[RFC PATCH v5 6/7] scripts/sorttable: Add ORC unwind tables sort concurrently

[Shile Zhang]

ORC unwinder have two tables, .orc_unwind_ip and .orc_unwind, which
needs sorted for binary search. To sort it at build time can save more
CPU cycles help to speed up kernel booting.

Add the ORC tables sorting in a sperated thread helps to avoid more link
cost of kernel building.

https://lore.kernel.org/lkml/20191108092136.GH4114@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Suggested-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Shile Zhang <shile.zhang@xxxxxxxxxxxxxxxxx>
---
 scripts/Makefile    |   6 ++
 scripts/sorttable.h | 180 ++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 181 insertions(+), 5 deletions(-)

diff --git a/scripts/Makefile b/scripts/Makefile
index 658d201f7f8b..d6670bd420f6 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -26,6 +26,12 @@ HOSTCFLAGS_asn1_compiler.o = -I$(srctree)/include
 HOSTLDLIBS_sign-file = -lcrypto
 HOSTLDLIBS_extract-cert = -lcrypto
 
+ifdef CONFIG_UNWINDER_ORC
+HOSTCFLAGS_sorttable.o += -I$(srctree)/tools/arch/$(ARCH)/include
+HOSTCFLAGS_sorttable.o += -DUNWINDER_ORC_ENABLED
+HOSTLDLIBS_sorttable = -lpthread
+endif
+
 always		:= $(hostprogs-y) $(hostprogs-m)
 
 # The following hostprogs-y programs are only build on demand
diff --git a/scripts/sorttable.h b/scripts/sorttable.h
index 82589ff90e25..8dee22a70cab 100644
--- a/scripts/sorttable.h
+++ b/scripts/sorttable.h
@@ -4,6 +4,13 @@
  *
  * Copyright 2011 - 2012 Cavium, Inc.
  *
+ * Added ORC unwind tables sort support, and other updates:
+ * Copyright (C) 1999-2019 Alibaba Group Holding Limited. by:
+ * Shile Zhang <shile.zhang@xxxxxxxxxxxxxxxxx>
+ *
+ * Some of code was taken out of arch/x86/kernel/unwind_orc.c written by:
+ * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
+ *
  * Some of this code was taken out of recordmcount.h written by:
  *
  * Copyright 2009 John F. Reiser <jreiser@xxxxxxxxxxxx>. All rights reserved.
@@ -75,6 +82,104 @@
 # define _w			w
 #endif
 
+#if defined(SORTTABLE_64) && defined(UNWINDER_ORC_ENABLED)
+/* ORC unwinder only support X86_64 */
+#include <errno.h>
+#include <pthread.h>
+#include <asm/orc_types.h>
+
+#define ERRSTR_MAXSZ	256
+
+char g_err[ERRSTR_MAXSZ];
+int *g_orc_ip_table;
+struct orc_entry *g_orc_table;
+
+pthread_t orc_sort_thread;
+
+static inline unsigned long orc_ip(const int *ip)
+{
+	return (unsigned long)ip + *ip;
+}
+
+static int orc_sort_cmp(const void *_a, const void *_b)
+{
+	struct orc_entry *orc_a;
+	const int *a = g_orc_ip_table + *(int *)_a;
+	const int *b = g_orc_ip_table + *(int *)_b;
+	unsigned long a_val = orc_ip(a);
+	unsigned long b_val = orc_ip(b);
+
+	if (a_val > b_val)
+		return 1;
+	if (a_val < b_val)
+		return -1;
+
+	/*
+	 * The "weak" section terminator entries need to always be on the left
+	 * to ensure the lookup code skips them in favor of real entries.
+	 * These terminator entries exist to handle any gaps created by
+	 * whitelisted .o files which didn't get objtool generation.
+	 */
+	orc_a = g_orc_table + (a - g_orc_ip_table);
+	return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
+}
+
+static void *sort_orctable(void *arg)
+{
+	int i;
+	int *idxs = NULL;
+	int *tmp_orc_ip_table = NULL;
+	struct orc_entry *tmp_orc_table = NULL;
+	unsigned int *orc_ip_size = (unsigned int *)arg;
+	unsigned int num_entries = *orc_ip_size / sizeof(int);
+	unsigned int orc_size = num_entries * sizeof(struct orc_entry);
+
+	idxs = (int *)malloc(*orc_ip_size);
+	if (!idxs) {
+		snprintf(g_err, ERRSTR_MAXSZ, "malloc idxs: %s",
+			 strerror(errno));
+		pthread_exit(g_err);
+	}
+
+	tmp_orc_ip_table = (int *)malloc(*orc_ip_size);
+	if (!tmp_orc_ip_table) {
+		snprintf(g_err, ERRSTR_MAXSZ, "malloc tmp_orc_ip_table: %s",
+			 strerror(errno));
+		pthread_exit(g_err);
+	}
+
+	tmp_orc_table = (struct orc_entry *)malloc(orc_size);
+	if (!tmp_orc_table) {
+		snprintf(g_err, ERRSTR_MAXSZ, "malloc tmp_orc_table: %s",
+			 strerror(errno));
+		pthread_exit(g_err);
+	}
+
+	/* initialize indices array, convert ip_table to absolute address */
+	for (i = 0; i < num_entries; i++) {
+		idxs[i] = i;
+		tmp_orc_ip_table[i] = g_orc_ip_table[i] + i * sizeof(int);
+	}
+	memcpy(tmp_orc_table, g_orc_table, orc_size);
+
+	qsort(idxs, num_entries, sizeof(int), orc_sort_cmp);
+
+	for (i = 0; i < num_entries; i++) {
+		if (idxs[i] == i)
+			continue;
+
+		/* convert back to relative address */
+		g_orc_ip_table[i] = tmp_orc_ip_table[idxs[i]] - i * sizeof(int);
+		g_orc_table[i] = tmp_orc_table[idxs[i]];
+	}
+
+	free(idxs);
+	free(tmp_orc_ip_table);
+	free(tmp_orc_table);
+	pthread_exit(NULL);
+}
+#endif
+
 static int compare_extable(const void *a, const void *b)
 {
 	Elf_Addr av = _r(a);
@@ -91,6 +196,7 @@ static int do_sort(Elf_Ehdr *ehdr,
 		   char const *const fname,
 		   table_sort_t custom_sort)
 {
+	int rc = -1;
 	Elf_Shdr *s, *shdr = (Elf_Shdr *)((char *)ehdr + _r(&ehdr->e_shoff));
 	Elf_Shdr *strtab_sec = NULL;
 	Elf_Shdr *symtab_sec = NULL;
@@ -111,6 +217,11 @@ static int do_sort(Elf_Ehdr *ehdr,
 	int idx;
 	unsigned int shnum;
 	unsigned int shstrndx;
+#if defined(SORTTABLE_64) && defined(UNWINDER_ORC_ENABLED)
+	unsigned int orc_ip_size = 0;
+	unsigned int orc_size = 0;
+	unsigned int orc_num_entries = 0;
+#endif
 
