x86: use ELF section to list CPU vendor specific code

Replace the hardcoded list of initialization functions for each CPU
vendor by a list in an ELF section, which is read at initialization in
arch/x86/kernel/cpu/cpu.c to fill the cpu_devs[] array. The ELF
section, named .x86cpuvendor.init, is reclaimed after boot, and
contains entries of type "struct cpu_vendor_dev" which associates a
vendor number with a pointer to a "struct cpu_dev" structure.

This first modification allows to remove all the VENDOR_init_cpu()
functions.

This patch also removes the hardcoded calls to early_init_amd() and
early_init_intel(). Instead, we add a "c_early_init" member to the
cpu_dev structure, which is then called if not NULL by the generic CPU
initialization code. Unfortunately, in early_cpu_detect(), this_cpu is
not yet set, so we have to use the cpu_devs[] array directly.

This patch is part of the Linux Tiny project, and is needed for
further patch that will allow to disable compilation of unused CPU
support code.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/cpu/amd.c

@@ -63,7 +63,7 @@ static __cpuinit int amd_apic_timer_broken(void)
 
 int force_mwait __cpuinitdata;
 
-void __cpuinit early_init_amd(struct cpuinfo_x86 *c)
+static void __cpuinit early_init_amd(struct cpuinfo_x86 *c)
 {
 	if (cpuid_eax(0x80000000) >= 0x80000007) {
 		c->x86_power = cpuid_edx(0x80000007);
@@ -336,6 +336,7 @@ static struct cpu_dev amd_cpu_dev __cpuinitdata = {
 		  }
 		},
 	},
+	.c_early_init   = early_init_amd,
 	.c_init		= init_amd,
 	.c_size_cache	= amd_size_cache,
 };
@@ -345,3 +346,5 @@ int __init amd_init_cpu(void)
 	cpu_devs[X86_VENDOR_AMD] = &amd_cpu_dev;
 	return 0;
 }
+
+cpu_vendor_dev_register(X86_VENDOR_AMD, &amd_cpu_dev);

arch/x86/kernel/cpu/centaur.c

@@ -464,8 +464,4 @@ static struct cpu_dev centaur_cpu_dev __cpuinitdata = {
 	.c_size_cache	= centaur_size_cache,
 };
 
-int __init centaur_init_cpu(void)
-{
-	cpu_devs[X86_VENDOR_CENTAUR] = &centaur_cpu_dev;
-	return 0;
-}
+cpu_vendor_dev_register(X86_VENDOR_CENTAUR, &centaur_cpu_dev);

arch/x86/kernel/cpu/common.c

@@ -328,14 +328,9 @@ static void __init early_cpu_detect(void)
 
 	get_cpu_vendor(c, 1);
 
-	switch (c->x86_vendor) {
-	case X86_VENDOR_AMD:
-		early_init_amd(c);
-		break;
-	case X86_VENDOR_INTEL:
-		early_init_intel(c);
-		break;
-	}
+	if (c->x86_vendor != X86_VENDOR_UNKNOWN &&
+	    cpu_devs[c->x86_vendor]->c_early_init)
+		cpu_devs[c->x86_vendor]->c_early_init(c);
 
 	early_get_cap(c);
 }
@@ -616,23 +611,15 @@ __setup("clearcpuid=", setup_disablecpuid);
 
 cpumask_t cpu_initialized __cpuinitdata = CPU_MASK_NONE;
 
-/* This is hacky. :)
- * We're emulating future behavior.
- * In the future, the cpu-specific init functions will be called implicitly
- * via the magic of initcalls.
- * They will insert themselves into the cpu_devs structure.
- * Then, when cpu_init() is called, we can just iterate over that array.
- */
 void __init early_cpu_init(void)
 {
-	intel_cpu_init();
-	cyrix_init_cpu();
-	nsc_init_cpu();
-	amd_init_cpu();
-	centaur_init_cpu();
-	transmeta_init_cpu();
-	nexgen_init_cpu();
-	umc_init_cpu();
+	struct cpu_vendor_dev *cvdev;
+
+	for (cvdev = __x86cpuvendor_start ;
+	     cvdev < __x86cpuvendor_end   ;
+	     cvdev++)
+		cpu_devs[cvdev->vendor] = cvdev->cpu_dev;
+
 	early_cpu_detect();
 }
 

arch/x86/kernel/cpu/cpu.h

@@ -14,6 +14,7 @@ struct cpu_dev {
 
 	struct		cpu_model_info c_models[4];
 
+	void            (*c_early_init)(struct cpuinfo_x86 *c);
 	void		(*c_init)(struct cpuinfo_x86 * c);
 	void		(*c_identify)(struct cpuinfo_x86 * c);
 	unsigned int	(*c_size_cache)(struct cpuinfo_x86 * c, unsigned int size);
@@ -21,18 +22,17 @@ struct cpu_dev {
 
 extern struct cpu_dev * cpu_devs [X86_VENDOR_NUM];
 
