[PATCH] powerpc/4xx: Fix setup_kuep() on SMP

On SMP, setup_kuep() is also called from start_secondary() since
commit 86f46f343272 ("powerpc/32s: Initialise KUAP and KUEP in C").

start_secondary() is not an __init function.

Remove the __init marker from setup_kuep() and bail out when
not caller on the first CPU as the work is already done.

Reported-by: kernel test robot <redacted>
Fixes: 10248dcba120 ("powerpc/44x: Implement Kernel Userspace Exec Protection (KUEP)")
Fixes: 86f46f343272 ("powerpc/32s: Initialise KUAP and KUEP in C").
Signed-off-by: Christophe Leroy <redacted>
---
 arch/powerpc/mm/nohash/44x.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/nohash/44x.c b/arch/powerpc/mm/nohash/44x.c
index 7da6d1e9fc9b..20c18bd5b9a0 100644
--- a/arch/powerpc/mm/nohash/44x.c
+++ b/arch/powerpc/mm/nohash/44x.c

@@ -241,8 +241,11 @@ void __init mmu_init_secondary(int cpu)
 #endif /* CONFIG_SMP */
 
 #ifdef CONFIG_PPC_KUEP
-void __init setup_kuep(bool disabled)
+void setup_kuep(bool disabled)
 {
+	if (smp_processor_id() != boot_cpuid)
+		return;
+
 	if (disabled)
 		patch_instruction_site(&patch__tlb_44x_kuep, ppc_inst(PPC_RAW_NOP()));
 	else

-- 
2.25.0

Christophe Leroy [off-list ref] writes:

Building ppc44x_defconfig gives me:

  /linux/arch/powerpc/mm/nohash/44x.c: In function 'setup_kuep':
  /linux/arch/powerpc/mm/nohash/44x.c:246:35: error: 'boot_cpuid' undeclared (first use in this function); did you mean 'boot_cpu_init'?
    246 |         if (smp_processor_id() != boot_cpuid)
        |                                   ^~~~~~~~~~
        |                                   boot_cpu_init
  /linux/arch/powerpc/mm/nohash/44x.c:246:35: note: each undeclared identifier is reported only once for each function it appears in

cheers

Le 29/06/2021 à 13:58, Michael Ellerman a écrit :

Christophe Leroy [off-list ref] writes:

quoted

On SMP, setup_kuep() is also called from start_secondary() since
commit 86f46f343272 ("powerpc/32s: Initialise KUAP and KUEP in C").

start_secondary() is not an __init function.

Remove the __init marker from setup_kuep() and bail out when
not caller on the first CPU as the work is already done.

Reported-by: kernel test robot <redacted>
Fixes: 10248dcba120 ("powerpc/44x: Implement Kernel Userspace Exec Protection (KUEP)")
Fixes: 86f46f343272 ("powerpc/32s: Initialise KUAP and KUEP in C").
Signed-off-by: Christophe Leroy <redacted>
---
  arch/powerpc/mm/nohash/44x.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/nohash/44x.c b/arch/powerpc/mm/nohash/44x.c
index 7da6d1e9fc9b..20c18bd5b9a0 100644
--- a/arch/powerpc/mm/nohash/44x.c
+++ b/arch/powerpc/mm/nohash/44x.c

@@ -241,8 +241,11 @@ void __init mmu_init_secondary(int cpu)
  #endif /* CONFIG_SMP */
  
  #ifdef CONFIG_PPC_KUEP
-void __init setup_kuep(bool disabled)
+void setup_kuep(bool disabled)
  {
+	if (smp_processor_id() != boot_cpuid)
+		return;
+
  	if (disabled)
  		patch_instruction_site(&patch__tlb_44x_kuep, ppc_inst(PPC_RAW_NOP()));
  	else

Building ppc44x_defconfig gives me:

   /linux/arch/powerpc/mm/nohash/44x.c: In function 'setup_kuep':
   /linux/arch/powerpc/mm/nohash/44x.c:246:35: error: 'boot_cpuid' undeclared (first use in this function); did you mean 'boot_cpu_init'?
     246 |         if (smp_processor_id() != boot_cpuid)
         |                                   ^~~~~~~~~~
         |                                   boot_cpu_init
   /linux/arch/powerpc/mm/nohash/44x.c:246:35: note: each undeclared identifier is reported only once for each function it appears in

Seems like we need <asm/smp.h> when we don't have CONFIG_SMP.

I tested it with akebono_defconfig, looks like it has CONFIG_SMP.