powerpc/ptrace: Add memory protection key regset

The AMR/IAMR/UAMOR are part of the program context.
Allow it to be accessed via ptrace and through core files.
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/pkeys.h

@@ -202,6 +202,11 @@ static inline int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 	return __arch_set_user_pkey_access(tsk, pkey, init_val);
 }
 
+static inline bool arch_pkeys_enabled(void)
+{
+	return !static_branch_likely(&pkey_disabled);
+}
+
 extern void pkey_mm_init(struct mm_struct *mm);
 extern void thread_pkey_regs_save(struct thread_struct *thread);
 extern void thread_pkey_regs_restore(struct thread_struct *new_thread,

arch/powerpc/include/uapi/asm/elf.h

@@ -97,6 +97,7 @@
 #define ELF_NTMSPRREG	3	/* include tfhar, tfiar, texasr */
 #define ELF_NEBB	3	/* includes ebbrr, ebbhr, bescr */
 #define ELF_NPMU	5	/* includes siar, sdar, sier, mmcr2, mmcr0 */
+#define ELF_NPKEY	3	/* includes amr, iamr, uamor */
 
 typedef unsigned long elf_greg_t64;
 typedef elf_greg_t64 elf_gregset_t64[ELF_NGREG];

arch/powerpc/kernel/ptrace.c

@@ -35,6 +35,7 @@
 #include <linux/context_tracking.h>
 
 #include <linux/uaccess.h>
+#include <linux/pkeys.h>
 #include <asm/page.h>
 #include <asm/pgtable.h>
 #include <asm/switch_to.h>
@@ -1787,6 +1788,61 @@ static int pmu_set(struct task_struct *target,
 	return ret;
 }
 #endif
+
+#ifdef CONFIG_PPC_MEM_KEYS
+static int pkey_active(struct task_struct *target,
+		       const struct user_regset *regset)
+{
+	if (!arch_pkeys_enabled())
+		return -ENODEV;
+
+	return regset->n;
+}
+
+static int pkey_get(struct task_struct *target,
+		    const struct user_regset *regset,
+		    unsigned int pos, unsigned int count,
+		    void *kbuf, void __user *ubuf)
+{
+	BUILD_BUG_ON(TSO(amr) + sizeof(unsigned long) != TSO(iamr));
+	BUILD_BUG_ON(TSO(iamr) + sizeof(unsigned long) != TSO(uamor));
+
+	if (!arch_pkeys_enabled())
+		return -ENODEV;
+
+	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+				   &target->thread.amr, 0,
+				   ELF_NPKEY * sizeof(unsigned long));
+}
+
+static int pkey_set(struct task_struct *target,
+		      const struct user_regset *regset,
+		      unsigned int pos, unsigned int count,
+		      const void *kbuf, const void __user *ubuf)
+{
+	u64 new_amr;
+	int ret;
+
+	if (!arch_pkeys_enabled())
+		return -ENODEV;
+
+	/* Only the AMR can be set from userspace */
+	if (pos != 0 || count != sizeof(new_amr))
+		return -EINVAL;
+
+	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+				 &new_amr, 0, sizeof(new_amr));
+	if (ret)
+		return ret;
+
+	/* UAMOR determines which bits of the AMR can be set from userspace. */
+	target->thread.amr = (new_amr & target->thread.uamor) |
+		(target->thread.amr & ~target->thread.uamor);
+
+	return 0;
+}
+#endif /* CONFIG_PPC_MEM_KEYS */
+
 /*
  * These are our native regset flavors.
  */
@@ -1821,6 +1877,9 @@ enum powerpc_regset {
 	REGSET_EBB,		/* EBB registers */
 	REGSET_PMR,		/* Performance Monitor Registers */
 #endif
+#ifdef CONFIG_PPC_MEM_KEYS
+	REGSET_PKEY,		/* AMR register */
+#endif
 };
 
 static const struct user_regset native_regsets[] = {
@@ -1926,6 +1985,13 @@ static const struct user_regset native_regsets[] = {
 		.active = pmu_active, .get = pmu_get, .set = pmu_set
 	},
 #endif
+#ifdef CONFIG_PPC_MEM_KEYS
+	[REGSET_PKEY] = {
+		.core_note_type = NT_PPC_PKEY, .n = ELF_NPKEY,
+		.size = sizeof(u64), .align = sizeof(u64),
+		.active = pkey_active, .get = pkey_get, .set = pkey_set
+	},
+#endif
 };
 
 static const struct user_regset_view user_ppc_native_view = {

arch/powerpc/kernel/traps.c

@@ -292,6 +292,13 @@ void _exception_pkey(int signr, struct pt_regs *regs, int code,
 		local_irq_enable();
 
 	current->thread.trap_nr = code;
+
+	/*
+	 * Save all the pkey registers AMR/IAMR/UAMOR. Eg: Core dumps need
+	 * to capture the content, if the task gets killed.
+	 */
+	thread_pkey_regs_save(&current->thread);
+
 	memset(&info, 0, sizeof(info));
 	info.si_signo = signr;
 	info.si_code = code;

include/uapi/linux/elf.h

@@ -396,6 +396,7 @@ typedef struct elf64_shdr {
 #define NT_PPC_TM_CTAR	0x10d		/* TM checkpointed Target Address Register */
 #define NT_PPC_TM_CPPR	0x10e		/* TM checkpointed Program Priority Register */
 #define NT_PPC_TM_CDSCR	0x10f		/* TM checkpointed Data Stream Control Register */
+#define NT_PPC_PKEY	0x110		/* Memory Protection Keys registers */
 #define NT_386_TLS	0x200		/* i386 TLS slots (struct user_desc) */
 #define NT_386_IOPERM	0x201		/* x86 io permission bitmap (1=deny) */
 #define NT_X86_XSTATE	0x202		/* x86 extended state using xsave */