Re: [rfc 45/45] Modules: Hack to handle symbols that have a zero value

Mathieu Desnoyers
2007-11-20T02:20:49Z

* clameter@sgi.com (clameter@sgi.com) wrote:
> The module subsystem cannot handle symbols that are zero. It prints out
> a message that these symbols are unresolved. Define a constant
>
> UNRESOLVED
>
> that is used to hold the value used for unresolved symbols. Set it to 1
> (its hopefully unlikely that a symbol will have the value 1). This is necessary
> so that the pda variable which is placed at offset 0 of the per cpu
> segment is handled correctly.
>

Wouldn't it be better to simply return a standard ERR_PTR(-ENO....) ?

> Signed-off-by: Christoph Lameter <clameter@sgi.com>
>
> ---
> kernel/module.c | 15 ++++++++-------
> 1 file changed, 8 insertions(+), 7 deletions(-)
>
> Index: linux-2.6/kernel/module.c
> ===================================================================
> --- linux-2.6.orig/kernel/module.c 2007-11-19 17:08:40.563625526 -0800
> +++ linux-2.6/kernel/module.c 2007-11-19 17:08:40.855625732 -0800
> @@ -62,6 +62,7 @@ extern int module_sysfs_initialized;
> /* If this is set, the section belongs in the init part of the module */
> #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
>
> +#define UNRESOLVED 1
> /* List of modules, protected by module_mutex or preempt_disable
> * (add/delete uses stop_machine). */
> static DEFINE_MUTEX(module_mutex);
> @@ -285,7 +286,7 @@ static unsigned long __find_symbol(const
> }
> }
> DEBUGP("Failed to find symbol %s\n", name);
> - return 0;
> + return UNRESOLVED;
> }
>
> /* Search for module by name: must hold module_mutex. */
> @@ -755,7 +756,7 @@ void __symbol_put(const char *symbol)
> const unsigned long *crc;
>
> preempt_disable();
> - if (!__find_symbol(symbol, &owner, &crc, 1))
> + if (__find_symbol(symbol, &owner, &crc, 1) == UNRESOLVED)
> BUG();
> module_put(owner);
> preempt_enable();
> @@ -899,7 +900,7 @@ static inline int check_modstruct_versio
> const unsigned long *crc;
> struct module *owner;
>
> - if (!__find_symbol("struct_module", &owner, &crc, 1))
> + if (__find_symbol("struct_module", &owner, &crc, 1) == UNRESOLVED)
> BUG();
> return check_version(sechdrs, versindex, "struct_module", mod,
> crc);
> @@ -952,7 +953,7 @@ static unsigned long resolve_symbol(Elf_
> /* use_module can fail due to OOM, or module unloading */
> if (!check_version(sechdrs, versindex, name, mod, crc) ||
> !use_module(mod, owner))
> - ret = 0;
> + ret = UNRESOLVED;
> }
> return ret;
> }
> @@ -1345,14 +1346,14 @@ static int verify_export_symbols(struct
> const unsigned long *crc;
>
> for (i = 0; i < mod->num_syms; i++)
> - if (__find_symbol(mod->syms[i].name, &owner, &crc, 1)) {
> + if (__find_symbol(mod->syms[i].name, &owner, &crc, 1) != UNRESOLVED) {
> name = mod->syms[i].name;
> ret = -ENOEXEC;
> goto dup;
> }
>
> for (i = 0; i < mod->num_gpl_syms; i++)
> - if (__find_symbol(mod->gpl_syms[i].name, &owner, &crc, 1)) {
> + if (__find_symbol(mod->gpl_syms[i].name, &owner, &crc, 1)!= UNRESOLVED) {
> name = mod->gpl_syms[i].name;
> ret = -ENOEXEC;
> goto dup;
> @@ -1402,7 +1403,7 @@ static int simplify_symbols(Elf_Shdr *se
> strtab + sym[i].st_name, mod);
>
> /* Ok if resolved. */
> - if (sym[i].st_value != 0)
> + if (sym[i].st_value != UNRESOLVED)
> break;
> /* Ok if weak. */
> if (ELF_ST_BIND(sym[i].st_info) == STB_WEAK)
>
> --

--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68