[PATCH 0/2] powerpc: Fix livepatch module re-patching issue

[PATCH 0/2] powerpc: Fix livepatch module re-patching issue

[Josh Poimboeuf]

Fix a livepatch bug seen when reloading a patched module.

This is the powerpc counterpart to Song Liu's fix for a similar issue on
x86:

  https://lkml.kernel.org/lkml/20230121004945.697003-2-song@kernel.org

Josh Poimboeuf (2):
  powerpc/module_64: Improve restore_r2() return semantics
  powerpc/module_64: Fix "expected nop" error on module re-patching

 arch/powerpc/kernel/module_64.c | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

-- 
2.39.0

[PATCH 1/2] powerpc/module_64: Improve restore_r2() return semantics

[Josh Poimboeuf]

restore_r2() returns 1 on success, which is surprising for a non-boolean
function.  Change it to return 0 on success and -errno on error to match
kernel coding convention.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/powerpc/kernel/module_64.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 1096d6b3a62c..016e79bba531 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -504,7 +504,7 @@ static int restore_r2(const char *name, u32 *instruction, struct module *me)
 	u32 *prev_insn = instruction - 1;
 
 	if (is_mprofile_ftrace_call(name))
-		return 1;
+		return 0;
 
 	/*
 	 * Make sure the branch isn't a sibling call.  Sibling calls aren't
@@ -512,19 +512,16 @@ static int restore_r2(const char *name, u32 *instruction, struct module *me)
 	 * restore afterwards.
 	 */
 	if (!instr_is_relative_link_branch(ppc_inst(*prev_insn)))
-		return 1;
+		return 0;
 
 	if (*instruction != PPC_RAW_NOP()) {
 		pr_err("%s: Expected nop after call, got %08x at %pS\n",
 			me->name, *instruction, instruction);
-		return 0;
+		return -ENOEXEC;
 	}
 
 	/* ld r2,R2_STACK_OFFSET(r1) */
-	if (patch_instruction(instruction, ppc_inst(PPC_INST_LD_TOC)))
-		return 0;
-
-	return 1;
+	return patch_instruction(instruction, ppc_inst(PPC_INST_LD_TOC));
 }
 
 int apply_relocate_add(Elf64_Shdr *sechdrs,
@@ -648,8 +645,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
 						strtab + sym->st_name);
 				if (!value)
 					return -ENOENT;
-				if (!restore_r2(strtab + sym->st_name,
-							(u32 *)location + 1, me))
+				if (restore_r2(strtab + sym->st_name,
+					       (u32 *)location + 1, me))
 					return -ENOEXEC;
 			} else
 				value += local_entry_offset(sym);
-- 
2.39.0

[PATCH 2/2] powerpc/module_64: Fix "expected nop" error on module re-patching

[Josh Poimboeuf]

When a module with a livepatched function is unloaded and then reloaded,
klp attempts to dynamically re-patch it.  On ppc64, that fails with the
following error:

  module_64: livepatch_nfsd: Expected nop after call, got e8410018 at e_show+0x60/0x548 [livepatch_nfsd]
  livepatch: failed to initialize patch 'livepatch_nfsd' for module 'nfsd' (-8)
  livepatch: patch 'livepatch_nfsd' failed for module 'nfsd', refusing to load module 'nfsd'

The error happens because the restore r2 instruction had already
previously been written into the klp module's replacement function when
the original function was patched the first time.  So the instruction
wasn't a nop as expected.

When the restore r2 instruction has already been patched in, detect that
and skip the warning and the instruction write.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/powerpc/kernel/module_64.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 016e79bba531..bf1da99fff74 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -502,6 +502,7 @@ static unsigned long stub_for_addr(const Elf64_Shdr *sechdrs,
 static int restore_r2(const char *name, u32 *instruction, struct module *me)
 {
 	u32 *prev_insn = instruction - 1;
+	u32 insn_val = *instruction;
 
 	if (is_mprofile_ftrace_call(name))
 		return 0;
@@ -514,9 +515,18 @@ static int restore_r2(const char *name, u32 *instruction, struct module *me)
 	if (!instr_is_relative_link_branch(ppc_inst(*prev_insn)))
 		return 0;
 
