openwrtv4/target/linux/generic/patches-4.9/305-mips_module_reloc.patch
Felix Fietkau 1e1a0592f8 kernel: fix crashes on MIPS when loading kernel modules under memory pressure
When memory is tight, modules may need to be loaded into vmalloc()
space. The code then has to generate jump trampolines which enable
relocations between vmalloc space and physical address space.

The code had a bug that was freeing these trampolines even when the
module was successfully loaded.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
2017-02-15 12:35:17 +01:00

354 lines
8.5 KiB
Diff

--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -93,8 +93,13 @@ all-$(CONFIG_SYS_SUPPORTS_ZBOOT)+= vmlin
cflags-y += -G 0 -mno-abicalls -fno-pic -pipe -mno-branch-likely
cflags-y += -msoft-float
LDFLAGS_vmlinux += -G 0 -static -n -nostdlib
+ifdef CONFIG_64BIT
KBUILD_AFLAGS_MODULE += -mlong-calls
KBUILD_CFLAGS_MODULE += -mlong-calls
+else
+KBUILD_AFLAGS_MODULE += -mno-long-calls
+KBUILD_CFLAGS_MODULE += -mno-long-calls
+endif
ifeq ($(CONFIG_RELOCATABLE),y)
LDFLAGS_vmlinux += --emit-relocs
--- a/arch/mips/include/asm/module.h
+++ b/arch/mips/include/asm/module.h
@@ -11,6 +11,11 @@ struct mod_arch_specific {
const struct exception_table_entry *dbe_start;
const struct exception_table_entry *dbe_end;
struct mips_hi16 *r_mips_hi16_list;
+
+ void *phys_plt_tbl;
+ void *virt_plt_tbl;
+ unsigned int phys_plt_offset;
+ unsigned int virt_plt_offset;
};
typedef uint8_t Elf64_Byte; /* Type for a 8-bit quantity. */
--- a/arch/mips/kernel/module.c
+++ b/arch/mips/kernel/module.c
@@ -44,14 +44,221 @@ struct mips_hi16 {
static LIST_HEAD(dbe_list);
static DEFINE_SPINLOCK(dbe_lock);
-#ifdef MODULE_START
+/*
+ * Get the potential max trampolines size required of the init and
+ * non-init sections. Only used if we cannot find enough contiguous
+ * physically mapped memory to put the module into.
+ */
+static unsigned int
+get_plt_size(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
+ const char *secstrings, unsigned int symindex, bool is_init)
+{
+ unsigned long ret = 0;
+ unsigned int i, j;
+ Elf_Sym *syms;
+
+ /* Everything marked ALLOC (this includes the exported symbols) */
+ for (i = 1; i < hdr->e_shnum; ++i) {
+ unsigned int info = sechdrs[i].sh_info;
+
+ if (sechdrs[i].sh_type != SHT_REL
+ && sechdrs[i].sh_type != SHT_RELA)
+ continue;
+
+ /* Not a valid relocation section? */
+ if (info >= hdr->e_shnum)
+ continue;
+
+ /* Don't bother with non-allocated sections */
+ if (!(sechdrs[info].sh_flags & SHF_ALLOC))
+ continue;
+
+ /* If it's called *.init*, and we're not init, we're
+ not interested */
+ if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != 0)
+ != is_init)
+ continue;
+
+ syms = (Elf_Sym *) sechdrs[symindex].sh_addr;
+ if (sechdrs[i].sh_type == SHT_REL) {
+ Elf_Mips_Rel *rel = (void *) sechdrs[i].sh_addr;
+ unsigned int size = sechdrs[i].sh_size / sizeof(*rel);
+
+ for (j = 0; j < size; ++j) {
+ Elf_Sym *sym;
+
+ if (ELF_MIPS_R_TYPE(rel[j]) != R_MIPS_26)
