sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 288 insertions, 0 deletions

diff --git a/drivers/video/fbdev/sbuslib.c b/drivers/video/fbdev/sbuslib.c
new file mode 100644
index 000000000..dd2002d08
--- /dev/null
+++ b/drivers/video/fbdev/sbuslib.c
@@ -0,0 +1,288 @@
+// SPDX-License-Identifier: GPL-2.0
+/* sbuslib.c: Helper library for SBUS framebuffer drivers.
+ *
+ * Copyright (C) 2003 David S. Miller (davem@redhat.com)
+ */
+
+#include <linux/compat.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/fb.h>
+#include <linux/mm.h>
+#include <linux/uaccess.h>
+#include <linux/of.h>
+
+#include <asm/fbio.h>
+
+#include "sbuslib.h"
+
+void sbusfb_fill_var(struct fb_var_screeninfo *var, struct device_node *dp,
+		     int bpp)
+{
+	memset(var, 0, sizeof(*var));
+
+	var->xres = of_getintprop_default(dp, "width", 1152);
+	var->yres = of_getintprop_default(dp, "height", 900);
+	var->xres_virtual = var->xres;
+	var->yres_virtual = var->yres;
+	var->bits_per_pixel = bpp;
+}
+
+EXPORT_SYMBOL(sbusfb_fill_var);
+
+static unsigned long sbusfb_mmapsize(long size, unsigned long fbsize)
+{
+	if (size == SBUS_MMAP_EMPTY) return 0;
+	if (size >= 0) return size;
+	return fbsize * (-size);
+}
+
+int sbusfb_mmap_helper(const struct sbus_mmap_map *map,
+		       unsigned long physbase,
+		       unsigned long fbsize,
+		       unsigned long iospace,
+		       struct vm_area_struct *vma)
+{
+	unsigned int size, page, r, map_size;
+	unsigned long map_offset = 0;
+	unsigned long off;
+	int i;
+
+	if (!(vma->vm_flags & (VM_SHARED | VM_MAYSHARE)))
+		return -EINVAL;
+
+	size = vma->vm_end - vma->vm_start;
+	if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT))
+		return -EINVAL;
+
+	off = vma->vm_pgoff << PAGE_SHIFT;
+
+	/* VM_IO | VM_DONTEXPAND | VM_DONTDUMP are set by remap_pfn_range() */
+
+	vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+	/* Each page, see which map applies */
+	for (page = 0; page < size; ){
+		map_size = 0;
+		for (i = 0; map[i].size; i++)
+			if (map[i].voff == off+page) {
+				map_size = sbusfb_mmapsize(map[i].size, fbsize);
+#ifdef __sparc_v9__
+#define POFF_MASK	(PAGE_MASK|0x1UL)
+#else
+#define POFF_MASK	(PAGE_MASK)
+#endif
+				map_offset = (physbase + map[i].poff) & POFF_MASK;
+				break;
+			}
+		if (!map_size) {
+			page += PAGE_SIZE;
+			continue;
+		}
+		if (page + map_size > size)
+			map_size = size - page;
+		r = io_remap_pfn_range(vma,
+					vma->vm_start + page,
+					MK_IOSPACE_PFN(iospace,
+						map_offset >> PAGE_SHIFT),
+					map_size,
+					vma->vm_page_prot);
+		if (r)
+			return -EAGAIN;
+		page += map_size;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(sbusfb_mmap_helper);
+
+int sbusfb_ioctl_helper(unsigned long cmd, unsigned long arg,
+			struct fb_info *info,
+			int type, int fb_depth, unsigned long fb_size)
+{
+	switch(cmd) {
+	case FBIOGTYPE: {
+		struct fbtype __user *f = (struct fbtype __user *) arg;
+
+		if (put_user(type, &f->fb_type) ||
+		    put_user(info->var.yres, &f->fb_height) ||
+		    put_user(info->var.xres, &f->fb_width) ||
+		    put_user(fb_depth, &f->fb_depth) ||
+		    put_user(0, &f->fb_cmsize) ||
+		    put_user(fb_size, &f->fb_cmsize))
+			return -EFAULT;
+		return 0;
+	}
+	case FBIOPUTCMAP_SPARC: {
+		struct fbcmap __user *c = (struct fbcmap __user *) arg;
+		struct fb_cmap cmap;
+		u16 red, green, blue;
+		u8 red8, green8, blue8;
+		unsigned char __user *ured;
+		unsigned char __user *ugreen;
+		unsigned char __user *ublue;
+		unsigned int index, count, i;
+
+		if (get_user(index, &c->index) ||
+		    get_user(count, &c->count) ||
+		    get_user(ured, &c->red) ||
+		    get_user(ugreen, &c->green) ||
+		    get_user(ublue, &c->blue))
