[PATCH] powerpc/lib: fix book3s/32 boot failure due to code patching

[PATCH] powerpc/lib: fix book3s/32 boot failure due to code patching

[Christophe Leroy]

Commit 51c3c62b58b3 ("powerpc: Avoid code patching freed init
sections") accesses 'init_mem_is_free' flag too early, before the
kernel is relocated. This provokes early boot failure (before the
console is active).

As it is not necessary to do this verification that early, this
patch moves the test into patch_instruction() instead of
__patch_instruction().

This modification also has the advantage of avoiding unnecessary
remappings.

Fixes: 51c3c62b58b3 ("powerpc: Avoid code patching freed init sections")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/lib/code-patching.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 6ae2777c220d..5ffee298745f 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -28,12 +28,6 @@ static int __patch_instruction(unsigned int *exec_addr, unsigned int instr,
 {
 	int err;
 
-	/* Make sure we aren't patching a freed init section */
-	if (init_mem_is_free && init_section_contains(exec_addr, 4)) {
-		pr_debug("Skipping init section patching addr: 0x%px\n", exec_addr);
-		return 0;
-	}
-
 	__put_user_size(instr, patch_addr, 4, err);
 	if (err)
 		return err;
@@ -148,7 +142,7 @@ static inline int unmap_patch_area(unsigned long addr)
 	return 0;
 }
 
-int patch_instruction(unsigned int *addr, unsigned int instr)
+static int do_patch_instruction(unsigned int *addr, unsigned int instr)
 {
 	int err;
 	unsigned int *patch_addr = NULL;
@@ -188,12 +182,22 @@ int patch_instruction(unsigned int *addr, unsigned int instr)
 }
 #else /* !CONFIG_STRICT_KERNEL_RWX */
 
-int patch_instruction(unsigned int *addr, unsigned int instr)
+static int do_patch_instruction(unsigned int *addr, unsigned int instr)
 {
 	return raw_patch_instruction(addr, instr);
 }
 
 #endif /* CONFIG_STRICT_KERNEL_RWX */
+
+int patch_instruction(unsigned int *addr, unsigned int instr)
+{
+	/* Make sure we aren't patching a freed init section */
+	if (init_mem_is_free && init_section_contains(addr, 4)) {
+		pr_debug("Skipping init section patching addr: 0x%px\n", addr);
+		return 0;
+	}
+	return do_patch_instruction(addr, instr);
+}
 NOKPROBE_SYMBOL(patch_instruction);
 
 int patch_branch(unsigned int *addr, unsigned long target, int flags)
-- 
2.13.3

Re: [PATCH] powerpc/lib: fix book3s/32 boot failure due to code patching

[Michael Neuling]

On Mon, 2018-10-01 at 12:21 +0000, Christophe Leroy wrote:
> Commit 51c3c62b58b3 ("powerpc: Avoid code patching freed init
> sections") accesses 'init_mem_is_free' flag too early, before the
> kernel is relocated. This provokes early boot failure (before the
> console is active).
> 
> As it is not necessary to do this verification that early, this
> patch moves the test into patch_instruction() instead of
> __patch_instruction().
> 
> This modification also has the advantage of avoiding unnecessary
> remappings.
> 
> Fixes: 51c3c62b58b3 ("powerpc: Avoid code patching freed init sections")
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Thanks

Acked-by: Michael Neuling <mikey@neuling.org>

The original patch was also marked for stable so we should do the same here.

Cc: stable@vger.kernel.org # 4.13+

> ---
>  arch/powerpc/lib/code-patching.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-
> patching.c
> index 6ae2777c220d..5ffee298745f 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -28,12 +28,6 @@ static int __patch_instruction(unsigned int *exec_addr,
> unsigned int instr,
>  {
>  	int err;
>  
> -	/* Make sure we aren't patching a freed init section */
> -	if (init_mem_is_free && init_section_contains(exec_addr, 4)) {
> -		pr_debug("Skipping init section patching addr: 0x%px\n",
> exec_addr);
> -		return 0;
> -	}
> -
>  	__put_user_size(instr, patch_addr, 4, err);
>  	if (err)
>  		return err;
> @@ -148,7 +142,7 @@ static inline int unmap_patch_area(unsigned long addr)
>  	return 0;
>  }
>  
> -int patch_instruction(unsigned int *addr, unsigned int instr)
> +static int do_patch_instruction(unsigned int *addr, unsigned int instr)
>  {
>  	int err;
>  	unsigned int *patch_addr = NULL;
> @@ -188,12 +182,22 @@ int patch_instruction(unsigned int *addr, unsigned int
> instr)
>  }
>  #else /* !CONFIG_STRICT_KERNEL_RWX */
>  
> -int patch_instruction(unsigned int *addr, unsigned int instr)
> +static int do_patch_instruction(unsigned int *addr, unsigned int instr)
>  {
>  	return raw_patch_instruction(addr, instr);
>  }
>  
>  #endif /* CONFIG_STRICT_KERNEL_RWX */
> +
> +int patch_instruction(unsigned int *addr, unsigned int instr)
> +{
> +	/* Make sure we aren't patching a freed init section */
> +	if (init_mem_is_free && init_section_contains(addr, 4)) {
> +		pr_debug("Skipping init section patching addr: 0x%px\n", addr);
> +		return 0;
> +	}
> +	return do_patch_instruction(addr, instr);
> +}
>  NOKPROBE_SYMBOL(patch_instruction);
>  
>  int patch_branch(unsigned int *addr, unsigned long target, int flags)

Re: powerpc/lib: fix book3s/32 boot failure due to code patching

[Michael Ellerman]

On Mon, 2018-10-01 at 12:21:10 UTC, Christophe Leroy wrote:
> Commit 51c3c62b58b3 ("powerpc: Avoid code patching freed init
> sections") accesses 'init_mem_is_free' flag too early, before the
> kernel is relocated. This provokes early boot failure (before the
> console is active).
> 
> As it is not necessary to do this verification that early, this
> patch moves the test into patch_instruction() instead of
> __patch_instruction().
> 
> This modification also has the advantage of avoiding unnecessary
> remappings.
> 
> Fixes: 51c3c62b58b3 ("powerpc: Avoid code patching freed init sections")
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/b45ba4a51cde29b2939365ef0c07ad

cheers