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, 366 insertions, 0 deletions

diff --git a/scripts/markup_oops.pl b/scripts/markup_oops.pl
new file mode 100755
index 000000000..e476caf52
--- /dev/null
+++ b/scripts/markup_oops.pl
@@ -0,0 +1,366 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0-only
+
+use File::Basename;
+use Math::BigInt;
+use Getopt::Long;
+
+# Copyright 2008, Intel Corporation
+#
+# This file is part of the Linux kernel
+#
+# Authors:
+# 	Arjan van de Ven <arjan@linux.intel.com>
+
+
+my $cross_compile = "";
+my $vmlinux_name = "";
+my $modulefile = "";
+
+# Get options
+Getopt::Long::GetOptions(
+	'cross-compile|c=s'	=> \$cross_compile,
+	'module|m=s'		=> \$modulefile,
+	'help|h'		=> \&usage,
+) || usage ();
+my $vmlinux_name = $ARGV[0];
+if (!defined($vmlinux_name)) {
+	my $kerver = `uname -r`;
+	chomp($kerver);
+	$vmlinux_name = "/lib/modules/$kerver/build/vmlinux";
+	print "No vmlinux specified, assuming $vmlinux_name\n";
+}
+my $filename = $vmlinux_name;
+
+# Parse the oops to find the EIP value
+
+my $target = "0";
+my $function;
+my $module = "";
+my $func_offset = 0;
+my $vmaoffset = 0;
+
+my %regs;
+
+
+sub parse_x86_regs
+{
+	my ($line) = @_;
+	if ($line =~ /EAX: ([0-9a-f]+) EBX: ([0-9a-f]+) ECX: ([0-9a-f]+) EDX: ([0-9a-f]+)/) {
+		$regs{"%eax"} = $1;
+		$regs{"%ebx"} = $2;
+		$regs{"%ecx"} = $3;
+		$regs{"%edx"} = $4;
+	}
+	if ($line =~ /ESI: ([0-9a-f]+) EDI: ([0-9a-f]+) EBP: ([0-9a-f]+) ESP: ([0-9a-f]+)/) {
+		$regs{"%esi"} = $1;
+		$regs{"%edi"} = $2;
+		$regs{"%esp"} = $4;
+	}
+	if ($line =~ /RAX: ([0-9a-f]+) RBX: ([0-9a-f]+) RCX: ([0-9a-f]+)/) {
+		$regs{"%eax"} = $1;
+		$regs{"%ebx"} = $2;
+		$regs{"%ecx"} = $3;
+	}
+	if ($line =~ /RDX: ([0-9a-f]+) RSI: ([0-9a-f]+) RDI: ([0-9a-f]+)/) {
+		$regs{"%edx"} = $1;
+		$regs{"%esi"} = $2;
+		$regs{"%edi"} = $3;
+	}
+	if ($line =~ /RBP: ([0-9a-f]+) R08: ([0-9a-f]+) R09: ([0-9a-f]+)/) {
+		$regs{"%r08"} = $2;
+		$regs{"%r09"} = $3;
+	}
+	if ($line =~ /R10: ([0-9a-f]+) R11: ([0-9a-f]+) R12: ([0-9a-f]+)/) {
+		$regs{"%r10"} = $1;
+		$regs{"%r11"} = $2;
+		$regs{"%r12"} = $3;
+	}
+	if ($line =~ /R13: ([0-9a-f]+) R14: ([0-9a-f]+) R15: ([0-9a-f]+)/) {
+		$regs{"%r13"} = $1;
+		$regs{"%r14"} = $2;
+		$regs{"%r15"} = $3;
+	}
+}
+
+sub reg_name
+{
+	my ($reg) = @_;
+	$reg =~ s/r(.)x/e\1x/;
+	$reg =~ s/r(.)i/e\1i/;
+	$reg =~ s/r(.)p/e\1p/;
+	return $reg;
+}
+
+sub process_x86_regs
+{
+	my ($line, $cntr) = @_;
+	my $str = "";
+	if (length($line) < 40) {
+		return ""; # not an asm istruction
+	}
+
+	# find the arguments to the instruction
+	if ($line =~ /([0-9a-zA-Z\,\%\(\)\-\+]+)$/) {
+		$lastword = $1;
+	} else {
+		return "";
+	}
+
+	# we need to find the registers that get clobbered,
+	# since their value is no longer relevant for previous
+	# instructions in the stream.
