| Message ID | 20170824081811.19299-9-takahiro.akashi@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 24 August 2017 at 09:18, AKASHI Takahiro <takahiro.akashi@linaro.org> wrote: > This is a basic purgtory, or a kind of glue code between the two kernel, > for arm64. We will later add a feature of verifying a digest check against > loaded memory segments. > > arch_kexec_apply_relocations_add() is responsible for re-linking any > relative symbols in purgatory. Please note that the purgatory is not > an executable, but a non-linked archive of binaries so relative symbols > contained here must be resolved at kexec load time. This sounds fragile to me. What is the reason we cannot let the linker deal with this, similar to, e.g., how the VDSO gets linked? Otherwise, couldn't we reuse the module loader to get these objects relocated in memory? I'm sure there are differences that would require some changes there, but implementing all of this again sounds like overkill to me. > Despite that arm64_kernel_start and arm64_dtb_addr are only such global > variables now, arch_kexec_apply_relocations_add() can manage more various > types of relocations. > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > --- > arch/arm64/Makefile | 1 + > arch/arm64/kernel/Makefile | 1 + > arch/arm64/kernel/machine_kexec_file.c | 199 +++++++++++++++++++++++++++++++++ > arch/arm64/purgatory/Makefile | 24 ++++ > arch/arm64/purgatory/entry.S | 28 +++++ > 5 files changed, 253 insertions(+) > create mode 100644 arch/arm64/kernel/machine_kexec_file.c > create mode 100644 arch/arm64/purgatory/Makefile > create mode 100644 arch/arm64/purgatory/entry.S > > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile > index 9b41f1e3b1a0..429f60728c0a 100644 > --- a/arch/arm64/Makefile > +++ b/arch/arm64/Makefile > @@ -105,6 +105,7 @@ core-$(CONFIG_XEN) += arch/arm64/xen/ > core-$(CONFIG_CRYPTO) += arch/arm64/crypto/ > libs-y := arch/arm64/lib/ $(libs-y) > core-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a > +core-$(CONFIG_KEXEC_FILE) += arch/arm64/purgatory/ > > # Default target when executing plain make > boot := arch/arm64/boot > diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile > index f2b4e816b6de..16e9f56b536a 100644 > --- a/arch/arm64/kernel/Makefile > +++ b/arch/arm64/kernel/Makefile > @@ -50,6 +50,7 @@ arm64-obj-$(CONFIG_RANDOMIZE_BASE) += kaslr.o > arm64-obj-$(CONFIG_HIBERNATION) += hibernate.o hibernate-asm.o > arm64-obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o \ > cpu-reset.o > +arm64-obj-$(CONFIG_KEXEC_FILE) += machine_kexec_file.o > arm64-obj-$(CONFIG_ARM64_RELOC_TEST) += arm64-reloc-test.o > arm64-reloc-test-y := reloc_test_core.o reloc_test_syms.o > arm64-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o > diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c > new file mode 100644 > index 000000000000..183f7776d6dd > --- /dev/null > +++ b/arch/arm64/kernel/machine_kexec_file.c > @@ -0,0 +1,199 @@ > +/* > + * kexec_file for arm64 > + * > + * Copyright (C) 2017 Linaro Limited > + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> > + * > + * Most code is derived from arm64 port of kexec-tools > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 as > + * published by the Free Software Foundation. > + */ > + > +#define pr_fmt(fmt) "kexec_file: " fmt > + > +#include <linux/elf.h> > +#include <linux/errno.h> > +#include <linux/kernel.h> > +#include <linux/types.h> > +#include <asm/byteorder.h> > + > +/* > + * Apply purgatory relocations. > + * > + * ehdr: Pointer to elf headers > + * sechdrs: Pointer to section headers. > + * relsec: section index of SHT_RELA section. > + * > + * Note: > + * Currently R_AARCH64_ABS64, R_AARCH64_LD_PREL_LO19 and R_AARCH64_CALL26 > + * are the only types to be generated from purgatory code. > + * If we add more functionalities, other types may also be used. > + */ > +int arch_kexec_apply_relocations_add(const Elf64_Ehdr *ehdr, > + Elf64_Shdr *sechdrs, unsigned int relsec) > +{ > + Elf64_Rela *rel; > + Elf64_Shdr *section, *symtabsec; > + Elf64_Sym *sym; > + const char *strtab, *name, *shstrtab; > + unsigned long address, sec_base, value; > + void *location; > + u64 *loc64; > + u32 *loc32, imm; > + unsigned int i; > + > + /* > + * ->sh_offset has been modified to keep the pointer to section > + * contents in memory > + */ > + rel = (void *)sechdrs[relsec].sh_offset; > + > + /* Section to which relocations apply */ > + section = &sechdrs[sechdrs[relsec].sh_info]; > + > + pr_debug("reloc: Applying relocate section %u to %u\n", relsec, > + sechdrs[relsec].sh_info); > + > + /* Associated symbol table */ > + symtabsec = &sechdrs[sechdrs[relsec].sh_link]; > + > + /* String table */ > + if (symtabsec->sh_link >= ehdr->e_shnum) { > + /* Invalid strtab section number */ > + pr_err("reloc: Invalid string table section index %d\n", > + symtabsec->sh_link); > + return -ENOEXEC; > + } > + > + strtab = (char *)sechdrs[symtabsec->sh_link].sh_offset; > + > + /* section header string table */ > + shstrtab = (char *)sechdrs[ehdr->e_shstrndx].sh_offset; > + > + for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { > + > + /* > + * rel[i].r_offset contains byte offset from beginning > + * of section to the storage unit affected. > + * > + * This is location to update (->sh_offset). This is temporary > + * buffer where section is currently loaded. This will finally > + * be loaded to a different address later, pointed to by > + * ->sh_addr. kexec takes care of moving it > + * (kexec_load_segment()). > + */ > + location = (void *)(section->sh_offset + rel[i].r_offset); > + > + /* Final address of the location */ > + address = section->sh_addr + rel[i].r_offset; > + > + /* > + * rel[i].r_info contains information about symbol table index > + * w.r.t which relocation must be made and type of relocation > + * to apply. ELF64_R_SYM() and ELF64_R_TYPE() macros get > + * these respectively. > + */ > + sym = (Elf64_Sym *)symtabsec->sh_offset + > + ELF64_R_SYM(rel[i].r_info); > + > + if (sym->st_name) > + name = strtab + sym->st_name; > + else > + name = shstrtab + sechdrs[sym->st_shndx].sh_name; > + > + pr_debug("Symbol: %-16s info: %02x shndx: %02x value=%llx size: %llx reloc type:%d\n", > + name, sym->st_info, sym->st_shndx, sym->st_value, > + sym->st_size, (int)ELF64_R_TYPE(rel[i].r_info)); > + > + if (sym->st_shndx == SHN_UNDEF) { > + pr_err("reloc: Undefined symbol: %s\n", name); > + return -ENOEXEC; > + } > + > + if (sym->st_shndx == SHN_COMMON) { > + pr_err("reloc: symbol '%s' in common section\n", name); > + return -ENOEXEC; > + } > + > + if (sym->st_shndx == SHN_ABS) { > + sec_base = 0; > + } else if (sym->st_shndx < ehdr->e_shnum) { > + sec_base = sechdrs[sym->st_shndx].sh_addr; > + } else { > + pr_err("reloc: Invalid section %d for symbol %s\n", > + sym->st_shndx, name); > + return -ENOEXEC; > + } > + > + value = sym->st_value; > + value += sec_base; > + value += rel[i].r_addend; > + > + switch (ELF64_R_TYPE(rel[i].r_info)) { > + case R_AARCH64_ABS64: > + loc64 = location; > + *loc64 = cpu_to_elf64(ehdr, > + elf64_to_cpu(ehdr, *loc64) + value); > + break; > + case R_AARCH64_PREL32: > + loc32 = location; > + *loc32 = cpu_to_elf32(ehdr, > + elf32_to_cpu(ehdr, *loc32) + value > + - address); > + break; > + case R_AARCH64_LD_PREL_LO19: > + loc32 = location; > + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) > + + (((value - address) << 3) & 0xffffe0)); > + break; > + case R_AARCH64_ADR_PREL_LO21: > + if (value & 3) { > + pr_err("reloc: Unaligned value: %lx\n", value); > + return -ENOEXEC; > + } > + loc32 = location; > + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) > + + (((value - address) << 3) & 0xffffe0)); > + break; > + case R_AARCH64_ADR_PREL_PG_HI21: > + imm = ((value & ~0xfff) - (address & ~0xfff)) >> 12; > + loc32 = location; > + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) > + + ((imm & 3) << 29) > + + ((imm & 0x1ffffc) << (5 - 