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Subject[RFC PATCH 1/9] Ksplice: Make find_symbol return a struct kernel_symbol
Date
From: Tim Abbott <tabbott@mit.edu>

Ksplice needs access to the kernel_symbol structure in order to
support modifications to the exported symbol table.

Signed-off-by: Tim Abbott <tabbott@mit.edu>
---
kernel/module.c | 80 ++++++++++++++++++++++++++----------------------------
1 files changed, 39 insertions(+), 41 deletions(-)
diff --git a/kernel/module.c b/kernel/module.c
index 6cedfc7..8954556 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -254,7 +254,7 @@ struct find_symbol_arg {
/* Output */
struct module *owner;
const unsigned long *crc;
- unsigned long value;
+ const struct kernel_symbol *sym;
};

static bool find_symbol_in_section(const struct symsearch *syms,
@@ -295,17 +295,17 @@ static bool find_symbol_in_section(const struct symsearch *syms,

fsa->owner = owner;
fsa->crc = symversion(syms->crcs, symnum);
- fsa->value = syms->start[symnum].value;
+ fsa->sym = &syms->start[symnum];
return true;
}

-/* Find a symbol, return value, (optional) crc and (optional) module
- * which owns it */
-static unsigned long find_symbol(const char *name,
- struct module **owner,
- const unsigned long **crc,
- bool gplok,
- bool warn)
+/* Find a symbol and return it, along with, (optional) crc and
+ * (optional) module which owns it */
+static const struct kernel_symbol *find_symbol(const char *name,
+ struct module **owner,
+ const unsigned long **crc,
+ bool gplok,
+ bool warn)
{
struct find_symbol_arg fsa;

@@ -318,11 +318,11 @@ static unsigned long find_symbol(const char *name,
*owner = fsa.owner;
if (crc)
*crc = fsa.crc;
- return fsa.value;
+ return fsa.sym;
}

DEBUGP("Failed to find symbol %s\n", name);
- return -ENOENT;
+ return NULL;
}

/* Search for module by name: must hold module_mutex. */
@@ -819,7 +819,7 @@ void __symbol_put(const char *symbol)
struct module *owner;

preempt_disable();
- if (IS_ERR_VALUE(find_symbol(symbol, &owner, NULL, true, false)))
+ if (find_symbol(symbol, &owner, NULL, true, false) == NULL)
BUG();
module_put(owner);
preempt_enable();
@@ -982,7 +982,7 @@ static inline int check_modstruct_version(Elf_Shdr *sechdrs,
{
const unsigned long *crc;

- if (IS_ERR_VALUE(find_symbol("struct_module", NULL, &crc, true, false)))
+ if (find_symbol("struct_module", NULL, &crc, true, false) == NULL)
BUG();
return check_version(sechdrs, versindex, "struct_module", mod, crc);
}
@@ -1023,25 +1023,23 @@ static inline int same_magic(const char *amagic, const char *bmagic,

/* Resolve a symbol for this module. I.e. if we find one, record usage.
Must be holding module_mutex. */
-static unsigned long resolve_symbol(Elf_Shdr *sechdrs,
- unsigned int versindex,
- const char *name,
- struct module *mod)
+static const struct kernel_symbol *resolve_symbol(Elf_Shdr *sechdrs,
+ unsigned int versindex,
+ const char *name,
+ struct module *mod)
{
struct module *owner;
- unsigned long ret;
+ const struct kernel_symbol *sym;
const unsigned long *crc;

- ret = find_symbol(name, &owner, &crc,
+ sym = find_symbol(name, &owner, &crc,
!(mod->taints & TAINT_PROPRIETARY_MODULE), true);
- if (!IS_ERR_VALUE(ret)) {
- /* use_module can fail due to OOM,
- or module initialization or unloading */
- if (!check_version(sechdrs, versindex, name, mod, crc) ||
- !use_module(mod, owner))
- ret = -EINVAL;
- }
- return ret;
+ /* use_module can fail due to OOM,
+ or module initialization or unloading */
+ if (!check_version(sechdrs, versindex, name, mod, crc) ||
+ !use_module(mod, owner))
+ sym = NULL;
+ return sym;
}

/*
@@ -1445,17 +1443,15 @@ static void free_module(struct module *mod)
void *__symbol_get(const char *symbol)
{
struct module *owner;
- unsigned long value;
+ const struct kernel_symbol *sym;

preempt_disable();
- value = find_symbol(symbol, &owner, NULL, true, true);
- if (IS_ERR_VALUE(value))
- value = 0;
- else if (strong_try_module_get(owner))
- value = 0;
+ sym = find_symbol(symbol, &owner, NULL, true, true);
+ if (sym != NULL && strong_try_module_get(owner))
+ sym = NULL;
preempt_enable();

- return (void *)value;
+ return sym == NULL ? (void *)0 : (void *)sym->value;
}
EXPORT_SYMBOL_GPL(__symbol_get);

@@ -1483,8 +1479,8 @@ static int verify_export_symbols(struct module *mod)

for (i = 0; i < ARRAY_SIZE(arr); i++) {
for (s = arr[i].sym; s < arr[i].sym + arr[i].num; s++) {
- if (!IS_ERR_VALUE(find_symbol(s->name, &owner,
- NULL, true, false))) {
+ if (find_symbol(s->name, &owner, NULL, true, false)
+ != NULL) {
printk(KERN_ERR
"%s: exports duplicate symbol %s"
" (owned by %s)\n",
@@ -1508,6 +1504,7 @@ static int simplify_symbols(Elf_Shdr *sechdrs,
unsigned long secbase;
unsigned int i, n = sechdrs[symindex].sh_size / sizeof(Elf_Sym);
int ret = 0;
+ const struct kernel_symbol *ksym;

for (i = 1; i < n; i++) {
switch (sym[i].st_shndx) {
@@ -1527,13 +1524,14 @@ static int simplify_symbols(Elf_Shdr *sechdrs,
break;

case SHN_UNDEF:
- sym[i].st_value
- = resolve_symbol(sechdrs, versindex,
- strtab + sym[i].st_name, mod);
-
+ ksym = resolve_symbol(sechdrs, versindex,
+ strtab + sym[i].st_name, mod);
/* Ok if resolved. */
- if (!IS_ERR_VALUE(sym[i].st_value))
+ if (ksym != NULL) {
+ sym[i].st_value = ksym->value;
break;
+ }
+
/* Ok if weak. */
if (ELF_ST_BIND(sym[i].st_info) == STB_WEAK)
break;
--
1.5.4.3


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