Supports placing immediate values in init code We need to put the immediate values in RW data section so we can edit them before init section unload. This code puts NULL pointers in lieu of original pointer referencing init code before the init sections are freed, both in the core kernel and in modules. TODO : support __exit section. Changelog: - Fix !CONFIG_IMMEDIATE Signed-off-by: Mathieu Desnoyers CC: Rusty Russell CC: "Frank Ch. Eigler" CC: KOSAKI Motohiro --- Documentation/immediate.txt | 8 ++++---- include/asm-generic/vmlinux.lds.h | 8 ++++---- include/asm-powerpc/immediate.h | 4 ++-- include/asm-x86/immediate.h | 6 +++--- include/linux/immediate.h | 4 ++++ include/linux/module.h | 2 +- init/main.c | 1 + kernel/immediate.c | 31 +++++++++++++++++++++++++++++-- kernel/module.c | 4 ++++ 9 files changed, 52 insertions(+), 16 deletions(-) Index: linux-2.6-sched-devel/kernel/immediate.c =================================================================== --- linux-2.6-sched-devel.orig/kernel/immediate.c 2008-04-22 20:21:52.000000000 -0400 +++ linux-2.6-sched-devel/kernel/immediate.c 2008-04-22 20:23:22.000000000 -0400 @@ -22,6 +22,7 @@ #include #include +#include #include /* @@ -30,8 +31,8 @@ static int imv_early_boot_complete; static int wrote_text; -extern const struct __imv __start___imv[]; -extern const struct __imv __stop___imv[]; +extern struct __imv __start___imv[]; +extern struct __imv __stop___imv[]; static int stop_machine_imv_update(void *imv_ptr) { @@ -118,6 +119,8 @@ void imv_update_range(const struct __imv int ret; for (iter = begin; iter < end; iter++) { mutex_lock(&imv_mutex); + if (!iter->imv) /* Skip removed __init immediate values */ + goto skip; ret = apply_imv_update(iter); if (imv_early_boot_complete && ret) printk(KERN_WARNING @@ -126,6 +129,7 @@ void imv_update_range(const struct __imv "instruction at %p, size %hu\n", (void *)iter->imv, (void *)iter->var, iter->size); +skip: mutex_unlock(&imv_mutex); } } @@ -143,6 +147,29 @@ void core_imv_update(void) } EXPORT_SYMBOL_GPL(core_imv_update); +/** + * imv_unref + * + * Deactivate any immediate value reference pointing into the code region in the + * range start to start + size. + */ +void imv_unref(struct __imv *begin, struct __imv *end, void *start, + unsigned long size) +{ + struct __imv *iter; + + for (iter = begin; iter < end; iter++) + if (iter->imv >= (unsigned long)start + && iter->imv < (unsigned long)start + size) + iter->imv = 0UL; +} + +void imv_unref_core_init(void) +{ + imv_unref(__start___imv, __stop___imv, __init_begin, + (unsigned long)__init_end - (unsigned long)__init_begin); +} + void __init imv_init_complete(void) { imv_early_boot_complete = 1; Index: linux-2.6-sched-devel/kernel/module.c =================================================================== --- linux-2.6-sched-devel.orig/kernel/module.c 2008-04-22 20:21:52.000000000 -0400 +++ linux-2.6-sched-devel/kernel/module.c 2008-04-22 20:23:22.000000000 -0400 @@ -2207,6 +2207,10 @@ sys_init_module(void __user *umod, /* Drop initial reference. */ module_put(mod); unwind_remove_table(mod->unwind_info, 1); +#ifdef CONFIG_IMMEDIATE + imv_unref(mod->immediate, mod->immediate + mod->num_immediate, + mod->module_init, mod->init_size); +#endif module_free(mod, mod->module_init); mod->module_init = NULL; mod->init_size = 0; Index: linux-2.6-sched-devel/include/linux/module.h =================================================================== --- linux-2.6-sched-devel.orig/include/linux/module.h 2008-04-22 20:21:52.000000000 -0400 +++ linux-2.6-sched-devel/include/linux/module.h 2008-04-22 20:23:22.000000000 -0400 @@ -357,7 +357,7 @@ struct module keeping pointers to this stuff */ char *args; #ifdef CONFIG_IMMEDIATE - const struct __imv *immediate; + struct __imv *immediate; unsigned int num_immediate; #endif #ifdef CONFIG_MARKERS Index: linux-2.6-sched-devel/include/asm-generic/vmlinux.lds.h =================================================================== --- linux-2.6-sched-devel.orig/include/asm-generic/vmlinux.lds.h 2008-04-22 20:21:52.000000000 -0400 +++ linux-2.6-sched-devel/include/asm-generic/vmlinux.lds.h 2008-04-22 20:23:22.000000000 -0400 @@ -52,7 +52,10 @@ . = ALIGN(8); \ VMLINUX_SYMBOL(__start___markers) = .; \ *(__markers) \ - VMLINUX_SYMBOL(__stop___markers) = .; + VMLINUX_SYMBOL(__stop___markers) = .; \ + VMLINUX_SYMBOL(__start___imv) = .; \ + *(__imv) /* Immediate values: pointers */ \ + VMLINUX_SYMBOL(__stop___imv) = .; #define RO_DATA(align) \ . = ALIGN((align)); \ @@ -61,9 +64,6 @@ *(.rodata) *(.rodata.