I will analyze this and respond. Thanks for mentioning this. Madhavan On 2/10/23 01:52, Tomohiro Misono (Fujitsu) wrote: > Hello, > > I see the following build warning after this commit (gcc12): > ld: warning: orphan section `.init.orc_unwind' from `arch/arm64/kernel/pi/kaslr_early.pi.o' being placed in section `.init.orc_unwind' > ld: warning: orphan section `.init.orc_unwind_ip' from `arch/arm64/kernel/pi/kaslr_early.pi.o' being placed in section `.init.orc_unwind_ip' > ... > > My understanding of the cause is that arch/arm64/kernel/pi has its > own Makefile and adds "init" prefix to sections by objcopy: > https://github.com/madvenka786/linux/blob/orc_v3/arch/arm64/kernel/pi/Makefile#L25 > > I assume these files are not relevant for livepatch perspective and so it is > safe to exclude these sections by --remove-section or should we care these as well? > > Regards, > Tomohiro > >> Subject: [RFC PATCH v3 18/22] arm64: Build the kernel with ORC information >> >> From: "Madhavan T. Venkataraman" <madvenka@xxxxxxxxxxxxxxxxxxx> >> >> Add code to scripts/Makefile.lib to define objtool options to generate >> ORC data for frame pointer validation. >> >> Define kernel configs: >> - to enable dynamic FRAME_POINTER_VALIDATION >> - to enable the generation of ORC data using objtool >> >> When these configs are enabled, objtool is invoked on relocatable files >> during kernel build with the following command: >> >> objtool --stackval --orc <object-file> >> >> Objtool creates special sections in the object files: >> >> .orc_unwind_ip PC array. >> .orc_unwind ORC structure table. >> .orc_lookup ORC lookup table. >> >> Change arch/arm64/kernel/vmlinux.lds.S to include ORC_UNWIND_TABLE in >> the data section so that the special sections get included there. For >> modules, these sections will be added to the kernel during module load. >> >> In the future, the kernel can use these sections to find the ORC for a >> given instruction address. The unwinder can then compute the FP at an >> instruction address and validate the actual FP with that. >> >> Signed-off-by: Madhavan T. Venkataraman <madvenka@xxxxxxxxxxxxxxxxxxx> >> --- >> arch/arm64/Kconfig | 2 ++ >> arch/arm64/Kconfig.debug | 32 >> ++++++++++++++++++++++++++++++++ >> arch/arm64/include/asm/module.h | 12 +++++++++++- >> arch/arm64/kernel/vmlinux.lds.S | 3 +++ >> include/linux/objtool.h | 2 ++ >> scripts/Makefile | 4 +++- >> scripts/Makefile.lib | 9 +++++++++ >> tools/include/linux/objtool.h | 2 ++ >> 8 files changed, 64 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index 505c8a1ccbe0..73c3f30a37c7 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -230,6 +230,8 @@ config ARM64 >> select TRACE_IRQFLAGS_SUPPORT >> select TRACE_IRQFLAGS_NMI_SUPPORT >> select HAVE_SOFTIRQ_ON_OWN_STACK >> + select HAVE_STACK_VALIDATION if >> FRAME_POINTER_VALIDATION >> + select STACK_VALIDATION if HAVE_STACK_VALIDATION >> help >> ARM 64-bit (AArch64) Linux support. >> >> diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug >> index 265c4461031f..a50caabdb18e 100644 >> --- a/arch/arm64/Kconfig.debug >> +++ b/arch/arm64/Kconfig.debug >> @@ -20,4 +20,36 @@ config ARM64_RELOC_TEST >> depends on m >> tristate "Relocation testing module" >> >> +config UNWINDER_ORC >> + bool "ORC unwinder" >> + depends on FRAME_POINTER_VALIDATION >> + select HAVE_MOD_ARCH_SPECIFIC >> + select OBJTOOL >> + help >> + This option enables ORC (Oops Rewind Capability) for ARM64. This >> + allows the unwinder to look up ORC data for an instruction address >> + and compute the frame pointer at that address. The computed frame >> + pointer is used to validate the actual frame pointer. >> + >> +config UNWINDER_FRAME_POINTER >> + bool "Frame pointer unwinder" >> + depends on FRAME_POINTER_VALIDATION >> + select FRAME_POINTER >> + help >> + ARM64 already uses the frame pointer for unwinding kernel stack >> + traces. We need to enable this config to enable STACK_VALIDATION. >> + STACK_VALIDATION is needed to get objtool to do static analysis >> + of kernel code. >> + >> +config FRAME_POINTER_VALIDATION >> + bool "Dynamic Frame pointer validation" >> + select UNWINDER_FRAME_POINTER >> + select UNWINDER_ORC >> + help >> + This invokes objtool on every object file causing it to >> + generate ORC