linux-kernel - [PATCH 2/2] head_32.S: Update the comments for the initial kernel mapping(KERNEL_IMAGE

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Date:	Sun, 27 Feb 2011 23:21:38 +0200
From:	Stratos Psomadakis <psomas@...ab.ece.ntua.gr>
To:	linux-kernel@...r.kernel.org
Cc:	Stratos Psomadakis <psomas@...ab.ece.ntua.gr>
Subject: [PATCH 2/2] head_32.S: Update the comments for the initial kernel mapping(KERNEL_IMAGE_SIZE no longer used)

Update the comments regarding the initial kernel mapping in head_32.S and 
cleanup the code(KERNEL_IMAGE_SIZE no longer used).

Signed-off-by: Stratos Psomadakis <psomas@...ab.ece.ntua.gr>
---
 arch/x86/kernel/head_32.S |   44 +++++++++++++++++---------------------------
 1 files changed, 17 insertions(+), 27 deletions(-)

diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 187aa63..77990a5 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -39,42 +39,32 @@
 #define X86_VENDOR_ID	new_cpu_data+CPUINFO_x86_vendor_id
 
 /*
- * This is how much memory in addition to the memory covered up to
- * and including _end we need mapped initially.
- * We need:
- *     (KERNEL_IMAGE_SIZE/4096) / 1024 pages (worst case, non PAE)
- *     (KERNEL_IMAGE_SIZE/4096) / 512 + 4 pages (worst case for PAE)
- *
- * Modulo rounding, each megabyte assigned here requires a kilobyte of
- * memory, which is currently unreclaimed.
- *
- * This should be a multiple of a page.
- *
- * KERNEL_IMAGE_SIZE should be greater than pa(_end)
- * and small than max_low_pfn, otherwise will waste some page table entries
+ * Worst-case size of the kernel mapping we need to make:
+ * a relocatable kernel can live anywhere in lowmem, so we need to be able
+ * to map all of lowmem.
  */
 
-#if PTRS_PER_PMD > 1
-#define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD)
-#else
-#define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)
-#endif
-
 /* Number of possible pages in the lowmem region */
 LOWMEM_PAGES = (((1<<32) - __PAGE_OFFSET) >> PAGE_SHIFT)
-	
-/* Enough space to fit pagetables for the low memory linear map */
-MAPPING_BEYOND_END = PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT
 
 /*
- * Worst-case size of the kernel mapping we need to make:
- * a relocatable kernel can live anywhere in lowmem, so we need to be able
- * to map all of lowmem.
+ * This is the size of the pagetable(in pages) we need for the kernel mapping.
+ * We need:
+ *     LOWMEM_PAGES / 1024 pages (worst case, non PAE)
+ *     LOWMEM_PAGES / 512 + 4 pages (worst casem, PAE)
  */
-KERNEL_PAGES = LOWMEM_PAGES
 
-INIT_MAP_SIZE = PAGE_TABLE_SIZE(KERNEL_PAGES) * PAGE_SIZE
+#if PTRS_PER_PMD > 1
+#define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PMD) + PTRS_PER_PGD
+#else
+#define PAGE_TABLE_SIZE(pages) (pages) / PTRS_PER_PGD
+#endif
+
+INIT_MAP_SIZE = PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT
 RESERVE_BRK(pagetables, INIT_MAP_SIZE)
+	
+/* Map enough space after _end for the lowmem linear map */
+MAPPING_BEYOND_END = INIT_MAP_SIZE
 
 /*
  * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
-- 
1.7.4.1

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