[PATCH v10 4/9] arm64: add conditional instruction simulation support

David Long
2016-03-01T03:02:10Z

From: "David A. Long" <dave.long@linaro.org>

Cease using the arm32 arm_check_condition() function and replace it with
a local version for use in deprecated instruction support on arm64. Also
make the function table used by this available for future use by kprobes
and/or uprobes.

This function is dervied from code written by Sandeepa Prabhu.

Signed-off-by: Sandeepa Prabhu <sandeepa.s.prabhu@gmail.com>
Signed-off-by: David A. Long <dave.long@linaro.org>
---
arch/arm64/include/asm/insn.h | 3 ++
arch/arm64/kernel/Makefile | 3 +-
arch/arm64/kernel/armv8_deprecated.c | 19 ++++++-
arch/arm64/kernel/insn.c | 96 ++++++++++++++++++++++++++++++++++++
4 files changed, 117 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
index 662b42a..72dda48 100644
--- a/arch/arm64/include/asm/insn.h
+++ b/arch/arm64/include/asm/insn.h
@@ -405,6 +405,9 @@ u32 aarch64_extract_system_register(u32 insn);
u32 aarch32_insn_extract_reg_num(u32 insn, int offset);
u32 aarch32_insn_mcr_extract_opc2(u32 insn);
u32 aarch32_insn_mcr_extract_crm(u32 insn);
+
+typedef bool (pstate_check_t)(unsigned long);
+extern pstate_check_t * const opcode_condition_checks[16];
#endif /* __ASSEMBLY__ */

#endif /* __ASM_INSN_H */
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 83cd7e6..fd5f163 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -26,8 +26,7 @@ $(obj)/%.stub.o: $(obj)/%.o FORCE
$(call if_changed,objcopy)

arm64-obj-$(CONFIG_COMPAT) += sys32.o kuser32.o signal32.o \
- sys_compat.o entry32.o \
- ../../arm/kernel/opcodes.o
+ sys_compat.o entry32.o
arm64-obj-$(CONFIG_FUNCTION_TRACER) += ftrace.o entry-ftrace.o
arm64-obj-$(CONFIG_MODULES) += arm64ksyms.o module.o
arm64-obj-$(CONFIG_PERF_EVENTS) += perf_regs.o perf_callchain.o
diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
index 3e01207..6d4d6fe 100644
--- a/arch/arm64/kernel/armv8_deprecated.c
+++ b/arch/arm64/kernel/armv8_deprecated.c
@@ -369,6 +369,21 @@ static int emulate_swpX(unsigned int address, unsigned int *data,
return res;
}

+#define ARM_OPCODE_CONDITION_UNCOND 0xf
+
+static unsigned int __kprobes arm64_check_condition(u32 opcode, u32 psr)
+{
+ u32 cc_bits = opcode >> 28;
+
+ if (cc_bits != ARM_OPCODE_CONDITION_UNCOND) {
+ if ((*opcode_condition_checks[cc_bits])(psr))
+ return ARM_OPCODE_CONDTEST_PASS;
+ else
+ return ARM_OPCODE_CONDTEST_FAIL;
+ }
+ return ARM_OPCODE_CONDTEST_UNCOND;
+}
+
/*
* swp_handler logs the id of calling process, dissects the instruction, sanity
* checks the memory location, calls emulate_swpX for the actual operation and
@@ -383,7 +398,7 @@ static int swp_handler(struct pt_regs *regs, u32 instr)

type = instr & TYPE_SWPB;

- switch (arm_check_condition(instr, regs->pstate)) {
+ switch (arm64_check_condition(instr, regs->pstate)) {
case ARM_OPCODE_CONDTEST_PASS:
break;
case ARM_OPCODE_CONDTEST_FAIL:
@@ -464,7 +479,7 @@ static int cp15barrier_handler(struct pt_regs *regs, u32 instr)
{
perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);

- switch (arm_check_condition(instr, regs->pstate)) {
+ switch (arm64_check_condition(instr, regs->pstate)) {
case ARM_OPCODE_CONDTEST_PASS:
break;
case ARM_OPCODE_CONDTEST_FAIL:
diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index 60c1c71..f7f2f95 100644
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -1234,3 +1234,99 @@ u32 aarch32_insn_mcr_extract_crm(u32 insn)
{
return insn & CRM_MASK;
}
+
+#define ARM_OPCODE_CONDITION_UNCOND 0xf
+
+static bool __kprobes __check_eq(unsigned long pstate)
+{
+ return (pstate & PSR_Z_BIT) != 0;
+}
+
+static bool __kprobes __check_ne(unsigned long pstate)
+{
+ return (pstate & PSR_Z_BIT) == 0;
+}
+
+static bool __kprobes __check_cs(unsigned long pstate)
+{
+ return (pstate & PSR_C_BIT) != 0;
+}
+
+static bool __kprobes __check_cc(unsigned long pstate)
+{
+ return (pstate & PSR_C_BIT) == 0;
+}
+
+static bool __kprobes __check_mi(unsigned long pstate)
+{
+ return (pstate & PSR_N_BIT) != 0;
+}
+
+static bool __kprobes __check_pl(unsigned long pstate)
+{
+ return (pstate & PSR_N_BIT) == 0;
+}
+
+static bool __kprobes __check_vs(unsigned long pstate)
+{
+ return (pstate & PSR_V_BIT) != 0;
+}
+
+static bool __kprobes __check_vc(unsigned long pstate)
+{
+ return (pstate & PSR_V_BIT) == 0;
+}
+
+static bool __kprobes __check_hi(unsigned long pstate)
+{
+ pstate &= ~(pstate >> 1); /* PSR_C_BIT &= ~PSR_Z_BIT */
+ return (pstate & PSR_C_BIT) != 0;
+}
+
+static bool __kprobes __check_ls(unsigned long pstate)
+{
+ pstate &= ~(pstate >> 1); /* PSR_C_BIT &= ~PSR_Z_BIT */
+ return (pstate & PSR_C_BIT) == 0;
+}
+
+static bool __kprobes __check_ge(unsigned long pstate)
+{
+ pstate ^= (pstate << 3); /* PSR_N_BIT ^= PSR_V_BIT */
+ return (pstate & PSR_N_BIT) == 0;
+}
+
+static bool __kprobes __check_lt(unsigned long pstate)
+{
+ pstate ^= (pstate << 3); /* PSR_N_BIT ^= PSR_V_BIT */
+ return (pstate & PSR_N_BIT) != 0;
+}
+
+static bool __kprobes __check_gt(unsigned long pstate)
+{
+ /*PSR_N_BIT ^= PSR_V_BIT */
+ unsigned long temp = pstate ^ (pstate << 3);
+
+ temp |= (pstate << 1); /*PSR_N_BIT |= PSR_Z_BIT */
+ return (temp & PSR_N_BIT) == 0;
+}
+
+static bool __kprobes __check_le(unsigned long pstate)
+{
+ /*PSR_N_BIT ^= PSR_V_BIT */
+ unsigned long temp = pstate ^ (pstate << 3);
+
+ temp |= (pstate << 1); /*PSR_N_BIT |= PSR_Z_BIT */
+ return (temp & PSR_N_BIT) != 0;
+}
+
+static bool __kprobes __check_al(unsigned long pstate)
+{
+ return true;
+}
+
+pstate_check_t * const opcode_condition_checks[16] = {
+ __check_eq, __check_ne, __check_cs, __check_cc,
+ __check_mi, __check_pl, __check_vs, __check_vc,
+ __check_hi, __check_ls, __check_ge, __check_lt,
+ __check_gt, __check_le, __check_al, __check_al
+};
--
2.5.0