Merge branch 'for-next/mops' into for-next/core

ctmarinas · ctmarinas · commit 437330d90c50 · 2024-11-14T12:07:28.000Z
* for-next/mops:
  : More FEAT_MOPS (memcpy instructions) uses - in-kernel routines
  arm64: mops: Document requirements for hypervisors
  arm64: lib: Use MOPS for copy_page() and clear_page()
  arm64: lib: Use MOPS for memcpy() routines
  arm64: mops: Document booting requirement for HCR_EL2.MCE2
  arm64: mops: Handle MOPS exceptions from EL1
  arm64: probes: Disable kprobes/uprobes on MOPS instructions

# Conflicts:
#	arch/arm64/kernel/entry-common.c
diff --git a/Documentation/arch/arm64/booting.rst b/Documentation/arch/arm64/booting.rst
@@ -388,6 +388,9 @@ Before jumping into the kernel, the following conditions must be met:
 
     - HCRX_EL2.MSCEn (bit 11) must be initialised to 0b1.
 
+    - HCRX_EL2.MCE2 (bit 10) must be initialised to 0b1 and the hypervisor
+      must handle MOPS exceptions as described in :ref:`arm64_mops_hyp`.
+
   For CPUs with the Extended Translation Control Register feature (FEAT_TCR2):
 
   - If EL3 is present:
diff --git a/Documentation/arch/arm64/index.rst b/Documentation/arch/arm64/index.rst
@@ -22,6 +22,7 @@ ARM64 Architecture
     legacy_instructions
     memory
     memory-tagging-extension
+    mops
     perf
     pointer-authentication
     ptdump
diff --git a/Documentation/arch/arm64/mops.rst b/Documentation/arch/arm64/mops.rst
@@ -0,0 +1,44 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================================
+Memory copy/set instructions (MOPS)
+===================================
+
+A MOPS memory copy/set operation consists of three consecutive CPY* or SET*
+instructions: a prologue, main and epilogue (for example: CPYP, CPYM, CPYE).
+
+A main or epilogue instruction can take a MOPS exception for various reasons,
+for example when a task is migrated to a CPU with a different MOPS
+implementation, or when the instruction's alignment and size requirements are
+not met. The software exception handler is then expected to reset the registers
+and restart execution from the prologue instruction. Normally this is handled
+by the kernel.
+
+For more details refer to "D1.3.5.7 Memory Copy and Memory Set exceptions" in
+the Arm Architecture Reference Manual DDI 0487K.a (Arm ARM).
+
+.. _arm64_mops_hyp:
+
+Hypervisor requirements
+-----------------------
+
+A hypervisor running a Linux guest must handle all MOPS exceptions from the
+guest kernel, as Linux may not be able to handle the exception at all times.
+For example, a MOPS exception can be taken when the hypervisor migrates a vCPU
+to another physical CPU with a different MOPS implementation.
+
+To do this, the hypervisor must:
+
+  - Set HCRX_EL2.MCE2 to 1 so that the exception is taken to the hypervisor.
+
+  - Have an exception handler that implements the algorithm from the Arm ARM
+    rules CNTMJ and MWFQH.
+
+  - Set the guest's PSTATE.SS to 0 in the exception handler, to handle a
+    potential step of the current instruction.
+
+    Note: Clearing PSTATE.SS is needed so that a single step exception is taken
+    on the next instruction (the prologue instruction). Otherwise prologue
+    would get silently stepped over and the single step exception taken on the
+    main instruction. Note that if the guest instruction is not being stepped
+    then clearing PSTATE.SS has no effect.
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
@@ -2160,6 +2160,9 @@ config ARM64_EPAN
 	  if the cpu does not implement the feature.
 endmenu # "ARMv8.7 architectural features"
 
+config AS_HAS_MOPS
+	def_bool $(as-instr,.arch_extension mops)
+
 menu "ARMv8.9 architectural features"
 
 config ARM64_POE
diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h
@@ -105,6 +105,7 @@ void kernel_enable_single_step(struct pt_regs *regs);
 void kernel_disable_single_step(void);
 int kernel_active_single_step(void);
 void kernel_rewind_single_step(struct pt_regs *regs);
+void kernel_fastforward_single_step(struct pt_regs *regs);
 
