Commit eb232b16 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Michael Ellerman
Browse files

powerpc/book3s64/kuap: Improve error reporting with KUAP 



With hash translation use DSISR_KEYFAULT to identify a wrong access.
With Radix we look at the AMR value and type of fault.

Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-17-aneesh.kumar@linux.ibm.com
parent 4d6c551e

arch/powerpc/include/asm/book3s/32/kup.h

+2 −2
Original line number Diff line number Diff line
@@ -177,8 +177,8 @@ static inline void restore_user_access(unsigned long flags) 
		allow_user_access(to, to, end - addr, KUAP_READ_WRITE);

}



static inline bool

bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)

static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address,

				  bool is_write, unsigned long error_code)

{

	unsigned long begin = regs->kuap & 0xf0000000;

	unsigned long end = regs->kuap << 28;

arch/powerpc/include/asm/book3s/64/kup.h

+22 −5
Original line number Diff line number Diff line
@@ -303,13 +303,30 @@ static inline void set_kuap(unsigned long value) 
	isync();

}



static inline bool

bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)

#define RADIX_KUAP_BLOCK_READ	UL(0x4000000000000000)

#define RADIX_KUAP_BLOCK_WRITE	UL(0x8000000000000000)



static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address,

				  bool is_write, unsigned long error_code)

{

	return WARN(mmu_has_feature(MMU_FTR_BOOK3S_KUAP) &&

		    (regs->kuap & (is_write ? AMR_KUAP_BLOCK_WRITE : AMR_KUAP_BLOCK_READ)),

	if (!mmu_has_feature(MMU_FTR_BOOK3S_KUAP))

		return false;



	if (radix_enabled()) {

		/*

		 * Will be a storage protection fault.

		 * Only check the details of AMR[0]

		 */

		return WARN((regs->kuap & (is_write ? RADIX_KUAP_BLOCK_WRITE : RADIX_KUAP_BLOCK_READ)),

			    "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");

	}

	/*

	 * We don't want to WARN here because userspace can setup

	 * keys such that a kernel access to user address can cause

	 * fault

	 */

	return !!(error_code & DSISR_KEYFAULT);

}



static __always_inline void allow_user_access(void __user *to, const void __user *from,

					      unsigned long size, unsigned long dir)

arch/powerpc/include/asm/kup.h

+2 −2
Original line number Diff line number Diff line
@@ -59,8 +59,8 @@ void setup_kuap(bool disabled); 
#else

static inline void setup_kuap(bool disabled) { }



static inline bool

bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)

static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address,

				  bool is_write, unsigned long error_code)

{

	return false;

}

arch/powerpc/include/asm/nohash/32/kup-8xx.h

+2 −2
Original line number Diff line number Diff line
@@ -60,8 +60,8 @@ static inline void restore_user_access(unsigned long flags) 
	mtspr(SPRN_MD_AP, flags);

}



static inline bool

bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)

static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address,

				  bool is_write, unsigned long error_code)

{

	return WARN(!((regs->kuap ^ MD_APG_KUAP) & 0xff000000),

		    "Bug: fault blocked by AP register !");

arch/powerpc/mm/fault.c

+1 −1
Original line number Diff line number Diff line
@@ -227,7 +227,7 @@ static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code, 


	// Read/write fault in a valid region (the exception table search passed

	// above), but blocked by KUAP is bad, it can never succeed.

	if (bad_kuap_fault(regs, address, is_write))

	if (bad_kuap_fault(regs, address, is_write, error_code))

		return true;



	// What's left? Kernel fault on user in well defined regions (extable