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kbuild: add verbose option to Section mismatch reporting in modpost
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If the config option CONFIG_SECTION_MISMATCH is not set and
we see a Section mismatch present the following to the user:

modpost: Found 1 section mismatch(es).
To see additional details select "Enable full Section mismatch analysis"
in the Kernel Hacking menu (CONFIG_SECTION_MISMATCH).

If the option CONFIG_SECTION_MISMATCH is selected
then be verbose in the Section mismatch reporting from mdopost.
Sample outputs:

WARNING: o-x86_64/vmlinux.o(.text+0x7396): Section mismatch in reference from the function discover_ebda() to the variable .init.data:ebda_addr
The function  discover_ebda() references
the variable __initdata ebda_addr.
This is often because discover_ebda lacks a __initdata
annotation or the annotation of ebda_addr is wrong.

WARNING: o-x86_64/vmlinux.o(.data+0x74d58): Section mismatch in reference from the variable pci_serial_quirks to the function .devexit.text:pci_plx9050_exit()
The variable pci_serial_quirks references
the function __devexit pci_plx9050_exit()
If the reference is valid then annotate the
variable with __exit* (see linux/init.h) or name the variable:
*driver, *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console,

WARNING: o-x86_64/vmlinux.o(__ksymtab+0x630): Section mismatch in reference from the variable __ksymtab_arch_register_cpu to the function .cpuinit.text:arch_register_cpu()
The symbol arch_register_cpu is exported and annotated __cpuinit
Fix this by removing the __cpuinit annotation of arch_register_cpu or drop the export.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
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Sam Ravnborg committed Jan 28, 2008
1 parent f5eaa32 commit 588ccd7
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Showing 3 changed files with 229 additions and 29 deletions.
2 changes: 2 additions & 0 deletions lib/Kconfig.debug
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Original file line number Diff line number Diff line change
Expand Up @@ -108,6 +108,8 @@ config DEBUG_SECTION_MISMATCH
will tell where the mismatch happens much closer to the
source. The drawback is that we will report the same
mismatch at least twice.
- Enable verbose reporting from modpost to help solving
the section mismatches reported.

config DEBUG_KERNEL
bool "Kernel debugging"
Expand Down
1 change: 1 addition & 0 deletions scripts/Makefile.modpost
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,7 @@ modpost = scripts/mod/modpost \
$(if $(KBUILD_EXTMOD),-i,-o) $(kernelsymfile) \
$(if $(KBUILD_EXTMOD),-I $(modulesymfile)) \
$(if $(KBUILD_EXTMOD),-o $(modulesymfile)) \
$(if $(CONFIG_DEBUG_SECTION_MISMATCH),,-S) \
$(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w)

quiet_cmd_modpost = MODPOST $(words $(filter-out vmlinux FORCE, $^)) modules
Expand Down
255 changes: 226 additions & 29 deletions scripts/mod/modpost.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,9 @@ static int vmlinux_section_warnings = 1;
/* Only warn about unresolved symbols */
static int warn_unresolved = 0;
/* How a symbol is exported */
static int sec_mismatch_count = 0;
static int sec_mismatch_verbose = 1;

enum export {
export_plain, export_unused, export_gpl,
export_unused_gpl, export_gpl_future, export_unknown
Expand Down Expand Up @@ -760,43 +763,78 @@ static const char *head_sections[] = { ".head.text*", NULL };
static const char *linker_symbols[] =
{ "__init_begin", "_sinittext", "_einittext", NULL };

enum mismatch {
NO_MISMATCH,
TEXT_TO_INIT,
DATA_TO_INIT,
TEXT_TO_EXIT,
DATA_TO_EXIT,
XXXINIT_TO_INIT,
XXXEXIT_TO_EXIT,
INIT_TO_EXIT,
EXIT_TO_INIT,
EXPORT_TO_INIT_EXIT,
};

struct sectioncheck {
const char *fromsec[20];
const char *tosec[20];
enum mismatch mismatch;
};

