Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 1213 insertions, 0 deletions

diff --git a/scripts/kconfig/expr.c b/scripts/kconfig/expr.c
new file mode 100644
index 000000000..2b91d16bf
--- /dev/null
+++ b/scripts/kconfig/expr.c
@@ -0,0 +1,1213 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2002 Roman Zippel <zippel@linux-m68k.org>
+ */
+
+#include <ctype.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <hash.h>
+#include <xalloc.h>
+#include "internal.h"
+#include "lkc.h"
+
+#define DEBUG_EXPR	0
+
+HASHTABLE_DEFINE(expr_hashtable, EXPR_HASHSIZE);
+
+static struct expr *expr_eliminate_yn(struct expr *e);
+
+/**
+ * expr_lookup - return the expression with the given type and sub-nodes
+ * This looks up an expression with the specified type and sub-nodes. If such
+ * an expression is found in the hash table, it is returned. Otherwise, a new
+ * expression node is allocated and added to the hash table.
+ * @type: expression type
+ * @l: left node
+ * @r: right node
+ * return: expression
+ */
+static struct expr *expr_lookup(enum expr_type type, void *l, void *r)
+{
+	struct expr *e;
+	int hash;
+
+	hash = hash_32((unsigned int)type ^ hash_ptr(l) ^ hash_ptr(r));
+
+	hash_for_each_possible(expr_hashtable, e, node, hash) {
+		if (e->type == type && e->left._initdata == l &&
+		    e->right._initdata == r)
+			return e;
+	}
+
+	e = xmalloc(sizeof(*e));
+	e->type = type;
+	e->left._initdata = l;
+	e->right._initdata = r;
+	e->val_is_valid = false;
+
+	hash_add(expr_hashtable, &e->node, hash);
+
+	return e;
+}
+
+struct expr *expr_alloc_symbol(struct symbol *sym)
+{
+	return expr_lookup(E_SYMBOL, sym, NULL);
+}
+
+struct expr *expr_alloc_one(enum expr_type type, struct expr *ce)
+{
+	return expr_lookup(type, ce, NULL);
+}
+
+struct expr *expr_alloc_two(enum expr_type type, struct expr *e1, struct expr *e2)
+{
+	return expr_lookup(type, e1, e2);
+}
+
+struct expr *expr_alloc_comp(enum expr_type type, struct symbol *s1, struct symbol *s2)
+{
+	return expr_lookup(type, s1, s2);
+}
+
+struct expr *expr_alloc_and(struct expr *e1, struct expr *e2)
+{
+	if (!e1)
+		return e2;
+	return e2 ? expr_alloc_two(E_AND, e1, e2) : e1;
+}
+
+struct expr *expr_alloc_or(struct expr *e1, struct expr *e2)
+{
+	if (!e1)
+		return e2;
+	return e2 ? expr_alloc_two(E_OR, e1, e2) : e1;
+}
+
+static int trans_count;
+
+/*
+ * expr_eliminate_eq() helper.
+ *
+ * Walks the two expression trees given in 'ep1' and 'ep2'. Any node that does
+ * not have type 'type' (E_OR/E_AND) is considered a leaf, and is compared
+ * against all other leaves. Two equal leaves are both replaced with either 'y'
+ * or 'n' as appropriate for 'type', to be eliminated later.
+ */
+static void __expr_eliminate_eq(enum expr_type type, struct expr **ep1, struct expr **ep2)
+{
+	struct expr *l, *r;
+
+	/* Recurse down to leaves */
+
+	if ((*ep1)->type == type) {
+		l = (*ep1)->left.expr;
+		r = (*ep1)->right.expr;
+		__expr_eliminate_eq(type, &l, ep2);
+		__expr_eliminate_eq(type, &r, ep2);
+		*ep1 = expr_alloc_two(type, l, r);
+		return;
+	}
+	if ((*ep2)->type == type) {
+		l = (*ep2)->left.expr;
+		r = (*ep2)->right.expr;
+		__expr_eliminate_eq(type, ep1, &l);
+		__expr_eliminate_eq(type, ep1, &r);
+		*ep2 = expr_alloc_two(type, l, r);
+		return;
+	}
+
+	/* *ep1 and *ep2 are leaves. Compare them. */
+
+	if ((*ep1)->type == E_SYMBOL && (*ep2)->type == E_SYMBOL &&
+	    (*ep1)->left.sym == (*ep2)->left.sym &&
+	    ((*ep1)->left.sym == &symbol_yes || (*ep1)->left.sym == &symbol_no))
+		return;
+	if (!expr_eq(*ep1, *ep2))
+		return;
+
+	/* *ep1 and *ep2 are equal leaves. Prepare them for elimination. */
+
+	trans_count++;
+	switch (type) {
+	case E_OR:
+		*ep1 = expr_alloc_symbol(&symbol_no);
+		*ep2 = expr_alloc_symbol(&symbol_no);
+		break;
+	case E_AND:
+		*ep1 = expr_alloc_symbol(&symbol_yes);
+		*ep2 = expr_alloc_symbol(&symbol_yes);
+		break;
+	default:
+		;
+	}
+}
+
+/*
+ * Rewrites the expressions 'ep1' and 'ep2' to remove operands common to both.
