Adds an initial prctl interface implementation. Unprivileged processes
can query the current prctl setting, including whether an aspect is
implemented by the hardware or is permitted to be modified by a setter
prctl. Editable aspects can be changed by a CAP_SYS_ADMIN privileged
process.
The prctl setting represents what the process itself has requested, and
does not account for any overrides. Either the kernel or a hypervisor
may enforce a different setting for an aspect.
Userspace can access a readonly view of the current DEXCR via SPR 812,
and a readonly view of the aspects enforced by the hypervisor via
SPR 455. A bitwise OR of these two SPRs will give the effective
DEXCR aspect state of the process.
Signed-off-by: Benjamin Gray <bg...@linux.ibm.com>
---
arch/powerpc/include/asm/processor.h | 13 +++
arch/powerpc/kernel/dexcr.c | 133 ++++++++++++++++++++++++++-
arch/powerpc/kernel/process.c | 6 ++
3 files changed, 151 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/processor.h
b/arch/powerpc/include/asm/processor.h
index 2381217c95dc..4c995258f668 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -265,6 +265,9 @@ struct thread_struct {
unsigned long sier2;
unsigned long sier3;
unsigned long hashkeyr;
+ unsigned int dexcr_override;
+ unsigned int dexcr_mask;
+ unsigned int dexcr_forced;
#endif
};
@@ -338,6 +341,16 @@ extern int set_endian(struct task_struct *tsk, unsigned
int val);
extern int get_unalign_ctl(struct task_struct *tsk, unsigned long adr);
extern int set_unalign_ctl(struct task_struct *tsk, unsigned int val);
+#ifdef CONFIG_PPC_BOOK3S_64
+
+#define PPC_GET_DEXCR_ASPECT(tsk, asp) dexcr_prctl_get((tsk), (asp))
+#define PPC_SET_DEXCR_ASPECT(tsk, asp, val) dexcr_prctl_set((tsk), (asp),
(val))
+
+int dexcr_prctl_get(struct task_struct *tsk, unsigned long asp);
+int dexcr_prctl_set(struct task_struct *tsk, unsigned long asp, unsigned long
val);
+
+#endif
+
extern void load_fp_state(struct thread_fp_state *fp);
extern void store_fp_state(struct thread_fp_state *fp);
extern void load_vr_state(struct thread_vr_state *vr);
diff --git a/arch/powerpc/kernel/dexcr.c b/arch/powerpc/kernel/dexcr.c
index 11515e67afac..9290beed722a 100644
--- a/arch/powerpc/kernel/dexcr.c
+++ b/arch/powerpc/kernel/dexcr.c
@@ -1,5 +1,8 @@
#include <linux/cache.h>
+#include <linux/capability.h>
#include <linux/init.h>
+#include <linux/prctl.h>
+#include <linux/sched.h>
#include <asm/cpu_has_feature.h>
#include <asm/cputable.h>
@@ -11,6 +14,10 @@
#define DEFAULT_DEXCR 0
+/* Allow process configuration of these by default */
+#define DEXCR_PRCTL_EDITABLE (DEXCR_PRO_SBHE | DEXCR_PRO_IBRTPD | \
+ DEXCR_PRO_SRAPD | DEXCR_PRO_NPHIE)
+
static int __init dexcr_init(void)
{
if (!early_cpu_has_feature(CPU_FTR_ARCH_31))
@@ -43,5 +50,129 @@ bool is_hashchk_trap(struct pt_regs const *regs)
unsigned long get_thread_dexcr(struct thread_struct const *t)
{
- return DEFAULT_DEXCR;
+ unsigned long dexcr = DEFAULT_DEXCR;
+
+ /* Apply prctl overrides */
+ dexcr = (dexcr & ~t->dexcr_mask) | t->dexcr_override;
+
+ return dexcr;
+}
+
+static void update_dexcr_on_cpu(void *info)
+{
+ mtspr(SPRN_DEXCR, get_thread_dexcr(¤t->thread));
+}
+
+static int dexcr_aspect_get(struct task_struct *task, unsigned int aspect)
+{
+ int ret = 0;
+
+ if (aspect & DEXCR_PRCTL_EDITABLE)
+ ret |= PR_PPC_DEXCR_PRCTL;
