x86: Make it so that __pa_symbol can only process kernel symbols on x86_64

PATCH New Alexander Duyck 1 participant 1 message Oct 10, 2012

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Alexander Duyck

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2012-10-10 23:46 UTC #0 lore raw

PATCH 1/1 x86: Make it so that __pa_symbol can only process kernel symbols on x86_64

I submitted an earlier patch that make __phys_addr an inline. This obviously results in an increase in the code size. One step I can take to reduce that is to make it so that the __pa_symbol call does a direct translation for kernel addresses instead of covering all of virtual memory.

On my system this reduced the size for __pa_symbol from 5 instructions totalling 30 bytes to 3 instructions totalling 16 bytes.

Signed-off-by Alexander Duyck <[email protected]>

---

 arch/x86/include/asm/page.h          |    3 ++-
 arch/x86/include/asm/page_32.h       |    1 +
 arch/x86/include/asm/page_64_types.h |    3 +++
 arch/x86/mm/physaddr.c               |   15 +++++++++++++++
 4 files changed, 21 insertions(+), 1 deletions(-)

arch/x86/include/asm/page.h +2 -1

index 8ca8283..3698a6a 100644
@@ -44,7 +44,8 @@ static inline void copy_user_page(void *to, void *from, unsigned long vaddr,
  * case properly. Once all supported versions of gcc understand it, we can
  * remove this Voodoo magic stuff. (i.e. once gcc3.x is deprecated)
  */
-#define __pa_symbol(x)	__pa(__phys_reloc_hide((unsigned long)(x)))
+#define __pa_symbol(x) \
+	__phys_addr_symbol(__phys_reloc_hide((unsigned long)(x)))
 
 #define __va(x)			((void *)((unsigned long)(x)+PAGE_OFFSET))

arch/x86/include/asm/page_32.h +1 -0

index da4e762..4d550d0 100644
@@ -15,6 +15,7 @@ extern unsigned long __phys_addr(unsigned long);
 #else
 #define __phys_addr(x)		__phys_addr_nodebug(x)
 #endif
+#define __phys_addr_symbol(x)	__phys_addr(x)
 #define __phys_reloc_hide(x)	RELOC_HIDE((x), 0)
 
 #ifdef CONFIG_FLATMEM

arch/x86/include/asm/page_64_types.h +3 -0

index a951e4d..217c7d5 100644
@@ -60,6 +60,7 @@ extern unsigned long phys_base;
 
 #ifdef CONFIG_DEBUG_VIRTUAL
 extern unsigned long __phys_addr(unsigned long);
+extern unsigned long __phys_addr_symbol(unsigned long);
 #else
 static inline unsigned long __phys_addr(unsigned long x)
 {

@@ -70,6 +71,8 @@ static inline unsigned long __phys_addr(unsigned long x)
 
 	return x;
 }
+#define __phys_addr_symbol(x) \
+	((unsigned long)(x) - __START_KERNEL_map + phys_base)
 #endif
 #define __phys_reloc_hide(x)	(x)

arch/x86/mm/physaddr.c +15 -0

index f63bec5..666edbd 100644
@@ -29,6 +29,21 @@ unsigned long __phys_addr(unsigned long x)
 	return x;
 }
 EXPORT_SYMBOL(__phys_addr);
+
+unsigned long __phys_addr_symbol(unsigned long x)
+{
+	unsigned long y = x - __START_KERNEL_map;
+
+	/* use the carry flag to determine if x was < __START_KERNEL_map */
+	VIRTUAL_BUG_ON(x < y);
+
+	x = y + phys_base;
+
+	VIRTUAL_BUG_ON(y >= KERNEL_IMAGE_SIZE);
+
+	return x;
+}
+EXPORT_SYMBOL(__phys_addr_symbol);
 #endif
 
 bool __virt_addr_valid(unsigned long x)