+ continue;
+
+ sym = syms + ELF_MIPS_R_SYM(rel[j]);
+ if (!is_init && sym->st_shndx != SHN_UNDEF)
+ continue;
+
+ ret += 4 * sizeof(int);
+ }
+ } else {
+ Elf_Mips_Rela *rela = (void *) sechdrs[i].sh_addr;
+ unsigned int size = sechdrs[i].sh_size / sizeof(*rela);
+
+ for (j = 0; j < size; ++j) {
+ Elf_Sym *sym;
+
+ if (ELF_MIPS_R_TYPE(rela[j]) != R_MIPS_26)
+ continue;
+
+ sym = syms + ELF_MIPS_R_SYM(rela[j]);
+ if (!is_init && sym->st_shndx != SHN_UNDEF)
+ continue;
+
+ ret += 4 * sizeof(int);
+ }
+ }
+ }
+
+ return ret;
+}
+
+#ifndef MODULE_START
+static void *alloc_phys(unsigned long size)
+{
+ unsigned order;
+ struct page *page;
+ struct page *p;
+
+ size = PAGE_ALIGN(size);
+ order = get_order(size);
+
+ page = alloc_pages(GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN |
+ __GFP_THISNODE, order);
+ if (!page)
+ return NULL;
+
+ split_page(page, order);
+
+ /* mark all pages except for the last one */
+ for (p = page; p + 1 < page + (size >> PAGE_SHIFT); ++p)
+ set_bit(PG_owner_priv_1, &p->flags);
+
+ for (p = page + (size >> PAGE_SHIFT); p < page + (1 << order); ++p)
+ __free_page(p);
+
+ return page_address(page);
+}
+#endif
+
+static void free_phys(void *ptr)
+{
+ struct page *page;
+ bool free;
+
+ page = virt_to_page(ptr);
+ do {
+ free = test_and_clear_bit(PG_owner_priv_1, &page->flags);
+ __free_page(page);
+ page++;
+ } while (free);
+}
+
+
void *module_alloc(unsigned long size)
{
+#ifdef MODULE_START
return __vmalloc_node_range(size, 1, MODULE_START, MODULE_END,
GFP_KERNEL, PAGE_KERNEL, 0, NUMA_NO_NODE,
__builtin_return_address(0));
+#else
+ void *ptr;
+
+ if (size == 0)
+ return NULL;
+
+ ptr = alloc_phys(size);
+
+ /* If we failed to allocate physically contiguous memory,
+ * fall back to regular vmalloc. The module loader code will
+ * create jump tables to handle long jumps */
+ if (!ptr)
+ return vmalloc(size);
+
+ return ptr;
+#endif
}
+
+static inline bool is_phys_addr(void *ptr)
+{
+#ifdef CONFIG_64BIT
+ return (KSEGX((unsigned long)ptr) == CKSEG0);
+#else
+ return (KSEGX(ptr) == KSEG0);
#endif
+}
+
+/* Free memory returned from module_alloc */
+void module_memfree(void *module_region)
+{
+ if (is_phys_addr(module_region))
+ free_phys(module_region);
+ else
+ vfree(module_region);
+}
+
+static void *__module_alloc(int size, bool phys)
+{
+ void *ptr;
+
+ if (phys)
+ ptr = kmalloc(size, GFP_KERNEL);
+ else
+ ptr = vmalloc(size);
+ return ptr;
+}
+
+static void __module_free(void *ptr)
+{
+ if (is_phys_addr(ptr))
+ kfree(ptr);
+ else
+ vfree(ptr);
+}
+
+int module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
+ char *secstrings, struct module *mod)
+{
+ unsigned int symindex = 0;
+ unsigned int core_size, init_size;
+ int i;
+
+ mod->arch.phys_plt_offset = 0;
+ mod->arch.virt_plt_offset = 0;
+ mod->arch.phys_plt_tbl = NULL;
+ mod->arch.virt_plt_tbl = NULL;
+
+ if (IS_ENABLED(CONFIG_64BIT))
+ return 0;
+
+ for (i = 1; i < hdr->e_shnum; i++)
+ if (sechdrs[i].sh_type == SHT_SYMTAB)
+ symindex = i;
+
