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Subject[PATCH] scripts/kallsyms: fix offset overflow of kallsyms_relative_base
Date
Since commit 5e5c4fa78745 ("scripts/kallsyms: shrink table before
sorting it"), kallsyms_relative_base can be larger than _text, which
causes overflow when building the 32-bit kernel.

https://lkml.org/lkml/2019/12/7/156

This is because _text is, unless --all-symbols is specified, now
trimmed from the symbol table before record_relative_base() is called.

Handle the offset signedness also for kallsyms_relative_base. Introduce
a new helper, output_address(), to reduce the code duplication.

Fixes: 5e5c4fa78745 ("scripts/kallsyms: shrink table before sorting it")
Reported-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

scripts/kallsyms.c | 38 ++++++++++++++++++--------------------
1 file changed, 18 insertions(+), 20 deletions(-)

diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index fb55f262f42d..94153732ec00 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -310,6 +310,15 @@ static void output_label(const char *label)
printf("%s:\n", label);
}

+/* Provide proper symbols relocatability by their '_text' relativeness. */
+static void output_address(unsigned long long addr)
+{
+ if (_text <= addr)
+ printf("\tPTR\t_text + %#llx\n", addr - _text);
+ else
+ printf("\tPTR\t_text - %#llx\n", _text - addr);
+}
+
/* uncompress a compressed symbol. When this function is called, the best table
* might still be compressed itself, so the function needs to be recursive */
static int expand_symbol(const unsigned char *data, int len, char *result)
@@ -360,19 +369,6 @@ static void write_src(void)

printf("\t.section .rodata, \"a\"\n");

- /* Provide proper symbols relocatability by their relativeness
- * to a fixed anchor point in the runtime image, either '_text'
- * for absolute address tables, in which case the linker will
- * emit the final addresses at build time. Otherwise, use the
- * offset relative to the lowest value encountered of all relative
- * symbols, and emit non-relocatable fixed offsets that will be fixed
- * up at runtime.
- *
- * The symbol names cannot be used to construct normal symbol
- * references as the list of symbols contains symbols that are
- * declared static and are private to their .o files. This prevents
- * .tmp_kallsyms.o or any other object from referencing them.
- */
if (!base_relative)
output_label("kallsyms_addresses");
else
@@ -380,6 +376,13 @@ static void write_src(void)

for (i = 0; i < table_cnt; i++) {
if (base_relative) {
+ /*
+ * Use the offset relative to the lowest value
+ * encountered of all relative symbols, and emit
+ * non-relocatable fixed offsets that will be fixed
+ * up at runtime.
+ */
+
long long offset;
int overflow;

@@ -402,12 +405,7 @@ static void write_src(void)
}
printf("\t.long\t%#x\n", (int)offset);
} else if (!symbol_absolute(&table[i])) {
- if (_text <= table[i].addr)
- printf("\tPTR\t_text + %#llx\n",
- table[i].addr - _text);
- else
- printf("\tPTR\t_text - %#llx\n",
- _text - table[i].addr);
+ output_address(table[i].addr);
} else {
printf("\tPTR\t%#llx\n", table[i].addr);
}
@@ -416,7 +414,7 @@ static void write_src(void)

if (base_relative) {
output_label("kallsyms_relative_base");
- printf("\tPTR\t_text - %#llx\n", _text - relative_base);
+ output_address(relative_base);
printf("\n");
}

--
2.17.1
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