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
 int reinstall_suspended_bps(struct pt_regs *regs);
diff --git a/arch/arm64/include/asm/exception.h b/arch/arm64/include/asm/exception.h
@@ -75,6 +75,7 @@ void do_el0_svc_compat(struct pt_regs *regs);
 void do_el0_fpac(struct pt_regs *regs, unsigned long esr);
 void do_el1_fpac(struct pt_regs *regs, unsigned long esr);
 void do_el0_mops(struct pt_regs *regs, unsigned long esr);
+void do_el1_mops(struct pt_regs *regs, unsigned long esr);
 void do_serror(struct pt_regs *regs, unsigned long esr);
 void do_signal(struct pt_regs *regs);
 
diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
@@ -353,6 +353,7 @@ __AARCH64_INSN_FUNCS(ldrsw_lit,	0xFF000000, 0x98000000)
 __AARCH64_INSN_FUNCS(exclusive,	0x3F800000, 0x08000000)
 __AARCH64_INSN_FUNCS(load_ex,	0x3F400000, 0x08400000)
 __AARCH64_INSN_FUNCS(store_ex,	0x3F400000, 0x08000000)
+__AARCH64_INSN_FUNCS(mops,	0x3B200C00, 0x19000400)
 __AARCH64_INSN_FUNCS(stp,	0x7FC00000, 0x29000000)
 __AARCH64_INSN_FUNCS(ldp,	0x7FC00000, 0x29400000)
 __AARCH64_INSN_FUNCS(stp_post,	0x7FC00000, 0x28800000)
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
@@ -440,6 +440,11 @@ void kernel_rewind_single_step(struct pt_regs *regs)
 	set_regs_spsr_ss(regs);
 }
 
+void kernel_fastforward_single_step(struct pt_regs *regs)
+{
+	clear_regs_spsr_ss(regs);
+}
+
 /* ptrace API */
 void user_enable_single_step(struct task_struct *task)
 {
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
@@ -472,6 +472,15 @@ static void noinstr el1_gcs(struct pt_regs *regs, unsigned long esr)
 	exit_to_kernel_mode(regs);
 }
 
+static void noinstr el1_mops(struct pt_regs *regs, unsigned long esr)
+{
+	enter_from_kernel_mode(regs);
+	local_daif_inherit(regs);
+	do_el1_mops(regs, esr);
+	local_daif_mask();
+	exit_to_kernel_mode(regs);
+}
+
 static void noinstr el1_dbg(struct pt_regs *regs, unsigned long esr)
 {
 	unsigned long far = read_sysreg(far_el1);
@@ -517,6 +526,9 @@ asmlinkage void noinstr el1h_64_sync_handler(struct pt_regs *regs)
 	case ESR_ELx_EC_GCS:
 		el1_gcs(regs, esr);
 		break;
+	case ESR_ELx_EC_MOPS:
+		el1_mops(regs, esr);
+		break;
 	case ESR_ELx_EC_BREAKPT_CUR:
 	case ESR_ELx_EC_SOFTSTP_CUR:
 	case ESR_ELx_EC_WATCHPT_CUR:
diff --git a/arch/arm64/kernel/probes/decode-insn.c b/arch/arm64/kernel/probes/decode-insn.c
@@ -58,10 +58,13 @@ static bool __kprobes aarch64_insn_is_steppable(u32 insn)
 	 * Instructions which load PC relative literals are not going to work
 	 * when executed from an XOL slot. Instructions doing an exclusive
 	 * load/store are not going to complete successfully when single-step
-	 * exception handling happens in the middle of the sequence.
+	 * exception handling happens in the middle of the sequence. Memory
+	 * copy/set instructions require that all three instructions be placed
+	 * consecutively in memory.
 	 */
 	if (aarch64_insn_uses_literal(insn) ||
-	    aarch64_insn_is_exclusive(insn))
+	    aarch64_insn_is_exclusive(insn) ||
+	    aarch64_insn_is_mops(insn))
 		return false;
 
 	return true;
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
@@ -541,6 +541,13 @@ void do_el0_mops(struct pt_regs *regs, unsigned long esr)
 	user_fastforward_single_step(current);
 }
 
