Commit 09317643 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/64e: Fix early TLB miss with KUAP 



With KUAP, the TLB miss handler bails out when an access to user
memory is performed with a nul TID.

But the normal TLB miss routine which is only used early during boot
does the check regardless for all memory areas, not only user memory.

By chance there is no early IO or vmalloc access, but when KASAN
come we will start having early TLB misses.

Fix it by creating a special branch for user accesses similar to the
one in the 'bolted' TLB miss handlers. Unfortunately SPRN_MAS1 is
now read too early and there are no registers available to preserve
it so it will be read a second time.

Fixes: 57bc9638 ("powerpc/kuap: Wire-up KUAP on book3e/64")
Cc: stable@vger.kernel.org
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/8d6c5859a45935d6e1a336da4dc20be421e8cea7.1656427701.git.christophe.leroy@csgroup.eu
parent dd8de84b

arch/powerpc/mm/nohash/tlb_low_64e.S

+8 −9
Original line number Diff line number Diff line
@@ -583,7 +583,7 @@ itlb_miss_fault_e6500: 
	 */

	rlwimi	r11,r14,32-19,27,27

	rlwimi	r11,r14,32-16,19,19

	beq	normal_tlb_miss

	beq	normal_tlb_miss_user

	/* XXX replace the RMW cycles with immediate loads + writes */

1:	mfspr	r10,SPRN_MAS1

	cmpldi	cr0,r15,8		/* Check for vmalloc region */
@@ -626,7 +626,7 @@ itlb_miss_fault_e6500: 


	cmpldi	cr0,r15,0			/* Check for user region */

	std	r14,EX_TLB_ESR(r12)		/* write crazy -1 to frame */

	beq	normal_tlb_miss

	beq	normal_tlb_miss_user



	li	r11,_PAGE_PRESENT|_PAGE_BAP_SX	/* Base perm */

	oris	r11,r11,_PAGE_ACCESSED@h
@@ -653,6 +653,12 @@ itlb_miss_fault_e6500: 
 * r11 = PTE permission mask

 * r10 = crap (free to use)

 */

normal_tlb_miss_user:

#ifdef CONFIG_PPC_KUAP

	mfspr	r14,SPRN_MAS1

	rlwinm.	r14,r14,0,0x3fff0000

	beq-	normal_tlb_miss_access_fault /* KUAP fault */

#endif

normal_tlb_miss:

	/* So we first construct the page table address. We do that by

	 * shifting the bottom of the address (not the region ID) by
@@ -683,11 +689,6 @@ finish_normal_tlb_miss: 
	/* Check if required permissions are met */

	andc.	r15,r11,r14

	bne-	normal_tlb_miss_access_fault

#ifdef CONFIG_PPC_KUAP

	mfspr	r11,SPRN_MAS1

	rlwinm.	r10,r11,0,0x3fff0000

	beq-	normal_tlb_miss_access_fault /* KUAP fault */

#endif



	/* Now we build the MAS:

	 *
@@ -709,9 +710,7 @@ finish_normal_tlb_miss: 
	rldicl	r10,r14,64-8,64-8

	cmpldi	cr0,r10,BOOK3E_PAGESZ_4K

	beq-	1f

#ifndef CONFIG_PPC_KUAP

	mfspr	r11,SPRN_MAS1

#endif

	rlwimi	r11,r14,31,21,24

	rlwinm	r11,r11,0,21,19

	mtspr	SPRN_MAS1,r11