+			return -EFAULT;
+
+		cmap.len = 1;
+		cmap.red = &red;
+		cmap.green = &green;
+		cmap.blue = &blue;
+		cmap.transp = NULL;
+		for (i = 0; i < count; i++) {
+			int err;
+
+			if (get_user(red8, &ured[i]) ||
+			    get_user(green8, &ugreen[i]) ||
+			    get_user(blue8, &ublue[i]))
+				return -EFAULT;
+
+			red = red8 << 8;
+			green = green8 << 8;
+			blue = blue8 << 8;
+
+			cmap.start = index + i;
+			err = fb_set_cmap(&cmap, info);
+			if (err)
+				return err;
+		}
+		return 0;
+	}
+	case FBIOGETCMAP_SPARC: {
+		struct fbcmap __user *c = (struct fbcmap __user *) arg;
+		unsigned char __user *ured;
+		unsigned char __user *ugreen;
+		unsigned char __user *ublue;
+		struct fb_cmap *cmap = &info->cmap;
+		unsigned int index, count, i;
+		u8 red, green, blue;
+
+		if (get_user(index, &c->index) ||
+		    get_user(count, &c->count) ||
+		    get_user(ured, &c->red) ||
+		    get_user(ugreen, &c->green) ||
+		    get_user(ublue, &c->blue))
+			return -EFAULT;
+
+		if (index > cmap->len || count > cmap->len - index)
+			return -EINVAL;
+
+		for (i = 0; i < count; i++) {
+			red = cmap->red[index + i] >> 8;
+			green = cmap->green[index + i] >> 8;
+			blue = cmap->blue[index + i] >> 8;
+			if (put_user(red, &ured[i]) ||
+			    put_user(green, &ugreen[i]) ||
+			    put_user(blue, &ublue[i]))
+				return -EFAULT;
+		}
+		return 0;
+	}
+	default:
+		return -EINVAL;
+	}
+}
+EXPORT_SYMBOL(sbusfb_ioctl_helper);
+
+#ifdef CONFIG_COMPAT
+int sbusfb_compat_ioctl(struct fb_info *info, unsigned int cmd, unsigned long arg)
+{
+	switch (cmd) {
+	case FBIOGTYPE:
+	case FBIOSATTR:
+	case FBIOGATTR:
+	case FBIOSVIDEO:
+	case FBIOGVIDEO:
+	case FBIOSCURSOR32:
+	case FBIOGCURSOR32:	/* This is not implemented yet.
+				   Later it should be converted... */
+	case FBIOSCURPOS:
+	case FBIOGCURPOS:
+	case FBIOGCURMAX:
+		return info->fbops->fb_ioctl(info, cmd, arg);
+	case FBIOPUTCMAP32:
+	case FBIOPUTCMAP_SPARC: {
+		struct fbcmap32 c;
+		struct fb_cmap cmap;
+		u16 red, green, blue;
+		u8 red8, green8, blue8;
+		unsigned char __user *ured;
+		unsigned char __user *ugreen;
+		unsigned char __user *ublue;
+		unsigned int i;
+
+		if (copy_from_user(&c, compat_ptr(arg), sizeof(c)))
+			return -EFAULT;
+		ured = compat_ptr(c.red);
+		ugreen = compat_ptr(c.green);
+		ublue = compat_ptr(c.blue);
+
+		cmap.len = 1;
+		cmap.red = &red;
+		cmap.green = &green;
+		cmap.blue = &blue;
+		cmap.transp = NULL;
+		for (i = 0; i < c.count; i++) {
+			int err;
+
+			if (get_user(red8, &ured[i]) ||
+			    get_user(green8, &ugreen[i]) ||
+			    get_user(blue8, &ublue[i]))
+				return -EFAULT;
+
+			red = red8 << 8;
+			green = green8 << 8;
+			blue = blue8 << 8;
+
+			cmap.start = c.index + i;
+			err = fb_set_cmap(&cmap, info);
+			if (err)
+				return err;
+		}
+		return 0;
+	}
+	case FBIOGETCMAP32: {
+		struct fbcmap32 c;
+		unsigned char __user *ured;
+		unsigned char __user *ugreen;
+		unsigned char __user *ublue;
+		struct fb_cmap *cmap = &info->cmap;
+		unsigned int index, i;
+		u8 red, green, blue;
+
+		if (copy_from_user(&c, compat_ptr(arg), sizeof(c)))
+			return -EFAULT;
+		index = c.index;
+		ured = compat_ptr(c.red);
+		ugreen = compat_ptr(c.green);
+		ublue = compat_ptr(c.blue);
+
+		if (index > cmap->len || c.count > cmap->len - index)
+			return -EINVAL;
+
+		for (i = 0; i < c.count; i++) {
+			red = cmap->red[index + i] >> 8;
+			green = cmap->green[index + i] >> 8;
+			blue = cmap->blue[index + i] >> 8;
+			if (put_user(red, &ured[i]) ||
+			    put_user(green, &ugreen[i]) ||
+			    put_user(blue, &ublue[i]))
+				return -EFAULT;
+		}
+		return 0;
+	}
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+EXPORT_SYMBOL(sbusfb_compat_ioctl);
+#endif