+ * Example reductions:
+ *
+ *	ep1: A && B           ->  ep1: y
+ *	ep2: A && B && C      ->  ep2: C
+ *
+ *	ep1: A || B           ->  ep1: n
+ *	ep2: A || B || C      ->  ep2: C
+ *
+ *	ep1: A && (B && FOO)  ->  ep1: FOO
+ *	ep2: (BAR && B) && A  ->  ep2: BAR
+ *
+ *	ep1: A && (B || C)    ->  ep1: y
+ *	ep2: (C || B) && A    ->  ep2: y
+ *
+ * Comparisons are done between all operands at the same "level" of && or ||.
+ * For example, in the expression 'e1 && (e2 || e3) && (e4 || e5)', the
+ * following operands will be compared:
+ *
+ *	- 'e1', 'e2 || e3', and 'e4 || e5', against each other
+ *	- e2 against e3
+ *	- e4 against e5
+ *
+ * Parentheses are irrelevant within a single level. 'e1 && (e2 && e3)' and
+ * '(e1 && e2) && e3' are both a single level.
+ *
+ * See __expr_eliminate_eq() as well.
+ */
+void expr_eliminate_eq(struct expr **ep1, struct expr **ep2)
+{
+	if (!*ep1 || !*ep2)
+		return;
+	switch ((*ep1)->type) {
+	case E_OR:
+	case E_AND:
+		__expr_eliminate_eq((*ep1)->type, ep1, ep2);
+	default:
+		;
+	}
+	if ((*ep1)->type != (*ep2)->type) switch ((*ep2)->type) {
+	case E_OR:
+	case E_AND:
+		__expr_eliminate_eq((*ep2)->type, ep1, ep2);
+	default:
+		;
+	}
+	*ep1 = expr_eliminate_yn(*ep1);
+	*ep2 = expr_eliminate_yn(*ep2);
+}
+
+/*
+ * Returns true if 'e1' and 'e2' are equal, after minor simplification. Two
+ * &&/|| expressions are considered equal if every operand in one expression
+ * equals some operand in the other (operands do not need to appear in the same
+ * order), recursively.
+ */
+bool expr_eq(struct expr *e1, struct expr *e2)
+{
+	int old_count;
+	bool res;
+
+	/*
+	 * A NULL expr is taken to be yes, but there's also a different way to
+	 * represent yes. expr_is_yes() checks for either representation.
+	 */
+	if (!e1 || !e2)
+		return expr_is_yes(e1) && expr_is_yes(e2);
+
+	if (e1->type != e2->type)
+		return false;
+	switch (e1->type) {
+	case E_EQUAL:
+	case E_GEQ:
+	case E_GTH:
+	case E_LEQ:
+	case E_LTH:
+	case E_UNEQUAL:
+		return e1->left.sym == e2->left.sym && e1->right.sym == e2->right.sym;
+	case E_SYMBOL:
+		return e1->left.sym == e2->left.sym;
+	case E_NOT:
+		return expr_eq(e1->left.expr, e2->left.expr);
+	case E_AND:
+	case E_OR:
+		old_count = trans_count;
+		expr_eliminate_eq(&e1, &e2);
+		res = (e1->type == E_SYMBOL && e2->type == E_SYMBOL &&
+		       e1->left.sym == e2->left.sym);
+		trans_count = old_count;
+		return res;
+	case E_RANGE:
+	case E_NONE:
+		/* panic */;
+	}
+
+	if (DEBUG_EXPR) {
+		expr_fprint(e1, stdout);
+		printf(" = ");
+		expr_fprint(e2, stdout);
+		printf(" ?\n");
+	}
+
+	return false;
+}
+
+/*
+ * Recursively performs the following simplifications (as well as the
+ * corresponding simplifications with swapped operands):
+ *
+ *	expr && n  ->  n
+ *	expr && y  ->  expr
+ *	expr || n  ->  expr
+ *	expr || y  ->  y
+ *
+ * Returns the optimized expression.
+ */
+static struct expr *expr_eliminate_yn(struct expr *e)
+{
+	struct expr *l, *r;
+
+	if (e) switch (e->type) {
+	case E_AND:
+		l = expr_eliminate_yn(e->left.expr);
+		r = expr_eliminate_yn(e->right.expr);
+		if (l->type == E_SYMBOL) {
+			if (l->left.sym == &symbol_no)
+				return l;
+			else if (l->left.sym == &symbol_yes)
+				return r;
+		}
+		if (r->type == E_SYMBOL) {
+			if (r->left.sym == &symbol_no)
+				return r;
+			else if (r->left.sym == &symbol_yes)
+				return l;
+		}
+		break;
+	case E_OR:
+		l = expr_eliminate_yn(e->left.expr);
+		r = expr_eliminate_yn(e->right.expr);
+		if (l->type == E_SYMBOL) {
+			if (l->left.sym == &symbol_no)
+				return r;
+			else if (l->left.sym == &symbol_yes)
+				return l;
+		}
+		if (r->type == E_SYMBOL) {
+			if (r->left.sym == &symbol_no)
+				return l;
+			else if (r->left.sym == &symbol_yes)
+				return r;
+		}
+		break;
+	default:
+		;
+	}
+	return e;
+}
+
+/*
+ * e1 || e2 -> ?
