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

David Long
2016-03-02T05:14:40Z

On 03/01/2016 12:43 PM, Marc Zyngier wrote:
> On 01/03/16 02:57, David Long wrote:
>> 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)
>
> Nit: since this is exclusively targeted at emulating 32bit code, having
> arm64_ as a prefix is mildly confusing. Either keep the arm_ prefix, or
> turn it into arm32_.
>

The goal was to make sure it didn't conflict with the definition in
arch/arm/include/asm/opcodes.h, but naming it arm32_check_condition()
will do that too.

>> +{
>> + 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
>
> This is the second time you define this, which makes me think that this
> should live in some include file. On the other hand, it doesn't seem to
> be used in the following code, so maybe get rid of it altogether?
>

Yeah, this looks like a leftover after moving the related code to
another file. Deleted.

>> +
>> +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
>> +};
>>
>
> Thanks,
>
> M.
>