On Tue, 6 Dec 2016, Abel Vesa wrote: > klp_get_ftrace_location is used by ftrace to get the entry for a > specific function from the mcount list. klp_arch_set_pc is used > to set the pc from the regs passed as an argument to the > ftrace_ops_no_ops function to the starting address of the patched > function. klp_write_module_reloc is not doing anything at this > moment. > > Signed-off-by: Abel Vesa <[email protected]> > --- > MAINTAINERS | 3 +++ > arch/arm/include/asm/livepatch.h | 46 > ++++++++++++++++++++++++++++++++++++++++ > arch/arm/kernel/livepatch.c | 43 +++++++++++++++++++++++++++++++++++++ > 3 files changed, 92 insertions(+) > create mode 100644 arch/arm/include/asm/livepatch.h > create mode 100644 arch/arm/kernel/livepatch.c > > diff --git a/MAINTAINERS b/MAINTAINERS > index bd182a1..d43b790 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -7466,12 +7466,15 @@ M: Josh Poimboeuf <[email protected]> > M: Jessica Yu <[email protected]> > M: Jiri Kosina <[email protected]> > M: Miroslav Benes <[email protected]> > +M: Abel Vesa <[email protected]> > R: Petr Mladek <[email protected]> > S: Maintained > F: kernel/livepatch/ > F: include/linux/livepatch.h > F: arch/x86/include/asm/livepatch.h > F: arch/x86/kernel/livepatch.c > +F: arch/arm/include/asm/livepatch.h > +F: arch/arm/kernel/livepatch.c > F: Documentation/livepatch/ > F: Documentation/ABI/testing/sysfs-kernel-livepatch > F: samples/livepatch/
Thanks for the offer but I think we manage quite well ;) > diff --git a/arch/arm/include/asm/livepatch.h > b/arch/arm/include/asm/livepatch.h > new file mode 100644 > index 0000000..d4e3ff0 > --- /dev/null > +++ b/arch/arm/include/asm/livepatch.h > @@ -0,0 +1,46 @@ > +/* > + * livepatch.h - arm specific Kernel Live Patching Core > + * > + * Copyright (C) 2016 Abel Vesa <[email protected]> > + * > + * 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_ARM_LIVEPATCH_H > +#define _ASM_ARM_LIVEPATCH_H > + > +#include <asm/setup.h> > +#include <linux/module.h> > +#include <linux/ftrace.h> > + > +static inline int klp_check_compiler_support(void) > +{ > + return 0; > +} > + > +int klp_write_module_reloc(struct module *mod, unsigned long type, > + unsigned long loc, unsigned long value); This is not needed. See below. > + > +static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip) > +{ > + regs->uregs[15] = ip; > +} > + > +#define klp_get_ftrace_location klp_get_ftrace_location > +static inline unsigned long klp_get_ftrace_location(unsigned long faddr) > +{ > + return ftrace_location_range(faddr, faddr + 24); Comment here about +24 would be great. See similar in powerpc header file. > +} > + > +#endif /* _ASM_ARM_LIVEPATCH_H */ > diff --git a/arch/arm/kernel/livepatch.c b/arch/arm/kernel/livepatch.c > new file mode 100644 > index 0000000..0656cd6 > --- /dev/null > +++ b/arch/arm/kernel/livepatch.c > @@ -0,0 +1,43 @@ > +/* > + * livepatch.c - arm specific Kernel Live Patching Core > + * > + * Copyright (C) 2016 Abel Vesa <[email protected]> > + * > + * 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 <linux/uaccess.h> > +#include <linux/ftrace.h> > +#include <asm/elf.h> > +#include <asm/livepatch.h> > +#include <asm/insn.h> > +#include <asm/ftrace.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) > +{ > + /* Not implemented yet */ > + return 0; > +} This whole file is not needed. Livepatching uses kernel's internal apply_relocate_add() for dealing with relocations. The only thing you need to do is to make sure that all needed arch-specific info is preserved during a module loading. Specifically mod_arch_specific structure needs to be examined in this respect. See commit f31e0960f395 ("module: s390: keep mod_arch_specific for livepatch modules") for s390 case. But apply_relocate_add() is not implemented on arm yet. I guess it would nice to have it... otherwise we could get to an unpleasant situation. Livepatch module can rely on its livepatching relocations (that is, there are some). apply_relocate_add() returns 0 on arm, so everything seems to be nice and then boom some time later. The question is what happens with normal modules. There are no SHT_RELA records probably. Miroslav
