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[PATCH v8 0/8] ftrace with regs + live patching for ppc64 LE (ABI v2)

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  [PATCH v8 0/8] ftrace with regs + live patching for ppc64 LE (ABI v2) Torsten Duwe <duwe@lst.de> - 2016-02-10 18:50 +0100
    [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Torsten Duwe <duwe@lst.de> - 2016-02-10 18:50 +0100
      Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Balbir Singh <bsingharora@gmail.com> - 2016-02-11 08:50 +0100
        Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> - 2016-02-11 09:50 +0100
          Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Balbir Singh <bsingharora@gmail.com> - 2016-02-11 10:40 +0100
            Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Murali Sampath <MSampath@alphion.com> - 2016-02-11 14:10 +0100
            Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Murali Sampath <MSampath@alphion.com> - 2016-02-11 14:10 +0100
        Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Torsten Duwe <duwe@lst.de> - 2016-02-11 09:50 +0100
          Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Balbir Singh <bsingharora@gmail.com> - 2016-02-11 10:40 +0100
          Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Michael Ellerman <mpe@ellerman.id.au> - 2016-02-15 11:30 +0100
            Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Jiri Kosina <jikos@kernel.org> - 2016-02-15 14:00 +0100
            Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Torsten Duwe <duwe@lst.de> - 2016-02-15 15:10 +0100
              Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Torsten Duwe <duwe@lst.de> - 2016-02-15 23:30 +0100
                Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Balbir Singh <bsingharora@gmail.com> - 2016-02-16 06:00 +0100
              Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Michael Ellerman <mpe@ellerman.id.au> - 2016-02-16 11:20 +0100
                Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables Torsten Duwe <duwe@lst.de> - 2016-02-16 11:40 +0100
    [PATCH v8 3/8] ppc use ftrace_modify_all_code default Torsten Duwe <duwe@lst.de> - 2016-02-10 18:50 +0100
    [PATCH v8 1/8] ppc64 (le): prepare for -mprofile-kernel Torsten Duwe <duwe@lst.de> - 2016-02-10 18:50 +0100
      Re: [PATCH v8 1/8] ppc64 (le): prepare for -mprofile-kernel Michael Ellerman <mpe@ellerman.id.au> - 2016-02-17 12:00 +0100
        Re: [PATCH v8 1/8] ppc64 (le): prepare for -mprofile-kernel Michael Ellerman <mpe@ellerman.id.au> - 2016-02-17 12:40 +0100
        Re: [PATCH v8 1/8] ppc64 (le): prepare for -mprofile-kernel Torsten Duwe <duwe@lst.de> - 2016-02-17 12:40 +0100
    [PATCH v8 6/8] Implement kernel live patching for ppc64le (ABIv2) Torsten Duwe <duwe@lst.de> - 2016-02-10 18:50 +0100
      Re: [PATCH v8 6/8] Implement kernel live patching for ppc64le  (ABIv2) Miroslav Benes <mbenes@suse.cz> - 2016-02-11 10:10 +0100
    Re: [PATCH v8 0/8] ftrace with regs + live patching for ppc64 LE  (ABI v2) Balbir Singh <bsingharora@gmail.com> - 2016-02-11 07:20 +0100
      Re: [PATCH v8 0/8] ftrace with regs + live patching for ppc64 LE  (ABI v2) Torsten Duwe <duwe@lst.de> - 2016-02-11 09:40 +0100

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#1336278 — Re: [PATCH v8 1/8] ppc64 (le): prepare for -mprofile-kernel

On Wed, Feb 17, 2016 at 09:55:40PM +1100, Michael Ellerman wrote:
> On Wed, 2016-02-10 at 17:21 +0100, Torsten Duwe wrote:
> 
> > --- a/arch/powerpc/kernel/module_64.c
> > +++ b/arch/powerpc/kernel/module_64.c
> > @@ -476,17 +474,44 @@ static unsigned long stub_for_addr(Elf64_Shdr *sechdrs,
> >  	return (unsigned long)&stubs[i];
> >  }
> >  
> > +#ifdef CC_USING_MPROFILE_KERNEL
> > +static int is_early_mcount_callsite(u32 *instruction)
> > +{
> > +	/* -mprofile-kernel sequence starting with
> > +	 * mflr r0 and maybe std r0, LRSAVE(r1).
> > +	 */
> > +	if ((instruction[-3] == PPC_INST_MFLR &&
> > +	     instruction[-2] == PPC_INST_STD_LR) ||
> > +	    instruction[-2] == PPC_INST_MFLR) {
> > +		/* Nothing to be done here, it's an _mcount
> > +		 * call location and r2 will have to be
> > +		 * restored in the _mcount function.
> > +		 */
> > +		return 1;
> > +	}
> > +	return 0;
> > +}
> 
> On a kernel built with the 2 instruction version this will fault when the
> function we're looking at is located at the beginning of a page. Because
> instruction[-3] goes off the front of the mapping.
> 
> We can probably fix that. But it's still a bit dicey.

Not necessarily. Now that it's a separate function, it can be nested a bit deeper,
so we don't take chances on compiler optimisation:

if (instruction[-2] == PPC_INST_STD_LR) /* where should R0 come from? there must be... */
  {
    if (instruction[-3] == PPC_INST_MFLR)
      return 1;
  }
else if (instruction[-2] == PPC_INST_MFLR)
    return 1;
return 0;

> I'm wondering if we want to just say we only support the 2 instruction version.
> Currently that means GCC 6 only, or a distro compiler with the backport of
> e95d0248dace. But we could also ask GCC to backport it to 4.9 and 5.
> 
> Thoughts?