+struct cpu_vendor_dev {
+	int vendor;
+	struct cpu_dev *cpu_dev;
+};
+
+#define cpu_vendor_dev_register(cpu_vendor_id, cpu_dev) \
+	static struct cpu_vendor_dev __cpu_vendor_dev_##cpu_vendor_id __used \
+	__attribute__((__section__(".x86cpuvendor.init"))) = \
+	{ cpu_vendor_id, cpu_dev }
+
+extern struct cpu_vendor_dev __x86cpuvendor_start[], __x86cpuvendor_end[];
+
 extern int get_model_name(struct cpuinfo_x86 *c);
 extern void display_cacheinfo(struct cpuinfo_x86 *c);
-
-extern void early_init_intel(struct cpuinfo_x86 *c);
-extern void early_init_amd(struct cpuinfo_x86 *c);
-
-/* Specific CPU type init functions */
-int intel_cpu_init(void);
-int amd_init_cpu(void);
-int cyrix_init_cpu(void);
-int nsc_init_cpu(void);
-int centaur_init_cpu(void);
-int transmeta_init_cpu(void);
-int nexgen_init_cpu(void);
-int umc_init_cpu(void);

arch/x86/kernel/cpu/cyrix.c

@@ -439,11 +439,7 @@ static struct cpu_dev cyrix_cpu_dev __cpuinitdata = {
 	.c_identify	= cyrix_identify,
 };
 
-int __init cyrix_init_cpu(void)
-{
-	cpu_devs[X86_VENDOR_CYRIX] = &cyrix_cpu_dev;
-	return 0;
-}
+cpu_vendor_dev_register(X86_VENDOR_CYRIX, &cyrix_cpu_dev);
 
 static struct cpu_dev nsc_cpu_dev __cpuinitdata = {
 	.c_vendor	= "NSC",
@@ -451,9 +447,4 @@ static struct cpu_dev nsc_cpu_dev __cpuinitdata = {
 	.c_init		= init_nsc,
 };
 
-int __init nsc_init_cpu(void)
-{
-	cpu_devs[X86_VENDOR_NSC] = &nsc_cpu_dev;
-	return 0;
-}
-
+cpu_vendor_dev_register(X86_VENDOR_NSC, &nsc_cpu_dev);

arch/x86/kernel/cpu/intel.c

@@ -30,7 +30,7 @@
 struct movsl_mask movsl_mask __read_mostly;
 #endif
 
-void __cpuinit early_init_intel(struct cpuinfo_x86 *c)
+static void __cpuinit early_init_intel(struct cpuinfo_x86 *c)
 {
 	/* Netburst reports 64 bytes clflush size, but does IO in 128 bytes */
 	if (c->x86 == 15 && c->x86_cache_alignment == 64)
@@ -290,15 +290,12 @@ static struct cpu_dev intel_cpu_dev __cpuinitdata = {
 		  }
 		},
 	},
+	.c_early_init   = early_init_intel,
 	.c_init		= init_intel,
 	.c_size_cache	= intel_size_cache,
 };
 
-__init int intel_cpu_init(void)
-{
-	cpu_devs[X86_VENDOR_INTEL] = &intel_cpu_dev;
-	return 0;
-}
+cpu_vendor_dev_register(X86_VENDOR_INTEL, &intel_cpu_dev);
 
 #ifndef CONFIG_X86_CMPXCHG
 unsigned long cmpxchg_386_u8(volatile void *ptr, u8 old, u8 new)

arch/x86/kernel/cpu/transmeta.c

@@ -102,8 +102,4 @@ static struct cpu_dev transmeta_cpu_dev __cpuinitdata = {
 	.c_identify	= transmeta_identify,
 };
 
-int __init transmeta_init_cpu(void)
-{
-	cpu_devs[X86_VENDOR_TRANSMETA] = &transmeta_cpu_dev;
-	return 0;
-}
+cpu_vendor_dev_register(X86_VENDOR_TRANSMETA, &transmeta_cpu_dev);

arch/x86/kernel/cpu/umc.c

@@ -19,8 +19,5 @@ static struct cpu_dev umc_cpu_dev __cpuinitdata = {
 	},
 };
 
-int __init umc_init_cpu(void)
-{
-	cpu_devs[X86_VENDOR_UMC] = &umc_cpu_dev;
-	return 0;
-}
+cpu_vendor_dev_register(X86_VENDOR_UMC, &umc_cpu_dev);
+

arch/x86/kernel/vmlinux_32.lds.S

@@ -149,6 +149,11 @@ SECTIONS
 	*(.con_initcall.init)
   	__con_initcall_end = .;
   }
+  .x86cpuvendor.init : AT(ADDR(.x86cpuvendor.init) - LOAD_OFFSET) {
+	__x86cpuvendor_start = .;
+	*(.x86cpuvendor.init)
+	__x86cpuvendor_end = .;
+  }
   SECURITY_INIT
   . = ALIGN(4);
   .altinstructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) {

arch/x86/kernel/vmlinux_64.lds.S

@@ -177,6 +177,11 @@ SECTIONS
 	*(.con_initcall.init)
   }
   __con_initcall_end = .;
+  __x86cpuvendor_start = .;
+  .x86cpuvendor.init : AT(ADDR(.x86cpuvendor.init) - LOAD_OFFSET) {
+	*(.x86cpuvendor.init)
+  }
+  __x86cpuvendor_end = .;
   SECURITY_INIT
 
   . = ALIGN(8);