const struct sectioncheck sectioncheck[] = {
/* Do not reference init/exit code/data from
* normal code and data
*/
{
.fromsec = { TEXT_SECTIONS, DATA_SECTIONS, NULL },
.tosec = { ALL_INIT_SECTIONS, ALL_EXIT_SECTIONS, NULL }
.fromsec = { TEXT_SECTIONS, NULL },
.tosec = { ALL_INIT_SECTIONS, NULL },
.mismatch = TEXT_TO_INIT,
},
{
.fromsec = { DATA_SECTIONS, NULL },
.tosec = { ALL_INIT_SECTIONS, NULL },
.mismatch = DATA_TO_INIT,
},
{
.fromsec = { TEXT_SECTIONS, NULL },
.tosec = { ALL_EXIT_SECTIONS, NULL },
.mismatch = TEXT_TO_EXIT,
},
{
.fromsec = { DATA_SECTIONS, NULL },
.tosec = { ALL_EXIT_SECTIONS, NULL },
.mismatch = DATA_TO_EXIT,
},
/* Do not reference init code/data from devinit/cpuinit/meminit code/data */
{
.fromsec = { DEV_INIT_SECTIONS, CPU_INIT_SECTIONS, MEM_INIT_SECTIONS, NULL },
.tosec = { INIT_SECTIONS, NULL }
.tosec = { INIT_SECTIONS, NULL },
.mismatch = XXXINIT_TO_INIT,
},
/* Do not reference exit code/data from devexit/cpuexit/memexit code/data */
{
.fromsec = { DEV_EXIT_SECTIONS, CPU_EXIT_SECTIONS, MEM_EXIT_SECTIONS, NULL },
.tosec = { EXIT_SECTIONS, NULL }
.tosec = { EXIT_SECTIONS, NULL },
.mismatch = XXXEXIT_TO_EXIT,
},
/* Do not use exit code/data from init code */
{
.fromsec = { ALL_INIT_SECTIONS, NULL },
.tosec = { ALL_EXIT_SECTIONS, NULL },
.mismatch = INIT_TO_EXIT,
},
/* Do not use init code/data from exit code */
{
.fromsec = { ALL_EXIT_SECTIONS, NULL },
.tosec = { ALL_INIT_SECTIONS, NULL }
.tosec = { ALL_INIT_SECTIONS, NULL },
.mismatch = EXIT_TO_INIT,
},
/* Do not export init/exit functions or data */
{
.fromsec = { "__ksymtab*", NULL },
.tosec = { ALL_INIT_SECTIONS, ALL_EXIT_SECTIONS, NULL }
.tosec = { ALL_INIT_SECTIONS, ALL_EXIT_SECTIONS, NULL },
.mismatch = EXPORT_TO_INIT_EXIT
}
};

Expand All @@ -809,10 +847,10 @@ static int section_mismatch(const char *fromsec, const char *tosec)
for (i = 0; i < elems; i++) {
if (match(fromsec, check->fromsec) &&
match(tosec, check->tosec))
return 1;
return check->mismatch;
check++;
}
return 0;
return NO_MISMATCH;
}

/**
Expand Down Expand Up @@ -988,48 +1026,198 @@ static Elf_Sym *find_elf_symbol2(struct elf_info *elf, Elf_Addr addr,
return near;
}

/*
* Convert a section name to the function/data attribute
* .init.text => __init
* .cpuinit.data => __cpudata
* .memexitconst => __memconst
* etc.
*/
static char *sec2annotation(const char *s)
{
if (match(s, init_exit_sections)) {
char *p = malloc(20);
char *r = p;

*p++ = '_';
*p++ = '_';
if (*s == '.')
s++;
while (*s && *s != '.')
*p++ = *s++;
*p = '\0';
if (*s == '.')
s++;
if (strstr(s, "rodata") != NULL)
strcat(p, "const ");
else if (strstr(s, "data") != NULL)
strcat(p, "data ");
else
strcat(p, " ");
return r; /* we leak her but we do not care */
} else {
return "";
}
}

static int is_function(Elf_Sym *sym)
{
if (sym)
return ELF_ST_TYPE(sym->st_info) == STT_FUNC;
else
return 0;
}

/*
* 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 report_sec_mismatch(const char *modname,
static void report_sec_mismatch(const char *modname, enum mismatch mismatch,
const char *fromsec,
unsigned long long fromaddr,
const char *fromsym,
const char *tosec, const char *tosym)
{
if (strlen(tosym)) {
warn("%s(%s+0x%llx): Section mismatch: reference to %s:%s "
"in '%s'\n",
modname, fromsec, fromaddr,
tosec, tosym, fromsym);
} else {
warn("%s(%s+0x%llx): Section mismatch: reference to %s:%s\n",
modname, fromsec, fromaddr,
tosec, tosym);
int from_is_func,
const char *tosec, const char *tosym,
int to_is_func)
{
const char *from, *from_p;
const char *to, *to_p;
from = from_is_func ? "function" : "variable";
from_p = from_is_func ? "()" : "";
to = to_is_func ? "function" : "variable";
to_p = to_is_func ? "()" : "";

fprintf(stderr, "WARNING: %s(%s+0x%llx): Section mismatch in"
" reference from the %s %s%s to the %s %s:%s%s\n",
modname, fromsec, fromaddr, from, fromsym, from_p,
to, tosec, tosym, to_p);

sec_mismatch_count++;
if (!sec_mismatch_verbose)
return;