+ */
+static struct expr *expr_join_or(struct expr *e1, struct expr *e2)
+{
+	struct expr *tmp;
+	struct symbol *sym1, *sym2;
+
+	if (expr_eq(e1, e2))
+		return e1;
+	if (e1->type != E_EQUAL && e1->type != E_UNEQUAL && e1->type != E_SYMBOL && e1->type != E_NOT)
+		return NULL;
+	if (e2->type != E_EQUAL && e2->type != E_UNEQUAL && e2->type != E_SYMBOL && e2->type != E_NOT)
+		return NULL;
+	if (e1->type == E_NOT) {
+		tmp = e1->left.expr;
+		if (tmp->type != E_EQUAL && tmp->type != E_UNEQUAL && tmp->type != E_SYMBOL)
+			return NULL;
+		sym1 = tmp->left.sym;
+	} else
+		sym1 = e1->left.sym;
+	if (e2->type == E_NOT) {
+		if (e2->left.expr->type != E_SYMBOL)
+			return NULL;
+		sym2 = e2->left.expr->left.sym;
+	} else
+		sym2 = e2->left.sym;
+	if (sym1 != sym2)
+		return NULL;
+	if (sym1->type != S_BOOLEAN && sym1->type != S_TRISTATE)
+		return NULL;
+	if (sym1->type == S_TRISTATE) {
+		if (e1->type == E_EQUAL && e2->type == E_EQUAL &&
+		    ((e1->right.sym == &symbol_yes && e2->right.sym == &symbol_mod) ||
+		     (e1->right.sym == &symbol_mod && e2->right.sym == &symbol_yes))) {
+			// (a='y') || (a='m') -> (a!='n')
+			return expr_alloc_comp(E_UNEQUAL, sym1, &symbol_no);
+		}
+		if (e1->type == E_EQUAL && e2->type == E_EQUAL &&
+		    ((e1->right.sym == &symbol_yes && e2->right.sym == &symbol_no) ||
+		     (e1->right.sym == &symbol_no && e2->right.sym == &symbol_yes))) {
+			// (a='y') || (a='n') -> (a!='m')
+			return expr_alloc_comp(E_UNEQUAL, sym1, &symbol_mod);
+		}
+		if (e1->type == E_EQUAL && e2->type == E_EQUAL &&
+		    ((e1->right.sym == &symbol_mod && e2->right.sym == &symbol_no) ||
+		     (e1->right.sym == &symbol_no && e2->right.sym == &symbol_mod))) {
+			// (a='m') || (a='n') -> (a!='y')
+			return expr_alloc_comp(E_UNEQUAL, sym1, &symbol_yes);
+		}
+	}
+	if (sym1->type == S_BOOLEAN) {
+		// a || !a -> y
+		if ((e1->type == E_NOT && e1->left.expr->type == E_SYMBOL && e2->type == E_SYMBOL) ||
+		    (e2->type == E_NOT && e2->left.expr->type == E_SYMBOL && e1->type == E_SYMBOL))
+			return expr_alloc_symbol(&symbol_yes);
+	}
+
+	if (DEBUG_EXPR) {
+		printf("optimize (");
+		expr_fprint(e1, stdout);
+		printf(") || (");
+		expr_fprint(e2, stdout);
+		printf(")?\n");
+	}
+	return NULL;
+}
+
+static struct expr *expr_join_and(struct expr *e1, struct expr *e2)
+{
+	struct expr *tmp;
+	struct symbol *sym1, *sym2;
+
+	if (expr_eq(e1, e2))
+		return e1;
+	if (e1->type != E_EQUAL && e1->type != E_UNEQUAL && e1->type != E_SYMBOL && e1->type != E_NOT)
+		return NULL;
+	if (e2->type != E_EQUAL && e2->type != E_UNEQUAL && e2->type != E_SYMBOL && e2->type != E_NOT)
+		return NULL;
+	if (e1->type == E_NOT) {
+		tmp = e1->left.expr;
+		if (tmp->type != E_EQUAL && tmp->type != E_UNEQUAL && tmp->type != E_SYMBOL)
+			return NULL;
+		sym1 = tmp->left.sym;
+	} else
+		sym1 = e1->left.sym;
+	if (e2->type == E_NOT) {
+		if (e2->left.expr->type != E_SYMBOL)
+			return NULL;
+		sym2 = e2->left.expr->left.sym;
+	} else
+		sym2 = e2->left.sym;
+	if (sym1 != sym2)
+		return NULL;
+	if (sym1->type != S_BOOLEAN && sym1->type != S_TRISTATE)
+		return NULL;
+
+	if ((e1->type == E_SYMBOL && e2->type == E_EQUAL && e2->right.sym == &symbol_yes) ||
+	    (e2->type == E_SYMBOL && e1->type == E_EQUAL && e1->right.sym == &symbol_yes))
+		// (a) && (a='y') -> (a='y')
+		return expr_alloc_comp(E_EQUAL, sym1, &symbol_yes);
+
+	if ((e1->type == E_SYMBOL && e2->type == E_UNEQUAL && e2->right.sym == &symbol_no) ||
+	    (e2->type == E_SYMBOL && e1->type == E_UNEQUAL && e1->right.sym == &symbol_no))
+		// (a) && (a!='n') -> (a)
+		return expr_alloc_symbol(sym1);
+
+	if ((e1->type == E_SYMBOL && e2->type == E_UNEQUAL && e2->right.sym == &symbol_mod) ||
+	    (e2->type == E_SYMBOL && e1->type == E_UNEQUAL && e1->right.sym == &symbol_mod))
+		// (a) && (a!='m') -> (a='y')
+		return expr_alloc_comp(E_EQUAL, sym1, &symbol_yes);
+
+	if (sym1->type == S_TRISTATE) {
+		if (e1->type == E_EQUAL && e2->type == E_UNEQUAL) {
+			// (a='b') && (a!='c') -> 'b'='c' ? 'n' : a='b'
+			sym2 = e1->right.sym;
+			if ((e2->right.sym->flags & SYMBOL_CONST) && (sym2->flags & SYMBOL_CONST))
