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From 4821b72a908ed4ded1f0a37afa238af62d0f778a Mon Sep 17 00:00:00 2001
From: Zhipeng Xie <xiezhipeng1@huawei.com>
Date: Wed, 26 Feb 2020 22:03:55 -0500
Subject: [PATCH 10/37] symbol lookup enhancement
For symbols which have same name in one module or have
length longger than KSYM_NAME_LEN(128 bytes). we add
some work around to lookup another unique symbol and add
relative offset to get the actual symbol. This patch
depend on a kernel patch to deal with new relocation
style.
Signed-off-by: Zhipeng Xie <xiezhipeng1@huawei.com>
---
kmod/patch/kpatch-patch.h | 4 +
kpatch-build/create-diff-object.c | 40 +++++++-
kpatch-build/create-klp-module.c | 25 ++++-
kpatch-build/kpatch-build | 12 +++
kpatch-build/kpatch-intermediate.h | 2 +
kpatch-build/lookup.c | 159 ++++++++++++++++++++++++++++-
kpatch-build/lookup.h | 15 +++
7 files changed, 247 insertions(+), 10 deletions(-)
diff --git a/kmod/patch/kpatch-patch.h b/kmod/patch/kpatch-patch.h
index da4f6a0..9df7818 100644
--- a/kmod/patch/kpatch-patch.h
+++ b/kmod/patch/kpatch-patch.h
@@ -30,6 +30,8 @@ struct kpatch_patch_func {
unsigned long sympos;
char *name;
char *objname;
+ char *ref_name;
+ long ref_offset;
};
struct kpatch_patch_dynrela {
@@ -41,6 +43,8 @@ struct kpatch_patch_dynrela {
char *objname;
int external;
long addend;
+ char *ref_name;
+ long ref_offset;
};
struct kpatch_pre_patch_callback {
diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c
index 7e415dd..e11a900 100644
--- a/kpatch-build/create-diff-object.c
+++ b/kpatch-build/create-diff-object.c
@@ -3087,6 +3087,14 @@ static void kpatch_create_patches_sections(struct kpatch_elf *kelf,
funcs[index].old_size = symbol.size;
funcs[index].new_size = sym->sym.st_size;
funcs[index].sympos = symbol.sympos;
+ if (lookup_is_duplicate_symbol(table, sym->name, objname, symbol.sympos)) {
+ if (!strcmp(objname, "vmlinux")) {
+ symbol.sympos = get_vmlinux_duplicate_symbol_pos(table, sym->name, symbol.addr);
+ log_debug("update %s sympos from %ld to %ld\n",
+ sym->name, funcs[index].sympos, symbol.sympos);
+ funcs[index].sympos = symbol.sympos;
+ }
+ }
/*
* Add a relocation that will populate the
@@ -3105,7 +3113,8 @@ static void kpatch_create_patches_sections(struct kpatch_elf *kelf,
ALLOC_LINK(rela, &relasec->relas);
rela->sym = strsym;
rela->type = absolute_rela_type(kelf);
- rela->addend = offset_of_string(&kelf->strings, sym->name);
+ rela->addend = offset_of_string(&kelf->strings,
+ strndup(sym->name, KSYM_NAME_LEN-1));
rela->offset = (unsigned int)(index * sizeof(*funcs) +
offsetof(struct kpatch_patch_func, name));
@@ -3345,6 +3354,7 @@ static void kpatch_create_intermediate_sections(struct kpatch_elf *kelf,
bool special;
bool vmlinux = !strcmp(objname, "vmlinux");
struct special_section *s;
+ long ref_offset;
/* count rela entries that need to be dynamic */
nr = 0;
@@ -3445,12 +3455,34 @@ static void kpatch_create_intermediate_sections(struct kpatch_elf *kelf,
rela->sym->name, symbol.objname,
symbol.sympos);
