From 4719513c0fa2a39a2410448120a83cb1a416b194 Mon Sep 17 00:00:00 2001 From: "Lorenzo Stoakes (ARM)" Date: Wed, 23 Sep 2026 18:17:53 +0100 Subject: sorttable: parse nm output correctly MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit sorttable reads a list of functions from vmlinux, provided by the output of nm, with the -S flag specified providing function sizes. It does so using fscanf(fp, "%16s %16s %c %*s\n", ...) reading address, size, type (a single character) and name. However, nm outputs no size for a symbol which has none, meaning that it misinterprets these entries - interpreting the type character as the size, and, if the name is a single character, ignores the newline and swallows the address of the next entry. Size-less single character names exist (e.g. the assemblers' loop counters left over as local absolute symbols): 0000000000000001 a i 000000000000000f a i 0000000000000050 a j 0000000000000052 a t 000000000000009f a i 0000000000000200 a i sorttable is looking for functions and these are not that, and with nm's output sorted, it just so happens to be that what's swallowed is never a function. However the next commit in this series stops sorting nm's output, so this bug can results in function names being lost. Fix the issue by using '%*[^\n]' in fscanf() rather than '%*s' such that the scan cannot move past the newline. Then, compare the address and size fields (which are always padded to the same width if output by nm) - if they differ, then this is a misread, so simply discard the entry. It's fine to discard these, as sorttable's raison d'être is to discover whether a call site is contained within a function and an empty function can't contain anything. Assisted-by: LLM Signed-off-by: Lorenzo Stoakes (ARM) Link: https://patch.msgid.link/20260923-build-speedup-v4-4-73128809a4a4@kernel.org Signed-off-by: Nathan Chancellor --- scripts/sorttable.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) (limited to 'scripts/sorttable.c') diff --git a/scripts/sorttable.c b/scripts/sorttable.c index d7b50581c732..88e49a5c4251 100644 --- a/scripts/sorttable.c +++ b/scripts/sorttable.c @@ -322,10 +322,23 @@ static int parse_symbols(const char *fname) return -1; } - while (fscanf(fp, "%16s %16s %c %*s\n", addr_str, size_str, &type) == 3) { + while (fscanf(fp, "%16s %16s %c%*[^\n]", addr_str, size_str, &type) == 3) { uint64_t addr; uint64_t size; + /* + * nm outputs size-less entries with a missing 2nd value, which + * means fscanf() just misread its fields. + * + * These don't matter as a call site cannot be in an empty + * function, so just skip them. + * + * nm pads address and size to the same width, so if their + * widths differ, this is a misread. + */ + if (strlen(size_str) != strlen(addr_str)) + continue; + /* Only care about functions */ if (type != 't' && type != 'T' && type != 'W') continue; -- cgit v1.2.3