+				return sym2 != e2->right.sym ? expr_alloc_comp(E_EQUAL, sym1, sym2)
+							     : expr_alloc_symbol(&symbol_no);
+		}
+		if (e1->type == E_UNEQUAL && e2->type == E_EQUAL) {
+			// (a='b') && (a!='c') -> 'b'='c' ? 'n' : a='b'
+			sym2 = e2->right.sym;
+			if ((e1->right.sym->flags & SYMBOL_CONST) && (sym2->flags & SYMBOL_CONST))
+				return sym2 != e1->right.sym ? expr_alloc_comp(E_EQUAL, sym1, sym2)
+							     : expr_alloc_symbol(&symbol_no);
+		}
+		if (e1->type == E_UNEQUAL && e2->type == E_UNEQUAL &&
+			   ((e1->right.sym == &symbol_yes && e2->right.sym == &symbol_no) ||
+			    (e1->right.sym == &symbol_no && e2->right.sym == &symbol_yes)))
+			// (a!='y') && (a!='n') -> (a='m')
+			return expr_alloc_comp(E_EQUAL, sym1, &symbol_mod);
+
+		if (e1->type == E_UNEQUAL && e2->type == E_UNEQUAL &&
+			   ((e1->right.sym == &symbol_yes && e2->right.sym == &symbol_mod) ||
+			    (e1->right.sym == &symbol_mod && e2->right.sym == &symbol_yes)))
+			// (a!='y') && (a!='m') -> (a='n')
+			return expr_alloc_comp(E_EQUAL, sym1, &symbol_no);
+
+		if (e1->type == E_UNEQUAL && e2->type == E_UNEQUAL &&
+			   ((e1->right.sym == &symbol_mod && e2->right.sym == &symbol_no) ||
+			    (e1->right.sym == &symbol_no && e2->right.sym == &symbol_mod)))
+			// (a!='m') && (a!='n') -> (a='m')
+			return expr_alloc_comp(E_EQUAL, sym1, &symbol_yes);
+
+		if ((e1->type == E_SYMBOL && e2->type == E_EQUAL && e2->right.sym == &symbol_mod) ||
+		    (e2->type == E_SYMBOL && e1->type == E_EQUAL && e1->right.sym == &symbol_mod) ||
+		    (e1->type == E_SYMBOL && e2->type == E_UNEQUAL && e2->right.sym == &symbol_yes) ||
+		    (e2->type == E_SYMBOL && e1->type == E_UNEQUAL && e1->right.sym == &symbol_yes))
+			return NULL;
+	}
+
+	if (DEBUG_EXPR) {
+		printf("optimize (");
+		expr_fprint(e1, stdout);
+		printf(") && (");
+		expr_fprint(e2, stdout);
+		printf(")?\n");
+	}
+	return NULL;
+}
+
+/*
+ * expr_eliminate_dups() helper.
+ *
+ * Walks the two expression trees given in 'ep1' and 'ep2'. Any node that does
+ * not have type 'type' (E_OR/E_AND) is considered a leaf, and is compared
+ * against all other leaves to look for simplifications.
+ */
+static void expr_eliminate_dups1(enum expr_type type, struct expr **ep1, struct expr **ep2)
+{
+	struct expr *tmp, *l, *r;
+
+	/* Recurse down to leaves */
+
+	if ((*ep1)->type == type) {
+		l = (*ep1)->left.expr;
+		r = (*ep1)->right.expr;
+		expr_eliminate_dups1(type, &l, ep2);
+		expr_eliminate_dups1(type, &r, ep2);
+		*ep1 = expr_alloc_two(type, l, r);
+		return;
+	}
+	if ((*ep2)->type == type) {
+		l = (*ep2)->left.expr;
+		r = (*ep2)->right.expr;
+		expr_eliminate_dups1(type, ep1, &l);
+		expr_eliminate_dups1(type, ep1, &r);
+		*ep2 = expr_alloc_two(type, l, r);
+		return;
+	}
+
+	/* *ep1 and *ep2 are leaves. Compare and process them. */
+
+	switch (type) {
+	case E_OR:
+		tmp = expr_join_or(*ep1, *ep2);
+		if (tmp) {
+			*ep1 = expr_alloc_symbol(&symbol_no);
+			*ep2 = tmp;
+			trans_count++;
+		}
+		break;
+	case E_AND:
+		tmp = expr_join_and(*ep1, *ep2);
+		if (tmp) {
+			*ep1 = expr_alloc_symbol(&symbol_yes);
+			*ep2 = tmp;
+			trans_count++;
+		}
+		break;
+	default:
+		;
+	}
+}
+
+/*
+ * Rewrites 'e' in-place to remove ("join") duplicate and other redundant
+ * operands.
+ *
+ * Example simplifications:
+ *
+ *	A || B || A    ->  A || B
+ *	A && B && A=y  ->  A=y && B
+ *
+ * Returns the deduplicated expression.
+ */
+struct expr *expr_eliminate_dups(struct expr *e)
+{
+	int oldcount;
+	if (!e)
+		return e;
+
+	oldcount = trans_count;
+	do {
+		struct expr *l, *r;
+
+		trans_count = 0;
+		switch (e->type) {
+		case E_OR: case E_AND:
+			l = expr_eliminate_dups(e->left.expr);
+			r = expr_eliminate_dups(e->right.expr);
+			expr_eliminate_dups1(e->type, &l, &r);
+			e = expr_alloc_two(e->type, l, r);
+		default:
+			;
+		}
+		e = expr_eliminate_yn(e);
+	} while (trans_count); /* repeat until we get no more simplifications */
+	trans_count = oldcount;
+	return e;
+}
+
+/*
+ * Performs various simplifications involving logical operators and
+ * comparisons.