-	if (*instruction != PPC_RAW_NOP()) {
+	/*
+	 * For livepatch, the restore r2 instruction might have already been
+	 * written previously, if the referenced symbol is in a previously
+	 * unloaded module which is now being loaded again.  In that case, skip
+	 * the warning and the instruction write.
+	 */
+	if (insn_val == PPC_INST_LD_TOC)
+		return 0;
+
+	if (insn_val != PPC_RAW_NOP()) {
 		pr_err("%s: Expected nop after call, got %08x at %pS\n",
-			me->name, *instruction, instruction);
+			me->name, insn_val, instruction);
 		return -ENOEXEC;
 	}
 
-- 
2.39.0

Re: [PATCH 1/2] powerpc/module_64: Improve restore_r2() return semantics

[Song Liu]

On Tue, Jan 24, 2023 at 7:38 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> restore_r2() returns 1 on success, which is surprising for a non-boolean
> function.  Change it to return 0 on success and -errno on error to match
> kernel coding convention.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Acked-by: Song Liu <song@kernel.org>

Re: [PATCH 2/2] powerpc/module_64: Fix "expected nop" error on module re-patching

[Song Liu]

On Tue, Jan 24, 2023 at 7:38 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> When a module with a livepatched function is unloaded and then reloaded,
> klp attempts to dynamically re-patch it.  On ppc64, that fails with the
> following error:
>
>   module_64: livepatch_nfsd: Expected nop after call, got e8410018 at e_show+0x60/0x548 [livepatch_nfsd]
>   livepatch: failed to initialize patch 'livepatch_nfsd' for module 'nfsd' (-8)
>   livepatch: patch 'livepatch_nfsd' failed for module 'nfsd', refusing to load module 'nfsd'
>
> The error happens because the restore r2 instruction had already
> previously been written into the klp module's replacement function when
> the original function was patched the first time.  So the instruction
> wasn't a nop as expected.
>
> When the restore r2 instruction has already been patched in, detect that
> and skip the warning and the instruction write.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> ---
>  arch/powerpc/kernel/module_64.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
> index 016e79bba531..bf1da99fff74 100644
> --- a/arch/powerpc/kernel/module_64.c
> +++ b/arch/powerpc/kernel/module_64.c
> @@ -502,6 +502,7 @@ static unsigned long stub_for_addr(const Elf64_Shdr *sechdrs,
>  static int restore_r2(const char *name, u32 *instruction, struct module *me)
>  {
>         u32 *prev_insn = instruction - 1;
> +       u32 insn_val = *instruction;
>
>         if (is_mprofile_ftrace_call(name))
>                 return 0;
> @@ -514,9 +515,18 @@ static int restore_r2(const char *name, u32 *instruction, struct module *me)
>         if (!instr_is_relative_link_branch(ppc_inst(*prev_insn)))
>                 return 0;
>
> -       if (*instruction != PPC_RAW_NOP()) {
> +       /*
> +        * For livepatch, the restore r2 instruction might have already been
> +        * written previously, if the referenced symbol is in a previously
> +        * unloaded module which is now being loaded again.  In that case, skip
> +        * the warning and the instruction write.
> +        */
> +       if (insn_val == PPC_INST_LD_TOC)
> +               return 0;

Do we need "sym->st_shndx == SHN_LIVEPATCH" here?

Thanks,
Song


> +
> +       if (insn_val != PPC_RAW_NOP()) {
>                 pr_err("%s: Expected nop after call, got %08x at %pS\n",
> -                       me->name, *instruction, instruction);
> +                       me->name, insn_val, instruction);
>                 return -ENOEXEC;
>         }
>
> --
> 2.39.0
>

Re: [PATCH 1/2] powerpc/module_64: Improve restore_r2() return semantics

[Petr Mladek]

On Tue 2023-01-24 19:38:04, Josh Poimboeuf wrote:
> restore_r2() returns 1 on success, which is surprising for a non-boolean
> function.  Change it to return 0 on success and -errno on error to match
> kernel coding convention.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Looks good:

Reviewed-by: Petr Mladek <pmladek@suse.com>

It is in the right direction. Just note that there are more functions
with the boolean semantic passed via int return value. But there
are also other functions already using the 0/-E* return values so
this is rather positive change.

