powerpc: Split systemcfg data out of vdso data page

The systemcfg data only has minimal overlap with the vdso data.
Splitting the two avoids mapping the implementation-defined vdso data
into /proc/ppc64/systemcfg.
It is also a preparation for the standardization of vdso data storage.

The only field actually used by both systemcfg and vdso is
tb_ticks_per_sec and it is only changed once during time_init().
Initialize it in both structures there.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241010-vdso-generic-base-v1-26-b64f0842d512@linutronix.de

Author: t-8ch

arch/powerpc/include/asm/vdso_datapage.h

@@ -10,21 +10,6 @@
  */
 
 
-/*
- * Note about this structure:
- *
- * This structure was historically called systemcfg and exposed to
- * userland via /proc/ppc64/systemcfg. Unfortunately, this became an
- * ABI issue as some proprietary software started relying on being able
- * to mmap() it, thus we have to keep the base layout at least for a
- * few kernel versions.
- *
- * However, since ppc32 doesn't suffer from this backward handicap,
- * a simpler version of the data structure is used there with only the
- * fields actually used by the vDSO.
- *
- */
-
 /*
  * If the major version changes we are incompatible.
  * Minor version changes are a hint.
@@ -40,13 +25,9 @@
 
 #define SYSCALL_MAP_SIZE      ((NR_syscalls + 31) / 32)
 
-/*
- * So here is the ppc64 backward compatible version
- */
-
 #ifdef CONFIG_PPC64
 
-struct vdso_arch_data {
+struct systemcfg {
 	__u8  eye_catcher[16];		/* Eyecatcher: SYSTEMCFG:PPC64	0x00 */
 	struct {			/* Systemcfg version numbers	     */
 		__u32 major;		/* Major number			0x10 */
@@ -71,10 +52,12 @@ struct vdso_arch_data {
 	__u32 dcache_line_size;		/* L1 d-cache line size		0x64 */
 	__u32 icache_size;		/* L1 i-cache size		0x68 */
 	__u32 icache_line_size;		/* L1 i-cache line size		0x6C */
+};
 
-	/* those additional ones don't have to be located anywhere
-	 * special as they were not part of the original systemcfg
-	 */
+extern struct systemcfg *systemcfg;
+
+struct vdso_arch_data {
+	__u64 tb_ticks_per_sec;			/* Timebase tics / sec */
 	__u32 dcache_block_size;		/* L1 d-cache block size     */
 	__u32 icache_block_size;		/* L1 i-cache block size     */
 	__u32 dcache_log_block_size;		/* L1 d-cache log block size */
@@ -88,9 +71,6 @@ struct vdso_arch_data {
 
 #else /* CONFIG_PPC64 */
 
-/*
- * And here is the simpler 32 bits version
- */
 struct vdso_arch_data {
 	__u64 tb_ticks_per_sec;		/* Timebase tics / sec */
 	__u32 syscall_map[SYSCALL_MAP_SIZE]; /* Map of syscalls */

arch/powerpc/kernel/proc_powerpc.c

@@ -4,6 +4,7 @@
  */
 
 #include <linux/init.h>
+#include <linux/memblock.h>
 #include <linux/mm.h>
 #include <linux/proc_fs.h>
 #include <linux/kernel.h>
@@ -44,13 +45,35 @@ static const struct proc_ops page_map_proc_ops = {
 	.proc_mmap	= page_map_mmap,
 };
 
+static union {
+	struct systemcfg	data;
+	u8			page[PAGE_SIZE];
+} systemcfg_data_store __page_aligned_data;
+struct systemcfg *systemcfg = &systemcfg_data_store.data;
 
 static int __init proc_ppc64_init(void)
 {
 	struct proc_dir_entry *pde;
 
+	strcpy((char *)systemcfg->eye_catcher, "SYSTEMCFG:PPC64");
+	systemcfg->version.major = SYSTEMCFG_MAJOR;
+	systemcfg->version.minor = SYSTEMCFG_MINOR;
+	systemcfg->processor = mfspr(SPRN_PVR);
+	/*
+	 * Fake the old platform number for pSeries and add
+	 * in LPAR bit if necessary
+	 */
+	systemcfg->platform = 0x100;
+	if (firmware_has_feature(FW_FEATURE_LPAR))
+		systemcfg->platform |= 1;
+	systemcfg->physicalMemorySize = memblock_phys_mem_size();
+	systemcfg->dcache_size = ppc64_caches.l1d.size;
+	systemcfg->dcache_line_size = ppc64_caches.l1d.line_size;
+	systemcfg->icache_size = ppc64_caches.l1i.size;
+	systemcfg->icache_line_size = ppc64_caches.l1i.line_size;
+
 	pde = proc_create_data("powerpc/systemcfg", S_IFREG | 0444, NULL,
-			       &page_map_proc_ops, vdso_data);
+			       &page_map_proc_ops, systemcfg);
 	if (!pde)
 		return 1;
 	proc_set_size(pde, PAGE_SIZE);

arch/powerpc/kernel/setup-common.c

@@ -560,7 +560,9 @@ void __init smp_setup_cpu_maps(void)
 	out:
 		of_node_put(dn);
 	}
-	vdso_data->processorCount = num_present_cpus();
+#endif
+#ifdef CONFIG_PPC64_PROC_SYSTEMCFG
+	systemcfg->processorCount = num_present_cpus();
 #endif /* CONFIG_PPC64 */
 