+ *
+ *   For bool type:
+ *     A=n        ->  !A
+ *     A=m        ->  n
+ *     A=y        ->  A
+ *     A!=n       ->  A
+ *     A!=m       ->  y
+ *     A!=y       ->  !A
+ *
+ *   For any type:
+ *     !!A        ->  A
+ *     !(A=B)     ->  A!=B
+ *     !(A!=B)    ->  A=B
+ *     !(A<=B)    ->  A>B
+ *     !(A>=B)    ->  A<B
+ *     !(A<B)     ->  A>=B
+ *     !(A>B)     ->  A<=B
+ *     !(A || B)  ->  !A && !B
+ *     !(A && B)  ->  !A || !B
+ *
+ *   For constant:
+ *     !y         ->  n
+ *     !m         ->  m
+ *     !n         ->  y
+ *
+ * Allocates and returns a new expression.
+ */
+struct expr *expr_transform(struct expr *e)
+{
+	if (!e)
+		return NULL;
+	switch (e->type) {
+	case E_EQUAL:
+	case E_GEQ:
+	case E_GTH:
+	case E_LEQ:
+	case E_LTH:
+	case E_UNEQUAL:
+	case E_SYMBOL:
+		break;
+	default:
+		e = expr_alloc_two(e->type,
+				   expr_transform(e->left.expr),
+				   expr_transform(e->right.expr));
+	}
+
+	switch (e->type) {
+	case E_EQUAL:
+		if (e->left.sym->type != S_BOOLEAN)
+			break;
+		if (e->right.sym == &symbol_no) {
+			// A=n -> !A
+			e = expr_alloc_one(E_NOT, expr_alloc_symbol(e->left.sym));
+			break;
+		}
+		if (e->right.sym == &symbol_mod) {
+			// A=m -> n
+			printf("boolean symbol %s tested for 'm'? test forced to 'n'\n", e->left.sym->name);
+			e = expr_alloc_symbol(&symbol_no);
+			break;
+		}
+		if (e->right.sym == &symbol_yes) {
+			// A=y -> A
+			e = expr_alloc_symbol(e->left.sym);
+			break;
+		}
+		break;
+	case E_UNEQUAL:
+		if (e->left.sym->type != S_BOOLEAN)
+			break;
+		if (e->right.sym == &symbol_no) {
+			// A!=n -> A
+			e = expr_alloc_symbol(e->left.sym);
+			break;
+		}
+		if (e->right.sym == &symbol_mod) {
+			// A!=m -> y
+			printf("boolean symbol %s tested for 'm'? test forced to 'y'\n", e->left.sym->name);
+			e = expr_alloc_symbol(&symbol_yes);
+			break;
+		}
+		if (e->right.sym == &symbol_yes) {
+			// A!=y -> !A
+			e = expr_alloc_one(E_NOT, e->left.expr);
+			break;
+		}
+		break;
+	case E_NOT:
+		switch (e->left.expr->type) {
+		case E_NOT:
+			// !!A -> A
+			e = e->left.expr->left.expr;
+			break;
+		case E_EQUAL:
+		case E_UNEQUAL:
+			// !(A=B) -> A!=B
+			e = expr_alloc_comp(e->left.expr->type == E_EQUAL ? E_UNEQUAL : E_EQUAL,
+					    e->left.expr->left.sym,
+					    e->left.expr->right.sym);
+			break;
+		case E_LEQ:
+		case E_GEQ:
+			// !(A<=B) -> A>B
+			e = expr_alloc_comp(e->left.expr->type == E_LEQ ? E_GTH : E_LTH,
+					    e->left.expr->left.sym,
+					    e->left.expr->right.sym);
+			break;
+		case E_LTH:
+		case E_GTH:
+			// !(A<B) -> A>=B
+			e = expr_alloc_comp(e->left.expr->type == E_LTH ? E_GEQ : E_LEQ,
+					    e->left.expr->left.sym,
+					    e->left.expr->right.sym);
+			break;
+		case E_OR:
+			// !(A || B) -> !A && !B
+			e = expr_alloc_and(expr_alloc_one(E_NOT, e->left.expr->left.expr),
+					   expr_alloc_one(E_NOT, e->left.expr->right.expr));
+			e = expr_transform(e);
+			break;
+		case E_AND:
+			// !(A && B) -> !A || !B
+			e = expr_alloc_or(expr_alloc_one(E_NOT, e->left.expr->left.expr),
+					  expr_alloc_one(E_NOT, e->left.expr->right.expr));
+			e = expr_transform(e);
+			break;
+		case E_SYMBOL:
+			if (e->left.expr->left.sym == &symbol_yes)
+				// !'y' -> 'n'
+				e = expr_alloc_symbol(&symbol_no);
+			else if (e->left.expr->left.sym == &symbol_mod)
+				// !'m' -> 'm'
+				e = expr_alloc_symbol(&symbol_mod);
+			else if (e->left.expr->left.sym == &symbol_no)
+				// !'n' -> 'y'
+				e = expr_alloc_symbol(&symbol_yes);
+			break;
+		default:
+			;
+		}
+		break;
+	default:
+		;
+	}
+	return e;
+}
+
+bool expr_contains_symbol(struct expr *dep, struct symbol *sym)
+{
+	if (!dep)
+		return false;
+
+	switch (dep->type) {
+	case E_AND:
+	case E_OR:
+		return expr_contains_symbol(dep->left.expr, sym) ||
+		       expr_contains_symbol(dep->right.expr, sym);
+	case E_SYMBOL:
+		return dep->left.sym == sym;
+	case E_EQUAL:
+	case E_GEQ:
+	case E_GTH:
+	case E_LEQ:
+	case E_LTH:
+	case E_UNEQUAL:
+		return dep->left.sym == sym ||
+		       dep->right.sym == sym;
+	case E_NOT:
+		return expr_contains_symbol(dep->left.expr, sym);
+	default:
+		;
+	}
+	return false;
+}
+
+/*
+ * Check if the expression references 'sym' in a way that is satisfiable
+ * with 'sym' disabled, e.g.'sym!=y'.
