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2ec13df167
On book3s/32, when STRICT_KERNEL_RWX is selected, modules are allocated on the segment just before kernel text, ie on the 0xb0000000-0xbfffffff when PAGE_OFFSET is 0xc0000000. On the 8xx, TASK_SIZE is 0x80000000. The space between TASK_SIZE and PAGE_OFFSET is not used and could be used for modules. The idea comes from ARM architecture. Having modules just below PAGE_OFFSET offers an opportunity to minimise the distance between kernel text and modules and avoid trampolines in modules to access kernel functions or other module functions. When MODULES_VADDR is defined, powerpc has it's own module_alloc() function. In that function, first try to allocate the module above the limit defined by '_etext - 32M'. Then if the allocation fails, fallback to the entire MODULES area. DEBUG logs in module_32.c without the patch: [ 1572.588822] module_32: Applying ADD relocate section 13 to 12 [ 1572.588891] module_32: Doing plt for call to 0xc00671a4 at 0xcae04024 [ 1572.588964] module_32: Initialized plt for 0xc00671a4 at cae04000 [ 1572.589037] module_32: REL24 value = CAE04000. location = CAE04024 [ 1572.589110] module_32: Location before: 48000001. [ 1572.589171] module_32: Location after: 4BFFFFDD. [ 1572.589231] module_32: ie. jump to 03FFFFDC+CAE04024 = CEE04000 [ 1572.589317] module_32: Applying ADD relocate section 15 to 14 [ 1572.589386] module_32: Doing plt for call to 0xc00671a4 at 0xcadfc018 [ 1572.589457] module_32: Initialized plt for 0xc00671a4 at cadfc000 [ 1572.589529] module_32: REL24 value = CADFC000. location = CADFC018 [ 1572.589601] module_32: Location before: 48000000. [ 1572.589661] module_32: Location after: 4BFFFFE8. [ 1572.589723] module_32: ie. jump to 03FFFFE8+CADFC018 = CEDFC000 With the patch: [ 279.404671] module_32: Applying ADD relocate section 13 to 12 [ 279.404741] module_32: REL24 value = C00671B4. location = BF808024 [ 279.404814] module_32: Location before: 48000001. [ 279.404874] module_32: Location after: 4885F191. [ 279.404933] module_32: ie. jump to 0085F190+BF808024 = C00671B4 [ 279.405016] module_32: Applying ADD relocate section 15 to 14 [ 279.405085] module_32: REL24 value = C00671B4. location = BF800018 [ 279.405156] module_32: Location before: 48000000. [ 279.405215] module_32: Location after: 4886719C. [ 279.405275] module_32: ie. jump to 0086719C+BF800018 = C00671B4 We see that with the patch, no plt entries are set. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/0c3d5cb8a4dfdf6ca1b8aeb385c01470d6628d55.1617283827.git.christophe.leroy@csgroup.eu
116 lines
3.1 KiB
C
116 lines
3.1 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* Kernel module help for powerpc.
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Copyright (C) 2001, 2003 Rusty Russell IBM Corporation.
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Copyright (C) 2008 Freescale Semiconductor, Inc.
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*/
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#include <linux/elf.h>
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#include <linux/moduleloader.h>
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#include <linux/err.h>
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#include <linux/vmalloc.h>
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#include <linux/bug.h>
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#include <asm/module.h>
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#include <linux/uaccess.h>
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#include <asm/firmware.h>
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#include <linux/sort.h>
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#include <asm/setup.h>
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#include <asm/sections.h>
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static LIST_HEAD(module_bug_list);
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static const Elf_Shdr *find_section(const Elf_Ehdr *hdr,
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const Elf_Shdr *sechdrs,
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const char *name)
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{
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char *secstrings;
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unsigned int i;
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secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
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for (i = 1; i < hdr->e_shnum; i++)
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if (strcmp(secstrings+sechdrs[i].sh_name, name) == 0)
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return &sechdrs[i];
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return NULL;
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}
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int module_finalize(const Elf_Ehdr *hdr,
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const Elf_Shdr *sechdrs, struct module *me)
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{
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const Elf_Shdr *sect;
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int rc;
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rc = module_finalize_ftrace(me, sechdrs);
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if (rc)
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return rc;
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/* Apply feature fixups */
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sect = find_section(hdr, sechdrs, "__ftr_fixup");
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if (sect != NULL)
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do_feature_fixups(cur_cpu_spec->cpu_features,
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(void *)sect->sh_addr,
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(void *)sect->sh_addr + sect->sh_size);
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sect = find_section(hdr, sechdrs, "__mmu_ftr_fixup");
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if (sect != NULL)
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do_feature_fixups(cur_cpu_spec->mmu_features,
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(void *)sect->sh_addr,
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(void *)sect->sh_addr + sect->sh_size);
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#ifdef CONFIG_PPC64
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sect = find_section(hdr, sechdrs, "__fw_ftr_fixup");
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if (sect != NULL)
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do_feature_fixups(powerpc_firmware_features,
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(void *)sect->sh_addr,
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(void *)sect->sh_addr + sect->sh_size);
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#endif /* CONFIG_PPC64 */
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#ifdef PPC64_ELF_ABI_v1
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sect = find_section(hdr, sechdrs, ".opd");
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if (sect != NULL) {
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me->arch.start_opd = sect->sh_addr;
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me->arch.end_opd = sect->sh_addr + sect->sh_size;
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}
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#endif /* PPC64_ELF_ABI_v1 */
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#ifdef CONFIG_PPC_BARRIER_NOSPEC
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sect = find_section(hdr, sechdrs, "__spec_barrier_fixup");
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if (sect != NULL)
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do_barrier_nospec_fixups_range(barrier_nospec_enabled,
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(void *)sect->sh_addr,
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(void *)sect->sh_addr + sect->sh_size);
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#endif /* CONFIG_PPC_BARRIER_NOSPEC */
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sect = find_section(hdr, sechdrs, "__lwsync_fixup");
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if (sect != NULL)
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do_lwsync_fixups(cur_cpu_spec->cpu_features,
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(void *)sect->sh_addr,
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(void *)sect->sh_addr + sect->sh_size);
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return 0;
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}
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#ifdef MODULES_VADDR
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static __always_inline void *
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__module_alloc(unsigned long size, unsigned long start, unsigned long end)
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{
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return __vmalloc_node_range(size, 1, start, end, GFP_KERNEL,
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PAGE_KERNEL_EXEC, VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
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__builtin_return_address(0));
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}
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void *module_alloc(unsigned long size)
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{
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unsigned long limit = (unsigned long)_etext - SZ_32M;
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void *ptr = NULL;
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BUILD_BUG_ON(TASK_SIZE > MODULES_VADDR);
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/* First try within 32M limit from _etext to avoid branch trampolines */
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if (MODULES_VADDR < PAGE_OFFSET && MODULES_END > limit)
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ptr = __module_alloc(size, limit, MODULES_END);
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if (!ptr)
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ptr = __module_alloc(size, MODULES_VADDR, MODULES_END);
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return ptr;
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}
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#endif
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