On 2023/6/16 1:00, Song Liu wrote:
> With CONFIG_LTO_CLANG, kallsyms.c:cleanup_symbol_name() removes symbols
> suffixes during comparison. This is problematic for livepatch, as
> kallsyms_on_each_match_symbol may find multiple matches for the same
> symbol, and fail with:
>
> livepatch: unresolvable ambiguity for symbol 'xxx' in object 'yyy'
Did you forget to specify 'old_sympos'? When there are multiple symbols with
the same name, we need to specify the sequence number of the symbols to be
matched.
>
> Make kallsyms_on_each_match_symbol() to match symbols exactly. Since
> livepatch is the only user of kallsyms_on_each_match_symbol(), this
> change is safe.
>
> Signed-off-by: Song Liu <song@xxxxxxxxxx>
> ---
> kernel/kallsyms.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> index 77747391f49b..2ab459b43084 100644
> --- a/kernel/kallsyms.c
> +++ b/kernel/kallsyms.c
> @@ -187,7 +187,7 @@ static bool cleanup_symbol_name(char *s)
> return false;
> }
>
> -static int compare_symbol_name(const char *name, char *namebuf)
> +static int compare_symbol_name(const char *name, char *namebuf, bool match_exactly)
> {
> int ret;
>
> @@ -195,7 +195,7 @@ static int compare_symbol_name(const char *name, char *namebuf)
> if (!ret)
> return ret;
>
> - if (cleanup_symbol_name(namebuf) && !strcmp(name, namebuf))
> + if (!match_exactly && cleanup_symbol_name(namebuf) && !strcmp(name, namebuf))
> return 0;
>
> return ret;
> @@ -213,7 +213,8 @@ static unsigned int get_symbol_seq(int index)
>
> static int kallsyms_lookup_names(const char *name,
> unsigned int *start,
> - unsigned int *end)
> + unsigned int *end,
> + bool match_exactly)
> {
> int ret;
> int low, mid, high;
> @@ -228,7 +229,7 @@ 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 = compare_symbol_name(name, namebuf, match_exactly);
> if (ret > 0)
> low = mid + 1;
> else if (ret < 0)
> @@ -245,7 +246,7 @@ 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 (compare_symbol_name(name, namebuf, match_exactly))
> break;
> low--;
> }
> @@ -257,7 +258,7 @@ 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 (compare_symbol_name(name, namebuf, match_exactly))
> break;
> high++;
> }
> @@ -277,7 +278,7 @@ unsigned long kallsyms_lookup_name(const char *name)
> if (!*name)
> return 0;
>
> - ret = kallsyms_lookup_names(name, &i, NULL);
> + ret = kallsyms_lookup_names(name, &i, NULL, false);
> if (!ret)
> return kallsyms_sym_address(get_symbol_seq(i));
>
> @@ -312,7 +313,7 @@ int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long),
> int ret;
> unsigned int i, start, end;
>
> - ret = kallsyms_lookup_names(name, &start, &end);
> + ret = kallsyms_lookup_names(name, &start, &end, true);
> if (ret)
> return 0;
>
>
--
Regards,
Zhen Lei
