Re: [PATCH v4 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2)

2015-12-03 Thread Petr Mladek 
On Wed 2015-11-25 17:53:17, Torsten Duwe wrote:
> Torsten Duwe (9):
>   ppc64 (le): prepare for -mprofile-kernel
>   ppc64le FTRACE_WITH_REGS implementation
>   ppc use ftrace_modify_all_code default
>   ppc64 ftrace_with_regs configuration variables
>   ppc64 ftrace_with_regs: spare early boot and low level
>   ppc64 ftrace: disable profiling for some functions
>   ppc64 ftrace: disable profiling for some files
>   Implement kernel live patching for ppc64le (ABIv2)
>   Enable LIVEPATCH to be configured on ppc64le and add livepatch.o if it
> is selected.

I had to add the patch below to get LivePatching working.

I tested it the following way:

# livepatching sample
CONFIG_SAMPLES=y
CONFIG_SAMPLE_LIVEPATCH=m

# booted the compiled kernel and printed the default cmdline
$> cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-4.4.0-rc3-11-default+ root=UUID=...

# loaded the patch and printed the patch cmdline
$> modprobe livepatch-sample
$> cat /proc/cmdline
this has been live patched

# tried to disable and enable the patch
$> echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled
$> cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-4.4.0-rc3-11-default+ root=UUID=...
$> echo 1 > /sys/kernel/livepatch/livepatch_sample/enabled
$> cat /proc/cmdline
this has been live patched

# also checked messages
$> dmesg | tail -n 4
[   33.673057] livepatch: tainting kernel with TAINT_LIVEPATCH
[   33.673068] livepatch: enabling patch 'livepatch_sample'
[ 1997.098257] livepatch: disabling patch 'livepatch_sample'
[ 2079.696277] livepatch: enabling patch 'livepatch_sample'


Here is the patch:

From 7eb6f9453c81a996b0f5ffcb8725facadd9ec718 Mon Sep 17 00:00:00 2001
From: Petr Mladek 
Date: Thu, 3 Dec 2015 13:28:19 +0100
Subject: [PATCH] livepatch: Support ftrace location with an offset

ftrace_set_filter_ip() function requires the exact ftrace location
as a parameter. It is the same as the function address on x86 and s390.
But it is after the TOC load and LR save on powerpc.

This patch adds klp_ftrace_location() arch-specific function that
will compute the ftrace location from the function address.

I thought about handling this with a constant (define) but I
am not sure if it always would be a constant. I also thought
about a weak function. But this seems to be a good compromise.
We are ready for complications and the compiler still might
optimize it.

I made it livepatch-specific to keep it simple. Ftrace supports
more locations of the handler, e.g. Mcount on x86. But livepatching
does not support most of them. Also ftrace does not know the offset
easily because it gets the ftrace locations from __mcount_loc
object section.

Signed-off-by: Petr Mladek 
---
 arch/powerpc/include/asm/livepatch.h | 10 ++
 arch/s390/include/asm/livepatch.h|  9 +
 arch/x86/include/asm/livepatch.h | 10 ++
 kernel/livepatch/core.c  | 10 +++---
 4 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/livepatch.h 
b/arch/powerpc/include/asm/livepatch.h
index 3200c1152122..aa7e15dae58c 100644
--- a/arch/powerpc/include/asm/livepatch.h
+++ b/arch/powerpc/include/asm/livepatch.h
@@ -34,6 +34,16 @@ static inline int klp_check_compiler_support(void)
 extern int klp_write_module_reloc(struct module *mod, unsigned long type,
   unsigned long loc, unsigned long value);
 
+/*
+ * LivePatching works on PPC only when the kernel is compiled with
+ * -mprofile-kernel. The ftrace handler is called after the TOC load
+ * and LR save (16 bytes).
+ */
+static inline unsigned long klp_ftrace_location(unsigned long faddr)
+{
+   return faddr + 16;
+}
+
 static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
 {
regs->nip = ip;
diff --git a/arch/s390/include/asm/livepatch.h 
b/arch/s390/include/asm/livepatch.h
index 7aa799134a11..b853a1e48d04 100644
--- a/arch/s390/include/asm/livepatch.h
+++ b/arch/s390/include/asm/livepatch.h
@@ -32,6 +32,15 @@ static inline int klp_write_module_reloc(struct module *mod, 
unsigned long
return -ENOSYS;
 }
 
+/*
+ * LivePatching works only when the ftrace handler is called from the first
+ * instruction of the patched function on s390.
+ */
+static inline unsigned long klp_ftrace_location(unsigned long faddr)
+{
+   return faddr;
+}
+
 static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
 {
regs->psw.addr = ip;
diff --git a/arch/x86/include/asm/livepatch.h b/arch/x86/include/asm/livepatch.h
index 19c099afa861..9a8c84d3fae2 100644
--- a/arch/x86/include/asm/livepatch.h
+++ b/arch/x86/include/asm/livepatch.h
@@ -36,6 +36,16 @@ static inline int klp_check_compiler_support(void)
 int klp_write_module_reloc(struct module *mod, unsigned long type,
   unsigned long loc, unsigned long value);
 
+
+/*
+ * LivePatching works only when ftrace uses fentry on x86. Therefore
+ * the ftrace location is the same as

[PATCH v4 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2)

2015-11-25 Thread Torsten Duwe 
Major changes since v3:
  * the graph tracer works now.
It turned out the stack frame it tried to manipulate does not
exist at that point.
  * changes only needed in order to support -mprofile-kernel are now
in a separate patch, prepended.
  * Kconfig cleanup so this is only selectable on ppc64le.

Torsten Duwe (9):
  ppc64 (le): prepare for -mprofile-kernel
  ppc64le FTRACE_WITH_REGS implementation
  ppc use ftrace_modify_all_code default
  ppc64 ftrace_with_regs configuration variables
  ppc64 ftrace_with_regs: spare early boot and low level
  ppc64 ftrace: disable profiling for some functions
  ppc64 ftrace: disable profiling for some files
  Implement kernel live patching for ppc64le (ABIv2)
  Enable LIVEPATCH to be configured on ppc64le and add livepatch.o if it
is selected.

 arch/powerpc/Kconfig |   7 ++
 arch/powerpc/Makefile|   7 ++
 arch/powerpc/include/asm/ftrace.h|   5 ++
 arch/powerpc/include/asm/livepatch.h |  45 ++
 arch/powerpc/kernel/Makefile |  13 +--
 arch/powerpc/kernel/entry_64.S   | 164 ++-
 arch/powerpc/kernel/ftrace.c |  88 ++-
 arch/powerpc/kernel/livepatch.c  |  38 
 arch/powerpc/kernel/module_64.c  |  38 +++-
 arch/powerpc/kernel/process.c|   2 +-
 arch/powerpc/lib/Makefile|   4 +-
 arch/powerpc/mm/fault.c  |   2 +-
 arch/powerpc/mm/hash_utils_64.c  |  18 ++--
 arch/powerpc/mm/hugetlbpage-hash64.c |   2 +-
 arch/powerpc/mm/hugetlbpage.c|   4 +-
 arch/powerpc/mm/mem.c|   2 +-
 arch/powerpc/mm/pgtable_64.c |   2 +-
 arch/powerpc/mm/slb.c|   6 +-
 arch/powerpc/mm/slice.c  |   8 +-
 kernel/trace/Kconfig |   5 ++
 20 files changed, 406 insertions(+), 54 deletions(-)
 create mode 100644 arch/powerpc/include/asm/livepatch.h
 create mode 100644 arch/powerpc/kernel/livepatch.c

-- 
1.8.5.6

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