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 | 10 +++
arch/powerpc/kernel/Makefile | 1 +
arch/powerpc/kernel/dexcr.c | 128 +++++++++++++++++++++++++++
3 files changed, 139 insertions(+)
create mode 100644 arch/powerpc/kernel/dexcr.c
diff --git a/arch/powerpc/include/asm/processor.h
b/arch/powerpc/include/asm/processor.h
index 28a72023f9bd..a9d83621dfad 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -336,6 +336,16 @@ 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) get_dexcr_prctl((tsk), (asp))
+#define PPC_SET_DEXCR_ASPECT(tsk, asp, val) set_dexcr_prctl((tsk), (asp),
(val))
+
+int get_dexcr_prctl(struct task_struct *tsk, unsigned long asp);
+int set_dexcr_prctl(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/Makefile b/arch/powerpc/kernel/Makefile
index 2919433be355..24f82b09246c 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -88,6 +88,7 @@ obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
obj-$(CONFIG_PPC_DAWR) += dawr.o
obj-$(CONFIG_PPC_BOOK3S_64) += cpu_setup_ppc970.o cpu_setup_pa6t.o
obj-$(CONFIG_PPC_BOOK3S_64) += cpu_setup_power.o
+obj-$(CONFIG_PPC_BOOK3S_64) += dexcr.o
obj-$(CONFIG_PPC_BOOK3S_64) += mce.o mce_power.o
obj-$(CONFIG_PPC_BOOK3E_64) += exceptions-64e.o idle_64e.o
obj-$(CONFIG_PPC_BARRIER_NOSPEC) += security.o
diff --git a/arch/powerpc/kernel/dexcr.c b/arch/powerpc/kernel/dexcr.c
new file mode 100644
index 000000000000..db663ce7b3ce
--- /dev/null
+++ b/arch/powerpc/kernel/dexcr.c
@@ -0,0 +1,128 @@
+#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>
+#include <asm/processor.h>
+#include <asm/reg.h>
+
+/* Allow thread local configuration of these by default */
+#define DEXCR_PRCTL_EDITABLE ( \
+ DEXCR_PR_IBRTPD | \
+ DEXCR_PR_SRAPD | \
+ DEXCR_PR_NPHIE)
+
+static unsigned long dexcr_supported __ro_after_init = 0;
+
+static int __init dexcr_init(void)
+{
+ if (!early_cpu_has_feature(CPU_FTR_ARCH_31))
+ return 0;
+
+ if (early_cpu_has_feature(CPU_FTR_DEXCR_SBHE))
+ dexcr_supported |= DEXCR_PR_SBHE;
+
+ if (early_cpu_has_feature(CPU_FTR_DEXCR_IBRTPD))
+ dexcr_supported |= DEXCR_PR_IBRTPD;
+
+ if (early_cpu_has_feature(CPU_FTR_DEXCR_SRAPD))
+ dexcr_supported |= DEXCR_PR_SRAPD;
+
+ if (early_cpu_has_feature(CPU_FTR_DEXCR_NPHIE))
+ dexcr_supported |= DEXCR_PR_NPHIE;
+
+ return 0;
+}
+early_initcall(dexcr_init);
+
+static int prctl_to_aspect(unsigned long which, unsigned int *aspect)
+{
+ switch (which) {
+ case PR_PPC_DEXCR_SBHE:
+ *aspect = DEXCR_PR_SBHE;
+ break;
+ case PR_PPC_DEXCR_IBRTPD:
+ *aspect = DEXCR_PR_IBRTPD;
+ break;
+ case PR_PPC_DEXCR_SRAPD:
+ *aspect = DEXCR_PR_SRAPD;
+ break;
+ case PR_PPC_DEXCR_NPHIE:
+ *aspect = DEXCR_PR_NPHIE;
+ break;
+ default:
+ return -ENODEV;
+ }
+
+ return 0;
+}
+
+int get_dexcr_prctl(struct task_struct *task, unsigned long which)
+{
+ unsigned int aspect;
+ int ret;
+
+ ret = prctl_to_aspect(which, &aspect);
+ if (ret)
+ return ret;
+
+ if (!(aspect & dexcr_supported))
+ return -ENODEV;
+
+ if (aspect & task->thread.dexcr_enabled)
+ ret |= PR_PPC_DEXCR_CTRL_ON;
+ else
+ ret |= PR_PPC_DEXCR_CTRL_OFF;
+
+ if (aspect & task->thread.dexcr_inherit)
+ ret |= PR_PPC_DEXCR_CTRL_INHERIT;
+
+ return ret;
+}
+
+int set_dexcr_prctl(struct task_struct *task, unsigned long which, unsigned
long ctrl)
+{
+ unsigned int aspect;
+ unsigned long enable;
+ unsigned long disable;
+ unsigned long inherit;
+ int err = 0;
+
+ /* We do not want an unprivileged process being able to set a value
that a setuid process may inherit (particularly for NPHIE) */
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ err = prctl_to_aspect(which, &aspect);
+ if (err)
+ return err;
+
+ if (!(aspect & dexcr_supported))
+ return -ENODEV;
+
+ enable = ctrl & PR_PPC_DEXCR_CTRL_ON;
+ disable = ctrl & PR_PPC_DEXCR_CTRL_OFF;
+ inherit = ctrl & PR_PPC_DEXCR_CTRL_INHERIT;
+ ctrl &= ~(PR_PPC_DEXCR_CTRL_ON | PR_PPC_DEXCR_CTRL_OFF |
PR_PPC_DEXCR_CTRL_INHERIT);
+
+ if (ctrl)
+ return -EINVAL;
+
+ if ((enable && disable) || !(enable || disable))
+ return -EINVAL;
+
+ if (enable)
+ task->thread.dexcr_enabled |= aspect;
+ else
+ task->thread.dexcr_enabled &= ~aspect;
+
+ if (inherit)
+ task->thread.dexcr_inherit |= aspect;
+ else
+ task->thread.dexcr_inherit &= ~aspect;
+
+ mtspr(SPRN_DEXCR, get_thread_dexcr(¤t->thread));
+
+ return 0;
+}
--
2.41.0