+ core_size = get_plt_size(hdr, sechdrs, secstrings, symindex, false);
+ init_size = get_plt_size(hdr, sechdrs, secstrings, symindex, true);
+
+ if ((core_size + init_size) == 0)
+ return 0;
+
+ mod->arch.phys_plt_tbl = __module_alloc(core_size + init_size, 1);
+ if (!mod->arch.phys_plt_tbl)
+ return -ENOMEM;
+
+ mod->arch.virt_plt_tbl = __module_alloc(core_size + init_size, 0);
+ if (!mod->arch.virt_plt_tbl) {
+ __module_free(mod->arch.phys_plt_tbl);
+ mod->arch.phys_plt_tbl = NULL;
+ return -ENOMEM;
+ }
+
+ return 0;
+}
int apply_r_mips_none(struct module *me, u32 *location, Elf_Addr v)
{
@@ -65,8 +272,39 @@ static int apply_r_mips_32_rel(struct mo
return 0;
}
+static Elf_Addr add_plt_entry_to(unsigned *plt_offset,
+ void *start, Elf_Addr v)
+{
+ unsigned *tramp = start + *plt_offset;
+ *plt_offset += 4 * sizeof(int);
+
+ /* adjust carry for addiu */
+ if (v & 0x00008000)
+ v += 0x10000;
+
+ tramp[0] = 0x3c190000 | (v >> 16); /* lui t9, hi16 */
+ tramp[1] = 0x27390000 | (v & 0xffff); /* addiu t9, t9, lo16 */
+ tramp[2] = 0x03200008; /* jr t9 */
+ tramp[3] = 0x00000000; /* nop */
+
+ return (Elf_Addr) tramp;
+}
+
+static Elf_Addr add_plt_entry(struct module *me, void *location, Elf_Addr v)
+{
+ if (is_phys_addr(location))
+ return add_plt_entry_to(&me->arch.phys_plt_offset,
+ me->arch.phys_plt_tbl, v);
+ else
+ return add_plt_entry_to(&me->arch.virt_plt_offset,
+ me->arch.virt_plt_tbl, v);
+
+}
+
static int apply_r_mips_26_rel(struct module *me, u32 *location, Elf_Addr v)
{
+ u32 ofs = *location & 0x03ffffff;
+
if (v % 4) {
pr_err("module %s: dangerous R_MIPS_26 REL relocation\n",
me->name);
@@ -74,13 +312,17 @@ static int apply_r_mips_26_rel(struct mo
}
if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
- pr_err("module %s: relocation overflow\n",
- me->name);
- return -ENOEXEC;
+ v = add_plt_entry(me, location, v + (ofs << 2));
+ if (!v) {
+ pr_err("module %s: relocation overflow\n",
+ me->name);
+ return -ENOEXEC;
+ }
+ ofs = 0;
}
*location = (*location & ~0x03ffffff) |
- ((*location + (v >> 2)) & 0x03ffffff);
+ ((ofs + (v >> 2)) & 0x03ffffff);
return 0;
}
@@ -349,9 +591,36 @@ int module_finalize(const Elf_Ehdr *hdr,
list_add(&me->arch.dbe_list, &dbe_list);
spin_unlock_irq(&dbe_lock);
}
+
+ /* Get rid of the fixup trampoline if we're running the module
+ * from physically mapped address space */
+ if (me->arch.phys_plt_offset == 0) {
+ __module_free(me->arch.phys_plt_tbl);
+ me->arch.phys_plt_tbl = NULL;
+ }
+ if (me->arch.virt_plt_offset == 0) {
+ __module_free(me->arch.virt_plt_tbl);
+ me->arch.virt_plt_tbl = NULL;
+ }
+
return 0;
}
+void module_arch_freeing_init(struct module *mod)
+{
+ if (mod->state == MODULE_STATE_LIVE)
+ return;
+
+ if (mod->arch.phys_plt_tbl) {
+ __module_free(mod->arch.phys_plt_tbl);
+ mod->arch.phys_plt_tbl = NULL;
+ }
+ if (mod->arch.virt_plt_tbl) {
+ __module_free(mod->arch.virt_plt_tbl);
+ mod->arch.virt_plt_tbl = NULL;
+ }
+}
+
void module_arch_cleanup(struct module *mod)
{
spin_lock_irq(&dbe_lock);