ARM: 9480/1: entry: expand comment in __switch_tografted

As per discussion between the developers in the mail thread
linked, expand the comment in __switch_to so that readers
of the code understand what is going on.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 133 insertions, 0 deletions

diff --git a/tools/perf/util/syscalltbl.c b/tools/perf/util/syscalltbl.c
new file mode 100644
index 000000000..67a8ec10e
--- /dev/null
+++ b/tools/perf/util/syscalltbl.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * System call table mapper
+ *
+ * (C) 2016 Arnaldo Carvalho de Melo <acme@redhat.com>
+ */
+
+#include "syscalltbl.h"
+#include <stdlib.h>
+#include <asm/bitsperlong.h>
+#include <linux/compiler.h>
+#include <linux/kernel.h>
+#include <linux/zalloc.h>
+
+#include <string.h>
+#include "string2.h"
+
+#include "trace/beauty/generated/syscalltbl.c"
+
+static const struct syscalltbl *find_table(int e_machine)
+{
+	static const struct syscalltbl *last_table;
+	static int last_table_machine = EM_NONE;
+
+	/* Tables only exist for EM_SPARC. */
+	if (e_machine == EM_SPARCV9)
+		e_machine = EM_SPARC;
+
+	if (last_table_machine == e_machine && last_table != NULL)
+		return last_table;
+
+	for (size_t i = 0; i < ARRAY_SIZE(syscalltbls); i++) {
+		const struct syscalltbl *entry = &syscalltbls[i];
+
+		if (entry->e_machine != e_machine && entry->e_machine != EM_NONE)
+			continue;
+
+		last_table = entry;
+		last_table_machine = e_machine;
+		return entry;
+	}
+	return NULL;
+}
+
+const char *syscalltbl__name(int e_machine, int id)
+{
+	const struct syscalltbl *table = find_table(e_machine);
+
+	if (e_machine == EM_MIPS && id > 1000) {
+		/*
+		 * MIPS may encode the N32/64/O32 type in the high part of
+		 * syscall number. Mask this off if present. See the values of
+		 * __NR_N32_Linux, __NR_64_Linux, __NR_O32_Linux and __NR_Linux.
+		 */
+		id = id % 1000;
+	}
+	if (table && id >= 0 && id < table->num_to_name_len)
+		return table->num_to_name[id];
+	return NULL;
+}
+
+struct syscall_cmp_key {
+	const char *name;
+	const char *const *tbl;
+};
+
+static int syscallcmpname(const void *vkey, const void *ventry)
+{
+	const struct syscall_cmp_key *key = vkey;
+	const uint16_t *entry = ventry;
+
+	return strcmp(key->name, key->tbl[*entry]);
+}
+
+int syscalltbl__id(int e_machine, const char *name)
+{
+	const struct syscalltbl *table = find_table(e_machine);
+	struct syscall_cmp_key key;
+	const uint16_t *id;
+
+	if (!table)
+		return -1;
+
+	key.name = name;
+	key.tbl = table->num_to_name;
+	id = bsearch(&key, table->sorted_names, table->sorted_names_len,
+		     sizeof(table->sorted_names[0]), syscallcmpname);
+
+	return id ? *id : -1;
+}
+
+int syscalltbl__num_idx(int e_machine)
+{
+	const struct syscalltbl *table = find_table(e_machine);
+
+	if (!table)
+		return 0;
+
+	return table->sorted_names_len;
+}
+
+int syscalltbl__id_at_idx(int e_machine, int idx)
+{
+	const struct syscalltbl *table = find_table(e_machine);
+
+	if (!table)
+		return -1;
+
+	assert(idx >= 0 && idx < table->sorted_names_len);
+	return table->sorted_names[idx];
+}
+
+int syscalltbl__strglobmatch_next(int e_machine, const char *syscall_glob, int *idx)
+{
+	const struct syscalltbl *table = find_table(e_machine);
+
+	for (int i = *idx + 1; table && i < table->sorted_names_len; ++i) {
+		const char *name = table->num_to_name[table->sorted_names[i]];
+
+		if (strglobmatch(name, syscall_glob)) {
+			*idx = i;
+			return table->sorted_names[i];
+		}
+	}
+
+	return -1;
+}
+
+int syscalltbl__strglobmatch_first(int e_machine, const char *syscall_glob, int *idx)
+{
+	*idx = -1;
+	return syscalltbl__strglobmatch_next(e_machine, syscall_glob, idx);
+}