kbuild: whitelist false section mismatch warnings
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>
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@ -451,6 +451,89 @@ static char *get_modinfo(void *modinfo, unsigned long modinfo_len,
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return NULL;
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}
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/**
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* Test if string s ends in string sub
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* return 0 if match
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**/
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static int strrcmp(const char *s, const char *sub)
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{
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int slen, sublen;
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if (!s || !sub)
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return 1;
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slen = strlen(s);
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sublen = strlen(sub);
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if ((slen == 0) || (sublen == 0))
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return 1;
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if (sublen > slen)
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return 1;
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return memcmp(s + slen - sublen, sub, sublen);
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}
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/**
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* Whitelist to allow certain references to pass with no warning.
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* Pattern 1:
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* If a module parameter is declared __initdata and permissions=0
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* then this is legal despite the warning generated.
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* We cannot see value of permissions here, so just ignore
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* this pattern.
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* The pattern is identified by:
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* tosec = .init.data
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* fromsec = .data
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* atsym =__param*
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*
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* Pattern 2:
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* Many drivers utilise a *_driver container with references to
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* add, remove, probe functions etc.
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* These functions may often be marked __init and we do not want to
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* warn here.
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* the pattern is identified by:
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* tosec = .init.text | .exit.text
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* fromsec = .data
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* atsym = *_driver, *_ops, *_probe, *probe_one
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**/
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static int secref_whitelist(const char *tosec, const char *fromsec,
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const char *atsym)
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{
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int f1 = 1, f2 = 1;
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const char **s;
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const char *pat2sym[] = {
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"_driver",
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"_ops",
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"_probe",
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"_probe_one",
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NULL
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};
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/* Check for pattern 1 */
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if (strcmp(tosec, ".init.data") != 0)
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f1 = 0;
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if (strcmp(fromsec, ".data") != 0)
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f1 = 0;
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if (strncmp(atsym, "__param", strlen("__param")) != 0)
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f1 = 0;
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if (f1)
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return f1;
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/* Check for pattern 2 */
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if ((strcmp(tosec, ".init.text") != 0) &&
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(strcmp(tosec, ".exit.text") != 0))
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f2 = 0;
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if (strcmp(fromsec, ".data") != 0)
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f2 = 0;
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for (s = pat2sym; *s; s++)
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if (strrcmp(atsym, *s) == 0)
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f1 = 1;
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return f1 && f2;
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}
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/**
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* Find symbol based on relocation record info.
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* In some cases the symbol supplied is a valid symbol so
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@ -518,6 +601,7 @@ static void find_symbols_between(struct elf_info *elf, Elf_Addr addr,
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/**
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* Print a warning about a section mismatch.
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* Try to find symbols near it so user can find it.
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* Check whitelist before warning - it may be a false positive.
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**/
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static void warn_sec_mismatch(const char *modname, const char *fromsec,
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struct elf_info *elf, Elf_Sym *sym, Elf_Rela r)
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@ -537,6 +621,11 @@ static void warn_sec_mismatch(const char *modname, const char *fromsec,
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if (refsym && strlen(elf->strtab + refsym->st_name))
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refsymname = elf->strtab + refsym->st_name;
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/* check whitelist - we may ignore it */
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if (before &&
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secref_whitelist(secname, fromsec, elf->strtab + before->st_name))
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return;
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if (before && after) {
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warn("%s - Section mismatch: reference to %s:%s from %s "
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"between '%s' (at offset 0x%llx) and '%s'\n",
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