+ ref_offset = 0;
/* Fill in ksyms[index] */
if (vmlinux)
ksyms[index].src = symbol.addr;
- else
+ else {
/* for modules, src is discovered at runtime */
ksyms[index].src = 0;
+ }
+
+ if (lookup_is_duplicate_symbol(table, rela->sym->name, objname,
+ symbol.sympos)) {
+ struct lookup_refsym refsym;
+
+ if (lookup_ref_symbol_offset(table, rela->sym,
+ &refsym, objname, &ref_offset))
+ ERROR("unresolvable ambiguity on symbol %s\n",
+ rela->sym->name);
+
+ /* add rela to fill in ref_name field */
+ ALLOC_LINK(rela2, &krela_sec->rela->relas);
+ rela2->sym = strsym;
+ rela2->type = absolute_rela_type(kelf);
+ rela2->addend = offset_of_string(&kelf->strings,
+ refsym.name);
+ rela2->offset = (unsigned int)(index * sizeof(*krelas) +
+ offsetof(struct kpatch_relocation, ref_name));
+ }
+
ksyms[index].sympos = symbol.sympos;
ksyms[index].type = rela->sym->type;
ksyms[index].bind = rela->sym->bind;
@@ -3459,7 +3491,8 @@ static void kpatch_create_intermediate_sections(struct kpatch_elf *kelf,
ALLOC_LINK(rela2, &ksym_sec->rela->relas);
rela2->sym = strsym;
rela2->type = absolute_rela_type(kelf);
- rela2->addend = offset_of_string(&kelf->strings, rela->sym->name);
+ rela2->addend = offset_of_string(&kelf->strings,
+ strndup(rela->sym->name, KSYM_NAME_LEN-1));
rela2->offset = (unsigned int)(index * sizeof(*ksyms) + \
offsetof(struct kpatch_symbol, name));
@@ -3478,6 +3511,7 @@ static void kpatch_create_intermediate_sections(struct kpatch_elf *kelf,
krelas[index].addend = rela->addend;
krelas[index].type = rela->type;
krelas[index].external = !vmlinux && symbol.exported;
+ krelas[index].ref_offset = ref_offset;
/* add rela to fill in krelas[index].dest field */
ALLOC_LINK(rela2, &krela_sec->rela->relas);
diff --git a/kpatch-build/create-klp-module.c b/kpatch-build/create-klp-module.c
index e942b9e..b77028f 100644
--- a/kpatch-build/create-klp-module.c
+++ b/kpatch-build/create-klp-module.c
@@ -38,7 +38,9 @@ enum loglevel loglevel = NORMAL;
*/
static struct symbol *find_or_add_ksym_to_symbols(struct kpatch_elf *kelf,
struct section *ksymsec,
- char *strings, int offset)
+ char *strings, int offset,
+ char *ref_name,
+ long ref_offset)
{
struct kpatch_symbol *ksyms, *ksym;
struct symbol *sym;
@@ -67,9 +69,14 @@ static struct symbol *find_or_add_ksym_to_symbols(struct kpatch_elf *kelf,
objname = strings + rela->addend;
- snprintf(pos, 32, "%lu", ksym->sympos);
/* .klp.sym.objname.name,pos */
- snprintf(buf, 256, KLP_SYM_PREFIX "%s.%s,%s", objname, name, pos);
+ if (!ref_name) {
+ snprintf(pos, 32, "%lu", ksym->sympos);
+ snprintf(buf, 256, KLP_SYM_PREFIX "%s.%s,%s", objname, name, pos);
+ } else {
+ snprintf(pos, 32, "%ld", ref_offset);
+ snprintf(buf, 256, KLP_SYM_PREFIX "%s-%s,%s", objname, ref_name, pos);
+ }
/* Look for an already allocated symbol */
list_for_each_entry(sym, &kelf->symbols, list) {
@@ -176,6 +183,7 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
struct rela *rela;
char *objname;
unsigned int nr, index, offset, dest_off;
+ char *ref_name;
krelas = krelasec->data->d_buf;
