[PATCH][v3] Enable livepatching on powerpc
Balbir Singh
bsingharora at gmail.com
Fri Mar 4 00:11:55 AEDT 2016
Changelog v3:
1. Moved -ENOSYS to -EINVAL in klp_write_module_reloc
2. Moved klp_matchaddr to use ftrace_location_range
Changelog v2:
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.
(See the reference [1] below) and adds logic for checking offset ranges
in livepatch with ftrace_location_range.
I tested the sample in the livepatch
References
1. https://patchwork.ozlabs.org/patch/581521/
Signed-off-by: Torsten Duwe <duwe at suse.de>
Signed-off-by: Balbir Singh <bsingharora at gmail.com>
---
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/livepatch.c | 54 ++++++++++++++++++++++++++++++++++++
include/linux/ftrace.h | 1 +
include/linux/livepatch.h | 2 ++
kernel/livepatch/core.c | 12 ++++++--
kernel/trace/ftrace.c | 2 +-
9 files changed, 162 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/Kconfig b/arch/powerpc/Kconfig
index df41537..1f4a24b 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
@@ -1110,3 +1111,5 @@ 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 at 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/livepatch.c b/arch/powerpc/kernel/livepatch.c
new file mode 100644
index 0000000..8c99e2d
--- /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 -EINVAL;
+}
+
+int klp_matchaddr(struct ftrace_ops *ops, unsigned long ip,
+ int remove, int reset)
+{
+ int ret = 1;
+ unsigned long correct_ip;
+
+ correct_ip = ftrace_location_range(ip, ip + 16);
+ if (!correct_ip)
+ goto done;
+
+ ret = ftrace_set_filter_ip(ops, correct_ip, remove, reset);
+done:
+ return ret;
+}
+
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index c2b340e..fb13cd3 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -455,6 +455,7 @@ int ftrace_update_record(struct dyn_ftrace *rec, int enable);
int ftrace_test_record(struct dyn_ftrace *rec, int enable);
void ftrace_run_stop_machine(int command);
unsigned long ftrace_location(unsigned long ip);
+unsigned long ftrace_location_range(unsigned long start, unsigned long end);
unsigned long ftrace_get_addr_new(struct dyn_ftrace *rec);
unsigned long ftrace_get_addr_curr(struct dyn_ftrace *rec);
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;
}
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 57a6eea..18b2969 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1533,7 +1533,7 @@ static int ftrace_cmp_recs(const void *a, const void *b)
return 0;
}
-static unsigned long ftrace_location_range(unsigned long start, unsigned long end)
+unsigned long ftrace_location_range(unsigned long start, unsigned long end)
{
struct ftrace_page *pg;
struct dyn_ftrace *rec;
--
2.5.0
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