switch (mismatch) {
case TEXT_TO_INIT:
fprintf(stderr,
"The function %s %s() references\n"
"the %s %s%s%s.\n"
"This is often because %s lacks a %s\n"
"annotation or the annotation of %s is wrong.\n",
sec2annotation(fromsec), fromsym,
to, sec2annotation(tosec), tosym, to_p,
fromsym, sec2annotation(tosec), tosym);
break;
case DATA_TO_INIT: {
const char **s = symbol_white_list;
fprintf(stderr,
"The variable %s references\n"
"the %s %s%s%s\n"
"If the reference is valid then annotate the\n"
"variable with __init* (see linux/init.h) "
"or name the variable:\n",
fromsym, to, sec2annotation(tosec), tosym, to_p);
while (*s)
fprintf(stderr, "%s, ", *s++);
fprintf(stderr, "\n");
break;
}
case TEXT_TO_EXIT:
fprintf(stderr,
"The function %s() references a %s in an exit section.\n"
"Often the %s %s%s has valid usage outside the exit section\n"
"and the fix is to remove the %sannotation of %s.\n",
fromsym, to, to, tosym, to_p, sec2annotation(tosec), tosym);
break;
case DATA_TO_EXIT: {
const char **s = symbol_white_list;
fprintf(stderr,
"The variable %s references\n"
"the %s %s%s%s\n"
"If the reference is valid then annotate the\n"
"variable with __exit* (see linux/init.h) or "
"name the variable:\n",
fromsym, to, sec2annotation(tosec), tosym, to_p);
while (*s)
fprintf(stderr, "%s, ", *s++);
fprintf(stderr, "\n");
break;
}
case XXXINIT_TO_INIT:
case XXXEXIT_TO_EXIT:
fprintf(stderr,
"The %s %s%s%s references\n"
"a %s %s%s%s.\n"
"If %s is only used by %s then\n"
"annotate %s with a matching annotation.\n",
from, sec2annotation(fromsec), fromsym, from_p,
to, sec2annotation(tosec), tosym, to_p,
fromsym, tosym, fromsym);
break;
case INIT_TO_EXIT:
fprintf(stderr,
"The %s %s%s%s references\n"
"a %s %s%s%s.\n"
"This is often seen when error handling "
"in the init function\n"
"uses functionality in the exit path.\n"
"The fix is often to remove the %sannotation of\n"
"%s%s so it may be used outside an exit section.\n",
from, sec2annotation(fromsec), fromsym, from_p,
to, sec2annotation(tosec), tosym, to_p,
sec2annotation(tosec), tosym, to_p);
break;
case EXIT_TO_INIT:
fprintf(stderr,
"The %s %s%s%s references\n"
"a %s %s%s%s.\n"
"This is often seen when error handling "
"in the exit function\n"
"uses functionality in the init path.\n"
"The fix is often to remove the %sannotation of\n"
"%s%s so it may be used outside an init section.\n",
from, sec2annotation(fromsec), fromsym, from_p,
to, sec2annotation(tosec), tosym, to_p,
sec2annotation(tosec), tosym, to_p);
break;
case EXPORT_TO_INIT_EXIT:
fprintf(stderr,
"The symbol %s is exported and annotated %s\n"
"Fix this by removing the %sannotation of %s "
"or drop the export.\n",
tosym, sec2annotation(tosec), sec2annotation(tosec), tosym);
case NO_MISMATCH:
/* To get warnings on missing members */
break;
}
fprintf(stderr, "\n");
}

static void check_section_mismatch(const char *modname, struct elf_info *elf,
Elf_Rela *r, Elf_Sym *sym, const char *fromsec)
{
const char *tosec;
enum mismatch mismatch;

tosec = sec_name(elf, sym->st_shndx);
if (section_mismatch(fromsec, tosec)) {
const char *fromsym;
mismatch = section_mismatch(fromsec, tosec);
if (mismatch != NO_MISMATCH) {
Elf_Sym *to;
Elf_Sym *from;
const char *tosym;
const char *fromsym;

fromsym = sym_name(elf,
find_elf_symbol2(elf, r->r_offset, fromsec));
tosym = sym_name(elf,
find_elf_symbol(elf, r->r_addend, sym));
from = find_elf_symbol2(elf, r->r_offset, fromsec);
fromsym = sym_name(elf, from);
to = find_elf_symbol(elf, r->r_addend, sym);
tosym = sym_name(elf, to);

/* check whitelist - we may ignore it */
if (secref_whitelist(fromsec, fromsym, tosec, tosym)) {
report_sec_mismatch(modname, fromsec, r->r_offset,
fromsym, tosec, tosym);
report_sec_mismatch(modname, mismatch,
fromsec, r->r_offset, fromsym,
is_function(from), tosec, tosym,
is_function(to));
}
}
}
Expand Down Expand Up @@ -1643,7 +1831,7 @@ int main(int argc, char **argv)
int opt;
int err;

while ((opt = getopt(argc, argv, "i:I:mso:aw")) != -1) {
while ((opt = getopt(argc, argv, "i:I:msSo:aw")) != -1) {
switch (opt) {
case 'i':
kernel_read = optarg;
Expand All @@ -1664,6 +1852,9 @@ int main(int argc, char **argv)
case 's':
vmlinux_section_warnings = 0;
break;
case 'S':
sec_mismatch_verbose = 0;
break;
case 'w':
warn_unresolved = 1;
break;
Expand Down Expand Up @@ -1708,6 +1899,12 @@ int main(int argc, char **argv)

if (dump_write)
write_dump(dump_write);
if (sec_mismatch_count && !sec_mismatch_verbose)
fprintf(stderr, "modpost: Found %d section mismatch(es).\n"
"To see additional details select \"Enable full "
"Section mismatch analysis\"\n"
"in the Kernel Hacking menu "
"(CONFIG_SECTION_MISMATCH).\n", sec_mismatch_count);

return err;
}

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