+ *
+ * Expects that expr_transform() was already called on 'expr'.
+ */
+bool expr_contains_symbol_negated(struct expr *dep, struct symbol *sym)
+{
+	if (!dep)
+		return false;
+
+	switch (dep->type) {
+	case E_AND:
+	case E_OR:
+		return expr_contains_symbol_negated(dep->left.expr, sym) ||
+		       expr_contains_symbol_negated(dep->right.expr, sym);
+	case E_NOT:
+		return dep->left.expr->type == E_SYMBOL &&
+		       dep->left.expr->left.sym == sym;
+	case E_EQUAL:
+		/* sym=n */
+		return dep->left.sym == sym && dep->right.sym == &symbol_no;
+	case E_UNEQUAL:
+		/* sym!=y, sym!=m */
+		return dep->left.sym == sym &&
+		       (dep->right.sym == &symbol_yes ||
+			dep->right.sym == &symbol_mod);
+	default:
+		break;
+	}
+	return false;
+}
+
+bool expr_depends_symbol(struct expr *dep, struct symbol *sym)
+{
+	if (!dep)
+		return false;
+
+	switch (dep->type) {
+	case E_AND:
+		return expr_depends_symbol(dep->left.expr, sym) ||
+		       expr_depends_symbol(dep->right.expr, sym);
+	case E_SYMBOL:
+		return dep->left.sym == sym;
+	case E_EQUAL:
+		if (dep->left.sym == sym) {
+			if (dep->right.sym == &symbol_yes || dep->right.sym == &symbol_mod)
+				return true;
+		}
+		break;
+	case E_UNEQUAL:
+		if (dep->left.sym == sym) {
+			if (dep->right.sym == &symbol_no)
+				return true;
+		}
+		break;
+	default:
+		;
+	}
+ 	return false;
+}
+
+/*
+ * Inserts explicit comparisons of type 'type' to symbol 'sym' into the
+ * expression 'e'.
+ *
+ * Examples transformations for type == E_UNEQUAL, sym == &symbol_no:
+ *
+ *	A              ->  A!=n
+ *	!A             ->  A=n
+ *	A && B         ->  !(A=n || B=n)
+ *	A || B         ->  !(A=n && B=n)
+ *	A && (B || C)  ->  !(A=n || (B=n && C=n))
+ *
+ * Allocates and returns a new expression.
+ */
+struct expr *expr_trans_compare(struct expr *e, enum expr_type type, struct symbol *sym)
+{
+	struct expr *e1, *e2;
+
+	if (!e) {
+		e = expr_alloc_symbol(sym);
+		if (type == E_UNEQUAL)
+			e = expr_alloc_one(E_NOT, e);
+		return e;
+	}
+	switch (e->type) {
+	case E_AND:
+		e1 = expr_trans_compare(e->left.expr, E_EQUAL, sym);
+		e2 = expr_trans_compare(e->right.expr, E_EQUAL, sym);
+		if (sym == &symbol_yes)
+			e = expr_alloc_two(E_AND, e1, e2);
+		if (sym == &symbol_no)
+			e = expr_alloc_two(E_OR, e1, e2);
+		if (type == E_UNEQUAL)
+			e = expr_alloc_one(E_NOT, e);
+		return e;
+	case E_OR:
+		e1 = expr_trans_compare(e->left.expr, E_EQUAL, sym);
+		e2 = expr_trans_compare(e->right.expr, E_EQUAL, sym);
+		if (sym == &symbol_yes)
+			e = expr_alloc_two(E_OR, e1, e2);
+		if (sym == &symbol_no)
+			e = expr_alloc_two(E_AND, e1, e2);
+		if (type == E_UNEQUAL)
+			e = expr_alloc_one(E_NOT, e);
+		return e;
+	case E_NOT:
+		return expr_trans_compare(e->left.expr, type == E_EQUAL ? E_UNEQUAL : E_EQUAL, sym);
+	case E_UNEQUAL:
+	case E_LTH:
+	case E_LEQ:
+	case E_GTH:
+	case E_GEQ:
+	case E_EQUAL:
+		if (type == E_EQUAL) {
+			if (sym == &symbol_yes)
+				return e;
+			if (sym == &symbol_mod)
+				return expr_alloc_symbol(&symbol_no);
+			if (sym == &symbol_no)
+				return expr_alloc_one(E_NOT, e);
+		} else {
+			if (sym == &symbol_yes)
+				return expr_alloc_one(E_NOT, e);
+			if (sym == &symbol_mod)
+				return expr_alloc_symbol(&symbol_yes);
+			if (sym == &symbol_no)
+				return e;
+		}
+		break;
+	case E_SYMBOL:
+		return expr_alloc_comp(type, e->left.sym, sym);
+	case E_RANGE:
+	case E_NONE:
+		/* panic */;
+	}
+	return NULL;
+}
+
+enum string_value_kind {
+	k_string,
+	k_signed,
+	k_unsigned,
+};
+
+union string_value {
+	unsigned long long u;
+	signed long long s;
+};
+
+static enum string_value_kind expr_parse_string(const char *str,
+						enum symbol_type type,
+						union string_value *val)
+{
+	char *tail;
+	enum string_value_kind kind;
