Commit 10248dcb authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/44x: Implement Kernel Userspace Exec Protection (KUEP) 



Powerpc 44x has two bits for exec protection in TLBs: one
for user (UX) and one for superviser (SX).

Clear SX on user pages in TLB miss handlers to provide KUEP.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/169310e08152aa1d96c979770291d165ec6896ae.1622616032.git.christophe.leroy@csgroup.eu
parent c0ca0fe0

arch/powerpc/include/asm/nohash/32/mmu-44x.h

+1 −0
Original line number Diff line number Diff line
@@ -113,6 +113,7 @@ typedef struct { 


/* patch sites */

extern s32 patch__tlb_44x_hwater_D, patch__tlb_44x_hwater_I;

extern s32 patch__tlb_44x_kuep, patch__tlb_47x_kuep;



#endif /* !__ASSEMBLY__ */

arch/powerpc/kernel/head_44x.S

+8 −0
Original line number Diff line number Diff line
@@ -532,6 +532,10 @@ finish_tlb_load_44x: 
	andi.	r10,r12,_PAGE_USER		/* User page ? */

	beq	1f				/* nope, leave U bits empty */

	rlwimi	r11,r11,3,26,28			/* yes, copy S bits to U */

#ifdef CONFIG_PPC_KUEP

0:	rlwinm	r11,r11,0,~PPC44x_TLB_SX	/* Clear SX if User page */

	patch_site 0b, patch__tlb_44x_kuep

#endif

1:	tlbwe	r11,r13,PPC44x_TLB_ATTRIB	/* Write ATTRIB */



	/* Done...restore registers and get out of here.
@@ -743,6 +747,10 @@ finish_tlb_load_47x: 
	andi.	r10,r12,_PAGE_USER		/* User page ? */

	beq	1f				/* nope, leave U bits empty */

	rlwimi	r11,r11,3,26,28			/* yes, copy S bits to U */

#ifdef CONFIG_PPC_KUEP

0:	rlwinm	r11,r11,0,~PPC47x_TLB2_SX	/* Clear SX if User page */

	patch_site 0b, patch__tlb_47x_kuep

#endif

1:	tlbwe	r11,r13,2



	/* Done...restore registers and get out of here.

arch/powerpc/mm/nohash/44x.c

+13 −0
Original line number Diff line number Diff line
@@ -239,3 +239,16 @@ void __init mmu_init_secondary(int cpu) 
	}

}

#endif /* CONFIG_SMP */



#ifdef CONFIG_PPC_KUEP

void __init setup_kuep(bool disabled)

{

	if (disabled)

		patch_instruction_site(&patch__tlb_44x_kuep, ppc_inst(PPC_RAW_NOP()));

	else

		pr_info("Activating Kernel Userspace Execution Prevention\n");



	if (IS_ENABLED(CONFIG_PPC_47x) && disabled)

		patch_instruction_site(&patch__tlb_47x_kuep, ppc_inst(PPC_RAW_NOP()));

}

#endif

arch/powerpc/platforms/Kconfig.cputype

+1 −0
Original line number Diff line number Diff line
@@ -61,6 +61,7 @@ config 44x 
	select 4xx_SOC

	select HAVE_PCI

	select PHYS_64BIT

	select PPC_HAVE_KUEP



endchoice