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From:   Brian Gerst <brgerst@gmail.com>
To:     linux-kernel@vger.kernel.org, x86@kernel.org
Cc:     Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Uros Bizjak <ubizjak@gmail.com>,
        Brian Gerst <brgerst@gmail.com>
Subject: [PATCH v2 11/11] kallsyms: Remove KALLSYMS_ABSOLUTE_PERCPU
Date:   Thu, 26 Oct 2023 12:01:00 -0400
Message-ID: <20231026160100.195099-12-brgerst@gmail.com>
In-Reply-To: <20231026160100.195099-1-brgerst@gmail.com>
References: <20231026160100.195099-1-brgerst@gmail.com>
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x86-64 was the only user.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
---
 init/Kconfig            | 11 +-----
 kernel/kallsyms.c       | 12 ++-----
 scripts/kallsyms.c      | 80 ++++++++---------------------------------
 scripts/link-vmlinux.sh |  4 ---
 4 files changed, 18 insertions(+), 89 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 1af31b23e376..4d91c5632aaf 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1715,11 +1715,6 @@ config KALLSYMS_ALL
 
 	  Say N unless you really need all symbols, or kernel live patching.
 
-config KALLSYMS_ABSOLUTE_PERCPU
-	bool
-	depends on KALLSYMS
-	default n
-
 config KALLSYMS_BASE_RELATIVE
 	bool
 	depends on KALLSYMS
@@ -1727,11 +1722,7 @@ config KALLSYMS_BASE_RELATIVE
 	help
 	  Instead of emitting them as absolute values in the native word size,
 	  emit the symbol references in the kallsyms table as 32-bit entries,
-	  each containing a relative value in the range [base, base + U32_MAX]
-	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
-	  an absolute value in the range [0, S32_MAX] or a relative value in the
-	  range [base, base + S32_MAX], where base is the lowest relative symbol
-	  address encountered in the image.
+	  each containing a relative value in the range [base, base + U32_MAX].
 
 	  On 64-bit builds, this reduces the size of the address table by 50%,
 	  but more importantly, it results in entries whose values are build
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 18edd57b5fe8..f4e8e531052a 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -151,16 +151,8 @@ unsigned long kallsyms_sym_address(int idx)
 	if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
 		return kallsyms_addresses[idx];
 
-	/* values are unsigned offsets if --absolute-percpu is not in effect */
-	if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
-		return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
-
-	/* ...otherwise, positive offsets are absolute values */
-	if (kallsyms_offsets[idx] >= 0)
-		return kallsyms_offsets[idx];
-
-	/* ...and negative offsets are relative to kallsyms_relative_base - 1 */
-	return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
+	/* values are unsigned offsets */
+	return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
 }
 
 static void cleanup_symbol_name(char *s)
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 653b92f6d4c8..501f978abf4b 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -5,8 +5,8 @@
  * This software may be used and distributed according to the terms
  * of the GNU General Public License, incorporated herein by reference.
  *
- * Usage: kallsyms [--all-symbols] [--absolute-percpu]
- *                         [--base-relative] [--lto-clang] in.map > out.S
+ * Usage: kallsyms [--all-symbols] [--base-relative] [--lto-clang]
+ *		   in.map > out.S
  *
  *      Table compression uses all the unused char codes on the symbols and
  *  maps these to the most used substrings (tokens). For instance, it might
@@ -37,7 +37,6 @@ struct sym_entry {
 	unsigned int len;
 	unsigned int seq;
 	unsigned int start_pos;
-	unsigned int percpu_absolute;
 	unsigned char sym[];
 };
 
@@ -55,14 +54,9 @@ static struct addr_range text_ranges[] = {
 #define text_range_text     (&text_ranges[0])
 #define text_range_inittext (&text_ranges[1])
 
-static struct addr_range percpu_range = {
-	"__per_cpu_start", "__per_cpu_end", -1ULL, 0
-};
-
 static struct sym_entry **table;
 static unsigned int table_size, table_cnt;
 static int all_symbols;
-static int absolute_percpu;
 static int base_relative;
 static int lto_clang;
 
@@ -75,7 +69,7 @@ static unsigned char best_table_len[256];
 
 static void usage(void)
 {
-	fprintf(stderr, "Usage: kallsyms [--all-symbols] [--absolute-percpu] "
+	fprintf(stderr, "Usage: kallsyms [--all-symbols] "
 			"[--base-relative] [--lto-clang] in.map > out.S\n");
 	exit(1);
 }
@@ -167,7 +161,6 @@ static struct sym_entry *read_symbol(FILE *in, char **buf, size_t *buf_len)
 		return NULL;
 
 	check_symbol_range(name, addr, text_ranges, ARRAY_SIZE(text_ranges));
-	check_symbol_range(name, addr, &percpu_range, 1);
 