*) \ *(__vermagic) /* Kernel version magic */ \ *(__markers_strings) /* Markers: strings */ \ - VMLINUX_SYMBOL(__start___imv) = .; \ - *(__imv) /* Immediate values: pointers */ \ - VMLINUX_SYMBOL(__stop___imv) = .; \ } \ \ .rodata1 : AT(ADDR(.rodata1) - LOAD_OFFSET) { \ Index: linux-2.6-sched-devel/include/linux/immediate.h =================================================================== --- linux-2.6-sched-devel.orig/include/linux/immediate.h 2008-04-22 20:21:52.000000000 -0400 +++ linux-2.6-sched-devel/include/linux/immediate.h 2008-04-22 20:23:22.000000000 -0400 @@ -46,6 +46,9 @@ struct __imv { extern void core_imv_update(void); extern void imv_update_range(const struct __imv *begin, const struct __imv *end); +extern void imv_unref_core_init(void); +extern void imv_unref(struct __imv *begin, struct __imv *end, void *start, + unsigned long size); #else @@ -73,6 +76,7 @@ extern void imv_update_range(const struc static inline void core_imv_update(void) { } static inline void module_imv_update(void) { } +static inline void imv_unref_core_init(void) { } #endif Index: linux-2.6-sched-devel/init/main.c =================================================================== --- linux-2.6-sched-devel.orig/init/main.c 2008-04-22 20:22:16.000000000 -0400 +++ linux-2.6-sched-devel/init/main.c 2008-04-22 20:23:22.000000000 -0400 @@ -808,6 +808,7 @@ static void run_init_process(char *init_ */ static int noinline init_post(void) { + imv_unref_core_init(); free_initmem(); unlock_kernel(); mark_rodata_ro(); Index: linux-2.6-sched-devel/include/asm-x86/immediate.h =================================================================== --- linux-2.6-sched-devel.orig/include/asm-x86/immediate.h 2008-04-22 20:22:29.000000000 -0400 +++ linux-2.6-sched-devel/include/asm-x86/immediate.h 2008-04-22 20:23:22.000000000 -0400 @@ -33,7 +33,7 @@ BUILD_BUG_ON(sizeof(value) > 8); \ switch (sizeof(value)) { \ case 1: \ - asm(".section __imv,\"a\",@progbits\n\t" \ + asm(".section __imv,\"aw\",@progbits\n\t" \ _ASM_PTR "%c1, (3f)-%c2\n\t" \ ".byte %c2\n\t" \ ".previous\n\t" \ @@ -45,7 +45,7 @@ break; \ case 2: \ case 4: \ - asm(".section __imv,\"a\",@progbits\n\t" \ + asm(".section __imv,\"aw\",@progbits\n\t" \ _ASM_PTR "%c1, (3f)-%c2\n\t" \ ".byte %c2\n\t" \ ".previous\n\t" \ @@ -60,7 +60,7 @@ value = name##__imv; \ break; \ } \ - asm(".section __imv,\"a\",@progbits\n\t" \ + asm(".section __imv,\"aw\",@progbits\n\t" \ _ASM_PTR "%c1, (3f)-%c2\n\t" \ ".byte %c2\n\t" \ ".previous\n\t" \ Index: linux-2.6-sched-devel/include/asm-powerpc/immediate.h =================================================================== --- linux-2.6-sched-devel.orig/include/asm-powerpc/immediate.h 2008-04-22 20:22:58.000000000 -0400 +++ linux-2.6-sched-devel/include/asm-powerpc/immediate.h 2008-04-22 20:23:22.000000000 -0400 @@ -26,7 +26,7 @@ BUILD_BUG_ON(sizeof(value) > 8); \ switch (sizeof(value)) { \ case 1: \ - asm(".section __imv,\"a\",@progbits\n\t" \ + asm(".section __imv,\"aw\",@progbits\n\t" \ PPC_LONG "%c1, ((1f)-1)\n\t" \ ".byte 1\n\t" \ ".previous\n\t" \ @@ -36,7 +36,7 @@ : "i" (&name##__imv)); \ break; \ case 2: \ - asm(".section __imv,\"a\",@progbits\n\t" \ + asm(".section __imv,\"aw\",@progbits\n\t" \ PPC_LONG "%c1, ((1f)-2)\n\t" \ ".byte 2\n\t" \ ".previous\n\t" \ Index: linux-2.6-sched-devel/Documentation/immediate.txt =================================================================== --- linux-2.6-sched-devel.orig/Documentation/immediate.txt 2008-04-22 20:23:21.000000000 -0400 +++ linux-2.6-sched-devel/Documentation/immediate.txt 2008-04-22 20:23:22.000000000 -0400 @@ -42,10 +42,10 @@ The immediate mechanism supports inserti immediate. Immediate values can be put in inline functions, inlined static functions, and unrolled loops. -If you have to read the immediate values from a function declared as __init or -__exit, you should explicitly use _imv_read(), which will fall back on a -global variable read. Failing to do so will leave a reference to the __init -section after it is freed (it would generate a modpost warning). +If you have to read the immediate values from a function declared as __exit, you +should explicitly use _imv_read(), which will fall back on a global variable +read. Failing to do so will leave a reference to the __exit section in kernel +without module unload support. imv_read() in the __init section is supported. You can choose to set an initial static value to the immediate by using, for instance: -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/