 	shstrndx = r2(&ehdr->e_shstrndx);
 	if (shstrndx == SHN_XINDEX)
@@ -141,21 +252,61 @@ static int do_sort(Elf_Ehdr *ehdr,
 		if (r(&s->sh_type) == SHT_SYMTAB_SHNDX)
 			symtab_shndx = (Elf32_Word *)((const char *)ehdr +
 						      _r(&s->sh_offset));
+
+#if defined(SORTTABLE_64) && defined(UNWINDER_ORC_ENABLED)
+		/* locate the ORC unwind tables */
+		if (!strcmp(secstrings + idx, ".orc_unwind_ip")) {
+			orc_ip_size = s->sh_size;
+			g_orc_ip_table = (int *)((void *)ehdr +
+						   s->sh_offset);
+		}
+		if (!strcmp(secstrings + idx, ".orc_unwind")) {
+			orc_size = s->sh_size;
+			g_orc_table = (struct orc_entry *)((void *)ehdr +
+							     s->sh_offset);
+		}
+#endif
+	} /* for loop */
+
+#if defined(SORTTABLE_64) && defined(UNWINDER_ORC_ENABLED)
+	if (!g_orc_ip_table || !g_orc_table) {
+		fprintf(stderr,
+			"incomplete ORC unwind tables in file: %s\n", fname);
+		goto out;
+	}
+
+	orc_num_entries = orc_ip_size / sizeof(int);
+	if (orc_ip_size % sizeof(int) != 0 ||
+	    orc_size % sizeof(struct orc_entry) != 0 ||
+	    orc_num_entries != orc_size / sizeof(struct orc_entry)) {
+		fprintf(stderr,
+			"inconsistent ORC unwind table entries in file: %s\n",
+			fname);
+		goto out;
 	}
 
+	/* create thread to sort ORC unwind tables concurrently */
+	if (pthread_create(&orc_sort_thread, NULL,
+			   sort_orctable, &orc_ip_size)) {
+		fprintf(stderr,
+			"pthread_create orc_sort_thread failed '%s': %s\n",
+			strerror(errno), fname);
+		goto out;
+	}
+#endif
 	if (!extab_sec) {
 		fprintf(stderr,	"no __ex_table in file: %s\n", fname);
-		return -1;
+		goto out;
 	}
 
 	if (!symtab_sec) {
 		fprintf(stderr,	"no .symtab in file: %s\n", fname);
-		return -1;
+		goto out;
 	}
 
 	if (!strtab_sec) {
 		fprintf(stderr,	"no .strtab in file: %s\n", fname);
-		return -1;
+		goto out;
 	}
 
 	extab_image = (void *)ehdr + _r(&extab_sec->sh_offset);
@@ -192,7 +343,7 @@ static int do_sort(Elf_Ehdr *ehdr,
 		fprintf(stderr,
 			"no main_extable_sort_needed symbol in file: %s\n",
 			fname);
-		return -1;
+		goto out;
 	}
 
 	sort_needed_sec = &shdr[get_secindex(r2(&sym->st_shndx),
@@ -205,6 +356,25 @@ static int do_sort(Elf_Ehdr *ehdr,
 
 	/* extable has been sorted, clear the flag */
 	w(0, sort_needed_loc);
+	rc = 0;
 
-	return 0;
+out:
+#if defined(SORTTABLE_64) && defined(UNWINDER_ORC_ENABLED)
+	if (orc_sort_thread) {
+		void *retval = NULL;
+		/* wait for ORC tables sort done */
+		rc = pthread_join(orc_sort_thread, &retval);
+		if (rc)
+			fprintf(stderr,
+				"pthread_join failed '%s': %s\n",
+				strerror(errno), fname);
+		else if (retval) {
+			rc = -1;
+			fprintf(stderr,
+				"failed to sort ORC tables '%s': %s\n",
+				(char *)retval, fname);
+		}
+	}
+#endif
+	return rc;
 }
-- 
2.24.0.rc2