[PATCH 26/46] kbuild: whitelist false section mismatch warnings

Sam Ravnborg
2006-03-21T16:24:42Z

In several cases the section mismatch check triggered false warnings.
Following patch introduce a whitelist to 'false positives' are not warned of.
Two types of patterns are recognised:
1) Typical case when a module parameter is _initdata
2) When a function pointer is assigned to a driver structure

In both patterns we rely on the actual name of the variable assigned

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

---

scripts/mod/modpost.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 89 insertions(+), 0 deletions(-)

4c8fbca5836aaafd165aa8732d92ab5d4f3a6841
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index de0a9ee..663b1ef 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -452,6 +452,89 @@ static char *get_modinfo(void *modinfo,
}

/**
+ * Test if string s ends in string sub
+ * return 0 if match
+ **/
+static int strrcmp(const char *s, const char *sub)
+{
+ int slen, sublen;
+
+ if (!s || !sub)
+ return 1;
+
+ slen = strlen(s);
+ sublen = strlen(sub);
+
+ if ((slen == 0) || (sublen == 0))
+ return 1;
+
+ if (sublen > slen)
+ return 1;
+
+ return memcmp(s + slen - sublen, sub, sublen);
+}
+
+/**
+ * Whitelist to allow certain references to pass with no warning.
+ * Pattern 1:
+ * If a module parameter is declared __initdata and permissions=0
+ * then this is legal despite the warning generated.
+ * We cannot see value of permissions here, so just ignore
+ * this pattern.
+ * The pattern is identified by:
+ * tosec = .init.data
+ * fromsec = .data
+ * atsym =__param*
+ *
+ * Pattern 2:
+ * Many drivers utilise a *_driver container with references to
+ * add, remove, probe functions etc.
+ * These functions may often be marked __init and we do not want to
+ * warn here.
+ * the pattern is identified by:
+ * tosec = .init.text | .exit.text
+ * fromsec = .data
+ * atsym = *_driver, *_ops, *_probe, *probe_one
+ **/
+static int secref_whitelist(const char *tosec, const char *fromsec,
+ const char *atsym)
+{
+ int f1 = 1, f2 = 1;
+ const char **s;
+ const char *pat2sym[] = {
+ "_driver",
+ "_ops",
+ "_probe",
+ "_probe_one",
+ NULL
+ };
+
+ /* Check for pattern 1 */
+ if (strcmp(tosec, ".init.data") != 0)
+ f1 = 0;
+ if (strcmp(fromsec, ".data") != 0)
+ f1 = 0;
+ if (strncmp(atsym, "__param", strlen("__param")) != 0)
+ f1 = 0;
+
+ if (f1)
+ return f1;
+
+ /* Check for pattern 2 */
+ if ((strcmp(tosec, ".init.text") != 0) &&
+ (strcmp(tosec, ".exit.text") != 0))
+ f2 = 0;
+ if (strcmp(fromsec, ".data") != 0)
+ f2 = 0;
+
+ for (s = pat2sym; *s; s++)
+ if (strrcmp(atsym, *s) == 0)
+ f1 = 1;
+
+ return f1 && f2;
+}
+
+/**
* Find symbol based on relocation record info.
* In some cases the symbol supplied is a valid symbol so
* return refsym. If st_name != 0 we assume this is a valid symbol.
@@ -518,6 +601,7 @@ static void find_symbols_between(struct
/**
* Print a warning about a section mismatch.
* Try to find symbols near it so user can find it.
+ * Check whitelist before warning - it may be a false positive.
**/
static void warn_sec_mismatch(const char *modname, const char *fromsec,
struct elf_info *elf, Elf_Sym *sym, Elf_Rela r)
@@ -536,6 +620,11 @@ static void warn_sec_mismatch(const char
refsym = find_elf_symbol(elf, r.r_addend, sym);
if (refsym && strlen(elf->strtab + refsym->st_name))
refsymname = elf->strtab + refsym->st_name;
+
+ /* check whitelist - we may ignore it */
+ if (before &&
+ secref_whitelist(secname, fromsec, elf->strtab + before->st_name))
+ return;

if (before && after) {
warn("%s - Section mismatch: reference to %s:%s from %s "
--
1.0.GIT