From mboxrd@z Thu Jan 1 00:00:00 1970 From: nicoleotsuka@gmail.com (Nicolin Chen) Date: Wed, 10 Jan 2018 20:43:36 -0800 Subject: [PATCH RFC v1] arm64: Handle traps from accessing CNTVCT/CNTFRQ for CONFIG_COMPAT Message-ID: <1515645816-14063-1-git-send-email-nicoleotsuka@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org CONFIG_COMPAT allows ARM64 machine to run 32-bit instructions. Since the ARCH_TIMER_USR_VCT_ACCESS_EN might be disabled if a timer workaround is detected, accessing cntvct via mrrc will also trigger a trap. So this patch adds support to handle this situation. Tested with a user program generated by 32-bit compiler: int main() { unsigned long long cval; asm volatile("mrrc p15, 1, %Q0, %R0, c14" : "=r" (cval)); return 0; } Signed-off-by: Nicolin Chen --- [ I also added cntfrq here for safety as theoretically it could trigger the trap as well. However, my another test case (with mrc insturction) doesn't seem to trigger a trap. So I would drop it in the next version if someone can confirm it's not required. Thanks -- Nicolin ] arch/arm64/include/asm/esr.h | 25 +++++++++++++++++++ arch/arm64/include/asm/ptrace.h | 15 ++++++++++++ arch/arm64/kernel/entry.S | 4 ++-- arch/arm64/kernel/traps.c | 53 +++++++++++++++++++++++++++++++++++++++-- 4 files changed, 93 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h index 014d7d8..55dea62 100644 --- a/arch/arm64/include/asm/esr.h +++ b/arch/arm64/include/asm/esr.h @@ -220,6 +220,31 @@ (((e) & ESR_ELx_SYS64_ISS_OP2_MASK) >> \ ESR_ELx_SYS64_ISS_OP2_SHIFT)) +/* ISS fields for MRC and MRS are very similar, so reuse SYS64 macros */ +#define ESR_ELx_CP15_32_ISS_MRC_MASK ESR_ELx_SYS64_ISS_SYS_MASK +#define ESR_ELx_CP15_32_ISS_MRC_CNTFRQ (ESR_ELx_SYS64_ISS_SYS_VAL(0, 0, 0, 14, 0) | \ + ESR_ELx_SYS64_ISS_DIR_READ) + +/* ISS field definitions for CP15 MRRC/MCRR instructions (same for CP14) */ +#define ESR_ELx_CP15_64_ISS_OPC1_SHIFT 16 +#define ESR_ELx_CP15_64_ISS_OPC1_MASK (UL(0xf) << ESR_ELx_CP15_64_ISS_OPC1_SHIFT) +#define ESR_ELx_CP15_64_ISS_RT2_SHIFT 10 +#define ESR_ELx_CP15_64_ISS_RT2_MASK (UL(0x1f) << ESR_ELx_CP15_64_ISS_RT2_SHIFT) +#define ESR_ELx_CP15_64_ISS_RT_SHIFT 5 +#define ESR_ELx_CP15_64_ISS_RT_MASK (UL(0x1f) << ESR_ELx_CP15_64_ISS_RT_SHIFT) +#define ESR_ELx_CP15_64_ISS_CRM_SHIFT 1 +#define ESR_ELx_CP15_64_ISS_CRM_MASK (UL(0xf) << ESR_ELx_CP15_64_ISS_CRM_SHIFT) +#define ESR_ELx_CP15_64_ISS_MRRC_MASK (ESR_ELx_CP15_64_ISS_OPC1_MASK | \ + ESR_ELx_CP15_64_ISS_CRM_MASK| \ + ESR_ELx_SYS64_ISS_DIR_MASK) + +#define ESR_ELx_CP15_64_ISS_MRRC_VAL(opc1, crm) \ + (((opc1) << ESR_ELx_CP15_64_ISS_OPC1_SHIFT) | \ + ((crm) << ESR_ELx_CP15_64_ISS_CRM_SHIFT)) + +#define ESR_ELx_CP15_64_ISS_MRRC_CNTVCT (ESR_ELx_CP15_64_ISS_MRRC_VAL(1, 14) | \ + ESR_ELx_SYS64_ISS_DIR_READ) + #ifndef __ASSEMBLY__ #include diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index 6069d66..50caf11 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -243,6 +243,21 @@ static inline void pt_regs_write_reg(struct pt_regs *regs, int r, regs->regs[r] = val; } +/* + * Write two