From 0ef054c3e7d7423d0f18edd7a29f62a9c6a811b4 Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@nbd.name>
Date: Tue, 27 Sep 2022 16:21:26 +0200
Subject: [PATCH 36/96] kernel: add a config option for keeping the kallsyms
 table uncompressed, saving ~9kb kernel size after lzma on ar71xx

[john@phrozen.org: added to my upstream queue 30.12.2016]
lede-commit: e0e3509b5ce2ccf93d4d67ea907613f5f7ec2eed
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 init/Kconfig            | 11 +++++++++++
 kernel/kallsyms.c       |  8 ++++++++
 scripts/kallsyms.c      | 12 ++++++++++++
 scripts/link-vmlinux.sh |  4 ++++
 4 files changed, 35 insertions(+)

diff --git a/init/Kconfig b/init/Kconfig
index c7900e8975f1..4d5f1ee66139 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1475,6 +1475,17 @@ config SYSCTL_ARCH_UNALIGN_ALLOW
 	  the unaligned access emulation.
 	  see arch/parisc/kernel/unaligned.c for reference
 
+config KALLSYMS_UNCOMPRESSED
+	bool "Keep kallsyms uncompressed"
+	depends on KALLSYMS
+	help
+		Normally kallsyms contains compressed symbols (using a token table),
+		reducing the uncompressed kernel image size. Keeping the symbol table
+		uncompressed significantly improves the size of this part in compressed
+		kernel images.
+
+		Say N unless you need compressed kernel images to be small.
+
 config HAVE_PCSPKR_PLATFORM
 	bool
 
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index fbdf8d3279ac..f30ecfedd293 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -81,6 +81,11 @@ static unsigned int kallsyms_expand_symbol(unsigned int off,
 	 * For every byte on the compressed symbol data, copy the table
 	 * entry for that byte.
 	 */
+#ifdef CONFIG_KALLSYMS_UNCOMPRESSED
+	memcpy(result, data + 1, len - 1);
+	result += len - 1;
+	len = 0;
+#endif
 	while (len) {
 		tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
 		data++;
@@ -113,6 +118,9 @@ static unsigned int kallsyms_expand_symbol(unsigned int off,
  */
 static char kallsyms_get_symbol_type(unsigned int off)
 {
+#ifdef CONFIG_KALLSYMS_UNCOMPRESSED
+	return kallsyms_names[off + 1];
+#endif
 	/*
 	 * Get just the first code, look it up in the token table,
 	 * and return the first char from this token.
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index f18e6dfc68c5..262a3799bae1 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -58,6 +58,7 @@ static struct addr_range percpu_range = {
 static struct sym_entry **table;
 static unsigned int table_size, table_cnt;
 static int all_symbols;
+static int uncompressed;
 static int absolute_percpu;
 static int base_relative;
 
@@ -487,6 +488,9 @@ static void write_src(void)
 
 	free(markers);
 
+	if (uncompressed)
+		return;
+
 	output_label("kallsyms_token_table");
 	off = 0;
 	for (i = 0; i < 256; i++) {
@@ -538,6 +542,9 @@ static unsigned char *find_token(unsigned char *str, int len,
 {
 	int i;
 
+	if (uncompressed)
+		return NULL;
+
 	for (i = 0; i < len - 1; i++) {
 		if (str[i] == token[0] && str[i+1] == token[1])
 			return &str[i];
@@ -610,6 +617,9 @@ static void optimize_result(void)
 {
 	int i, best;
 
+	if (uncompressed)
+		return;
+
 	/* using the '\0' symbol last allows compress_symbols to use standard
 	 * fast string functions */
 	for (i = 255; i >= 0; i--) {
@@ -774,6 +784,8 @@ int main(int argc, char **argv)
 				absolute_percpu = 1;
 			else if (strcmp(argv[i], "--base-relative") == 0)
 				base_relative = 1;
+			else if (strcmp(argv[i], "--uncompressed") == 0)
+				uncompressed = 1;
 			else
 				usage();
 		}
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index eecc1863e556..8b8c9000892a 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -156,6 +156,10 @@ kallsyms()
 		kallsymopt="${kallsymopt} --base-relative"
 	fi
 
+	if [ -n "${CONFIG_KALLSYMS_UNCOMPRESSED}" ]; then
+		kallsymopt="${kallsymopt} --uncompressed"
+	fi
+
 	info KSYMS ${2}
 	${NM} -n ${1} | scripts/kallsyms ${kallsymopt} > ${2}
 }
-- 
2.37.2