IMHO that's a too weak reason for a too strong limitation. OTOH getting everyone
to use the 2 insn version sounds appealing...

Is e95d0248dace self-sufficient or does it depend on other improvements?

	Torsten

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#1331382 — [PATCH v8 6/8] Implement kernel live patching for ppc64le (ABIv2)

  * 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@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;
+}
+
+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 c063564..52c7a15 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -1202,6 +1202,9 @@ _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)
@@ -1218,7 +1221,10 @@ 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)
@@ -1231,6 +1237,27 @@ 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
@@ -1240,15 +1267,31 @@ _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..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;
+}
-- 
1.8.5.6

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#1331753 — Re: [PATCH v8 6/8] Implement kernel live patching for ppc64le (ABIv2)

On Wed, 10 Feb 2016, Torsten Duwe wrote:

> 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;
> +}
> +
> +extern int klp_write_module_reloc(struct module *mod, unsigned long type,
> +				   unsigned long loc, unsigned long value);

It would be better to make this one static inline and move 'return 
-ENOSYS;' here. Thus there would be no arch/powerpc/kernel/livepatch.c. 
See s390 code for reference.

> +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

Change the error to

#error Include linux/livepatch.h, not asm/livepatch.h

please. See 383bf44d1a8b ("livepatch: change the error message in 
asm/livepatch.h header files").

Thanks Torsten,
Miroslav

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#1331705 — Re: [PATCH v8 0/8] ftrace with regs + live patching for ppc64 LE (ABI v2)

On Wed, 2016-02-10 at 18:29 +0100, Torsten Duwe wrote:
> Changes since V7:
>   * drop "notrace" attribute for MMU-aiding functions
>     and their callees.
>   * merge "-mprofile-kernel"-stripping patches into one.
> 
> Changes since v6:
>   * include Petr's patch, on popular demand ;)
>   * move #ifdefs out of functions for readability;
>     introduce static helper functions instead.
>   * No more literal binary instructions in hex,
>     at least not added by this patch set.
>   * add compile time checker to detect the presence
>     of known-good -mprofile-kernel support.
>   * limit Kconfig / compile to the configurations really supported:
>     + (static) FTRACE with -pg
>     +  DYNAMIC_FTRACE with -pg with or without -mprofile-kernel
>        (depending on the compiler)
>     +  DYNAMIC_FTRACE_WITH_REGS only with -mprofile-kernel
>        (will error out if the compiler is broken)
> 
> Changes since v5:
>   * extra "std r0,LRSAVE(r1)" for gcc-6
>     This makes the code compiler-agnostic.
>   * Follow Petr Mladek's suggestion to avoid
>     redefinition of HAVE_LIVEPATCH
> 
> Changes since v4:
>   * change comment style in entry_64.S to C89
>     (nobody is using assembler syntax comments there).
>   * the bool function restore_r2 shouldn't return 2,
>     that's a little confusing.
>   * Test whether the compiler supports -mprofile-kernel
>     and only then define CC_USING_MPROFILE_KERNEL
>   * also make the return value of klp_check_compiler_support
>     depend on that.
> 
> 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.
> 
> Petr Mladek (1):
>   livepatch: Detect offset for the ftrace location during build
> 
> Torsten Duwe (7):
>   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: 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                        |   6 +
>  arch/powerpc/Makefile                       |  17 +++
>  arch/powerpc/gcc-mprofile-kernel-notrace.sh |  33 ++++++
>  arch/powerpc/include/asm/code-patching.h    |  24 ++++
>  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              | 169
> +++++++++++++++++++++++++++-
>  arch/powerpc/kernel/ftrace.c                | 129 ++++++++++++++++-----
>  arch/powerpc/kernel/livepatch.c             |  38 +++++++
>  arch/powerpc/kernel/module_64.c             |  56 ++++++++-
>  arch/powerpc/lib/Makefile                   |   4 +-
>  arch/s390/Kconfig                           |   1 +
>  kernel/livepatch/Makefile                   |  13 +++
>  kernel/livepatch/core.c                     |  12 +-
>  kernel/livepatch/ftrace-test.c              |   6 +
>  kernel/trace/Kconfig                        |   5 +
>  scripts/recordmcount.c                      |   6 +-
>  scripts/recordmcount.h                      |  17 ++-
>  19 files changed, 552 insertions(+), 47 deletions(-)
>  create mode 100755 arch/powerpc/gcc-mprofile-kernel-notrace.sh
>  create mode 100644 arch/powerpc/include/asm/livepatch.h
>  create mode 100644 arch/powerpc/kernel/livepatch.c
>  create mode 100644 kernel/livepatch/ftrace-test.c
> 

Quick question - I presume these apply on top of 4.5.0-rc2?

Balbir Singh.

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#1331732 — Re: [PATCH v8 0/8] ftrace with regs + live patching for ppc64 LE (ABI v2)

On Thu, Feb 11, 2016 at 05:18:23PM +1100, Balbir Singh wrote:
> 
> Quick question - I presume these apply on top of 4.5.0-rc2?

Yes.
	Torsten

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