Changelog: 1. Implement review comments by Michael 2. The previous version compared _NIP from the wrong location to check for whether we are going to a patched location This applies on top of the patches posted by Michael https://patchwork.ozlabs.org/patch/589791/ It enables livepatching. This takes patch 6/8 and 7/8 of v8 as the base. Removes the extra strict check in gcc-profile-kernel-notrace.sh and adds logic for checking offsets in livepatch. The patch for HAVE_C_RECORDMCOUNT is not required and not used here. Depending on whether or not a TOC is generated, the offset for _mcount can be +16,+12,+8,+4. The changes are such that the offset checks are specific to powerpc. TODOs 1. Build a version with offsets removed and rebuild ftrace_location() sort of functionality 2. Make livepatching experimental on powerpc Comments? Testing? I tested the sample in the livepatch directory References 1. https://patchwork.ozlabs.org/patch/581521/ 2. https://patchwork.ozlabs.org/patch/587464/ Signed-off-by: Torsten Duwe <duwe@xxxxxxx> Signed-off-by: Balbir Singh <bsingharora@xxxxxxxxx> --- arch/powerpc/Kconfig | 3 ++ arch/powerpc/include/asm/livepatch.h | 41 +++++++++++++++++++++++++++ arch/powerpc/kernel/Makefile | 1 + arch/powerpc/kernel/entry_64.S | 50 +++++++++++++++++++++++++++++++++ arch/powerpc/kernel/kgdb.c | 4 +++ arch/powerpc/kernel/livepatch.c | 54 ++++++++++++++++++++++++++++++++++++ include/linux/livepatch.h | 2 ++ kernel/livepatch/core.c | 12 ++++++-- 8 files changed, 164 insertions(+), 3 deletions(-) create mode 100644 arch/powerpc/include/asm/livepatch.h create mode 100644 arch/powerpc/kernel/livepatch.c diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 792e169..8278e5e 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -159,6 +159,7 @@ config PPC select ARCH_HAS_DEVMEM_IS_ALLOWED select HAVE_ARCH_SECCOMP_FILTER select ARCH_HAS_UBSAN_SANITIZE_ALL + select HAVE_LIVEPATCH if HAVE_DYNAMIC_FTRACE_WITH_REGS config GENERIC_CSUM def_bool CPU_LITTLE_ENDIAN @@ -1109,3 +1110,5 @@ config PPC_LIB_RHEAP bool source "arch/powerpc/kvm/Kconfig" + +source "kernel/livepatch/Kconfig" diff --git a/arch/powerpc/include/asm/livepatch.h b/arch/powerpc/include/asm/livepatch.h new file mode 100644 index 0000000..9ecd879 --- /dev/null +++ b/arch/powerpc/include/asm/livepatch.h @@ -0,0 +1,41 @@ +/* + * livepatch.h - powerpc-specific Kernel Live Patching Core + * + * Copyright (C) 2015 SUSE + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ +#ifndef _ASM_POWERPC64_LIVEPATCH_H +#define _ASM_POWERPC64_LIVEPATCH_H + +#include <linux/module.h> +#include <linux/ftrace.h> + +#ifdef CONFIG_LIVEPATCH + +static inline int klp_check_compiler_support(void) +{ + return 0; +} + +extern int klp_write_module_reloc(struct module *mod, unsigned long type, + unsigned long loc, unsigned long value); + +static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip) +{ + regs->nip = ip; +} + +#endif /* CONFIG_LIVEPATCH */ +#endif /* _ASM_POWERPC64_LIVEPATCH_H */ diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index 2da380f..b767e14 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -119,6 +119,7 @@ obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.o obj-$(CONFIG_TRACING) += trace_clock.o +obj-$(CONFIG_LIVEPATCH) += livepatch.o ifneq ($(CONFIG_PPC_INDIRECT_PIO),y) obj-y += iomap.o diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index ec7f8aa..2d5333c 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -1224,6 +1224,9 @@ _GLOBAL(ftrace_caller) addi r3,r3,function_trace_op@toc@l ld r5,0(r3) +#ifdef CONFIG_LIVEPATCH + mr r14,r7 /* remember old NIP */ +#endif /* Calculate ip from nip-4 into r3 for call below */ subi r3, r7, MCOUNT_INSN_SIZE @@ -1248,6 +1251,9 @@ ftrace_call: /* Load ctr with the possibly modified NIP */ ld r3, _NIP(r1) mtctr r3 +#ifdef CONFIG_LIVEPATCH + cmpd r14,r3 /* has NIP been altered? */ +#endif /* Restore gprs */ REST_8GPRS(0,r1) @@ -1265,6 +1271,31 @@ ftrace_call: ld r0, LRSAVE(r1) mtlr r0 +#ifdef CONFIG_LIVEPATCH + beq+ 4f /* likely(old_NIP == new_NIP) */ + /* + * For a local call, restore this TOC after calling the patch function. + * For a global call, it does not matter what we restore here, + * since the global caller does its own restore right afterwards, + * anyway. Just insert a klp_return_helper frame in any case, + * so a patch function can always count on the changed stack offsets. + * The patch introduces a frame such that from the patched function + * we return back to klp_return helper. For ABI compliance r12, + * lr and LRSAVE(r1) contain the address of klp_return_helper. + * We loaded ctr with the address of the patched function earlier + */ + stdu r1, -32(r1) /* open new mini stack frame */ + std r2, 24(r1) /* save TOC now, unconditionally. */ + bl 5f +5: mflr r12 + addi r12, r12, (klp_return_helper + 4 - .)