+
+	$clobber = $lastword;
+	# first, remove all memory operands, they're read only
+	$clobber =~ s/\([a-z0-9\%\,]+\)//g;
+	# then, remove everything before the comma, thats the read part
+	$clobber =~ s/.*\,//g;
+
+	# if this is the instruction that faulted, we haven't actually done
+	# the write yet... nothing is clobbered.
+	if ($cntr == 0) {
+		$clobber = "";
+	}
+
+	foreach $reg (keys(%regs)) {
+		my $clobberprime = reg_name($clobber);
+		my $lastwordprime = reg_name($lastword);
+		my $val = $regs{$reg};
+		if ($val =~ /^[0]+$/) {
+			$val = "0";
+		} else {
+			$val =~ s/^0*//;
+		}
+
+		# first check if we're clobbering this register; if we do
+		# we print it with a =>, and then delete its value
+		if ($clobber =~ /$reg/ || $clobberprime =~ /$reg/) {
+			if (length($val) > 0) {
+				$str = $str . " $reg => $val ";
+			}
+			$regs{$reg} = "";
+			$val = "";
+		}
+		# now check if we're reading this register
+		if ($lastword =~ /$reg/ || $lastwordprime =~ /$reg/) {
+			if (length($val) > 0) {
+				$str = $str . " $reg = $val ";
+			}
+		}
+	}
+	return $str;
+}
+
+# parse the oops
+while (<STDIN>) {
+	my $line = $_;
+	if ($line =~ /EIP: 0060:\[\<([a-z0-9]+)\>\]/) {
+		$target = $1;
+	}
+	if ($line =~ /RIP: 0010:\[\<([a-z0-9]+)\>\]/) {
+		$target = $1;
+	}
+	if ($line =~ /EIP is at ([a-zA-Z0-9\_]+)\+0x([0-9a-f]+)\/0x[a-f0-9]/) {
+		$function = $1;
+		$func_offset = $2;
+	}
+	if ($line =~ /RIP: 0010:\[\<[0-9a-f]+\>\]  \[\<[0-9a-f]+\>\] ([a-zA-Z0-9\_]+)\+0x([0-9a-f]+)\/0x[a-f0-9]/) {
+		$function = $1;
+		$func_offset = $2;
+	}
+
+	# check if it's a module
+	if ($line =~ /EIP is at ([a-zA-Z0-9\_]+)\+(0x[0-9a-f]+)\/0x[a-f0-9]+\W\[([a-zA-Z0-9\_\-]+)\]/) {
+		$module = $3;
+	}
+	if ($line =~ /RIP: 0010:\[\<[0-9a-f]+\>\]  \[\<[0-9a-f]+\>\] ([a-zA-Z0-9\_]+)\+(0x[0-9a-f]+)\/0x[a-f0-9]+\W\[([a-zA-Z0-9\_\-]+)\]/) {
+		$module = $3;
+	}
+	parse_x86_regs($line);
+}
+
+my $decodestart = Math::BigInt->from_hex("0x$target") - Math::BigInt->from_hex("0x$func_offset");
+my $decodestop = Math::BigInt->from_hex("0x$target") + 8192;
+if ($target eq "0") {
+	print "No oops found!\n";
+	usage();
+}
+
+# if it's a module, we need to find the .ko file and calculate a load offset
+if ($module ne "") {
+	if ($modulefile eq "") {
+		$modulefile = `modinfo -F filename $module`;
+		chomp($modulefile);
+	}
+	$filename = $modulefile;
+	if ($filename eq "") {
+		print "Module .ko file for $module not found. Aborting\n";
+		exit;
+	}
+	# ok so we found the module, now we need to calculate the vma offset
+	open(FILE, $cross_compile."objdump -dS $filename |") || die "Cannot start objdump";
+	while (<FILE>) {
+		if ($_ =~ /^([0-9a-f]+) \<$function\>\:/) {
+			my $fu = $1;
+			$vmaoffset = Math::BigInt->from_hex("0x$target") - Math::BigInt->from_hex("0x$fu") - Math::BigInt->from_hex("0x$func_offset");
+		}
+	}
+	close(FILE);
+}
+
+my $counter = 0;
+my $state   = 0;
+my $center  = -1;
+my @lines;
+my @reglines;
+
+sub InRange {