+
+ if (aspect & task->thread.dexcr_mask) {
+ if (aspect & task->thread.dexcr_override) {
+ if (aspect & task->thread.dexcr_forced)
+ ret |= PR_PPC_DEXCR_FORCE_SET_ASPECT;
+ else
+ ret |= PR_PPC_DEXCR_SET_ASPECT;
+ } else {
+ ret |= PR_PPC_DEXCR_CLEAR_ASPECT;
+ }
+ }
+
+ return ret;
+}
+
+int dexcr_prctl_get(struct task_struct *task, unsigned long which)
+{
+ switch (which) {
+ case PR_PPC_DEXCR_SBHE:
+ if (!cpu_has_feature(CPU_FTR_DEXCR_SBHE))
+ return -ENODEV;
+ return dexcr_aspect_get(task, DEXCR_PRO_SBHE);
+ case PR_PPC_DEXCR_IBRTPD:
+ if (!cpu_has_feature(CPU_FTR_DEXCR_IBRTPD))
+ return -ENODEV;
+ return dexcr_aspect_get(task, DEXCR_PRO_IBRTPD);
+ case PR_PPC_DEXCR_SRAPD:
+ if (!cpu_has_feature(CPU_FTR_DEXCR_SRAPD))
+ return -ENODEV;
+ return dexcr_aspect_get(task, DEXCR_PRO_SRAPD);
+ case PR_PPC_DEXCR_NPHIE:
+ if (!cpu_has_feature(CPU_FTR_DEXCR_NPHIE))
+ return -ENODEV;
+ return dexcr_aspect_get(task, DEXCR_PRO_NPHIE);
+ default:
+ return -ENODEV;
+ }
+}
+
+static int dexcr_aspect_set(struct task_struct *task, unsigned int aspect,
unsigned long ctrl)
+{
+ if (!(aspect & DEXCR_PRCTL_EDITABLE))
+ return -ENXIO; /* Aspect is not allowed to be changed by prctl
*/
+
+ if (aspect & task->thread.dexcr_forced)
+ return -EPERM; /* Aspect has been forced to current state */
+
+ switch (ctrl) {
+ case PR_PPC_DEXCR_SET_ASPECT:
+ task->thread.dexcr_mask |= aspect;
+ task->thread.dexcr_override |= aspect;
+ break;
+ case PR_PPC_DEXCR_FORCE_SET_ASPECT:
+ task->thread.dexcr_mask |= aspect;
+ task->thread.dexcr_override |= aspect;
+ task->thread.dexcr_forced |= aspect;
+ break;
+ case PR_PPC_DEXCR_CLEAR_ASPECT:
+ task->thread.dexcr_mask |= aspect;
+ task->thread.dexcr_override &= ~aspect;
+ break;
+ default:
+ return -ERANGE;
+ }
+
+ return 0;
+}
+
+int dexcr_prctl_set(struct task_struct *task, unsigned long which, unsigned
long ctrl)
+{
+ int err = 0;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ switch (which) {
+ case PR_PPC_DEXCR_SBHE:
+ if (!cpu_has_feature(CPU_FTR_DEXCR_SBHE))
+ return -ENODEV;
+ err = dexcr_aspect_set(task, DEXCR_PRO_SBHE, ctrl);
+ break;
+ case PR_PPC_DEXCR_IBRTPD:
+ if (!cpu_has_feature(CPU_FTR_DEXCR_IBRTPD))
+ return -ENODEV;
+ err = dexcr_aspect_set(task, DEXCR_PRO_IBRTPD, ctrl);
+ break;
+ case PR_PPC_DEXCR_SRAPD:
+ if (!cpu_has_feature(CPU_FTR_DEXCR_SRAPD))
+ return -ENODEV;
+ err = dexcr_aspect_set(task, DEXCR_PRO_SRAPD, ctrl);
+ break;
+ case PR_PPC_DEXCR_NPHIE:
+ if (!cpu_has_feature(CPU_FTR_DEXCR_NPHIE))
+ return -ENODEV;
+ err = dexcr_aspect_set(task, DEXCR_PRO_NPHIE, ctrl);
+ break;
+ default:
+ return -ENODEV;
+ }
+
+ if (err)
+ return err;
+
+ update_dexcr_on_cpu(NULL);
+
+ return 0;
}
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 4d7b0c7641d0..a280842750f9 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1825,6 +1825,12 @@ int copy_thread(struct task_struct *p, const struct
kernel_clone_args *args)
#ifdef CONFIG_PPC_BOOK3S_64
if (cpu_has_feature(CPU_FTR_DEXCR_NPHIE))
p->thread.hashkeyr = current->thread.hashkeyr;
+
+ if (cpu_has_feature(CPU_FTR_ARCH_31)) {
+ p->thread.dexcr_override = current->thread.dexcr_override;
+ p->thread.dexcr_mask = current->thread.dexcr_mask;
+ p->thread.dexcr_forced = current->thread.dexcr_forced;
+ }
#endif
/*
* Run with the current AMR value of the kernel
--
2.38.1
