem_used_pages ++;
+	  break;
+
+	default:
+	  /* Reserved page: nop */
+	  break;
+	}
+    }
+
+  return SOS_OK;
+}
+
+
+sos_paddr_t sos_physmem_ref_physpage_new(sos_bool_t can_block)
+{
+  struct physical_page_descr *ppage_descr;
+
+  if (! free_ppage)
+    return (sos_paddr_t)NULL;
+
+  /* Retrieve a page in the free list */
+  ppage_descr = list_pop_head(free_ppage);
+
+  /* The page is assumed not to be already used */
+  SOS_ASSERT_FATAL(ppage_descr->ref_cnt == 0);
+
+  /* Mark the page as used (this of course sets the ref count to 1) */
+  ppage_descr->ref_cnt ++;
+
+  /* Put the page in the used list */
+  list_add_tail(used_ppage, ppage_descr);
+  physmem_used_pages ++;
+
+  return ppage_descr->paddr;
+}
+
+
+/**
+ * Helper function to get the physical page descriptor for the given
+ * physical page address.
+ *
+ * @return NULL when out-of-bounds or non-page-aligned
+ */
+inline static struct physical_page_descr *
+get_page_descr_at_paddr(sos_paddr_t ppage_paddr)
+{
+  /* Don't handle non-page-aligned addresses */
+  if (ppage_paddr & SOS_PAGE_MASK)
+    return NULL;
+  
+  /* Don't support out-of-bounds requests */
+  if ((ppage_paddr < physmem_base) || (ppage_paddr >= physmem_top))
+    return NULL;
+
+  return physical_page_descr_array + (ppage_paddr >> SOS_PAGE_SHIFT);
+}
+
+
+sos_ret_t sos_physmem_ref_physpage_at(sos_paddr_t ppage_paddr)
+{
+  struct physical_page_descr *ppage_descr
+    = get_page_descr_at_paddr(ppage_paddr);
+
+  if (! ppage_descr)
+    return -SOS_EINVAL;
+
+  /* Increment the reference count for the page */
+  ppage_descr->ref_cnt ++;
+
+  /* If the page is newly referenced (ie we are the only owners of the
+     page => ref cnt == 1), transfer it in the used pages list */
+  if (ppage_descr->ref_cnt == 1)
+    {
+      list_delete(free_ppage, ppage_descr);
+      list_add_tail(used_ppage, ppage_descr);
+      physmem_used_pages ++;
+
+      /* The page is newly referenced */
+      return FALSE;
+    }
+
+  /* The page was already referenced by someone */
+  return TRUE;
+}
+
+
+sos_ret_t
+sos_physmem_unref_physpage(sos_paddr_t ppage_paddr)
+{
+  /* By default the return value indicates that the page is still
+     used */
+  sos_ret_t retval = FALSE;
+
+  struct physical_page_descr *ppage_descr
+    = get_page_descr_at_paddr(ppage_paddr);
+
+  if (! ppage_descr)
+    return -SOS_EINVAL;
+
+  /* Don't do anything if the page is not in the used list */
+  if (ppage_descr->ref_cnt <= 0)
+    return -SOS_EINVAL;
+
+  /* Unreference the page, and, when no mapping is active anymore, put
+     the page in the free list */
+  ppage_descr->ref_cnt--;
+  if (ppage_descr->ref_cnt <= 0)
+    {
+      /* Transfer the page, considered USED, to the free list */
+      list_delete(used_ppage, ppage_descr);
+      physmem_used_pages --;
+      list_add_head(free_ppage, ppage_descr);
+
+      /* Indicate that the page is now unreferenced */
+      retval = TRUE;
+    }
+
+  return retval;
+}