registers given architectural register index r and r2. + * Used by 32-bit MRRC and MCRR instrutions for 64-bit results + */ +static inline void pt_regs_write_regs(struct pt_regs *regs, int r, int r2, + unsigned long val) +{ + if (r != 31 && r2 != 31) { + /* Save lower 32 bits to register r */ + regs->regs[r] = val & 0xffffffff; + /* Save higher 32 bits to register r2 */ + regs->regs[r2] = val >> 32; + } +} + /* Valid only for Kernel mode traps. */ static inline unsigned long kernel_stack_pointer(struct pt_regs *regs) { diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 6d14b8f..9d6cd95 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -636,9 +636,9 @@ el0_sync_compat: cmp x24, #ESR_ELx_EC_UNKNOWN // unknown exception in EL0 b.eq el0_undef cmp x24, #ESR_ELx_EC_CP15_32 // CP15 MRC/MCR trap - b.eq el0_undef + b.eq el0_sys cmp x24, #ESR_ELx_EC_CP15_64 // CP15 MRRC/MCRR trap - b.eq el0_undef + b.eq el0_sys cmp x24, #ESR_ELx_EC_CP14_MR // CP14 MRC/MCR trap b.eq el0_undef cmp x24, #ESR_ELx_EC_CP14_LS // CP14 LDC/STC trap diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 3d3588f..211cce7 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -454,6 +454,17 @@ static void cntvct_read_handler(unsigned int esr, struct pt_regs *regs) arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE); } +#ifdef CONFIG_COMPAT +static void cntvct_read_32_handler(unsigned int esr, struct pt_regs *regs) +{ + int rt2 = (esr & ESR_ELx_CP15_64_ISS_RT2_MASK) >> ESR_ELx_CP15_64_ISS_RT2_SHIFT; + int rt = (esr & ESR_ELx_CP15_64_ISS_RT_MASK) >> ESR_ELx_CP15_64_ISS_RT_SHIFT; + + pt_regs_write_regs(regs, rt, rt2, arch_counter_get_cntvct()); + arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE); +} +#endif + static void cntfrq_read_handler(unsigned int esr, struct pt_regs *regs) { int rt = (esr & ESR_ELx_SYS64_ISS_RT_MASK) >> ESR_ELx_SYS64_ISS_RT_SHIFT; @@ -495,11 +506,49 @@ static struct sys64_hook sys64_hooks[] = { {}, }; +#ifdef CONFIG_COMPAT +static struct sys64_hook cp15_32_hooks[] = { + { + /* Trap read access to CNTFRQ via 32-bit insturction MRC */ + .esr_mask = ESR_ELx_CP15_32_ISS_MRC_MASK, + .esr_val = ESR_ELx_CP15_32_ISS_MRC_CNTFRQ, + .handler = cntfrq_read_handler, + }, + {}, +}; + +static struct sys64_hook cp15_64_hooks[] = { + { + /* Trap read access to CNTVCT via 32-bit insturction MRRC */ + .esr_mask = ESR_ELx_CP15_64_ISS_MRRC_MASK, + .esr_val = ESR_ELx_CP15_64_ISS_MRRC_CNTVCT, + .handler = cntvct_read_32_handler, + }, + {}, +}; +#endif + asmlinkage void __exception do_sysinstr(unsigned int esr, struct pt_regs *regs) { - struct sys64_hook *hook; + struct sys64_hook *hook = NULL; + + switch (ESR_ELx_EC(esr)) { +#ifdef CONFIG_COMPAT + case ESR_ELx_EC_CP15_32: + hook = cp15_32_hooks; + break; + case ESR_ELx_EC_CP15_64: + hook = cp15_64_hooks; + break; +#endif + case ESR_ELx_EC_SYS64: + hook = sys64_hooks; + break; + default: + break; + } - for (hook = sys64_hooks; hook->handler; hook++) + for (; hook && hook->handler; hook++) if ((hook->esr_mask & esr) == hook->esr_val) { hook->handler(esr, regs); return; -- 2.1.4