[RFC][PATCH] Enable livepatching for powerpc
Balbir Singh
bsingharora at gmail.com
Thu Feb 25 23:11:45 AEDT 2016
This applies on top of the patches posted by Michael today
Enable 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 or +8. The changes are such that the
offset checks are specific to 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 at suse.de>
Signed-off-by: Balbir Singh <bsingharora at gmail.com>
---
arch/powerpc/Kconfig | 3 ++
arch/powerpc/gcc-mprofile-kernel-notrace.sh | 7 ----
arch/powerpc/include/asm/livepatch.h | 61 +++++++++++++++++++++++++++++
arch/powerpc/kernel/Makefile | 1 +
arch/powerpc/kernel/entry_64.S | 46 ++++++++++++++++++++++
arch/powerpc/kernel/livepatch.c | 38 ++++++++++++++++++
include/linux/livepatch.h | 13 ++++++
kernel/livepatch/core.c | 4 +-
8 files changed, 164 insertions(+), 9 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 9f72565..72e46b0 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -160,6 +160,7 @@ config PPC
select ARCH_HAS_DEVMEM_IS_ALLOWED
select HAVE_ARCH_SECCOMP_FILTER
select ARCH_HAS_UBSAN_SANITIZE_ALL
+ select HAVE_LIVEPATCH if PPC64 && CPU_LITTLE_ENDIAN
config GENERIC_CSUM
def_bool CPU_LITTLE_ENDIAN
@@ -1093,3 +1094,5 @@ config PPC_LIB_RHEAP
bool
source "arch/powerpc/kvm/Kconfig"
+
+source "kernel/livepatch/Kconfig"
diff --git a/arch/powerpc/gcc-mprofile-kernel-notrace.sh b/arch/powerpc/gcc-mprofile-kernel-notrace.sh
index 68d6482..6dafff6 100755
--- a/arch/powerpc/gcc-mprofile-kernel-notrace.sh
+++ b/arch/powerpc/gcc-mprofile-kernel-notrace.sh
@@ -12,12 +12,6 @@ echo "int func() { return 0; }" | \
trace_result=$?
-echo "int func() { return 0; }" | \
- $* -S -x c -O2 -p -mprofile-kernel - -o - 2> /dev/null | \
- sed -n -e '/func:/,/bl _mcount/p' | grep -q TOC
-
-leaf_toc_result=$?
-
/bin/echo -e "#include <linux/compiler.h>\nnotrace int func() { return 0; }" | \
$* -S -x c -O2 -p -mprofile-kernel - -o - 2> /dev/null | \
grep -q "mcount"
@@ -25,7 +19,6 @@ leaf_toc_result=$?
notrace_result=$?
if [ "$trace_result" -eq "0" -a \
- "$leaf_toc_result" -eq "0" -a \
"$notrace_result" -eq "1" ]; then
echo y
else
diff --git a/arch/powerpc/include/asm/livepatch.h b/arch/powerpc/include/asm/livepatch.h
new file mode 100644
index 0000000..6abb69c
--- /dev/null
+++ b/arch/powerpc/include/asm/livepatch.h
@@ -0,0 +1,61 @@
+/*
+ * 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;
+}
+
+#define ARCH_HAVE_KLP_MATCHADDR
+static inline int klp_matchaddr(struct ftrace_ops *ops, unsigned long ip,
+ int remove, int reset)
+{
+ int offsets[] = {8, 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;
+}
+
+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/Makefile b/arch/powerpc/kernel/Makefile
index 44667fd..405efce 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 f347f50..853717f 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -1225,6 +1225,9 @@ _GLOBAL(ftrace_caller)
/* Calculate ip from nip-4 into r3 for call below */
subi r3, r7, MCOUNT_INSN_SIZE
+#ifdef CONFIG_LIVEPATCH
+ mr r14,r3 /* remember old NIP */
+#endif
/* Put the original return address in r4 as parent_ip */
mr r4, r0
@@ -1247,6 +1250,9 @@ 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)
@@ -1264,6 +1270,27 @@ 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.
+ */
+ 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
@@ -1279,6 +1306,25 @@ _GLOBAL(ftrace_graph_stub)
#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..cdd15f1
--- /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("klp_write_module_reloc not yet supported\n");
+ return -ENOSYS;
+}
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index a882865..e63a5b3 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -134,6 +134,19 @@ int klp_unregister_patch(struct klp_patch *);
int klp_enable_patch(struct klp_patch *);
int klp_disable_patch(struct klp_patch *);
+#ifndef ARCH_HAVE_KLP_MATCHADDR
+static inline int klp_matchaddr(struct ftrace_ops *ops, unsigned long ip,
+ int remove, int reset)
+{
+ return ftrace_set_filter_ip(ops, ip, remove, reset);
+}
+
+#else
+int klp_matchaddr(struct ftrace_ops *ops, unsigned long ip,
+ int remove, int reset);
+
+#endif
+
#endif /* CONFIG_LIVEPATCH */
#endif /* _LINUX_LIVEPATCH_H_ */
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index bc2c85c..6625b06 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -313,7 +313,7 @@ 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 +352,7 @@ 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);
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