[PATCH v6 8/9] Implement kernel live patching for ppc64le (ABIv2)
Denis Kirjanov
kda at linux-powerpc.org
Wed Feb 3 00:46:27 AEDT 2016
On 1/25/16, Torsten Duwe <duwe at lst.de> wrote:
> * create the appropriate files+functions
> arch/powerpc/include/asm/livepatch.h
> klp_check_compiler_support,
> klp_arch_set_pc
> arch/powerpc/kernel/livepatch.c with a stub for
> klp_write_module_reloc
> This is architecture-independent work in progress.
> * introduce a fixup in arch/powerpc/kernel/entry_64.S
> for local calls that are becoming global due to live patching.
> And of course do the main KLP thing: return to a maybe different
> address, possibly altered by the live patching ftrace op.
>
> Signed-off-by: Torsten Duwe <duwe at suse.de>
> ---
> arch/powerpc/include/asm/livepatch.h | 45 +++++++++++++++++++++++++++++++
> arch/powerpc/kernel/entry_64.S | 51
> +++++++++++++++++++++++++++++++++---
> arch/powerpc/kernel/livepatch.c | 38 +++++++++++++++++++++++++++
> 3 files changed, 130 insertions(+), 4 deletions(-)
> create mode 100644 arch/powerpc/include/asm/livepatch.h
> create mode 100644 arch/powerpc/kernel/livepatch.c
>
> diff --git a/arch/powerpc/include/asm/livepatch.h
> b/arch/powerpc/include/asm/livepatch.h
> new file mode 100644
> index 0000000..44e8a2d
> --- /dev/null
> +++ b/arch/powerpc/include/asm/livepatch.h
> @@ -0,0 +1,45 @@
> +/*
> + * 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)
> +{
> +#if !defined(_CALL_ELF) || _CALL_ELF != 2 ||
> !defined(CC_USING_MPROFILE_KERNEL)
> + return 1;
> +#endif
> + return 0;
> +}
This function can be boolean.
> +
> +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;
> +}
> +#else
> +#error Live patching support is disabled; check CONFIG_LIVEPATCH
> +#endif
> +
> +#endif /* _ASM_POWERPC64_LIVEPATCH_H */
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index 9e98aa1..f6e3ee7 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -1267,6 +1267,9 @@ _GLOBAL(ftrace_caller)
> mflr r3
> std r3, _NIP(r1)
> std r3, 16(r1)
> +#ifdef CONFIG_LIVEPATCH
> + mr r14,r3 /* remember old NIP */
> +#endif
> subi r3, r3, MCOUNT_INSN_SIZE
> mfmsr r4
> std r4, _MSR(r1)
> @@ -1283,7 +1286,10 @@ ftrace_call:
> nop
>
> ld r3, _NIP(r1)
> - mtlr r3
> + mtctr r3 /* prepare to jump there */
> +#ifdef CONFIG_LIVEPATCH
> + cmpd r14,r3 /* has NIP been altered? */
> +#endif
>
> REST_8GPRS(0,r1)
> REST_8GPRS(8,r1)
> @@ -1296,6 +1302,27 @@ ftrace_call:
> mtlr r12
> mr r2,r0 /* restore callee's TOC */
>
> +#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.
> + */
> + stdu r1,-32(r1) /* open new mini stack frame */
> + std r0,24(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
> @@ -1305,15 +1332,31 @@ _GLOBAL(ftrace_graph_stub)
> addi r1, r1, 112
> #endif
>
> - mflr r0 /* move this LR to CTR */
> - mtctr r0
> -
> ld r0,LRSAVE(r1) /* restore callee's lr at _mcount site */
> mtlr r0
> bctr /* jump after _mcount site */
> #endif /* CC_USING_MPROFILE_KERNEL */
> _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/livepatch.c
> b/arch/powerpc/kernel/livepatch.c
> new file mode 100644
> index 0000000..564eafa
> --- /dev/null
> +++ b/arch/powerpc/kernel/livepatch.c
> @@ -0,0 +1,38 @@
> +/*
> + * 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("lpc_write_module_reloc not yet supported\n");
> + return -ENOSYS;
> +}
> --
> 1.8.5.6
>
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