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Subject[RFC PATCH v4 6/7] scripts/sorttable: Add ORC unwind tables sort concurrently
Date
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@hirez.programming.kicks-ass.net/
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Shile Zhang <shile.zhang@linux.alibaba.com>
---
scripts/Makefile | 6 ++
scripts/sorttable.h | 201 ++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 202 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..41c8dd9c75fc 100644
--- a/scripts/sorttable.h
+++ b/scripts/sorttable.h
@@ -4,6 +4,14 @@
*
* 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@linux.alibaba.com>
+ *
+ * Some of code was taken out of /lib/sort.c, and
+ * arch/x86/kernel/unwind_orc.c written by:
+ * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.com>
+ *
* Some of this code was taken out of recordmcount.h written by:
*
* Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved.
@@ -75,6 +83,131 @@
# 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>
+
+int *g_orc_ip_table;
+struct orc_entry *g_orc_table;
+
+pthread_t orc_sort_thread;
+
+/**
+ * sort - sort an array of elements
+ * @base: pointer to data to sort
+ * @num: number of elements
+ * @size: size of each element
+ * @cmp_func: pointer to comparison function
+ * @swap_func: pointer to swap function
+ *
+ * This function does a heapsort on the given array. You may provide a
+ * swap_func function optimized to your element type.
+ *
+ * Sorting time is O(n log n) both on average and worst-case. While
+ * qsort is about 20% faster on average, it suffers from exploitable
+ * O(n*n) worst-case behavior and extra memory requirements that make
+ * it less suitable for kernel use.
+ *
+ * This code token out of /lib/sort.c.
+ */
+static void sort(void *base, size_t num, size_t size,
+ int (*cmp_func)(const void *, const void *),
+ void (*swap_func)(void *, void *, int size))
+{
+ /* pre-scale counters for performance */
+ int i = (num/2 - 1) * size, n = num * size, c, r;
+
+ /* heapify */
+ for ( ; i >= 0; i -= size) {
+ for (r = i; r * 2 + size < n; r = c) {
+ c = r * 2 + size;
+ if (c < n - size &&
+ cmp_func(base + c, base + c + size) < 0)
+ c += size;
+ if (cmp_func(base + r, base + c) >= 0)
+ break;
+ swap_func(base + r, base + c, size);
+ }
+ }
+
+ /* sort */
+ for (i = n - size; i > 0; i -= size) {
+ swap_func(base, base + i, size);
+ for (r = 0; r * 2 + size < i; r = c) {
+ c = r * 2 + size;
+ if (c < i - size &&
+ cmp_func(base + c, base + c + size) < 0)
+ c += size;
+ if (cmp_func(base + r, base + c) >= 0)
+ break;
+ swap_func(base + r, base + c, size);
+ }
+ }
+}
+
+static inline unsigned long orc_ip(const int *ip)
+{
+ return (unsigned long)ip + *ip;
+}
+
+static void orc_sort_swap(void *_a, void *_b, int size)
+{
+ struct orc_entry *orc_a, *orc_b;
+ struct orc_entry orc_tmp;
+ int *a = _a, *b = _b, tmp;
+ int delta = _b - _a;
+
+ /* Swap the .orc_unwind_ip entries: */
+ tmp = *a;
+ *a = *b + delta;
+ *b = tmp - delta;
+
+ /* Swap the corresponding .orc_unwind entries: */
+ orc_a = g_orc_table + (a - g_orc_ip_table);
+ orc_b = g_orc_table + (b - g_orc_ip_table);
+ orc_tmp = *orc_a;
+ *orc_a = *orc_b;
+ *orc_b = orc_tmp;
+}
+
+static int orc_sort_cmp(const void *_a, const void *_b)
+{
+ struct orc_entry *orc_a;
+ const int *a = _a, *b = _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)
+{
+ unsigned int *size = (unsigned int *)arg;
+ unsigned int num_entries;
+
+ num_entries = *size / sizeof(int);
+
+ sort(g_orc_ip_table, num_entries, sizeof(int),
+ orc_sort_cmp, orc_sort_swap);
+
+ pthread_exit(NULL);
+}
+#endif
+
static int compare_extable(const void *a, const void *b)
{
Elf_Addr av = _r(a);
@@ -91,6 +224,7 @@ 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 +245,11 @@ 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 +280,61 @@ 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 +371,7 @@ 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 +384,18 @@ 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) {
+ /* wait for ORC tables sort done */
+ rc = pthread_join(orc_sort_thread, NULL);
+ if (rc)
+ fprintf(stderr,
+ "pthread_join orc_sort_thread failed "
+ "'%s': %s\n", strerror(errno), fname);
+ }
+#endif
+ return rc;
}
--
2.24.0.rc2
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