Best Regards,
Petr

Re: [PATCH 2/2] powerpc/module_64: Fix "expected nop" error on module re-patching

[Petr Mladek]

On Tue 2023-01-24 19:38:05, Josh Poimboeuf wrote:
> When a module with a livepatched function is unloaded and then reloaded,
> klp attempts to dynamically re-patch it.  On ppc64, that fails with the
> following error:
> 
>   module_64: livepatch_nfsd: Expected nop after call, got e8410018 at e_show+0x60/0x548 [livepatch_nfsd]
>   livepatch: failed to initialize patch 'livepatch_nfsd' for module 'nfsd' (-8)
>   livepatch: patch 'livepatch_nfsd' failed for module 'nfsd', refusing to load module 'nfsd'
> 
> The error happens because the restore r2 instruction had already
> previously been written into the klp module's replacement function when
> the original function was patched the first time.  So the instruction
> wasn't a nop as expected.
> 
> When the restore r2 instruction has already been patched in, detect that
> and skip the warning and the instruction write.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

It seems that the function does what it says. And it seems to be the
only location where an instruction is checked before it is modified.
I am fine with this approach.

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr

Re: [PATCH 2/2] powerpc/module_64: Fix "expected nop" error on module re-patching

[Josh Poimboeuf]

On Tue, Jan 24, 2023 at 10:09:56PM -0800, Song Liu wrote:
> > @@ -514,9 +515,18 @@ static int restore_r2(const char *name, u32 *instruction, struct module *me)
> >         if (!instr_is_relative_link_branch(ppc_inst(*prev_insn)))
> >                 return 0;
> >
> > -       if (*instruction != PPC_RAW_NOP()) {
> > +       /*
> > +        * For livepatch, the restore r2 instruction might have already been
> > +        * written previously, if the referenced symbol is in a previously
> > +        * unloaded module which is now being loaded again.  In that case, skip
> > +        * the warning and the instruction write.
> > +        */
> > +       if (insn_val == PPC_INST_LD_TOC)
> > +               return 0;
> 
> Do we need "sym->st_shndx == SHN_LIVEPATCH" here?

My original patch had that check, but I dropped it for simplicity.

In the non-livepatch case, the condition should never be true, but it
doesn't hurt to check it anyway.

-- 
Josh

Re: [PATCH 2/2] powerpc/module_64: Fix "expected nop" error on module re-patching

[Song Liu]

On Wed, Jan 25, 2023 at 8:46 AM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> On Tue, Jan 24, 2023 at 10:09:56PM -0800, Song Liu wrote:
> > > @@ -514,9 +515,18 @@ static int restore_r2(const char *name, u32 *instruction, struct module *me)
> > >         if (!instr_is_relative_link_branch(ppc_inst(*prev_insn)))
> > >                 return 0;
> > >
> > > -       if (*instruction != PPC_RAW_NOP()) {
> > > +       /*
> > > +        * For livepatch, the restore r2 instruction might have already been
> > > +        * written previously, if the referenced symbol is in a previously
> > > +        * unloaded module which is now being loaded again.  In that case, skip
> > > +        * the warning and the instruction write.
> > > +        */
> > > +       if (insn_val == PPC_INST_LD_TOC)
> > > +               return 0;
> >
> > Do we need "sym->st_shndx == SHN_LIVEPATCH" here?
>
> My original patch had that check, but I dropped it for simplicity.
>
> In the non-livepatch case, the condition should never be true, but it
> doesn't hurt to check it anyway.

While this is the only place we use PPC_INST_LD_TOC, there is another
place we use "PPC_RAW_STD(_R2, _R1, R2_STACK_OFFSET)", which
is identical to PPC_INST_LD_TOC. So I am not quite sure whether this
happens for non-livepatch.