+
+	errno = 0;
+	switch (type) {
+	case S_BOOLEAN:
+	case S_TRISTATE:
+		val->s = !strcmp(str, "n") ? 0 :
+			 !strcmp(str, "m") ? 1 :
+			 !strcmp(str, "y") ? 2 : -1;
+		return k_signed;
+	case S_INT:
+		val->s = strtoll(str, &tail, 10);
+		kind = k_signed;
+		break;
+	case S_HEX:
+		val->u = strtoull(str, &tail, 16);
+		kind = k_unsigned;
+		break;
+	default:
+		val->s = strtoll(str, &tail, 0);
+		kind = k_signed;
+		break;
+	}
+	return !errno && !*tail && tail > str && isxdigit(tail[-1])
+	       ? kind : k_string;
+}
+
+static tristate __expr_calc_value(struct expr *e)
+{
+	tristate val1, val2;
+	const char *str1, *str2;
+	enum string_value_kind k1 = k_string, k2 = k_string;
+	union string_value lval = {}, rval = {};
+	int res;
+
+	switch (e->type) {
+	case E_SYMBOL:
+		sym_calc_value(e->left.sym);
+		return e->left.sym->curr.tri;
+	case E_AND:
+		val1 = expr_calc_value(e->left.expr);
+		val2 = expr_calc_value(e->right.expr);
+		return EXPR_AND(val1, val2);
+	case E_OR:
+		val1 = expr_calc_value(e->left.expr);
+		val2 = expr_calc_value(e->right.expr);
+		return EXPR_OR(val1, val2);
+	case E_NOT:
+		val1 = expr_calc_value(e->left.expr);
+		return EXPR_NOT(val1);
+	case E_EQUAL:
+	case E_GEQ:
+	case E_GTH:
+	case E_LEQ:
+	case E_LTH:
+	case E_UNEQUAL:
+		break;
+	default:
+		printf("expr_calc_value: %d?\n", e->type);
+		return no;
+	}
+
+	sym_calc_value(e->left.sym);
+	sym_calc_value(e->right.sym);
+	str1 = sym_get_string_value(e->left.sym);
+	str2 = sym_get_string_value(e->right.sym);
+
+	if (e->left.sym->type != S_STRING || e->right.sym->type != S_STRING) {
+		k1 = expr_parse_string(str1, e->left.sym->type, &lval);
+		k2 = expr_parse_string(str2, e->right.sym->type, &rval);
+	}
+
+	if (k1 == k_string || k2 == k_string)
+		res = strcmp(str1, str2);
+	else if (k1 == k_unsigned || k2 == k_unsigned)
+		res = (lval.u > rval.u) - (lval.u < rval.u);
+	else /* if (k1 == k_signed && k2 == k_signed) */
+		res = (lval.s > rval.s) - (lval.s < rval.s);
+
+	switch(e->type) {
+	case E_EQUAL:
+		return res ? no : yes;
+	case E_GEQ:
+		return res >= 0 ? yes : no;
+	case E_GTH:
+		return res > 0 ? yes : no;
+	case E_LEQ:
+		return res <= 0 ? yes : no;
+	case E_LTH:
+		return res < 0 ? yes : no;
+	case E_UNEQUAL:
+		return res ? yes : no;
+	default:
+		printf("expr_calc_value: relation %d?\n", e->type);
+		return no;
+	}
+}
+
+/**
+ * expr_calc_value - return the tristate value of the given expression
+ * @e: expression
+ * return: tristate value of the expression
+ */
+tristate expr_calc_value(struct expr *e)
+{
+	if (!e)
+		return yes;
+
+	if (!e->val_is_valid) {
+		e->val = __expr_calc_value(e);
+		e->val_is_valid = true;
+	}
+
+	return e->val;
+}
+
+/**
+ * expr_invalidate_all - invalidate all cached expression values
+ */
+void expr_invalidate_all(void)
+{
+	struct expr *e;
+
+	hash_for_each(expr_hashtable, e, node)
+		e->val_is_valid = false;
+}
+
+static int expr_compare_type(enum expr_type t1, enum expr_type t2)
+{
+	if (t1 == t2)
+		return 0;
+	switch (t1) {
+	case E_LEQ:
+	case E_LTH:
+	case E_GEQ:
+	case E_GTH:
+		if (t2 == E_EQUAL || t2 == E_UNEQUAL)
+			return 1;
+		/* fallthrough */
+	case E_EQUAL:
+	case E_UNEQUAL:
+		if (t2 == E_NOT)
+			return 1;
+		/* fallthrough */
+	case E_NOT:
+		if (t2 == E_AND)
+			return 1;
+		/* fallthrough */
+	case E_AND:
+		if (t2 == E_OR)
+			return 1;
+		/* fallthrough */
+	default:
+		break;
+	}
+	return 0;
+}
+
+void expr_print(const struct expr *e,
+		void (*fn)(void *, struct symbol *, const char *),
+		void *data, int prevtoken)
+{
+	if (!e) {
+		fn(data, NULL, "y");
+		return;
+	}
+
+	if (expr_compare_type(prevtoken, e->type) > 0)
+		fn(data, NULL, "(");
+	switch (e->type) {
+	case E_SYMBOL:
+		if (e->left.sym->name)
