ad6561dffa
It's theoretically possible that there are exception table entries which point into the (freed) init text of modules. These could cause future problems if other modules get loaded into that memory and cause an exception as we'd see the wrong fixup. The only case I know of is kvm-intel.ko (when CONFIG_CC_OPTIMIZE_FOR_SIZE=n). Amerigo fixed this long-standing FIXME in the x86 version, but this patch is more general. This implements trim_init_extable(); most archs are simple since they use the standard lib/extable.c sort code. Alpha and IA64 use relative addresses in their fixups, so thier trimming is a slight variation. Sparc32 is unique; it doesn't seem to define ARCH_HAS_SORT_EXTABLE, yet it defines its own sort_extable() which overrides the one in lib. It doesn't sort, so we have to mark deleted entries instead of actually trimming them. Inspired-by: Amerigo Wang <amwang@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: linux-alpha@vger.kernel.org Cc: sparclinux@vger.kernel.org Cc: linux-ia64@vger.kernel.org
105 lines
2.2 KiB
C
105 lines
2.2 KiB
C
/*
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* linux/arch/sparc/mm/extable.c
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*/
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#include <linux/module.h>
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#include <asm/uaccess.h>
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void sort_extable(struct exception_table_entry *start,
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struct exception_table_entry *finish)
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{
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}
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/* Caller knows they are in a range if ret->fixup == 0 */
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const struct exception_table_entry *
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search_extable(const struct exception_table_entry *start,
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const struct exception_table_entry *last,
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unsigned long value)
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{
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const struct exception_table_entry *walk;
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/* Single insn entries are encoded as:
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* word 1: insn address
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* word 2: fixup code address
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*
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* Range entries are encoded as:
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* word 1: first insn address
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* word 2: 0
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* word 3: last insn address + 4 bytes
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* word 4: fixup code address
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*
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* Deleted entries are encoded as:
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* word 1: unused
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* word 2: -1
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*
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* See asm/uaccess.h for more details.
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*/
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/* 1. Try to find an exact match. */
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for (walk = start; walk <= last; walk++) {
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if (walk->fixup == 0) {
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/* A range entry, skip both parts. */
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walk++;
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continue;
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}
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/* A deleted entry; see trim_init_extable */
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if (walk->fixup == -1)
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continue;
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if (walk->insn == value)
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return walk;
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}
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/* 2. Try to find a range match. */
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for (walk = start; walk <= (last - 1); walk++) {
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if (walk->fixup)
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continue;
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if (walk[0].insn <= value && walk[1].insn > value)
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return walk;
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walk++;
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}
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return NULL;
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}
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#ifdef CONFIG_MODULES
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/* We could memmove them around; easier to mark the trimmed ones. */
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void trim_init_extable(struct module *m)
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{
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unsigned int i;
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bool range;
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for (i = 0; i < m->num_exentries; i += range ? 2 : 1) {
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range = m->extable[i].fixup == 0;
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if (within_module_init(m->extable[i].insn, m)) {
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m->extable[i].fixup = -1;
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if (range)
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m->extable[i+1].fixup = -1;
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}
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if (range)
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i++;
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}
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}
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#endif /* CONFIG_MODULES */
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/* Special extable search, which handles ranges. Returns fixup */
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unsigned long search_extables_range(unsigned long addr, unsigned long *g2)
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{
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const struct exception_table_entry *entry;
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entry = search_exception_tables(addr);
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if (!entry)
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return 0;
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/* Inside range? Fix g2 and return correct fixup */
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if (!entry->fixup) {
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*g2 = (addr - entry->insn) / 4;
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return (entry + 1)->fixup;
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}
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return entry->fixup;
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}
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