Thanks,
Song

Re: [PATCH 2/2] powerpc/module_64: Fix "expected nop" error on module re-patching

[Josh Poimboeuf]

On Wed, Jan 25, 2023 at 09:36:02AM -0800, Song Liu wrote:
> On Wed, Jan 25, 2023 at 8:46 AM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
> >
> > On Tue, Jan 24, 2023 at 10:09:56PM -0800, Song Liu wrote:
> > > > @@ -514,9 +515,18 @@ static int restore_r2(const char *name, u32 *instruction, struct module *me)
> > > >         if (!instr_is_relative_link_branch(ppc_inst(*prev_insn)))
> > > >                 return 0;
> > > >
> > > > -       if (*instruction != PPC_RAW_NOP()) {
> > > > +       /*
> > > > +        * For livepatch, the restore r2 instruction might have already been
> > > > +        * written previously, if the referenced symbol is in a previously
> > > > +        * unloaded module which is now being loaded again.  In that case, skip
> > > > +        * the warning and the instruction write.
> > > > +        */
> > > > +       if (insn_val == PPC_INST_LD_TOC)
> > > > +               return 0;
> > >
> > > Do we need "sym->st_shndx == SHN_LIVEPATCH" here?
> >
> > My original patch had that check, but I dropped it for simplicity.
> >
> > In the non-livepatch case, the condition should never be true, but it
> > doesn't hurt to check it anyway.
> 
> While this is the only place we use PPC_INST_LD_TOC, there is another
> place we use "PPC_RAW_STD(_R2, _R1, R2_STACK_OFFSET)", which
> is identical to PPC_INST_LD_TOC. So I am not quite sure whether this
> happens for non-livepatch.

It's not actually identical.  That's the "store r2 to the stack"
counterpart to the load in PPC_INST_LD_TOC, which loads r2 from the
stack.

For R_PPC_REL24 relocations, when calling a function which lives outside
the module, 24 bits isn't enough to encode the relative branch target
address.  So it has to save r2 (TOC pointer) to the stack, and branch to
a stub, which then branches to the external function.

When the external function returns execution to the instruction after
the original branch, that instruction needs to restore the TOC pointer
from the stack to r2.

The compiler knows this, and emits the instruction after the branch as a
NOP.  The module code replaces that NOP with a "restore r2 from the
stack".  That's what restore_r2() does.

Long story short, restore_r2() needs to ensure the instruction after the
branch restores r2 from the stack.  If that instruction is already
there, it doesn't need to do anything.

-- 
Josh

Re: [PATCH 2/2] powerpc/module_64: Fix "expected nop" error on module re-patching

[Song Liu]

On Wed, Jan 25, 2023 at 10:53 AM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> On Wed, Jan 25, 2023 at 09:36:02AM -0800, Song Liu wrote:
> > On Wed, Jan 25, 2023 at 8:46 AM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
> > >
> > > On Tue, Jan 24, 2023 at 10:09:56PM -0800, Song Liu wrote:
> > > > > @@ -514,9 +515,18 @@ static int restore_r2(const char *name, u32 *instruction, struct module *me)
> > > > >         if (!instr_is_relative_link_branch(ppc_inst(*prev_insn)))
> > > > >                 return 0;
> > > > >
> > > > > -       if (*instruction != PPC_RAW_NOP()) {
> > > > > +       /*
> > > > > +        * For livepatch, the restore r2 instruction might have already been
> > > > > +        * written previously, if the referenced symbol is in a previously
> > > > > +        * unloaded module which is now being loaded again.  In that case, skip
> > > > > +        * the warning and the instruction write.
> > > > > +        */
> > > > > +       if (insn_val == PPC_INST_LD_TOC)
> > > > > +               return 0;
> > > >
> > > > Do we need "sym->st_shndx == SHN_LIVEPATCH" here?
> > >
> > > My original patch had that check, but I dropped it for simplicity.
> > >
> > > In the non-livepatch case, the condition should never be true, but it
> > > doesn't hurt to check it anyway.
> >
> > While this is the only place we use PPC_INST_LD_TOC, there is another
> > place we use "PPC_RAW_STD(_R2, _R1, R2_STACK_OFFSET)", which
> > is identical to PPC_INST_LD_TOC. So I am not quite sure whether this
> > happens for non-livepatch.
>
> It's not actually identical.  That's the "store r2 to the stack"
> counterpart to the load in PPC_INST_LD_TOC, which loads r2 from the
> stack.