         /* Initialize CPU <=> thread mapping/

arch/powerpc/kernel/smp.c

@@ -1186,8 +1186,8 @@ int generic_cpu_disable(void)
 		return -EBUSY;
 
 	set_cpu_online(cpu, false);
-#ifdef CONFIG_PPC64
-	vdso_data->processorCount--;
+#ifdef CONFIG_PPC64_PROC_SYSTEMCFG
+	systemcfg->processorCount--;
 #endif
 	/* Update affinity of all IRQs previously aimed at this CPU */
 	irq_migrate_all_off_this_cpu();
@@ -1642,10 +1642,12 @@ void start_secondary(void *unused)
 
 	secondary_cpu_time_init();
 
-#ifdef CONFIG_PPC64
+#ifdef CONFIG_PPC64_PROC_SYSTEMCFG
 	if (system_state == SYSTEM_RUNNING)
-		vdso_data->processorCount++;
+		systemcfg->processorCount++;
+#endif
 
+#ifdef CONFIG_PPC64
 	vdso_getcpu_init();
 #endif
 	set_numa_node(numa_cpu_lookup_table[cpu]);

arch/powerpc/kernel/time.c

@@ -950,6 +950,9 @@ void __init time_init(void)
 	}
 
 	vdso_data->tb_ticks_per_sec = tb_ticks_per_sec;
+#ifdef CONFIG_PPC64_PROC_SYSTEMCFG
+	systemcfg->tb_ticks_per_sec = tb_ticks_per_sec;
+#endif
 
 	/* initialise and enable the large decrementer (if we have one) */
 	set_decrementer_max();

arch/powerpc/kernel/vdso.c

@@ -16,7 +16,6 @@
 #include <linux/user.h>
 #include <linux/elf.h>
 #include <linux/security.h>
-#include <linux/memblock.h>
 #include <linux/syscalls.h>
 #include <linux/time_namespace.h>
 #include <vdso/datapage.h>
@@ -349,25 +348,6 @@ static struct page ** __init vdso_setup_pages(void *start, void *end)
 static int __init vdso_init(void)
 {
 #ifdef CONFIG_PPC64
-	/*
-	 * Fill up the "systemcfg" stuff for backward compatibility
-	 */
-	strcpy((char *)vdso_data->eye_catcher, "SYSTEMCFG:PPC64");
-	vdso_data->version.major = SYSTEMCFG_MAJOR;
-	vdso_data->version.minor = SYSTEMCFG_MINOR;
-	vdso_data->processor = mfspr(SPRN_PVR);
-	/*
-	 * Fake the old platform number for pSeries and add
-	 * in LPAR bit if necessary
-	 */
-	vdso_data->platform = 0x100;
-	if (firmware_has_feature(FW_FEATURE_LPAR))
-		vdso_data->platform |= 1;
-	vdso_data->physicalMemorySize = memblock_phys_mem_size();
-	vdso_data->dcache_size = ppc64_caches.l1d.size;
-	vdso_data->dcache_line_size = ppc64_caches.l1d.line_size;
-	vdso_data->icache_size = ppc64_caches.l1i.size;
-	vdso_data->icache_line_size = ppc64_caches.l1i.line_size;
 	vdso_data->dcache_block_size = ppc64_caches.l1d.block_size;
 	vdso_data->icache_block_size = ppc64_caches.l1i.block_size;
 	vdso_data->dcache_log_block_size = ppc64_caches.l1d.log_block_size;

arch/powerpc/platforms/powernv/smp.c

@@ -136,7 +136,9 @@ static int pnv_smp_cpu_disable(void)
 	 * the generic fixup_irqs. --BenH.
 	 */
 	set_cpu_online(cpu, false);
-	vdso_data->processorCount--;
+#ifdef CONFIG_PPC64_PROC_SYSTEMCFG
+	systemcfg->processorCount--;
+#endif
 	if (cpu == boot_cpuid)
 		boot_cpuid = cpumask_any(cpu_online_mask);
 	if (xive_enabled())

arch/powerpc/platforms/pseries/hotplug-cpu.c

@@ -83,7 +83,9 @@ static int pseries_cpu_disable(void)
 	int cpu = smp_processor_id();
 
 	set_cpu_online(cpu, false);
-	vdso_data->processorCount--;
+#ifdef CONFIG_PPC64_PROC_SYSTEMCFG
+	systemcfg->processorCount--;
+#endif
 
 	/*fix boot_cpuid here*/
 	if (cpu == boot_cpuid)