@@ -473,6 +473,11 @@ config PGTABLE_LEVELS
default 2 if !PPC64
default 4
+config PPC_USER_ENFORCE_ROP_PROTECT
+ bool
+ depends on PPC_BOOK3S_64
+ default y
+
source "arch/powerpc/sysdev/Kconfig"
source "arch/powerpc/platforms/Kconfig"
@@ -1,6 +1,8 @@
+#include <linux/cache.h>
#include <linux/capability.h>
#include <linux/cpu.h>
#include <linux/init.h>
+#include <linux/kconfig.h>
#include <linux/prctl.h>
#include <linux/sched.h>
#include <linux/sysctl.h>
@@ -14,7 +16,7 @@
#define DEXCR_PRCTL_EDITABLE ( \
DEXCR_PR_IBRTPD | \
DEXCR_PR_SRAPD | \
- DEXCR_PR_NPHIE)
+ (!IS_ENABLED(CONFIG_PPC_USER_ENFORCE_ROP_PROTECT) ? DEXCR_PR_NPHIE : 0))
static unsigned long dexcr_supported __ro_after_init = 0;
@@ -45,6 +47,9 @@ unsigned long get_thread_dexcr(struct thread_struct const *thread)
{
unsigned long dexcr = thread->dexcr_enabled;
+ if (IS_ENABLED(CONFIG_PPC_USER_ENFORCE_ROP_PROTECT))
+ dexcr |= DEXCR_PR_NPHIE;
+
/*
* spec_branch_hint_enable may be written to concurrently via sysctl.
* The sysctl handler is careful to use WRITE_ONCE, so we avoid
The DEXCR Non-Privileged Hash Instruction Enable (NPHIE) aspect controls whether the hashst and hashchk instructions are treated as no-ops by the CPU. NPHIE behaviour per ISA 3.1B: 0: hashst and hashchk instructions are executed as no-ops (even when allowed by PCR) 1: hashst and hashchk instructions are executed normally (if allowed by PCR) Currently this aspect may be set per-process by prctl() or enforced globally by the hypervisor. Add a kernel config option PPC_USER_ENFORCE_ROP_PROTECT to enforce DEXCR[NPHIE] globally regardless of prctl() or hypervisor. If set, don't report NPHIE as editable via prctl(), as the prctl() value can never take effect. Signed-off-by: Benjamin Gray <bgray@linux.ibm.com> --- arch/powerpc/Kconfig | 5 +++++ arch/powerpc/kernel/dexcr.c | 7 ++++++- 2 files changed, 11 insertions(+), 1 deletion(-)