Ooops.. I misread the code.

>
> For R_PPC_REL24 relocations, when calling a function which lives outside
> the module, 24 bits isn't enough to encode the relative branch target
> address.  So it has to save r2 (TOC pointer) to the stack, and branch to
> a stub, which then branches to the external function.
>
> When the external function returns execution to the instruction after
> the original branch, that instruction needs to restore the TOC pointer
> from the stack to r2.
>
> The compiler knows this, and emits the instruction after the branch as a
> NOP.  The module code replaces that NOP with a "restore r2 from the
> stack".  That's what restore_r2() does.
>
> Long story short, restore_r2() needs to ensure the instruction after the
> branch restores r2 from the stack.  If that instruction is already
> there, it doesn't need to do anything.

Thanks for the explanation!

Acked-by: Song Liu <song@kernel.org>

Re: [PATCH 1/2] powerpc/module_64: Improve restore_r2() return semantics

[Miroslav Benes]

On Tue, 24 Jan 2023, Josh Poimboeuf wrote:

> restore_r2() returns 1 on success, which is surprising for a non-boolean
> function.  Change it to return 0 on success and -errno on error to match
> kernel coding convention.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Reviewed-by: Miroslav Benes <mbenes@suse.cz>

M

Re: [PATCH 2/2] powerpc/module_64: Fix "expected nop" error on module re-patching

[Miroslav Benes]

On Tue, 24 Jan 2023, Josh Poimboeuf wrote:

> When a module with a livepatched function is unloaded and then reloaded,
> klp attempts to dynamically re-patch it.  On ppc64, that fails with the
> following error:
> 
>   module_64: livepatch_nfsd: Expected nop after call, got e8410018 at e_show+0x60/0x548 [livepatch_nfsd]
>   livepatch: failed to initialize patch 'livepatch_nfsd' for module 'nfsd' (-8)
>   livepatch: patch 'livepatch_nfsd' failed for module 'nfsd', refusing to load module 'nfsd'
> 
> The error happens because the restore r2 instruction had already
> previously been written into the klp module's replacement function when
> the original function was patched the first time.  So the instruction
> wasn't a nop as expected.
> 
> When the restore r2 instruction has already been patched in, detect that
> and skip the warning and the instruction write.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Reviewed-by: Miroslav Benes <mbenes@suse.cz>

M

Re: [PATCH 0/2] powerpc: Fix livepatch module re-patching issue

[Joe Lawrence]

On Tue, Jan 24, 2023 at 07:38:03PM -0800, Josh Poimboeuf wrote:
> Fix a livepatch bug seen when reloading a patched module.
> 
> This is the powerpc counterpart to Song Liu's fix for a similar issue on
> x86:
> 
>   https://lkml.kernel.org/lkml/20230121004945.697003-2-song@kernel.org
> 
> Josh Poimboeuf (2):
>   powerpc/module_64: Improve restore_r2() return semantics
>   powerpc/module_64: Fix "expected nop" error on module re-patching
> 
>  arch/powerpc/kernel/module_64.c | 29 ++++++++++++++++++-----------
>  1 file changed, 18 insertions(+), 11 deletions(-)
> 
> -- 
> 2.39.0
> 

For the series,

Reviewed-and-tested-by: Joe Lawrence <joe.lawrence@redhat.com>

--
Joe

Re: [PATCH 0/2] powerpc: Fix livepatch module re-patching issue

[Josh Poimboeuf]

On Tue, Jan 24, 2023 at 07:38:03PM -0800, Josh Poimboeuf wrote:
> Fix a livepatch bug seen when reloading a patched module.
> 
> This is the powerpc counterpart to Song Liu's fix for a similar issue on
> x86:
> 
>   https://lkml.kernel.org/lkml/20230121004945.697003-2-song@kernel.org
> 
> Josh Poimboeuf (2):
>   powerpc/module_64: Improve restore_r2() return semantics
>   powerpc/module_64: Fix "expected nop" error on module re-patching
> 
>  arch/powerpc/kernel/module_64.c | 29 ++++++++++++++++++-----------
>  1 file changed, 18 insertions(+), 11 deletions(-)

Hi Michael,

Ping?  Any objections to this?