nr = (unsigned int)(krelasec->data->d_size / sizeof(*krelas));
@@ -200,6 +208,15 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
objname = strings + rela->addend;
+ /* Get the unique ref_name */
+ rela = find_rela_by_offset(krelasec->rela,
+ (unsigned int)(offset + offsetof(struct kpatch_relocation,
+ ref_name)));
+ if (!rela)
+ ref_name = NULL;
+ else
+ ref_name = strings + rela->addend;
+
/* Get the .kpatch.symbol entry for the rela src */
rela = find_rela_by_offset(krelasec->rela,
(unsigned int)(offset + offsetof(struct kpatch_relocation, ksym)));
@@ -208,7 +225,7 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
/* Create (or find) a klp symbol from the rela src entry */
sym = find_or_add_ksym_to_symbols(kelf, ksymsec, strings,
- (unsigned int)rela->addend);
+ (unsigned int)rela->addend, ref_name, krelas[index].ref_offset);
if (!sym)
ERROR("error finding or adding ksym to symtab");
diff --git a/kpatch-build/kpatch-build b/kpatch-build/kpatch-build
index 139ebb1..f6855ed 100755
--- a/kpatch-build/kpatch-build
+++ b/kpatch-build/kpatch-build
@@ -1148,6 +1148,18 @@ for i in $FILES; do
SYMTAB="${KOBJFILE_PATH}.symtab"
SYMVERS_FILE="$BUILDDIR/Module.symvers"
+ unset KCFLAGS
+ remove_patches
+ cd "$BUILDDIR" || die
+ if [ -z "$USERMODBUILDDIR" ];then
+ make "-j$CPUS" $TARGETS 2>&1 | logger || die
+ else
+ make -C "$USERMODBUILDDIR" M="$USERMODBUILDDIR" $USERMODFLAGS "-j$CPUS" $TARGETS 2>&1 | logger || die
+ fi
+ cp ${KOBJFILE} ${KOBJFILE_PATH}
+ apply_patches
+ cd "$TEMPDIR" || die
+
if [ "$OOT_MODULE" == "yes" ];then
SYMVERS_FILE="$TEMPDIR/Module.symvers"
[[ -e $BUILDDIR/Module.symvers ]] && cp "$BUILDDIR/Module.symvers" "$SYMVERS_FILE"
diff --git a/kpatch-build/kpatch-intermediate.h b/kpatch-build/kpatch-intermediate.h
index 2036cb3..2589959 100644
--- a/kpatch-build/kpatch-intermediate.h
+++ b/kpatch-build/kpatch-intermediate.h
@@ -39,6 +39,8 @@ struct kpatch_relocation {
long addend;
char *objname; /* object to which this rela applies to */
struct kpatch_symbol *ksym;
+ char *ref_name;
+ long ref_offset;
};
struct kpatch_arch {
diff --git a/kpatch-build/lookup.c b/kpatch-build/lookup.c
index 829250f..71ede78 100644
--- a/kpatch-build/lookup.c
+++ b/kpatch-build/lookup.c
@@ -45,6 +45,7 @@ struct object_symbol {
unsigned long size;
char *name;
int type, bind;
+ int sec_index;
};
struct export_symbol {
@@ -299,6 +300,7 @@ static void symtab_read(struct lookup_table *table, char *path)
table->obj_syms[i].addr = addr;
table->obj_syms[i].size = strtoul(size, NULL, 0);
+ table->obj_syms[i].sec_index = atoi(ndx);
if (!strcmp(bind, "LOCAL")) {
table->obj_syms[i].bind = STB_LOCAL;
@@ -459,6 +461,17 @@ static bool lookup_local_symbol(struct lookup_table *table,
if (sym->bind == STB_LOCAL && !strcmp(sym->name,
lookup_sym->name))
sympos++;
+ else {
+ /*
+ * symbol name longer than KSYM_NAME_LEN will be truncated
+ * by kernel, so we can not find it using its original
+ * name. we need to add pos for symbols which have same
+ * KSYM_NAME_LEN-1 long prefix.
