[Xen-devel] [PATCH v1 1/6] arm: add SMC wrapper that is compatible with SMCCC

[Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>]

Existing SMC wrapper call_smc() allows only 4 parameters and
returns only one value. This is enough for existing
use in PSCI code, but TEE mediator will need a call that is
fully compatible with ARM SMCCC.
This patch adds this call for both arm32 and arm64.

There was similar patch by Edgar E. Iglesias ([1]), but looks
like it is abandoned.

[1] https://lists.xenproject.org/archives/html/xen-devel/2017-02/msg00636.html

CC: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxxx>

Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
---

changes from "RFC":
  - response now stored in structure instead of array
  - added comments for arm32 assembly code
  - added offset (instead of magic values) for arm32 asm code

 xen/arch/arm/arm32/Makefile      |  1 +
 xen/arch/arm/arm32/smc.S         | 39 +++++++++++++++++++++++++++++++++++++++
 xen/arch/arm/arm64/Makefile      |  1 +
 xen/arch/arm/arm64/asm-offsets.c |  4 ++++
 xen/arch/arm/arm64/smc.S         | 30 ++++++++++++++++++++++++++++++
 xen/include/asm-arm/processor.h  | 11 +++++++++++
 6 files changed, 86 insertions(+)
 create mode 100644 xen/arch/arm/arm32/smc.S
 create mode 100644 xen/arch/arm/arm64/smc.S

diff --git a/xen/arch/arm/arm32/Makefile b/xen/arch/arm/arm32/Makefile
index 0ac254f..c69f35e 100644
--- a/xen/arch/arm/arm32/Makefile
+++ b/xen/arch/arm/arm32/Makefile
@@ -10,4 +10,5 @@ obj-y += proc-v7.o proc-caxx.o
 obj-y += smpboot.o
 obj-y += traps.o
 obj-y += vfp.o
+obj-y += smc.o
 
diff --git a/xen/arch/arm/arm32/smc.S b/xen/arch/arm/arm32/smc.S
new file mode 100644
index 0000000..56f7982
--- /dev/null
+++ b/xen/arch/arm/arm32/smc.S
@@ -0,0 +1,39 @@
+/*
+ * xen/arch/arm/arm32/smc.S
+ *
+ * Wrapper for Secure Monitors Calls
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <asm/macros.h>
+
+/*
+ * void call_smccc_smc(register_t a0, register_t a1, register_t a2,
+ *                     register_t a3, register_t a4, register_t a5,
+ *                     register_t a6, register_t a7, struct smccc_res *res)
+ */
+ENTRY(call_smccc_smc)
+        mov     r12, sp
+        push    {r4-r7}
+       /*
+        * According to ARMv7 (or aarch32) ABI, first 4 parameters of
+        * call_smccc_smc are passed in r0-r3 and other 4 are on stack.
+        * Load a4-a7 from stack to r4-r7.
+        */
+        ldm     r12, {r4-r7}
+        smc     #0
+        pop     {r4-r7}
+       /* Load pointer to res (4th parameter on stack) to r12 */
+        ldr     r12, [sp, #(4 * 4)]
+       /* Store returned results from r0-r3 to res */
+        stm     r12, {r0-r3}
+        bx      lr
diff --git a/xen/arch/arm/arm64/Makefile b/xen/arch/arm/arm64/Makefile
index bb5c610..7ecdad7 100644
--- a/xen/arch/arm/arm64/Makefile
+++ b/xen/arch/arm/arm64/Makefile
@@ -9,6 +9,7 @@ obj-y += entry.o
 obj-y += insn.o
 obj-$(CONFIG_LIVEPATCH) += livepatch.o
 obj-y += smpboot.o
+obj-y += smc.o
 obj-y += traps.o
 obj-y += vfp.o
 obj-y += vsysreg.o
diff --git a/xen/arch/arm/arm64/asm-offsets.c b/xen/arch/arm/arm64/asm-offsets.c
index ce24e44..5353fe8 100644
--- a/xen/arch/arm/arm64/asm-offsets.c
+++ b/xen/arch/arm/arm64/asm-offsets.c
@@ -50,6 +50,10 @@ void __dummy__(void)
 
    BLANK();
    OFFSET(INITINFO_stack, struct init_info, stack);
+
+   BLANK();
+   OFFSET(SMCCC_RES_a0, struct smccc_res, a0);
+   OFFSET(SMCCC_RES_a2, struct smccc_res, a2);
 }
 
 /*
diff --git a/xen/arch/arm/arm64/smc.S b/xen/arch/arm/arm64/smc.S
new file mode 100644
index 0000000..40843c0
--- /dev/null
+++ b/xen/arch/arm/arm64/smc.S
@@ -0,0 +1,30 @@
+/*
+ * xen/arch/arm/arm64/smc.S
+ *
+ * Wrapper for Secure Monitors Calls
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <asm/asm_defns.h>
+#include <asm/macros.h>
+
+/*
+ * void call_smccc_smc(register_t a0, register_t a1, register_t a2,
+ *                     register_t a3, register_t a4, register_t a5,
+ *                     register_t a6, register_t a7, struct smccc_res *res)
+ */
+ENTRY(call_smccc_smc)
+        smc     #0
+        ldr     x4, [sp]
+        stp     x0, x1, [x4, #SMCCC_RES_a0]
+        stp     x2, x3, [x4, #SMCCC_RES_a2]
+        ret
diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index 222a02d..946a2db 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -650,6 +650,13 @@ union hsr {
 
 
 };
+
+struct smccc_res {
+    register_t a0;
+    register_t a1;
+    register_t a2;
+    register_t a3;
+};
 #endif
 
 /* HSR.EC == HSR_CP{15,14,10}_32 */
@@ -815,6 +822,10 @@ void vcpu_regs_user_to_hyp(struct vcpu *vcpu,
 int call_smc(register_t function_id, register_t arg0, register_t arg1,
              register_t arg2);
 
+void call_smccc_smc(register_t a0, register_t a1, register_t a2,
+                    register_t a3, register_t a4, register_t a5,
+                    register_t a6, register_t a7, struct smccc_res *res);
+
 void do_trap_hyp_serror(struct cpu_user_regs *regs);
 
 void do_trap_guest_serror(struct cpu_user_regs *regs);
-- 
2.7.4


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