[Crash-utility] [PATCH] Fix for 4.19-rc1 and later "relative __ksymtab entries"
Dominique Martinet
asmadeus at codewreck.org
Tue Aug 28 23:34:50 UTC 2018
kernels which have CONFIG_HAVE_ARCH_PREL32_RELOCATIONS will now store
module symbol values relative to themselves since linux kernel's commit
7290d580957 ("module: use relative references for __ksymtab entries")
Do the lookup one way or another depending on the kernel's kernel_symbol
struct, the case without the ARCH_PREL32_RELOCATIONS is the same as the
old behaviour
---
Hi! This is a follow-up on the bz I opened yesterday[1]
I'll let you commit your part of the tasks_struct pids, with both patches
I can start crash normally and could check that address of symbols within
a module look correct when compared to /proc/kallsyms, so I guess this
isn't too bad.
I also tried with an older kernel without problem.
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1623127
defs.h | 1 +
symbols.c | 98 +++++++++++++++++++++++++++++++++++++------------------
2 files changed, 68 insertions(+), 31 deletions(-)
diff --git a/defs.h b/defs.h
index 8687ff1..166ee48 100644
--- a/defs.h
+++ b/defs.h
@@ -2036,6 +2036,7 @@ struct offset_table { /* stash of commonly-used offsets */
long memcg_cache_params___root_caches_node;
long memcg_cache_params_children;
long memcg_cache_params_children_node;
+ long kernel_symbol_value;
};
struct size_table { /* stash of commonly-used sizes */
diff --git a/symbols.c b/symbols.c
index 2e6713a..7e73bad 100644
--- a/symbols.c
+++ b/symbols.c
@@ -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)
{
@@ -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];
@@ -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",
@@ -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) {
@@ -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);
@@ -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) {
@@ -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);
--
2.17.1
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