x86/build changes for v6.10:

- Use -fpic to build the kexec 'purgatory' (self-contained code that runs between two kernels)
 
  - Clean up vmlinux.lds.S generation
 
  - Simplify the X86_EXTENDED_PLATFORM section of the x86 Kconfig
 
  - Misc cleanups & fixes
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-build-2024-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 build updates from Ingo Molnar:

 - Use -fpic to build the kexec 'purgatory' (the self-contained
   code that runs between two kernels)

 - Clean up vmlinux.lds.S generation

 - Simplify the X86_EXTENDED_PLATFORM section of the x86 Kconfig

 - Misc cleanups & fixes

* tag 'x86-build-2024-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/Kconfig: Merge the two CONFIG_X86_EXTENDED_PLATFORM entries
  x86/purgatory: Switch to the position-independent small code model
  x86/boot: Replace __PHYSICAL_START with LOAD_PHYSICAL_ADDR
  x86/vmlinux.lds.S: Take __START_KERNEL out conditional definition
  x86/vmlinux.lds.S: Remove conditional definition of LOAD_OFFSET
  vmlinux.lds.h: Fix a typo in comment

arch/x86/Kconfig

@@ -503,10 +503,9 @@ config X86_FRED
 	  ring transitions and exception/interrupt handling if the
 	  system supports.
 
-if X86_32
 config X86_BIGSMP
 	bool "Support for big SMP systems with more than 8 CPUs"
-	depends on SMP
+	depends on SMP && X86_32
 	help
 	  This option is needed for the systems that have more than 8 CPUs.
 
@@ -519,7 +518,10 @@ config X86_EXTENDED_PLATFORM
 	  systems out there.)
 
 	  If you enable this option then you'll be able to select support
-	  for the following (non-PC) 32 bit x86 platforms:
+	  for the following non-PC x86 platforms, depending on the value of
+	  CONFIG_64BIT.
+
+	  32-bit platforms (CONFIG_64BIT=n):
 		Goldfish (Android emulator)
 		AMD Elan
 		RDC R-321x SoC
@@ -527,28 +529,14 @@ config X86_EXTENDED_PLATFORM
 		STA2X11-based (e.g. Northville)
 		Moorestown MID devices
 
-	  If you have one of these systems, or if you want to build a
-	  generic distribution kernel, say Y here - otherwise say N.
-endif # X86_32
-
-if X86_64
-config X86_EXTENDED_PLATFORM
-	bool "Support for extended (non-PC) x86 platforms"
-	default y
-	help
-	  If you disable this option then the kernel will only support
-	  standard PC platforms. (which covers the vast majority of
-	  systems out there.)
-
-	  If you enable this option then you'll be able to select support
-	  for the following (non-PC) 64 bit x86 platforms:
+	  64-bit platforms (CONFIG_64BIT=y):
 		Numascale NumaChip
 		ScaleMP vSMP
 		SGI Ultraviolet
 
 	  If you have one of these systems, or if you want to build a
 	  generic distribution kernel, say Y here - otherwise say N.
-endif # X86_64
+
 # This is an alphabetically sorted list of 64 bit extended platforms
 # Please maintain the alphabetic order if and when there are additions
 config X86_NUMACHIP

arch/x86/include/asm/boot.h

@@ -6,11 +6,6 @@
 #include <asm/pgtable_types.h>
 #include <uapi/asm/boot.h>
 
-/* Physical address where kernel should be loaded. */
-#define LOAD_PHYSICAL_ADDR ((CONFIG_PHYSICAL_START \
-				+ (CONFIG_PHYSICAL_ALIGN - 1)) \
-				& ~(CONFIG_PHYSICAL_ALIGN - 1))
-
 /* Minimum kernel alignment, as a power of two */
 #ifdef CONFIG_X86_64
 # define MIN_KERNEL_ALIGN_LG2	PMD_SHIFT

arch/x86/include/asm/page_types.h

@@ -31,10 +31,12 @@
 
 #define VM_DATA_DEFAULT_FLAGS	VM_DATA_FLAGS_TSK_EXEC
 
-#define __PHYSICAL_START	ALIGN(CONFIG_PHYSICAL_START, \
-				      CONFIG_PHYSICAL_ALIGN)
+/* Physical address where kernel should be loaded. */
+#define LOAD_PHYSICAL_ADDR ((CONFIG_PHYSICAL_START \
+				+ (CONFIG_PHYSICAL_ALIGN - 1)) \
+				& ~(CONFIG_PHYSICAL_ALIGN - 1))
 
-#define __START_KERNEL		(__START_KERNEL_map + __PHYSICAL_START)
+#define __START_KERNEL		(__START_KERNEL_map + LOAD_PHYSICAL_ADDR)
 
 #ifdef CONFIG_X86_64
 #include <asm/page_64_types.h>

arch/x86/kernel/vmlinux.lds.S

@@ -15,11 +15,7 @@
  * put it inside the section definition.
  */
 
-#ifdef CONFIG_X86_32
-#define LOAD_OFFSET __PAGE_OFFSET
-#else
 #define LOAD_OFFSET __START_KERNEL_map
-#endif
 
 #define RUNTIME_DISCARD_EXIT
 #define EMITS_PT_NOTE
@@ -114,11 +110,10 @@ PHDRS {
 
 SECTIONS
 {
+	. = __START_KERNEL;
 #ifdef CONFIG_X86_32
-	. = LOAD_OFFSET + LOAD_PHYSICAL_ADDR;
 	phys_startup_32 = ABSOLUTE(startup_32 - LOAD_OFFSET);
 #else
-	. = __START_KERNEL;
 	phys_startup_64 = ABSOLUTE(startup_64 - LOAD_OFFSET);
 #endif
 

arch/x86/purgatory/Makefile

@@ -42,7 +42,8 @@ KCOV_INSTRUMENT := n
 # make up the standalone purgatory.ro
 
 PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
-PURGATORY_CFLAGS := -mcmodel=large -ffreestanding -fno-zero-initialized-in-bss -g0
+PURGATORY_CFLAGS := -mcmodel=small -ffreestanding -fno-zero-initialized-in-bss -g0
+PURGATORY_CFLAGS += -fpic -fvisibility=hidden
 PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN) -DDISABLE_BRANCH_PROFILING
 PURGATORY_CFLAGS += -fno-stack-protector
 

include/asm-generic/vmlinux.lds.h

@@ -3,7 +3,7 @@
  * linker scripts.
  *
  * A minimal linker scripts has following content:
- * [This is a sample, architectures may have special requiriements]
+ * [This is a sample, architectures may have special requirements]
  *
  * OUTPUT_FORMAT(...)
  * OUTPUT_ARCH(...)