+			fn(data, e->left.sym, e->left.sym->name);
+		else
+			fn(data, NULL, "<choice>");
+		break;
+	case E_NOT:
+		fn(data, NULL, "!");
+		expr_print(e->left.expr, fn, data, E_NOT);
+		break;
+	case E_EQUAL:
+		if (e->left.sym->name)
+			fn(data, e->left.sym, e->left.sym->name);
+		else
+			fn(data, NULL, "<choice>");
+		fn(data, NULL, "=");
+		fn(data, e->right.sym, e->right.sym->name);
+		break;
+	case E_LEQ:
+	case E_LTH:
+		if (e->left.sym->name)
+			fn(data, e->left.sym, e->left.sym->name);
+		else
+			fn(data, NULL, "<choice>");
+		fn(data, NULL, e->type == E_LEQ ? "<=" : "<");
+		fn(data, e->right.sym, e->right.sym->name);
+		break;
+	case E_GEQ:
+	case E_GTH:
+		if (e->left.sym->name)
+			fn(data, e->left.sym, e->left.sym->name);
+		else
+			fn(data, NULL, "<choice>");
+		fn(data, NULL, e->type == E_GEQ ? ">=" : ">");
+		fn(data, e->right.sym, e->right.sym->name);
+		break;
+	case E_UNEQUAL:
+		if (e->left.sym->name)
+			fn(data, e->left.sym, e->left.sym->name);
+		else
+			fn(data, NULL, "<choice>");
+		fn(data, NULL, "!=");
+		fn(data, e->right.sym, e->right.sym->name);
+		break;
+	case E_OR:
+		expr_print(e->left.expr, fn, data, E_OR);
+		fn(data, NULL, " || ");
+		expr_print(e->right.expr, fn, data, E_OR);
+		break;
+	case E_AND:
+		expr_print(e->left.expr, fn, data, E_AND);
+		fn(data, NULL, " && ");
+		expr_print(e->right.expr, fn, data, E_AND);
+		break;
+	case E_RANGE:
+		fn(data, NULL, "[");
+		fn(data, e->left.sym, e->left.sym->name);
+		fn(data, NULL, " ");
+		fn(data, e->right.sym, e->right.sym->name);
+		fn(data, NULL, "]");
+		break;
+	default:
+	  {
+		char buf[32];
+		sprintf(buf, "<unknown type %d>", e->type);
+		fn(data, NULL, buf);
+		break;
+	  }
+	}
+	if (expr_compare_type(prevtoken, e->type) > 0)
+		fn(data, NULL, ")");
+}
+
+static void expr_print_file_helper(void *data, struct symbol *sym, const char *str)
+{
+	xfwrite(str, strlen(str), 1, data);
+}
+
+void expr_fprint(struct expr *e, FILE *out)
+{
+	expr_print(e, expr_print_file_helper, out, E_NONE);
+}
+
+static void expr_print_gstr_helper(void *data, struct symbol *sym, const char *str)
+{
+	struct gstr *gs = (struct gstr*)data;
+	const char *sym_str = NULL;
+
+	if (sym)
+		sym_str = sym_get_string_value(sym);
+
+	if (gs->max_width) {
+		unsigned extra_length = strlen(str);
+		const char *last_cr = strrchr(gs->s, '\n');
+		unsigned last_line_length;
+
+		if (sym_str)
+			extra_length += 4 + strlen(sym_str);
+
+		if (!last_cr)
+			last_cr = gs->s;
+
+		last_line_length = strlen(gs->s) - (last_cr - gs->s);
+
+		if ((last_line_length + extra_length) > gs->max_width)
+			str_append(gs, "\\\n");
+	}
+
+	str_append(gs, str);
+	if (sym && sym->type != S_UNKNOWN)
+		str_printf(gs, " [=%s]", sym_str);
+}
+
+void expr_gstr_print(const struct expr *e, struct gstr *gs)
+{
+	expr_print(e, expr_print_gstr_helper, gs, E_NONE);
+}
+
+/*
+ * Transform the top level "||" tokens into newlines and prepend each
+ * line with a minus. This makes expressions much easier to read.
+ * Suitable for reverse dependency expressions.
+ */
+static void expr_print_revdep(struct expr *e,
+			      void (*fn)(void *, struct symbol *, const char *),
+			      void *data, tristate pr_type, const char **title)
+{
+	if (e->type == E_OR) {
+		expr_print_revdep(e->left.expr, fn, data, pr_type, title);
+		expr_print_revdep(e->right.expr, fn, data, pr_type, title);
+	} else if (expr_calc_value(e) == pr_type) {
+		if (*title) {
+			fn(data, NULL, *title);
+			*title = NULL;
+		}
+
+		fn(data, NULL, "  - ");
+		expr_print(e, fn, data, E_NONE);
+		fn(data, NULL, "\n");
+	}
+}
+
+void expr_gstr_print_revdep(struct expr *e, struct gstr *gs,
+			    tristate pr_type, const char *title)
+{
+	expr_print_revdep(e, expr_print_gstr_helper, gs, pr_type, &title);
+}