2))); > + break; > + case R_AARCH64_ADD_ABS_LO12_NC: > + loc32 = location; > + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) > + + ((value & 0xfff) << 10)); > + break; > + case R_AARCH64_JUMP26: > + loc32 = location; > + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) > + + (((value - address) >> 2) & 0x3ffffff)); > + break; > + case R_AARCH64_CALL26: > + loc32 = location; > + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) > + + (((value - address) >> 2) & 0x3ffffff)); > + break; > + case R_AARCH64_LDST64_ABS_LO12_NC: > + if (value & 7) { > + pr_err("reloc: Unaligned value: %lx\n", value); > + return -ENOEXEC; > + } > + loc32 = location; > + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) > + + ((value & 0xff8) << (10 - 3))); > + break; > + default: > + pr_err("reloc: Unknown relocation type: %llu\n", > + ELF64_R_TYPE(rel[i].r_info)); > + return -ENOEXEC; > + } > + } > + > + return 0; > +} > diff --git a/arch/arm64/purgatory/Makefile b/arch/arm64/purgatory/Makefile > new file mode 100644 > index 000000000000..c2127a2cbd51 > --- /dev/null > +++ b/arch/arm64/purgatory/Makefile > @@ -0,0 +1,24 @@ > +OBJECT_FILES_NON_STANDARD := y > + > +purgatory-y := entry.o > + > +targets += $(purgatory-y) > +PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y)) > + > +LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined \ > + -nostdlib -z nodefaultlib > +targets += purgatory.ro > + > +$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE > + $(call if_changed,ld) > + > +targets += kexec_purgatory.c > + > +CMD_BIN2C = $(objtree)/scripts/basic/bin2c > +quiet_cmd_bin2c = BIN2C $@ > + cmd_bin2c = $(CMD_BIN2C) kexec_purgatory < $< > $@ > + > +$(obj)/kexec_purgatory.c: $(obj)/purgatory.ro FORCE > + $(call if_changed,bin2c) > + > +obj-${CONFIG_KEXEC_FILE} += kexec_purgatory.o > diff --git a/arch/arm64/purgatory/entry.S b/arch/arm64/purgatory/entry.S > new file mode 100644 > index 000000000000..bc4e6b3bf8a1 > --- /dev/null > +++ b/arch/arm64/purgatory/entry.S > @@ -0,0 +1,28 @@ > +/* > + * kexec core purgatory > + */ > +#include <linux/linkage.h> > + > +.text > + > +ENTRY(purgatory_start) > + /* Start new image. */ > + ldr x17, arm64_kernel_entry > + ldr x0, arm64_dtb_addr > + mov x1, xzr > + mov x2, xzr > + mov x3, xzr > + br x17 > +END(purgatory_start) > + > +.data > + > +.align 3 > + > +ENTRY(arm64_kernel_entry) > + .quad 0 > +END(arm64_kernel_entry) > + > +ENTRY(arm64_dtb_addr) > + .quad 0 > +END(arm64_dtb_addr) > -- > 2.14.1 >
On Thu, Aug 24, 2017 at 05:18:05PM +0900, AKASHI Takahiro wrote: > This is a basic purgtory, or a kind of glue code between the two kernel, > for arm64. We will later add a feature of verifying a digest check against > loaded memory segments. > > arch_kexec_apply_relocations_add() is responsible for re-linking any > relative symbols in purgatory. Please note that the purgatory is not > an executable, but a non-linked archive of binaries so relative symbols > contained here must be resolved at kexec load time. > Despite that arm64_kernel_start and arm64_dtb_addr are only such global > variables now, arch_kexec_apply_relocations_add() can manage more various > types of relocations. Why does the purgatory code need to be so complex? Why is it not possible to write this as position-independent asm? > +/* > + * Apply purgatory relocations. > + * > + * ehdr: Pointer to elf headers > + * sechdrs: Pointer to section headers. > + * relsec: section index of SHT_RELA section. > + * > + * Note: > + * Currently R_AARCH64_ABS64, R_AARCH64_LD_PREL_LO19 and R_AARCH64_CALL26 > + * are the only types to be generated from purgatory code. Is this all that has been observed, or is this ensured somehow? The arch_kexec_apply_relocations_add() function below duplicates a lot of logic that already exists in the arm64 module loader's apply_relocate_add() function. Please reuse that code. Having a duplicate or alternative implementation is just asking for subtle bugs. Thanks, Mark.
