kallsyms: Correctly sequence symbols when CONFIG_LTO_CLANG=y

LLVM appends various suffixes for local functions and variables, suffixes
observed:
 - foo.llvm.[0-9a-f]+
 - foo.[0-9a-f]+

Therefore, when CONFIG_LTO_CLANG=y, kallsyms_lookup_name() needs to
truncate the suffix of the symbol name before comparing the local function
or variable name.

Old implementation code:
-	if (strcmp(namebuf, name) == 0)
-		return kallsyms_sym_address(i);
-	if (cleanup_symbol_name(namebuf) && strcmp(namebuf, name) == 0)
-		return kallsyms_sym_address(i);

The preceding process is traversed by address from low to high. That is,
for those with the same name after the suffix is removed, the one with
the smallest address is returned first. Therefore, when sorting in the
tool, if the raw names are the same, they should be sorted by address in
ascending order.

ASCII[.]   = 2e
ASCII[0-9] = 30,39
ASCII[A-Z] = 41,5a
ASCII[_]   = 5f
ASCII[a-z] = 61,7a

According to the preceding ASCII code values, the following sorting result
is strictly followed.
 ---------------------------------
|    main-key     |    sub-key    |
|---------------------------------|
|                 |  addr_lowest  |
| <name>          |      ...      |
| <name>.<suffix> |      ...      |
|                 |  addr_highest |
|---------------------------------|
| <name>?<others> |               |   //? is [_A-Za-z0-9]
 ---------------------------------

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 918470d768e9..32e573943cf0 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -156,6 +156,10 @@ kallsyms()
 		kallsymopt="${kallsymopt} --base-relative"
 	fi
 
+	if is_enabled CONFIG_LTO_CLANG; then
+		kallsymopt="${kallsymopt} --lto-clang"
+	fi
+
 	info KSYMS ${2}
 	scripts/kallsyms ${kallsymopt} ${1} > ${2}
 }