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Revision 18bc7bd523e0fc5be8d76bf84bde733a97a8c375 authored by Andy Lutomirski on 10 August 2016, 09:29:14 UTC, committed by Ingo Molnar on 11 August 2016, 09:15:00 UTC 
x86/boot: Synchronize trampoline_cr4_features and mmu_cr4_features directly
 
The initialization process for trampoline_cr4_features and
mmu_cr4_features was confusing.  The intent is for mmu_cr4_features
and *trampoline_cr4_features to stay in sync, but
trampoline_cr4_features is NULL until setup_real_mode() runs.  The
old code synchronized *trampoline_cr4_features *twice*, once in
setup_real_mode() and once in setup_arch().  It also initialized
mmu_cr4_features in setup_real_mode(), which causes the actual value
of mmu_cr4_features to potentially depend on when setup_real_mode()
is called.

With this patch, mmu_cr4_features is initialized directly in
setup_arch(), and *trampoline_cr4_features is synchronized to
mmu_cr4_features when the trampoline is set up.

After this patch, it should be safe to defer setup_real_mode().

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mario Limonciello <mario_limonciello@dell.com>
Cc: Matt Fleming <mfleming@suse.de>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/d48a263f9912389b957dd495a7127b009259ffe0.1470821230.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1 parent 007b756
Raw File
stacktrace.c 
/*
 * kernel/stacktrace.c
 *
 * Stack trace management functions
 *
 *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 */
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/kallsyms.h>
#include <linux/stacktrace.h>

void print_stack_trace(struct stack_trace *trace, int spaces)
{
	int i;

	if (WARN_ON(!trace->entries))
		return;

	for (i = 0; i < trace->nr_entries; i++) {
		printk("%*c", 1 + spaces, ' ');
		print_ip_sym(trace->entries[i]);
	}
}
EXPORT_SYMBOL_GPL(print_stack_trace);

int snprint_stack_trace(char *buf, size_t size,
			struct stack_trace *trace, int spaces)
{
	int i;
	unsigned long ip;
	int generated;
	int total = 0;

	if (WARN_ON(!trace->entries))
		return 0;

	for (i = 0; i < trace->nr_entries; i++) {
		ip = trace->entries[i];
		generated = snprintf(buf, size, "%*c[<%p>] %pS\n",
				1 + spaces, ' ', (void *) ip, (void *) ip);

		total += generated;

		/* Assume that generated isn't a negative number */
		if (generated >= size) {
			buf += size;
			size = 0;
		} else {
			buf += generated;
			size -= generated;
		}
	}

	return total;
}
EXPORT_SYMBOL_GPL(snprint_stack_trace);

/*
 * Architectures that do not implement save_stack_trace_tsk or
 * save_stack_trace_regs get this weak alias and a once-per-bootup warning
 * (whenever this facility is utilized - for example by procfs):
 */
__weak void
save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
	WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
}

__weak void
save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
{
	WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
}
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