On Thu, Aug 24, 2017 at 05:56:17PM +0100, Mark Rutland wrote: > On Thu, Aug 24, 2017 at 05:18:05PM +0900, AKASHI Takahiro wrote: > > This is a basic purgtory, or a kind of glue code between the two kernel, > > for arm64. We will later add a feature of verifying a digest check against > > loaded memory segments. > > > > arch_kexec_apply_relocations_add() is responsible for re-linking any > > relative symbols in purgatory. Please note that the purgatory is not > > an executable, but a non-linked archive of binaries so relative symbols > > contained here must be resolved at kexec load time. > > Despite that arm64_kernel_start and arm64_dtb_addr are only such global > > variables now, arch_kexec_apply_relocations_add() can manage more various > > types of relocations. > > Why does the purgatory code need to be so complex? > > Why is it not possible to write this as position-independent asm? I don't get your point, but please note that these values are also re-written by the 1st kernel when it loads the 2nd kernel and so they must appear as globals. > > +/* > > + * Apply purgatory relocations. > > + * > > + * ehdr: Pointer to elf headers > > + * sechdrs: Pointer to section headers. > > + * relsec: section index of SHT_RELA section. > > + * > > + * Note: > > + * Currently R_AARCH64_ABS64, R_AARCH64_LD_PREL_LO19 and R_AARCH64_CALL26 > > + * are the only types to be generated from purgatory code. > > Is this all that has been observed, or is this ensured somehow? It was observed by inserting a debug print message in this function, I'm not sure whether we can restrict only those three types. > The arch_kexec_apply_relocations_add() function below duplicates a lot > of logic that already exists in the arm64 module loader's > apply_relocate_add() function. > > Please reuse that code. Having a duplicate or alternative implementation > is just asking for subtle bugs. Okey, I'll look at it. Thanks, -Takahiro AKASHI > Thanks, > Mark.
On Thu, Aug 24, 2017 at 10:10:37AM +0100, Ard Biesheuvel wrote: > On 24 August 2017 at 09:18, AKASHI Takahiro <takahiro.akashi@linaro.org> wrote: > > This is a basic purgtory, or a kind of glue code between the two kernel, > > for arm64. We will later add a feature of verifying a digest check against > > loaded memory segments. > > > > arch_kexec_apply_relocations_add() is responsible for re-linking any > > relative symbols in purgatory. Please note that the purgatory is not > > an executable, but a non-linked archive of binaries so relative symbols > > contained here must be resolved at kexec load time. > > This sounds fragile to me. What is the reason we cannot let the linker > deal with this, similar to, e.g., how the VDSO gets linked? Please note this is exactly what x86 code does. I guess that the reason is that x86 guys borrowed the logic directly from kexec-tools. > Otherwise, couldn't we reuse the module loader to get these objects > relocated in memory? I'm sure there are differences that would require > some changes there, but implementing all of this again sounds like > overkill to me. I'll look at both of your suggestions. Thanks, -Takahiro AKASHI
On Fri, Aug 25, 2017 at 10:00:59AM +0900, AKASHI Takahiro wrote: > On Thu, Aug 24, 2017 at 05:56:17PM +0100, Mark Rutland wrote: > > On Thu, Aug 24, 2017 at 05:18:05PM +0900, AKASHI Takahiro wrote: > > > This is a basic purgtory, or a kind of glue code between the two kernel, > > > for arm64. We will later add a feature of verifying a digest check against > > > loaded memory segments. > > > > > > arch_kexec_apply_relocations_add() is responsible for re-linking any > > > relative symbols in purgatory. Please note that the purgatory is not > > > an executable, but a non-linked archive of binaries so relative symbols > > > contained here must be resolved at kexec load time. > > > Despite that arm64_kernel_start and arm64_dtb_addr are only such global > > > variables now, arch_kexec_apply_relocations_add() can manage more various > > > types of relocations. > > > > Why does the purgatory code need to be so complex? > > > > Why is it not possible to write this as position-independent asm? > > I don't get your point, but please note that these values are also > re-written by the 1st kernel when it loads the 2nd kernel