[PATCH] arm64: remove kaslr-seed node when it had used

[PATCH] arm64: remove kaslr-seed node when it had used

[Enlin Mu]

From: Enlin Mu <enlin.mu@unisoc.com>

If this node value is zero,it means that kaslr is enabled.
Removing it for the system safe,nobody knows if this feature is
enable or not.

Signed-off-by: Enlin Mu <enlin.mu@unisoc.com>
---
 arch/arm64/kernel/pi/kaslr_early.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/pi/kaslr_early.c b/arch/arm64/kernel/pi/kaslr_early.c
index 17bff6e399e4..bc35d4ed84b7 100644
--- a/arch/arm64/kernel/pi/kaslr_early.c
+++ b/arch/arm64/kernel/pi/kaslr_early.c
@@ -81,7 +81,7 @@ static u64 get_kaslr_seed(void *fdt)
 		return 0;
 
 	ret = fdt64_to_cpu(*prop);
-	*prop = 0;
+	fdt_nop_property(fdt, node, "kaslr-seed");
 	return ret;
 }
 
-- 
2.25.1

Re: [PATCH] arm64: remove kaslr-seed node when it had used

[Will Deacon]

On Tue, Nov 14, 2023 at 09:55:51PM +0800, Enlin Mu wrote:
> From: Enlin Mu <enlin.mu@unisoc.com>
> 
> If this node value is zero,it means that kaslr is enabled.
> Removing it for the system safe,nobody knows if this feature is
> enable or not.
> 
> Signed-off-by: Enlin Mu <enlin.mu@unisoc.com>
> ---
>  arch/arm64/kernel/pi/kaslr_early.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/pi/kaslr_early.c b/arch/arm64/kernel/pi/kaslr_early.c
> index 17bff6e399e4..bc35d4ed84b7 100644
> --- a/arch/arm64/kernel/pi/kaslr_early.c
> +++ b/arch/arm64/kernel/pi/kaslr_early.c
> @@ -81,7 +81,7 @@ static u64 get_kaslr_seed(void *fdt)
>  		return 0;
>  
>  	ret = fdt64_to_cpu(*prop);
> -	*prop = 0;
> +	fdt_nop_property(fdt, node, "kaslr-seed");
>  	return ret;
>  }

Why is it a problem to know that KASLR is enabled? Wouldn't the presence
of the FDT_NOPs also give a pretty good hint?

Will

Re: [PATCH] arm64: remove kaslr-seed node when it had used

[kernel test robot]

Hi Enlin,

kernel test robot noticed the following build errors:

[auto build test ERROR on arm64/for-next/core]
[also build test ERROR on linus/master v6.7-rc1 next-20231117]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Enlin-Mu/arm64-remove-kaslr-seed-node-when-it-had-used/20231114-220115
base:   https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core
patch link:    https://lore.kernel.org/r/TYSPR04MB7084AFDB414AA7AE49A02D608AB2A%40TYSPR04MB7084.apcprd04.prod.outlook.com
patch subject: [PATCH] arm64: remove kaslr-seed node when it had used
config: arm64-defconfig (https://download.01.org/0day-ci/archive/20231117/202311172203.QJYSLPKE-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231117/202311172203.QJYSLPKE-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202311172203.QJYSLPKE-lkp@intel.com/

All errors (new ones prefixed by >>):

   aarch64-linux-ld: arch/arm64/kernel/pi/kaslr_early.pi.o: in function `get_kaslr_seed':
>> arch/arm64/kernel/pi/kaslr_early.c:84:(.init.text+0x18c): undefined reference to `__pi_fdt_nop_property'
   arch/arm64/kernel/pi/kaslr_early.c:84:(.init.text+0x18c): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `__pi_fdt_nop_property'
   aarch64-linux-ld: .tmp_vmlinux.kallsyms1: hidden symbol `__pi_fdt_nop_property' isn't defined
   aarch64-linux-ld: final link failed: bad value


vim +84 arch/arm64/kernel/pi/kaslr_early.c

    68	
    69	static u64 get_kaslr_seed(void *fdt)
    70	{
    71		int node, len;
    72		fdt64_t *prop;
    73		u64 ret;
    74	
    75		node = fdt_path_offset(fdt, "/chosen");
    76		if (node < 0)
    77			return 0;
    78	
    79		prop = fdt_getprop_w(fdt, node, "kaslr-seed", &len);
    80		if (!prop || len != sizeof(u64))
    81			return 0;
    82	
    83		ret = fdt64_to_cpu(*prop);
  > 84		fdt_nop_property(fdt, node, "kaslr-seed");
    85		return ret;
    86	}
    87	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki