Recognise and pass the appropriate signal to the user program when a
hashchk instruction triggers. This is independent of allowing
configuration of DEXCR[NPHIE], as a hypervisor can enforce this aspect
regardless of the kernel.
The signal mirrors how ARM reports their similar check failure. For
example, their FPAC handler in arch/arm64/kernel/traps.c do_el0_fpac()
does this. When we fail to read the instruction that caused the fault
we send a segfault, similar to how emulate_math() does it.
Signed-off-by: Benjamin Gray <bg...@linux.ibm.com>
---
v1: * Refactor the hashchk check to return 0 on success, an error
code on failure. Determine what to do based on specific error
code.
* Motivate signal and code
---
arch/powerpc/include/asm/ppc-opcode.h | 1 +
arch/powerpc/include/asm/processor.h | 9 +++++++
arch/powerpc/kernel/Makefile | 1 +
arch/powerpc/kernel/dexcr.c | 36 +++++++++++++++++++++++++++
arch/powerpc/kernel/traps.c | 10 ++++++++
5 files changed, 57 insertions(+)
create mode 100644 arch/powerpc/kernel/dexcr.c
diff --git a/arch/powerpc/include/asm/ppc-opcode.h
b/arch/powerpc/include/asm/ppc-opcode.h
index 21e33e46f4b8..89b316466ed1 100644
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -215,6 +215,7 @@
#define OP_31_XOP_STFSX 663
#define OP_31_XOP_STFSUX 695
#define OP_31_XOP_STFDX 727
+#define OP_31_XOP_HASHCHK 754
#define OP_31_XOP_STFDUX 759
#define OP_31_XOP_LHBRX 790
#define OP_31_XOP_LFIWAX 855
diff --git a/arch/powerpc/include/asm/processor.h
b/arch/powerpc/include/asm/processor.h
index e96c9b8c2a60..bad64d6a5d36 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -455,6 +455,15 @@ int exit_vmx_usercopy(void);
int enter_vmx_ops(void);
void *exit_vmx_ops(void *dest);
+#ifdef CONFIG_PPC_BOOK3S_64
+int check_hashchk_trap(struct pt_regs const *regs);
+#else
+static inline int check_hashchk_trap(struct pt_regs const *regs)
+{
+ return -EINVAL;
+}
+#endif /* CONFIG_PPC_BOOK3S_64 */
+
#endif /* __KERNEL__ */
#endif /* __ASSEMBLY__ */
#endif /* _ASM_POWERPC_PROCESSOR_H */
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 9bf2be123093..07181e508754 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..f263e5439cc6
--- /dev/null
+++ b/arch/powerpc/kernel/dexcr.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * DEXCR infrastructure
+ *
+ * Copyright 2023, Benjamin Gray, IBM Corporation.
+ */
+#include <linux/compiler_types.h>
+
+#include <asm/cpu_has_feature.h>
+#include <asm/cputable.h>
+#include <asm/disassemble.h>
+#include <asm/errno.h>
+#include <asm/inst.h>
+#include <asm/ppc-opcode.h>
+#include <asm/ptrace.h>
+#include <asm/reg.h>
+
+int check_hashchk_trap(struct pt_regs const *regs)
+{
+ ppc_inst_t insn;
+
+ if (!cpu_has_feature(CPU_FTR_DEXCR_NPHIE))
+ return -EINVAL;
+
+ if (!user_mode(regs))
+ return -EINVAL;
+
+ if (get_user_instr(insn, (void __user *)regs->nip))
+ return -EFAULT;
+
+ if (ppc_inst_primary_opcode(insn) != 31 ||
+ get_xop(ppc_inst_val(insn)) != OP_31_XOP_HASHCHK)
+ return -EINVAL;
+
+ return 0;
+}
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 9bdd79aa51cf..ade67e23b974 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1516,6 +1516,16 @@ static void do_program_check(struct pt_regs *regs)
return;
}
}
+
+ switch (check_hashchk_trap(regs)) {
+ case 0:
+ _exception(SIGILL, regs, ILL_ILLOPN, regs->nip);
+ return;
+ case -EFAULT:
+ _exception(SIGSEGV, regs, SEGV_MAPERR, regs->nip);
+ return;
+ }
+
_exception(SIGTRAP, regs, TRAP_BRKPT, regs->nip);
return;
}
--
2.39.2