and so > they must appear as globals. My fear about complexity is that we must "re-link" the purgatory. I don't understand why that has to be necessary. Surely we can have the purgatory code be position independent, and store those globals in a single struct purgatory_info that we can fill in from the host? i.e. similar to what we do for values shared with the VDSO, where we just poke vdso_data->field, no re-linking required. Otherwise, why can't the purgatory code be written in assembly? AFAICT, the only complex part is the hashing code, which I don't beleive is strictly necessary. [...] > > > +/* > > > + * Apply purgatory relocations. > > > + * > > > + * ehdr: Pointer to elf headers > > > + * sechdrs: Pointer to section headers. > > > + * relsec: section index of SHT_RELA section. > > > + * > > > + * Note: > > > + * Currently R_AARCH64_ABS64, R_AARCH64_LD_PREL_LO19 and R_AARCH64_CALL26 > > > + * are the only types to be generated from purgatory code. > > > > Is this all that has been observed, or is this ensured somehow? > > It was observed by inserting a debug print message in this function, > I'm not sure whether we can restrict only those three types. If we have to perform linking, I don't think we can assume the above is sufficient. > > The arch_kexec_apply_relocations_add() function below duplicates a lot > > of logic that already exists in the arm64 module loader's > > apply_relocate_add() function. > > > > Please reuse that code. Having a duplicate or alternative implementation > > is just asking for subtle bugs. > > Okey, I'll look at it. Ok. As above, I think it would be preferable that we avoid linking entirely. Thanks, Mark.
Mark Rutland <mark.rutland@arm.com> writes: > On Fri, Aug 25, 2017 at 10:00:59AM +0900, AKASHI Takahiro wrote: >> On Thu, Aug 24, 2017 at 05:56:17PM +0100, Mark Rutland wrote: >> > On Thu, Aug 24, 2017 at 05:18:05PM +0900, AKASHI Takahiro wrote: >> > > This is a basic purgtory, or a kind of glue code between the two kernel, >> > > for arm64. We will later add a feature of verifying a digest check against >> > > loaded memory segments. >> > > >> > > arch_kexec_apply_relocations_add() is responsible for re-linking any >> > > relative symbols in purgatory. Please note that the purgatory is not >> > > an executable, but a non-linked archive of binaries so relative symbols >> > > contained here must be resolved at kexec load time. >> > > Despite that arm64_kernel_start and arm64_dtb_addr are only such global >> > > variables now, arch_kexec_apply_relocations_add() can manage more various >> > > types of relocations. >> > >> > Why does the purgatory code need to be so complex? >> > >> > Why is it not possible to write this as position-independent asm? >> >> I don't get your point, but please note that these values are also >> re-written by the 1st kernel when it loads the 2nd kernel and so >> they must appear as globals. > > My fear about complexity is that we must "re-link" the purgatory. > > I don't understand why that has to be necessary. Surely we can have the > purgatory code be position independent, and store those globals in a > single struct purgatory_info that we can fill in from the host? > > i.e. similar to what we do for values shared with the VDSO, where we > just poke vdso_data->field, no re-linking required. Right. I'm not sure why it is a partially linked object. I believe that the purgatory could be linked at build time into a PIE executable with exported symbols for the variables that need to be filled in from the host. On some architectures (e.g., powerpc), this would greatly reduce the number of relocation types that the kernel needs to know how to process. On x86 it make less of a difference because the partially linked object already has just a handful of relocation types. > Otherwise, why can't the purgatory code be written in assembly? AFAICT, > the only complex part is the hashing code, which I don't beleive is > strictly necessary. When I posted a similar series for powerpc with similar changes to handle a partially linked purgatory in the kernel, Michael Ellerman preferred to go for a purgatory written in assembly, partially based on the one from kexec-lite. That purgatory doesn't do the checksum verification of the segments.