The x86 counterpart to this is queued for 6.3, it would be nice if this
also landed.  We could take it through the livepatch tree if needed.

-- 
Josh

Re: [PATCH 0/2] powerpc: Fix livepatch module re-patching issue

[Michael Ellerman]

Josh Poimboeuf <jpoimboe@kernel.org> writes:
> On Tue, Jan 24, 2023 at 07:38:03PM -0800, Josh Poimboeuf wrote:
>> Fix a livepatch bug seen when reloading a patched module.
>> 
>> This is the powerpc counterpart to Song Liu's fix for a similar issue on
>> x86:
>> 
>>   https://lkml.kernel.org/lkml/20230121004945.697003-2-song@kernel.org
>> 
>> Josh Poimboeuf (2):
>>   powerpc/module_64: Improve restore_r2() return semantics
>>   powerpc/module_64: Fix "expected nop" error on module re-patching
>> 
>>  arch/powerpc/kernel/module_64.c | 29 ++++++++++++++++++-----------
>>  1 file changed, 18 insertions(+), 11 deletions(-)
>
> Hi Michael,
>
> Ping?  Any objections to this?
>
> The x86 counterpart to this is queued for 6.3, it would be nice if this
> also landed.  We could take it through the livepatch tree if needed.

It's in my next since about a week. Sorry I forgot to send the
"accepted" emails (which I still don't have automated :/ ).

337251c7114e1 ("powerpc/module_64: Fix "expected nop" error on module re-patching")

cheers

Re: [PATCH 0/2] powerpc: Fix livepatch module re-patching issue

[Michael Ellerman]

On Tue, 24 Jan 2023 19:38:03 -0800, Josh Poimboeuf wrote:
> Fix a livepatch bug seen when reloading a patched module.
> 
> This is the powerpc counterpart to Song Liu's fix for a similar issue on
> x86:
> 
>   https://lkml.kernel.org/lkml/20230121004945.697003-2-song@kernel.org
> 
> [...]

Applied to powerpc/next.

[1/2] powerpc/module_64: Improve restore_r2() return semantics
      https://git.kernel.org/powerpc/c/bc2c6f5695ffa05c838b8b6fc5cd581a672151a1
[2/2] powerpc/module_64: Fix "expected nop" error on module re-patching
      https://git.kernel.org/powerpc/c/37251c7114e1b743b077ca74b93557c1ad92a97e

cheers

Re: [PATCH 0/2] powerpc: Fix livepatch module re-patching issue

[Josh Poimboeuf]

On Sun, Feb 05, 2023 at 11:46:12AM +1100, Michael Ellerman wrote:
> Josh Poimboeuf <jpoimboe@kernel.org> writes:
> > On Tue, Jan 24, 2023 at 07:38:03PM -0800, Josh Poimboeuf wrote:
> >> Fix a livepatch bug seen when reloading a patched module.
> >> 
> >> This is the powerpc counterpart to Song Liu's fix for a similar issue on
> >> x86:
> >> 
> >>   https://lkml.kernel.org/lkml/20230121004945.697003-2-song@kernel.org
> >> 
> >> Josh Poimboeuf (2):
> >>   powerpc/module_64: Improve restore_r2() return semantics
> >>   powerpc/module_64: Fix "expected nop" error on module re-patching
> >> 
> >>  arch/powerpc/kernel/module_64.c | 29 ++++++++++++++++++-----------
> >>  1 file changed, 18 insertions(+), 11 deletions(-)
> >
> > Hi Michael,
> >
> > Ping?  Any objections to this?
> >
> > The x86 counterpart to this is queued for 6.3, it would be nice if this
> > also landed.  We could take it through the livepatch tree if needed.
> 
> It's in my next since about a week. Sorry I forgot to send the
> "accepted" emails (which I still don't have automated :/ ).
> 
> 337251c7114e1 ("powerpc/module_64: Fix "expected nop" error on module re-patching")

Ah, I didn't think to look in -next.  Thanks!

-- 
Josh