+void do_el1_mops(struct pt_regs *regs, unsigned long esr)
+{
+	arm64_mops_reset_regs(&regs->user_regs, esr);
+
+	kernel_fastforward_single_step(regs);
+}
+
 #define __user_cache_maint(insn, address, res)			\
 	if (address >= TASK_SIZE_MAX) {				\
 		res = -EFAULT;					\
diff --git a/arch/arm64/lib/clear_page.S b/arch/arm64/lib/clear_page.S
@@ -15,6 +15,19 @@
  *	x0 - dest
  */
 SYM_FUNC_START(__pi_clear_page)
+#ifdef CONFIG_AS_HAS_MOPS
+	.arch_extension mops
+alternative_if_not ARM64_HAS_MOPS
+	b	.Lno_mops
+alternative_else_nop_endif
+
+	mov	x1, #PAGE_SIZE
+	setpn	[x0]!, x1!, xzr
+	setmn	[x0]!, x1!, xzr
+	seten	[x0]!, x1!, xzr
+	ret
+.Lno_mops:
+#endif
 	mrs	x1, dczid_el0
 	tbnz	x1, #4, 2f	/* Branch if DC ZVA is prohibited */
 	and	w1, w1, #0xf
diff --git a/arch/arm64/lib/copy_page.S b/arch/arm64/lib/copy_page.S
@@ -18,6 +18,19 @@
  *	x1 - src
  */
 SYM_FUNC_START(__pi_copy_page)
+#ifdef CONFIG_AS_HAS_MOPS
+	.arch_extension mops
+alternative_if_not ARM64_HAS_MOPS
+	b	.Lno_mops
+alternative_else_nop_endif
+
+	mov	x2, #PAGE_SIZE
+	cpypwn	[x0]!, [x1]!, x2!
+	cpymwn	[x0]!, [x1]!, x2!
+	cpyewn	[x0]!, [x1]!, x2!
+	ret
+.Lno_mops:
+#endif
 	ldp	x2, x3, [x1]
 	ldp	x4, x5, [x1, #16]
 	ldp	x6, x7, [x1, #32]
diff --git a/arch/arm64/lib/memcpy.S b/arch/arm64/lib/memcpy.S
@@ -57,7 +57,7 @@
    The loop tail is handled by always copying 64 bytes from the end.
 */
 
-SYM_FUNC_START(__pi_memcpy)
+SYM_FUNC_START_LOCAL(__pi_memcpy_generic)
 	add	srcend, src, count
 	add	dstend, dstin, count
 	cmp	count, 128
@@ -238,7 +238,24 @@ L(copy64_from_start):
 	stp	B_l, B_h, [dstin, 16]
 	stp	C_l, C_h, [dstin]
 	ret
+SYM_FUNC_END(__pi_memcpy_generic)
+
+#ifdef CONFIG_AS_HAS_MOPS
+	.arch_extension mops
+SYM_FUNC_START(__pi_memcpy)
+alternative_if_not ARM64_HAS_MOPS
+	b	__pi_memcpy_generic
+alternative_else_nop_endif
+
+	mov	dst, dstin
+	cpyp	[dst]!, [src]!, count!
+	cpym	[dst]!, [src]!, count!
+	cpye	[dst]!, [src]!, count!
+	ret
 SYM_FUNC_END(__pi_memcpy)
+#else
+SYM_FUNC_ALIAS(__pi_memcpy, __pi_memcpy_generic)
+#endif
 
 SYM_FUNC_ALIAS(__memcpy, __pi_memcpy)
 EXPORT_SYMBOL(__memcpy)
diff --git a/arch/arm64/lib/memset.S b/arch/arm64/lib/memset.S
@@ -26,6 +26,7 @@
  */
 
 dstin		.req	x0
+val_x		.req	x1
 val		.req	w1
 count		.req	x2
 tmp1		.req	x3
@@ -42,7 +43,7 @@ dst		.req	x8
 tmp3w		.req	w9
 tmp3		.req	x9
 
-SYM_FUNC_START(__pi_memset)
+SYM_FUNC_START_LOCAL(__pi_memset_generic)
 	mov	dst, dstin	/* Preserve return value.  */
 	and	A_lw, val, #255
 	orr	A_lw, A_lw, A_lw, lsl #8
@@ -201,7 +202,24 @@ SYM_FUNC_START(__pi_memset)
 	ands	count, count, zva_bits_x
 	b.ne	.Ltail_maybe_long
 	ret
+SYM_FUNC_END(__pi_memset_generic)
+
+#ifdef CONFIG_AS_HAS_MOPS
+	.arch_extension mops
+SYM_FUNC_START(__pi_memset)
+alternative_if_not ARM64_HAS_MOPS
+	b	__pi_memset_generic
+alternative_else_nop_endif
+
+	mov	dst, dstin
+	setp	[dst]!, count!, val_x
+	setm	[dst]!, count!, val_x
+	sete	[dst]!, count!, val_x
+	ret
 SYM_FUNC_END(__pi_memset)
+#else
+SYM_FUNC_ALIAS(__pi_memset, __pi_memset_generic)
+#endif
 
 SYM_FUNC_ALIAS(__memset, __pi_memset)
 EXPORT_SYMBOL(__memset)

Original file line number	Diff line number	Diff line change
`@@ -440,6 +440,11 @@ void kernel_rewind_single_step(struct pt_regs *regs)`
`440`	`440`	`set_regs_spsr_ss(regs);`
`441`	`441`	`}`
`442`	`442`
	`443`	`+void kernel_fastforward_single_step(struct pt_regs *regs)`
	`444`	`+{`
	`445`	`+ clear_regs_spsr_ss(regs);`
	`446`	`+}`
	`447`	`+`
`443`	`448`	`/* ptrace API */`
`444`	`449`	`void user_enable_single_step(struct task_struct *task)`
`445`	`450`	`{`