On Fri, Aug 25, 2017 at 01:16:06PM -0300, Thiago Jung Bauermann wrote: > > Mark Rutland <mark.rutland@arm.com> writes: > > > On Fri, Aug 25, 2017 at 10:00:59AM +0900, AKASHI Takahiro wrote: > >> On Thu, Aug 24, 2017 at 05:56:17PM +0100, Mark Rutland wrote: > >> > On Thu, Aug 24, 2017 at 05:18:05PM +0900, AKASHI Takahiro wrote: > >> > > This is a basic purgtory, or a kind of glue code between the two kernel, > >> > > for arm64. We will later add a feature of verifying a digest check against > >> > > loaded memory segments. > >> > > > >> > > arch_kexec_apply_relocations_add() is responsible for re-linking any > >> > > relative symbols in purgatory. Please note that the purgatory is not > >> > > an executable, but a non-linked archive of binaries so relative symbols > >> > > contained here must be resolved at kexec load time. > >> > > Despite that arm64_kernel_start and arm64_dtb_addr are only such global > >> > > variables now, arch_kexec_apply_relocations_add() can manage more various > >> > > types of relocations. > >> > > >> > Why does the purgatory code need to be so complex? > >> > > >> > Why is it not possible to write this as position-independent asm? > >> > >> I don't get your point, but please note that these values are also > >> re-written by the 1st kernel when it loads the 2nd kernel and so > >> they must appear as globals. > > > > My fear about complexity is that we must "re-link" the purgatory. > > > > I don't understand why that has to be necessary. Surely we can have the > > purgatory code be position independent, and store those globals in a > > single struct purgatory_info that we can fill in from the host? > > > > i.e. similar to what we do for values shared with the VDSO, where we > > just poke vdso_data->field, no re-linking required. > > Right. I'm not sure why it is a partially linked object. I believe that > the purgatory could be linked at build time into a PIE executable with > exported symbols for the variables that need to be filled in from the > host. For clarification, generic kexec code expects that the purgatory is *relocatable* (not executable in ELF terms) as compiled with -r gcc option. On arm64, in this case, all the *global* symbols remain to be un-resolved even if the references are local within a single section (in a file). This would require re-linking at purgatory load time. I'm going to resolve this issue by adding extra *local labels*. (See my v2.) > On some architectures (e.g., powerpc), this would greatly reduce the > number of relocation types that the kernel needs to know how to process. > On x86 it make less of a difference because the partially linked object > already has just a handful of relocation types. > > > Otherwise, why can't the purgatory code be written in assembly? AFAICT, > > the only complex part is the hashing code, which I don't beleive is > > strictly necessary. > > When I posted a similar series for powerpc with similar changes to > handle a partially linked purgatory in the kernel, Michael Ellerman > preferred to go for a purgatory written in assembly, partially based on > the one from kexec-lite. That purgatory doesn't do the checksum > verification of the segments. Anyhow, I will drop hash-check code from the purgatory in v2 so that it will now be quite a simple asm. Thanks, -Takahiro AKASHI > -- > Thiago Jung Bauermann > IBM Linux Technology Center >
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 9b41f1e3b1a0..429f60728c0a 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -105,6 +105,7 @@ core-$(CONFIG_XEN) += arch/arm64/xen/ core-$(CONFIG_CRYPTO) += arch/arm64/crypto/ libs-y := arch/arm64/lib/ $(libs-y) core-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a +core-$(CONFIG_KEXEC_FILE) += arch/arm64/purgatory/ # Default target when executing plain make boot := arch/arm64/boot diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index f2b4e816b6de..16e9f56b536a 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -50,6 +50,7 @@ arm64-obj-$(CONFIG_RANDOMIZE_BASE) += kaslr.o arm64-obj-$(CONFIG_HIBERNATION) += hibernate.o hibernate-asm.o arm64-obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o \ cpu-reset.o +arm64-obj-$(CONFIG_KEXEC_FILE) += machine_kexec_file.o arm64-obj-$(CONFIG_ARM64_RELOC_TEST) += arm64-reloc-test.o arm64-reloc-test-y := reloc_test_core.o reloc_test_syms.o arm64-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c new file mode 100644 index 000000000000..183f7776d6dd --- /dev/null +++ b/arch/arm64/kernel/machine_kexec_file.c @@ -0,0 +1,199 @@ +/* + * kexec_file for arm64 + * + * Copyright (C) 2017 Linaro Limited + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> + * + * Most code is derived from arm64 port of kexec-tools + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#define pr_fmt(fmt) "kexec_file: " fmt + +#include <linux/elf.h> +#include <linux/errno.h> +#include <linux/kernel.h> +#include <linux/types.h> +#include <asm/byteorder.h> + +/* + * Apply purgatory relocations. + * + * ehdr: Pointer to elf headers + * sechdrs: Pointer to section headers. + * relsec: section index of SHT_RELA section. + * + * Note: + * Currently R_AARCH64_ABS64, R_AARCH64_LD_PREL_LO19 and R_AARCH64_CALL26 + * are the only types to be generated from purgatory code. + * If we add more functionalities, other types may also be used. + */ +int arch_kexec_apply_relocations_add(const Elf64_Ehdr *ehdr, + Elf64_Shdr *sechdrs, unsigned int relsec) +{ + Elf64_Rela *rel; + Elf64_Shdr *section, *symtabsec; + Elf64_Sym *sym; + const char *strtab, *name, *shstrtab; + unsigned long address, sec_base, value; + void *location; + u64 *loc64; + u32 *loc32, imm; + unsigned int i; + + /* + * ->sh_offset has been modified to keep the pointer to section + * contents in memory + */ + rel = (void *)sechdrs[relsec].sh_offset; + + /* Section to which relocations apply */ + section = &sechdrs[sechdrs[relsec].sh_info]; + + pr_debug("reloc: Applying relocate section %u to %u\n", relsec, + sechdrs[relsec].sh_info); + + /* Associated symbol table */ + symtabsec = &sechdrs[sechdrs[relsec].sh_link]; + + /* String table */ + if (symtabsec->sh_link >= ehdr->e_shnum) { + /* Invalid strtab section number */ + pr_err("reloc: Invalid string table section index %d\n", + symtabsec->sh_link); + return -ENOEXEC; + } + + strtab = (char *)sechdrs[symtabsec->sh_link].sh_offset; + + /* section header string table */ + shstrtab = (char *)sechdrs[ehdr->e_shstrndx].sh_offset; + + for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { + + /* + * rel[i].r_offset contains byte offset from beginning + * of section to the storage unit affected. + * + * This is location to update (->sh_offset). This is temporary + * buffer where section is currently loaded. This will finally + * be loaded to a different address later, pointed to by + * ->sh_addr. kexec takes care of moving it + * (kexec_load_segment()). + */ + location = (void *)(section->sh_offset + rel[i].r_offset); + + /* Final address of the location */ + address = section->sh_addr + rel[i].r_offset; + + /* + * rel[i].r_info contains information about symbol table index + * w.r.t which relocation must be made and type of relocation + * to apply. ELF64_R_SYM() and ELF64_R_TYPE() macros get + * these respectively. + */ + sym = (Elf64_Sym *)symtabsec->sh_offset + + ELF64_R_SYM(rel[i].r_info); + + if (sym->st_name) + name = strtab + sym->st_name; + else + name = shstrtab + sechdrs[sym->st_shndx].sh_name; + + pr_debug("Symbol: %-16s info: %02x shndx: %02x value=%llx size: %llx reloc type:%d\n", + name, sym->st_info, sym->st_shndx, sym->st_value, + sym->st_size, (int)ELF64_R_TYPE(rel[i].r_info)); + + if (sym->st_shndx == SHN_UNDEF) { + pr_err("reloc: Undefined symbol: %s\n", name); + return -ENOEXEC; + } + + if (sym->st_shndx == SHN_COMMON) { + pr_err("reloc: symbol '%s' in common section\n", name); + return -ENOEXEC; + } + + if (sym->st_shndx == SHN_ABS) { + sec_base = 0; + } else if (sym->st_shndx < ehdr->e_shnum) { + sec_base = sechdrs[sym->st_shndx].sh_addr; + } else { + pr_err("reloc: Invalid section %d for symbol %s\n", + sym->st_shndx, name); + return -ENOEXEC; + } + + value = sym->st_value; + value += sec_base; + value += rel[i].r_addend; + + switch (ELF64_R_TYPE(rel[i].r_info)) { + case R_AARCH64_ABS64: + loc64 = location; + *loc64 = cpu_to_elf64(ehdr, + elf64_to_cpu(ehdr, *loc64) + value); + break; + case R_AARCH64_PREL32: + loc32 = location; + *loc32 = cpu_to_elf32(ehdr, + elf32_to_cpu(ehdr, *loc32) + value + - address); + break; + case R_AARCH64_LD_PREL_LO19: + loc32 = location; + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) + + (((value - address) << 3) & 0xffffe0)); + break; + case R_AARCH64_ADR_PREL_LO21: + if (value & 3) { + pr_err("reloc: Unaligned value: %lx\n", value); + return -ENOEXEC; + } + loc32 = location; + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) + + (((value - address) << 3) & 0xffffe0)); + break; + case R_AARCH64_ADR_PREL_PG_HI21: + imm = ((value & ~0xfff) - (address & ~0xfff)) >> 12; + loc32 = location; + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) + + ((imm & 3) << 29) + + ((imm & 0x1ffffc) << (5 - 2))); + break; + case R_AARCH64_ADD_ABS_LO12_NC: + loc32 = location; + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) + + ((value & 0xfff) << 10)); + break; + case R_AARCH64_JUMP26: + loc32 = location; + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) + + (((value - address) >> 2) & 0x3ffffff)); + break; + case R_AARCH64_CALL26: + loc32 = location; + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) + + (((value - address) >> 2) & 0x3ffffff)); + break; + case R_AARCH64_LDST64_ABS_LO12_NC: + if (value & 7) { + pr_err("reloc: Unaligned value: %lx\n", value); + return -ENOEXEC; + } + loc32 = location; + *loc32 = cpu_to_le32(le32_to_cpu(*loc32) + + ((value & 0xff8) << (10 - 3))); + break; + default: + pr_err("reloc: Unknown relocation type: %llu\n", + ELF64_R_TYPE(rel[i].r_info)); + return -ENOEXEC; + } + } + + return 0; +} diff --git a/arch/arm64/purgatory/Makefile b/arch/arm64/purgatory/Makefile new file mode 100644 index 000000000000..c2127a2cbd51 --- /dev/null +++ b/arch/arm64/purgatory/Makefile @@ -0,0 +1,24 @@ +OBJECT_FILES_NON_STANDARD := y + +purgatory-y := entry.o + +targets += $(purgatory-y) +PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y)) + +LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined \ + -nostdlib -z nodefaultlib +targets += purgatory.ro + +$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE + $(call if_changed,ld) + +targets += kexec_purgatory.c + +CMD_BIN2C = $(objtree)/scripts/basic/bin2c +quiet_cmd_bin2c = BIN2C $@ + cmd_bin2c = $(CMD_BIN2C) kexec_purgatory < $< > $@ + +$(obj)/kexec_purgatory.c: $(obj)/purgatory.ro FORCE + $(call if_changed,bin2c) + +obj-${CONFIG_KEXEC_FILE} += kexec_purgatory.o diff --git a/arch/arm64/purgatory/entry.S b/arch/arm64/purgatory/entry.S new file mode 100644 index 000000000000..bc4e6b3bf8a1 --- /dev/null +++ b/arch/arm64/purgatory/entry.S @@ -0,0 +1,28 @@ +/* + * kexec core purgatory + */ +#include <linux/linkage.h> + +.text + +ENTRY(purgatory_start) + /* Start new image. */ + ldr x17, arm64_kernel_entry + ldr x0, arm64_dtb_addr + mov x1, xzr + mov x2, xzr + mov x3, xzr + br x17 +END(purgatory_start) + +.data + +.align 3 + +ENTRY(arm64_kernel_entry) + .quad 0 +END(arm64_kernel_entry) + +ENTRY(arm64_dtb_addr) + .quad 0 +END(arm64_dtb_addr)
This is a basic purgtory, or a kind of glue code between the two kernel, for arm64. We will later add a feature of verifying a digest check against loaded memory segments. arch_kexec_apply_relocations_add() is responsible for re-linking any relative symbols in purgatory. Please note that the purgatory is not an executable, but a non-linked archive of binaries so relative symbols contained here must be resolved at kexec load time. Despite that arm64_kernel_start and arm64_dtb_addr are only such global variables now, arch_kexec_apply_relocations_add() can manage more various types of relocations. Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> --- arch/arm64/Makefile | 1 + arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/machine_kexec_file.c | 199 +++++++++++++++++++++++++++++++++ arch/arm64/purgatory/Makefile | 24 ++++ arch/arm64/purgatory/entry.S | 28 +++++ 5 files changed, 253 insertions(+) create mode 100644 arch/arm64/kernel/machine_kexec_file.c create mode 100644 arch/arm64/purgatory/Makefile create mode 100644 arch/arm64/purgatory/entry.S