 	/* include the type field in the symbol name, so that it gets
 	 * compressed together */
@@ -183,7 +176,6 @@ static struct sym_entry *read_symbol(FILE *in, char **buf, size_t *buf_len)
 	sym->len = len;
 	sym->sym[0] = type;
 	strcpy(sym_name(sym), name);
-	sym->percpu_absolute = 0;
 
 	return sym;
 }
@@ -334,11 +326,6 @@ static int expand_symbol(const unsigned char *data, int len, char *result)
 	return total;
 }
 
-static int symbol_absolute(const struct sym_entry *s)
-{
-	return s->percpu_absolute;
-}
-
 static void cleanup_symbol_name(char *s)
 {
 	char *p;
@@ -499,30 +486,17 @@ static void write_src(void)
 			 */
 
 			long long offset;
-			int overflow;
-
-			if (!absolute_percpu) {
-				offset = table[i]->addr - relative_base;
-				overflow = (offset < 0 || offset > UINT_MAX);
-			} else if (symbol_absolute(table[i])) {
-				offset = table[i]->addr;
-				overflow = (offset < 0 || offset > INT_MAX);
-			} else {
-				offset = relative_base - table[i]->addr - 1;
-				overflow = (offset < INT_MIN || offset >= 0);
-			}
-			if (overflow) {
+
+			offset = table[i]->addr - relative_base;
+			if (offset < 0 || offset > UINT_MAX) {
 				fprintf(stderr, "kallsyms failure: "
-					"%s symbol value %#llx out of range in relative mode\n",
-					symbol_absolute(table[i]) ? "absolute" : "relative",
+					"symbol value %#llx out of range in relative mode\n",
 					table[i]->addr);
 				exit(EXIT_FAILURE);
 			}
 			printf("\t.long\t%#x	/* %s */\n", (int)offset, table[i]->sym);
-		} else if (!symbol_absolute(table[i])) {
-			output_address(table[i]->addr);
 		} else {
-			printf("\tPTR\t%#llx\n", table[i]->addr);
+			output_address(table[i]->addr);
 		}
 	}
 	printf("\n");
@@ -775,36 +749,15 @@ static void sort_symbols(void)
 	qsort(table, table_cnt, sizeof(table[0]), compare_symbols);
 }
 
-static void make_percpus_absolute(void)
-{
-	unsigned int i;
-
-	for (i = 0; i < table_cnt; i++)
-		if (symbol_in_range(table[i], &percpu_range, 1)) {
-			/*
-			 * Keep the 'A' override for percpu symbols to
-			 * ensure consistent behavior compared to older
-			 * versions of this tool.
-			 */
-			table[i]->sym[0] = 'A';
-			table[i]->percpu_absolute = 1;
-		}
-}
-
-/* find the minimum non-absolute symbol address */
+/* find the minimum symbol address */
 static void record_relative_base(void)
 {
-	unsigned int i;
-
-	for (i = 0; i < table_cnt; i++)
-		if (!symbol_absolute(table[i])) {
-			/*
-			 * The table is sorted by address.
-			 * Take the first non-absolute symbol value.
-			 */
-			relative_base = table[i]->addr;
-			return;
-		}
+	/*
+	 * The table is sorted by address.
+	 * Take the first symbol value.
+	 */
+	if (table_cnt)
+		relative_base = table[0]->addr;
 }
 
 int main(int argc, char **argv)
@@ -812,7 +765,6 @@ int main(int argc, char **argv)
 	while (1) {
 		static const struct option long_options[] = {
 			{"all-symbols",     no_argument, &all_symbols,     1},
-			{"absolute-percpu", no_argument, &absolute_percpu, 1},
 			{"base-relative",   no_argument, &base_relative,   1},
 			{"lto-clang",       no_argument, &lto_clang,       1},
 			{},
@@ -831,8 +783,6 @@ int main(int argc, char **argv)
 
 	read_map(argv[optind]);
 	shrink_table();
-	if (absolute_percpu)
-		make_percpus_absolute();
 	sort_symbols();
 	if (base_relative)
 		record_relative_base();
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index a432b171be82..d25b6d5de45e 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -148,10 +148,6 @@ kallsyms()
 		kallsymopt="${kallsymopt} --all-symbols"
 	fi
 
-	if is_enabled CONFIG_KALLSYMS_ABSOLUTE_PERCPU; then
-		kallsymopt="${kallsymopt} --absolute-percpu"
-	fi
-
 	if is_enabled CONFIG_KALLSYMS_BASE_RELATIVE; then
 		kallsymopt="${kallsymopt} --base-relative"
 	fi
-- 
2.41.0