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Fix for Linux 4.19-rc1 and later kernels that contain kernel commit 
7290d58095712a89f845e1bca05334796dd49ed2, titled "module: use
relative references for __ksymtab entries".  Without the patch,
kernels configured with CONFIG_HAVE_ARCH_PREL32_RELOCATIONS fail
during session initialization, with a dump of the internel buffer
allocation stats followed by the message "crash: cannot allocate
any more memory!"
(asmadeus@codewreck.org)
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Dave Anderson committed Aug 29, 2018
1 parent d7eec45 commit 001f77a
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Showing 2 changed files with 70 additions and 32 deletions.
1 change: 1 addition & 0 deletions defs.h
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Expand Up @@ -2037,6 +2037,7 @@ struct offset_table { /* stash of commonly-used offsets */
long memcg_cache_params_children;
long memcg_cache_params_children_node;
long task_struct_pid_links;
long long kernel_symbol_value;
};

struct size_table { /* stash of commonly-used sizes */
Expand Down
101 changes: 69 additions & 32 deletions symbols.c
View file
Expand Up @@ -1595,12 +1595,40 @@ store_module_symbols_v1(ulong total, int mods_installed)
st->flags |= INSMOD_BUILTIN;
}

struct kernel_symbol
{
unsigned long value;
const char *name;
union kernel_symbol {
struct kernel_symbol_v1 {
unsigned long value;
const char *name;
} v1;
/* kernel 4.19 introduced relative symbol positionning */
struct kernel_symbol_v2 {
int value_offset;
int name_offset;
} v2;
};

static ulong
modsym_name(ulong syms, union kernel_symbol *modsym, int i)
{
if (VALID_MEMBER(kernel_symbol_value))
return (ulong)modsym->v1.name;

return syms + i * sizeof(struct kernel_symbol_v2) +
offsetof(struct kernel_symbol_v2, name_offset) +
modsym->v2.name_offset;
}

static ulong
modsym_value(ulong syms, union kernel_symbol *modsym, int i)
{
if (VALID_MEMBER(kernel_symbol_value))
return (ulong)modsym->v1.value;

return syms + i * sizeof(struct kernel_symbol_v2) +
offsetof(struct kernel_symbol_v2, value_offset) +
modsym->v2.value_offset;
}

void
store_module_symbols_v2(ulong total, int mods_installed)
{
Expand All @@ -1614,7 +1642,8 @@ store_module_symbols_v2(ulong total, int mods_installed)
long strbuflen;
ulong size;
int mcnt, lm_mcnt;
struct kernel_symbol *modsym;
union kernel_symbol *modsym;
size_t kernel_symbol_size;
struct load_module *lm;
char buf1[BUFSIZE];
char buf2[BUFSIZE];
Expand All @@ -1639,6 +1668,13 @@ store_module_symbols_v2(ulong total, int mods_installed)
"re-initialization of module symbols not implemented yet!\n");
}

MEMBER_OFFSET_INIT(kernel_symbol_value, "kernel_symbol", "value");
if (VALID_MEMBER(kernel_symbol_value)) {
kernel_symbol_size = sizeof(struct kernel_symbol_v1);
} else {
kernel_symbol_size = sizeof(struct kernel_symbol_v2);
}

if ((st->ext_module_symtable = (struct syment *)
calloc(total, sizeof(struct syment))) == NULL)
error(FATAL, "v2 module syment space malloc (%ld symbols): %s\n",
Expand Down Expand Up @@ -1750,20 +1786,20 @@ store_module_symbols_v2(ulong total, int mods_installed)
}

if (nsyms) {
modsymbuf = GETBUF(sizeof(struct kernel_symbol)*nsyms);
modsymbuf = GETBUF(kernel_symbol_size*nsyms);
readmem((ulong)syms, KVADDR, modsymbuf,
nsyms * sizeof(struct kernel_symbol),
nsyms * kernel_symbol_size,
"module symbols", FAULT_ON_ERROR);
}