+	my ($address, $target) = @_;
+	my $ad = "0x".$address;
+	my $ta = "0x".$target;
+	my $delta = Math::BigInt->from_hex($ad) - Math::BigInt->from_hex($ta);
+
+	if (($delta > -4096) && ($delta < 4096)) {
+		return 1;
+	}
+	return 0;
+}
+
+
+
+# first, parse the input into the lines array, but to keep size down,
+# we only do this for 4Kb around the sweet spot
+
+open(FILE, $cross_compile."objdump -dS --adjust-vma=$vmaoffset --start-address=$decodestart --stop-address=$decodestop $filename |") || die "Cannot start objdump";
+
+while (<FILE>) {
+	my $line = $_;
+	chomp($line);
+	if ($state == 0) {
+		if ($line =~ /^([a-f0-9]+)\:/) {
+			if (InRange($1, $target)) {
+				$state = 1;
+			}
+		}
+	}
+	if ($state == 1) {
+		if ($line =~ /^([a-f0-9][a-f0-9][a-f0-9][a-f0-9][a-f0-9][a-f0-9]+)\:/) {
+			my $val = $1;
+			if (!InRange($val, $target)) {
+				last;
+			}
+			if ($val eq $target) {
+				$center = $counter;
+			}
+		}
+		$lines[$counter] = $line;
+
+		$counter = $counter + 1;
+	}
+}
+
+close(FILE);
+
+if ($counter == 0) {
+	print "No matching code found \n";
+	exit;
+}
+
+if ($center == -1) {
+	print "No matching code found \n";
+	exit;
+}
+
+my $start;
+my $finish;
+my $codelines = 0;
+my $binarylines = 0;
+# now we go up and down in the array to find how much we want to print
+
+$start = $center;
+
+while ($start > 1) {
+	$start = $start - 1;
+	my $line = $lines[$start];
+	if ($line =~ /^([a-f0-9]+)\:/) {
+		$binarylines = $binarylines + 1;
+	} else {
+		$codelines = $codelines + 1;
+	}
+	if ($codelines > 10) {
+		last;
+	}
+	if ($binarylines > 20) {
+		last;
+	}
+}
+
+
+$finish = $center;
+$codelines = 0;
+$binarylines = 0;
+while ($finish < $counter) {
+	$finish = $finish + 1;
+	my $line = $lines[$finish];
+	if ($line =~ /^([a-f0-9]+)\:/) {
+		$binarylines = $binarylines + 1;
+	} else {
+		$codelines = $codelines + 1;
+	}
+	if ($codelines > 10) {
+		last;
+	}
+	if ($binarylines > 20) {
+		last;
+	}
+}
+
+
+my $i;
+
+
+# start annotating the registers in the asm.
+# this goes from the oopsing point back, so that the annotator
+# can track (opportunistically) which registers got written and
+# whos value no longer is relevant.
+
+$i = $center;
+while ($i >= $start) {
+	$reglines[$i] = process_x86_regs($lines[$i], $center - $i);
+	$i = $i - 1;
+}
+
+$i = $start;
+while ($i < $finish) {
+	my $line;
+	if ($i == $center) {
+		$line =  "*$lines[$i] ";
+	} else {
+		$line =  " $lines[$i] ";
+	}
+	print $line;
+	if (defined($reglines[$i]) && length($reglines[$i]) > 0) {
+		my $c = 60 - length($line);
+		while ($c > 0) { print " "; $c = $c - 1; };
+		print "| $reglines[$i]";
+	}
+	if ($i == $center) {
+		print "<--- faulting instruction";
+	}
+	print "\n";
+	$i = $i +1;
+}
+
+sub usage {
+	print <<EOT;
+Usage:
+  dmesg | perl $0 [OPTION] [VMLINUX]
+
+OPTION:
+  -c, --cross-compile CROSS_COMPILE	Specify the prefix used for toolchain.
+  -m, --module MODULE_DIRNAME		Specify the module filename.
+  -h, --help				Help.
+EOT
+	exit;
+}