+ */
+ if (strlen(lookup_sym->name) >= KSYM_NAME_LEN-1 &&
+ !strncmp(sym->name, lookup_sym->name, KSYM_NAME_LEN-1))
+ sympos++;
+ }
if (lookup_sym->lookup_table_file_sym == sym) {
in_file = 1;
@@ -529,11 +542,22 @@ static bool lookup_global_symbol(struct lookup_table *table, char *name,
{
struct object_symbol *sym;
int i;
+ unsigned long sympos = 0;
memset(result, 0, sizeof(*result));
for_each_obj_symbol(i, sym, table) {
-+ if ((sym->bind == STB_GLOBAL || sym->bind == STB_WEAK
-+ || sym->bind == STB_GNU_UNIQUE) &&
+ /*
+ * symbol name longer than KSYM_NAME_LEN will be truncated
+ * by kernel, so we can not find it using its original
+ * name. we need to add pos for symbols which have same
+ * KSYM_NAME_LEN-1 long prefix.
+ */
+ if (strlen(name) >= KSYM_NAME_LEN-1 &&
+ !strncmp(sym->name, name, KSYM_NAME_LEN-1))
+ sympos++;
+
+ if ((sym->bind == STB_GLOBAL || sym->bind == STB_WEAK
+ || sym->bind == STB_GNU_UNIQUE) &&
!strcmp(sym->name, name)) {
if (result->objname)
@@ -542,7 +566,7 @@ static bool lookup_global_symbol(struct lookup_table *table, char *name,
result->objname = table->objname;
result->addr = sym->addr;
result->size = sym->size;
- result->sympos = 0; /* always 0 for global symbols */
+ result->sympos = sympos;
result->global = true;
result->exported = is_exported(table, name);
}
@@ -562,3 +586,132 @@ bool lookup_symbol(struct lookup_table *table, struct symbol *sym,
return lookup_exported_symbol(table, sym->name, result);
}
+
+int lookup_is_duplicate_symbol(struct lookup_table *table, char *name,
+ char *objname, unsigned long pos)
+{
+ struct object_symbol *sym;
+ int i, count = 0;
+ char posstr[32], buf[256];
+
+ for_each_obj_symbol(i, sym, table)
+ if (!strcmp(sym->name, name)) {
+ count++;
+ if (count > 1)
+ return 1;
+ }
+
+ /*
+ * symbol name longer than KSYM_NAME_LEN will be truncated
+ * by kernel, so we can not find it using its original
+ * name. Here, we consider these long name symbol as duplicated
+ * symbols. since create_klp_module will create symbol name
+ * format like .klp.sym.objname.symbol,pos, so we consider name
+ * length longer than KSYM_NAME_LEN-1 bytes as duplicated symbol
+ */
+ snprintf(posstr, 32, "%lu", pos);
+ snprintf(buf, 256, KLP_SYM_PREFIX "%s.%s,%s", objname, name, posstr);
+ if (strlen(buf) >= KSYM_NAME_LEN-1)
+ return 1;
+
+ return 0;
+}
+
+struct object_symbol *lookup_find_symbol(struct lookup_table *table,
+ struct symbol *lookup_sym)
+{
+ struct object_symbol *sym;
+ unsigned long pos = 0;
+ int i, match = 0, in_file = 0;
+
+ if (!lookup_sym->lookup_table_file_sym)
+ return NULL;
+
+ for_each_obj_symbol(i, sym, table) {
+ if (sym->bind == STB_LOCAL && !strcmp(sym->name, lookup_sym->name))
+ pos++;
+
+ if (lookup_sym->lookup_table_file_sym == sym) {
+ in_file = 1;
+ continue;
+ }
+
+ if (!in_file)
+ continue;
+
+ if (sym->type == STT_FILE)
+ break;
+