for (i = first = last = 0; i < nsyms; i++) {
modsym = (struct kernel_symbol *)
(modsymbuf + (i * sizeof(struct kernel_symbol)));
modsym = (union kernel_symbol *)
(modsymbuf + (i * kernel_symbol_size));
if (!first
|| first > (ulong)modsym->name)
first = (ulong)modsym->name;
if ((ulong)modsym->name > last)
last = (ulong)modsym->name;
|| first > modsym_name(syms, modsym, i))
first = modsym_name(syms, modsym, i);
if (modsym_name(syms, modsym, i) > last)
last = modsym_name(syms, modsym, i);
}

if (last > first) {
Expand All @@ -1787,21 +1823,21 @@ store_module_symbols_v2(ulong total, int mods_installed)

for (i = 0; i < nsyms; i++) {

modsym = (struct kernel_symbol *)
(modsymbuf + (i * sizeof(struct kernel_symbol)));
modsym = (union kernel_symbol *)
(modsymbuf + (i * kernel_symbol_size));

BZERO(buf1, BUFSIZE);

if (strbuf)
strcpy(buf1,
&strbuf[(ulong)modsym->name - first]);
&strbuf[modsym_name(syms, modsym, i) - first]);
else
read_string((ulong)modsym->name, buf1,
read_string(modsym_name(syms, modsym, i), buf1,
BUFSIZE-1);

if (strlen(buf1)) {
st->ext_module_symtable[mcnt].value =
modsym->value;
modsym_value(syms, modsym, i);
st->ext_module_symtable[mcnt].type = '?';
st->ext_module_symtable[mcnt].flags |= MODULE_SYMBOL;
strip_module_symbol_end(buf1);
Expand All @@ -1823,21 +1859,21 @@ store_module_symbols_v2(ulong total, int mods_installed)
FREEBUF(strbuf);

if (ngplsyms) {
modsymbuf = GETBUF(sizeof(struct kernel_symbol) *
modsymbuf = GETBUF(kernel_symbol_size *
ngplsyms);
readmem((ulong)gpl_syms, KVADDR, modsymbuf,
ngplsyms * sizeof(struct kernel_symbol),
ngplsyms * kernel_symbol_size,
"module gpl symbols", FAULT_ON_ERROR);
}

for (i = first = last = 0; i < ngplsyms; i++) {
modsym = (struct kernel_symbol *)
(modsymbuf + (i * sizeof(struct kernel_symbol)));
modsym = (union kernel_symbol *)
(modsymbuf + (i * kernel_symbol_size));
if (!first
|| first > (ulong)modsym->name)
first = (ulong)modsym->name;
if ((ulong)modsym->name > last)
last = (ulong)modsym->name;
|| first > modsym_name(gpl_syms, modsym, i))
first = modsym_name(gpl_syms, modsym, i);
if (modsym_name(gpl_syms, modsym, i) > last)
last = modsym_name(gpl_syms, modsym, i);
}

if (last > first) {
Expand All @@ -1860,21 +1896,21 @@ store_module_symbols_v2(ulong total, int mods_installed)

for (i = 0; i < ngplsyms; i++) {

modsym = (struct kernel_symbol *)
(modsymbuf + (i * sizeof(struct kernel_symbol)));
modsym = (union kernel_symbol *)
(modsymbuf + (i * kernel_symbol_size));

BZERO(buf1, BUFSIZE);

if (strbuf)
strcpy(buf1,
&strbuf[(ulong)modsym->name - first]);
&strbuf[modsym_name(gpl_syms, modsym, i) - first]);
else
read_string((ulong)modsym->name, buf1,
read_string(modsym_name(gpl_syms, modsym, i), buf1,
BUFSIZE-1);

if (strlen(buf1)) {
st->ext_module_symtable[mcnt].value =
modsym->value;
modsym_value(gpl_syms, modsym, i);
st->ext_module_symtable[mcnt].type = '?';
st->ext_module_symtable[mcnt].flags |= MODULE_SYMBOL;
strip_module_symbol_end(buf1);
Expand Down Expand Up @@ -8975,7 +9011,8 @@ dump_offset_table(char *spec, ulong makestruct)
OFFSET(kallsyms_section_size));
fprintf(fp, " kallsyms_section_name_off: %ld\n",
OFFSET(kallsyms_section_name_off));

fprintf(fp, " kernel_symbol_value: %ld\n",
OFFSET(kernel_symbol_value));
fprintf(fp, " module_taints: %ld\n",
OFFSET(module_taints));
fprintf(fp, " module_license_gplok: %ld\n",
Expand Down

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