6.10-stable review patch. If anyone has any objections, please let me know.
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From: Song Liu song@kernel.org
[ Upstream commit fb6a421fb6153d97cf3058f9bd550b377b76a490 ]
With CONFIG_LTO_CLANG=y, the compiler may add .llvm.<hash> suffix to function names to avoid duplication. APIs like kallsyms_lookup_name() and kallsyms_on_each_match_symbol() tries to match these symbol names without the .llvm.<hash> suffix, e.g., match "c_stop" with symbol c_stop.llvm.17132674095431275852. This turned out to be problematic for use cases that require exact match, for example, livepatch.
Fix this by making the APIs to match symbols exactly.
Also cleanup kallsyms_selftests accordingly.
Signed-off-by: Song Liu song@kernel.org Fixes: 8cc32a9bbf29 ("kallsyms: strip LTO-only suffixes from promoted global functions") Tested-by: Masami Hiramatsu (Google) mhiramat@kernel.org Reviewed-by: Masami Hiramatsu (Google) mhiramat@kernel.org Acked-by: Petr Mladek pmladek@suse.com Reviewed-by: Sami Tolvanen samitolvanen@google.com Reviewed-by: Luis Chamberlain mcgrof@kernel.org Link: https://lore.kernel.org/r/20240807220513.3100483-3-song@kernel.org Signed-off-by: Kees Cook kees@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/kallsyms.c | 55 +++++--------------------------------- kernel/kallsyms_selftest.c | 22 +-------------- 2 files changed, 7 insertions(+), 70 deletions(-)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index fb2c77368d187..a9a0ca605d4a8 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -160,38 +160,6 @@ unsigned long kallsyms_sym_address(int idx) return kallsyms_relative_base - 1 - kallsyms_offsets[idx]; }
-static void cleanup_symbol_name(char *s) -{ - char *res; - - if (!IS_ENABLED(CONFIG_LTO_CLANG)) - return; - - /* - * LLVM appends various suffixes for local functions and variables that - * must be promoted to global scope as part of LTO. This can break - * hooking of static functions with kprobes. '.' is not a valid - * character in an identifier in C. Suffixes only in LLVM LTO observed: - * - foo.llvm.[0-9a-f]+ - */ - res = strstr(s, ".llvm."); - if (res) - *res = '\0'; - - return; -} - -static int compare_symbol_name(const char *name, char *namebuf) -{ - /* The kallsyms_seqs_of_names is sorted based on names after - * cleanup_symbol_name() (see scripts/kallsyms.c) if clang lto is enabled. - * To ensure correct bisection in kallsyms_lookup_names(), do - * cleanup_symbol_name(namebuf) before comparing name and namebuf. - */ - cleanup_symbol_name(namebuf); - return strcmp(name, namebuf); -} - static unsigned int get_symbol_seq(int index) { unsigned int i, seq = 0; @@ -219,7 +187,7 @@ static int kallsyms_lookup_names(const char *name, seq = get_symbol_seq(mid); off = get_symbol_offset(seq); kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf)); - ret = compare_symbol_name(name, namebuf); + ret = strcmp(name, namebuf); if (ret > 0) low = mid + 1; else if (ret < 0) @@ -236,7 +204,7 @@ static int kallsyms_lookup_names(const char *name, seq = get_symbol_seq(low - 1); off = get_symbol_offset(seq); kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf)); - if (compare_symbol_name(name, namebuf)) + if (strcmp(name, namebuf)) break; low--; } @@ -248,7 +216,7 @@ static int kallsyms_lookup_names(const char *name, seq = get_symbol_seq(high + 1); off = get_symbol_offset(seq); kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf)); - if (compare_symbol_name(name, namebuf)) + if (strcmp(name, namebuf)) break; high++; } @@ -407,8 +375,7 @@ static int kallsyms_lookup_buildid(unsigned long addr, if (modbuildid) *modbuildid = NULL;
- ret = strlen(namebuf); - goto found; + return strlen(namebuf); }
/* See if it's in a module or a BPF JITed image. */ @@ -422,8 +389,6 @@ static int kallsyms_lookup_buildid(unsigned long addr, ret = ftrace_mod_address_lookup(addr, symbolsize, offset, modname, namebuf);
-found: - cleanup_symbol_name(namebuf); return ret; }
@@ -450,8 +415,6 @@ const char *kallsyms_lookup(unsigned long addr,
int lookup_symbol_name(unsigned long addr, char *symname) { - int res; - symname[0] = '\0'; symname[KSYM_NAME_LEN - 1] = '\0';
@@ -462,16 +425,10 @@ int lookup_symbol_name(unsigned long addr, char *symname) /* Grab name */ kallsyms_expand_symbol(get_symbol_offset(pos), symname, KSYM_NAME_LEN); - goto found; + return 0; } /* See if it's in a module. */ - res = lookup_module_symbol_name(addr, symname); - if (res) - return res; - -found: - cleanup_symbol_name(symname); - return 0; + return lookup_module_symbol_name(addr, symname); }
/* Look up a kernel symbol and return it in a text buffer. */ diff --git a/kernel/kallsyms_selftest.c b/kernel/kallsyms_selftest.c index 2f84896a7bcbd..873f7c445488c 100644 --- a/kernel/kallsyms_selftest.c +++ b/kernel/kallsyms_selftest.c @@ -187,31 +187,11 @@ static void test_perf_kallsyms_lookup_name(void) stat.min, stat.max, div_u64(stat.sum, stat.real_cnt)); }
-static bool match_cleanup_name(const char *s, const char *name) -{ - char *p; - int len; - - if (!IS_ENABLED(CONFIG_LTO_CLANG)) - return false; - - p = strstr(s, ".llvm."); - if (!p) - return false; - - len = strlen(name); - if (p - s != len) - return false; - - return !strncmp(s, name, len); -} - static int find_symbol(void *data, const char *name, unsigned long addr) { struct test_stat *stat = (struct test_stat *)data;
- if (strcmp(name, stat->name) == 0 || - (!stat->perf && match_cleanup_name(name, stat->name))) { + if (!strcmp(name, stat->name)) { stat->real_cnt++; stat->addr = addr;