+ if (sym->bind == STB_LOCAL && !strcmp(sym->name, lookup_sym->name)) {
+ match = 1;
+ break;
+ }
+ }
+
+ if (!match) {
+ for_each_obj_symbol(i, sym, table) {
+ if ((sym->bind == STB_GLOBAL || sym->bind == STB_WEAK) &&
+ !strcmp(sym->name, lookup_sym->name)) {
+ return sym;
+ }
+ }
+ return NULL;
+ }
+
+ return sym;
+}
+
+int lookup_ref_symbol_offset(struct lookup_table *table,
+ struct symbol *lookup_sym,
+ struct lookup_refsym *refsym,
+ char *objname, long *offset)
+{
+ struct object_symbol *orig_sym, *sym;
+ int i;
+
+ orig_sym = lookup_find_symbol(table, lookup_sym);
+ if (!orig_sym)
+ ERROR("lookup_ref_symbol_offset");
+ memset(refsym, 0, sizeof(*refsym));
+
+ /*find a unique symbol in the same section first*/
+ for_each_obj_symbol(i, sym, table) {
+ if (!strcmp(sym->name, lookup_sym->name) || sym->type == STT_FILE ||
+ sym->sec_index != orig_sym->sec_index ||
+ strchr(sym->name, '.'))
+ continue;
+
+ if (!lookup_is_duplicate_symbol(table, sym->name, objname, 1)) {
+ refsym->name = sym->name;
+ refsym->addr = sym->addr;
+ *offset = (long)orig_sym->addr- (long)sym->addr;
+ return 0;
+ }
+ }
+
+ return 1;
+}
+
+/*
+ * In case sometimes the sympos of duplicate symbols are different in vmlinux and
+ * /proc/kallsyms, and causes lookup_local_symbol to save wrong sympos in result,
+ * this function returns correct sympos of the symbol, by comparing
+ * address value with the symbol in vmlinux symbol table.
+ */
+unsigned long get_vmlinux_duplicate_symbol_pos(struct lookup_table *table,
+ char *name, unsigned long addr)
+{
+ struct object_symbol *sym;
+ unsigned long pos = 1;
+ int i;
+
+ for_each_obj_symbol(i, sym, table) {
+ if (strcmp(sym->name, name))
+ continue;
+
+ if (sym->addr < addr)
+ pos++;
+ }
+
+ return pos;
+}
diff --git a/kpatch-build/lookup.h b/kpatch-build/lookup.h
index e1277f1..21aceb4 100644
--- a/kpatch-build/lookup.h
+++ b/kpatch-build/lookup.h
@@ -4,6 +4,8 @@
#include <stdbool.h>
#include "kpatch-elf.h"
+#define KSYM_NAME_LEN 128
+
struct lookup_table;
struct lookup_result {
@@ -14,10 +16,23 @@ struct lookup_result {
bool global, exported;
};
+struct lookup_refsym {
+ char *name;
+ unsigned long addr;
+};
+
struct lookup_table *lookup_open(char *symtab_path, char *objname,
char *symvers_path, struct kpatch_elf *kelf);
void lookup_close(struct lookup_table *table);
bool lookup_symbol(struct lookup_table *table, struct symbol *sym,
struct lookup_result *result);
+int lookup_is_duplicate_symbol(struct lookup_table *table, char *name,
+ char *objname, unsigned long pos);
+int lookup_ref_symbol_offset(struct lookup_table *table,
+ struct symbol *lookup_sym,
+ struct lookup_refsym *refsym, char *objname,
+ long *offset);
+unsigned long get_vmlinux_duplicate_symbol_pos(struct lookup_table *table, char *name,
+ unsigned long addr);
#endif /* _LOOKUP_H_ */
--
2.33.0
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