data for the object file. ORC data is in a custom >> + data format which is a simplified version of the DWARF >> + Call Frame Information standard. See UNWINDER_ORC for more >> + details. >> + >> source "drivers/hwtracing/coresight/Kconfig" >> diff --git a/arch/arm64/include/asm/module.h >> b/arch/arm64/include/asm/module.h >> index 18734fed3bdd..4362f44aae61 100644 >> --- a/arch/arm64/include/asm/module.h >> +++ b/arch/arm64/include/asm/module.h >> @@ -6,6 +6,7 @@ >> #define __ASM_MODULE_H >> >> #include <asm-generic/module.h> >> +#include <asm/orc_types.h> >> >> #ifdef CONFIG_ARM64_MODULE_PLTS >> struct mod_plt_sec { >> @@ -13,15 +14,24 @@ struct mod_plt_sec { >> int plt_num_entries; >> int plt_max_entries; >> }; >> +#endif >> >> +#ifdef CONFIG_HAVE_MOD_ARCH_SPECIFIC >> struct mod_arch_specific { >> +#ifdef CONFIG_ARM64_MODULE_PLTS >> struct mod_plt_sec core; >> struct mod_plt_sec init; >> >> /* for CONFIG_DYNAMIC_FTRACE */ >> struct plt_entry *ftrace_trampolines; >> -}; >> #endif >> +#ifdef CONFIG_UNWINDER_ORC >> + unsigned int num_orcs; >> + int *orc_unwind_ip; >> + struct orc_entry *orc_unwind; >> +#endif >> +}; >> +#endif /* CONFIG_HAVE_MOD_ARCH_SPECIFIC */ >> >> u64 module_emit_plt_entry(struct module *mod, Elf64_Shdr *sechdrs, >> void *loc, const Elf64_Rela *rela, >> diff --git a/arch/arm64/kernel/vmlinux.lds.S >> b/arch/arm64/kernel/vmlinux.lds.S >> index 45131e354e27..bf7b55ae10ee 100644 >> --- a/arch/arm64/kernel/vmlinux.lds.S >> +++ b/arch/arm64/kernel/vmlinux.lds.S >> @@ -61,6 +61,7 @@ >> #define RUNTIME_DISCARD_EXIT >> >> #include <asm-generic/vmlinux.lds.h> >> +#include <asm-generic/orc_lookup.h> >> #include <asm/cache.h> >> #include <asm/kernel-pgtable.h> >> #include <asm/kexec.h> >> @@ -294,6 +295,8 @@ SECTIONS >> __mmuoff_data_end = .; >> } >> >> + ORC_UNWIND_TABLE >> + >> PECOFF_EDATA_PADDING >> __pecoff_data_rawsize = ABSOLUTE(. - __initdata_begin); >> _edata = .; >> diff --git a/include/linux/objtool.h b/include/linux/objtool.h >> index dcbd365944f6..c980522190f7 100644 >> --- a/include/linux/objtool.h >> +++ b/include/linux/objtool.h >> @@ -31,7 +31,9 @@ >> >> #ifdef CONFIG_OBJTOOL >> >> +#ifndef CONFIG_ARM64 >> #include <asm/asm.h> >> +#endif >> >> #ifndef __ASSEMBLY__ >> >> diff --git a/scripts/Makefile b/scripts/Makefile >> index 1575af84d557..df3e4d90f195 100644 >> --- a/scripts/Makefile >> +++ b/scripts/Makefile >> @@ -23,8 +23,10 @@ HOSTLDLIBS_sign-file = $(shell $(HOSTPKG_CONFIG) >> --libs libcrypto 2> /dev/null | >> ifdef CONFIG_UNWINDER_ORC >> ifeq ($(ARCH),x86_64) >> ARCH := x86 >> -endif >> HOSTCFLAGS_sorttable.o += -I$(srctree)/tools/arch/x86/include >> +else >> +HOSTCFLAGS_sorttable.o += -I$(srctree)/tools/arch/$(ARCH)/include >> +endif >> HOSTCFLAGS_sorttable.o += -DUNWINDER_ORC_ENABLED >> endif >> >> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib >> index 3aa384cec76b..d364871a1046 100644 >> --- a/scripts/Makefile.lib >> +++ b/scripts/Makefile.lib >> @@ -252,6 +252,13 @@ ifdef CONFIG_OBJTOOL >> >> objtool := $(objtree)/tools/objtool/objtool >> >> +ifdef CONFIG_FRAME_POINTER_VALIDATION >> + >> +objtool-args-$(CONFIG_STACK_VALIDATION) += >> --stackval >> +objtool-args-$(CONFIG_UNWINDER_ORC) += --orc >> + >> +else >> + >> objtool-args-$(CONFIG_HAVE_JUMP_LABEL_HACK) += >> --hacks=jump_label >> objtool-args-$(CONFIG_HAVE_NOINSTR_HACK) += --hacks=noinstr >> objtool-args-$(CONFIG_X86_KERNEL_IBT) += --ibt >> @@ -265,6 +272,8 @@ objtool-args-$(CONFIG_HAVE_STATIC_CALL_INLINE) >> += --static-call >> objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION) += >> --uaccess >> objtool-args-$(CONFIG_GCOV_KERNEL) += >> --no-unreachable >> >> +endif >> + >> objtool-args = $(objtool-args-y) \ >> $(if $(delay-objtool), --link) \ >> $(if $(part-of-module), --module) >> diff --git a/tools/include/linux/objtool.h b/tools/include/linux/objtool.h >> index dcbd365944f6..c980522190f7 100644 >> --- a/tools/include/linux/objtool.h >> +++ b/tools/include/linux/objtool.h >> @@ -31,7 +31,9 @@ >> >> #ifdef CONFIG_OBJTOOL >> >> +#ifndef CONFIG_ARM64 >> #include <asm/asm.h> >> +#endif >> >> #ifndef __ASSEMBLY__ >> >> -- >> 2.25.1 >> >> >> _______________________________________________ >> linux-arm-kernel mailing list >> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