@l + std r12, LRSAVE(r1) + mtlr r12 + mfctr r12 /* allow for TOC calculation in newfunc */ + bctr +4: +#endif + #ifdef CONFIG_FUNCTION_GRAPH_TRACER stdu r1, -112(r1) .globl ftrace_graph_call @@ -1281,6 +1312,25 @@ _GLOBAL(ftrace_graph_stub) _GLOBAL(ftrace_stub) blr +#ifdef CONFIG_LIVEPATCH +/* Helper function for local calls that are becoming global + * due to live patching. + * We can't simply patch the NOP after the original call, + * because, depending on the consistency model, some kernel + * threads may still have called the original, local function + * *without* saving their TOC in the respective stack frame slot, + * so the decision is made per-thread during function return by + * maybe inserting a klp_return_helper frame or not. +*/ +klp_return_helper: + ld r2, 24(r1) /* restore TOC (saved by ftrace_caller) */ + addi r1, r1, 32 /* destroy mini stack frame */ + ld r0, LRSAVE(r1) /* get the real return address */ + mtlr r0 + blr +#endif + + #else _GLOBAL_TOC(_mcount) /* Taken from output of objdump from lib64/glibc */ diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c index e77c3cc..dbf0981 100644 --- a/arch/powerpc/kernel/kgdb.c +++ b/arch/powerpc/kernel/kgdb.c @@ -445,7 +445,11 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code, * Global data */ struct kgdb_arch arch_kgdb_ops = { +#ifdef __LITTLE_ENDIAN__ + .gdb_bpt_instr = {0x08, 0x10, 0x82, 0x7d}, +#else .gdb_bpt_instr = {0x7d, 0x82, 0x10, 0x08}, +#endif }; static int kgdb_not_implemented(struct pt_regs *regs) diff --git a/arch/powerpc/kernel/livepatch.c b/arch/powerpc/kernel/livepatch.c new file mode 100644 index 0000000..fd8802b --- /dev/null +++ b/arch/powerpc/kernel/livepatch.c @@ -0,0 +1,54 @@ +/* + * livepatch.c - powerpc-specific Kernel Live Patching Core + * + * Copyright (C) 2015 SUSE + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ +#include <linux/module.h> +#include <asm/livepatch.h> + +/** + * klp_write_module_reloc() - write a relocation in a module + * @mod: module in which the section to be modified is found + * @type: ELF relocation type (see asm/elf.h) + * @loc: address that the relocation should be written to + * @value: relocation value (sym address + addend) + * + * This function writes a relocation to the specified location for + * a particular module. + */ +int klp_write_module_reloc(struct module *mod, unsigned long type, + unsigned long loc, unsigned long value) +{ + /* This requires infrastructure changes; we need the loadinfos. */ + pr_err("klp_write_module_reloc not yet supported\n"); + return -ENOSYS; +} + +int klp_matchaddr(struct ftrace_ops *ops, unsigned long ip, + int remove, int reset) +{ + int offsets[] = {4, 8, 12, 16}; + int i; + int ret = 1; + + for (i = 0; i < ARRAY_SIZE(offsets); i++) { + ret = ftrace_set_filter_ip(ops, ip+offsets[i], remove, reset); + if (!ret) + break; + } + return ret; +} + diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index a882865..29cea3a 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -134,6 +134,8 @@ int klp_unregister_patch(struct klp_patch *); int klp_enable_patch(struct klp_patch *); int klp_disable_patch(struct klp_patch *); +int klp_matchaddr(struct ftrace_ops *ops, unsigned long ip, + int remove, int reset); #endif /* CONFIG_LIVEPATCH */ #endif /* _LINUX_LIVEPATCH_H_ */ diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index bc2c85c..c484a4b 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -298,6 +298,12 @@ unlock: rcu_read_unlock(); } +int __weak klp_matchaddr(struct ftrace_ops *ops, unsigned long ip, + int remove, int reset) +{ + return ftrace_set_filter_ip(ops, ip, remove, reset); +} + static void klp_disable_func(struct klp_func *func) { struct klp_ops *ops; @@ -313,7 +319,7 @@ static void klp_disable_func(struct klp_func *func) if (list_is_singular(&ops->func_stack)) { WARN_ON(unregister_ftrace_function(&ops->fops)); - WARN_ON(ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0)); + WARN_ON(klp_matchaddr(&ops->fops, func->old_addr, 1, 0)); list_del_rcu(&func->stack_node); list_del(&ops->node); @@ -352,7 +358,7 @@ static int klp_enable_func(struct klp_func *func) INIT_LIST_HEAD(&ops->func_stack); list_add_rcu(&func->stack_node, &ops->func_stack); - ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0); + ret = klp_matchaddr(&ops->fops, func->old_addr, 0, 0); if (ret) { pr_err("failed to set ftrace filter for function '%s' (%d)\n", func->old_name, ret); @@ -363,7 +369,7 @@ static int klp_enable_func(struct klp_func *func) if (ret) { pr_err("failed to register ftrace handler for function '%s' (%d)\n", func->old_name, ret); - ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0); + klp_matchaddr(&ops->fops, func->old_addr, 1, 0); goto err; } -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
