Re: [PATCH 2/3] Detect instruction fetch denied and report

On 09/11/16 03:09, Aneesh Kumar K.V wrote:

Balbir Singh [off-list ref] writes:

quoted

ISA 3 allows for prevention of instruction fetch and execution
of user mode pages. If such an error occurs, SRR1 bit 35
reports the error. We catch and report the error in do_page_fault()

Signed-off-by: Balbir Singh <bsingharora@gmail.com>
---
 arch/powerpc/mm/fault.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index d0b137d..835fd03 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c

@@ -404,6 +404,10 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
 		    (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
 		     !(vma->vm_flags & (VM_READ | VM_WRITE))))
 			goto bad_area;
+
+		if (radix_enabled() && (regs->msr & SRR1_ISI_N_OR_G))
+			goto bad_area;

Why is this within radix_enabled() ? Hash can also generate an
interrupt with that SRR1 value right ?

Yes the bits are not specific to radix. I suspect the check above took
care of instruction exceptions, so we've never needed it before. I'll
remove the check

Balbir