[Xen-devel] [PATCH v2 1/3] arm/arm64/xen: use C inlines for privcmd_call

[Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>]

privcmd_call requires to enable access to userspace for the
duration of the hypercall.

Currently, this is done via assembly macros. Change it to C
inlines instead.

Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
---
 arch/arm/include/asm/assembler.h       |  2 +-
 arch/arm/include/asm/xen/hypercall.h   | 10 +++++++++
 arch/arm/xen/enlighten.c               |  2 +-
 arch/arm/xen/hypercall.S               |  4 ++--
 arch/arm64/include/asm/xen/hypercall.h | 28 ++++++++++++++++++++++++++
 arch/arm64/xen/hypercall.S             | 19 ++---------------
 include/xen/arm/hypercall.h            | 12 +++++------
 7 files changed, 50 insertions(+), 27 deletions(-)

diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 99929122dad7..8e9262a0f016 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -480,7 +480,7 @@ THUMB(      orr     \reg , \reg , #PSR_T_BIT        )
        .macro  uaccess_disable, tmp, isb=1
 #ifdef CONFIG_CPU_SW_DOMAIN_PAN
        /*
-        * Whenever we re-enter userspace, the domains should always be
+        * Whenever we re-enter kernel, the domains should always be
         * set appropriately.
         */
        mov     \tmp, #DACR_UACCESS_DISABLE
diff --git a/arch/arm/include/asm/xen/hypercall.h 
b/arch/arm/include/asm/xen/hypercall.h
index 3522cbaed316..cac5bd9ef519 100644
--- a/arch/arm/include/asm/xen/hypercall.h
+++ b/arch/arm/include/asm/xen/hypercall.h
@@ -1 +1,11 @@
+#ifndef _ASM_ARM_XEN_HYPERCALL_H
+#define _ASM_ARM_XEN_HYPERCALL_H
 #include <xen/arm/hypercall.h>
+
+static inline long privcmd_call(unsigned int call, unsigned long a1,
+                               unsigned long a2, unsigned long a3,
+                               unsigned long a4, unsigned long a5)
+{
+       return arch_privcmd_call(call, a1, a2, a3, a4, a5);
+}
+#endif /* _ASM_ARM_XEN_HYPERCALL_H */
diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index dd6804a64f1a..e87280c6d25d 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -440,4 +440,4 @@ EXPORT_SYMBOL_GPL(HYPERVISOR_platform_op_raw);
 EXPORT_SYMBOL_GPL(HYPERVISOR_multicall);
 EXPORT_SYMBOL_GPL(HYPERVISOR_vm_assist);
 EXPORT_SYMBOL_GPL(HYPERVISOR_dm_op);
-EXPORT_SYMBOL_GPL(privcmd_call);
+EXPORT_SYMBOL_GPL(arch_privcmd_call);
diff --git a/arch/arm/xen/hypercall.S b/arch/arm/xen/hypercall.S
index b11bba542fac..277078c7da49 100644
--- a/arch/arm/xen/hypercall.S
+++ b/arch/arm/xen/hypercall.S
@@ -94,7 +94,7 @@ HYPERCALL2(multicall);
 HYPERCALL2(vm_assist);
 HYPERCALL3(dm_op);
 
-ENTRY(privcmd_call)
+ENTRY(arch_privcmd_call)
        stmdb sp!, {r4}
        mov r12, r0
        mov r0, r1
@@ -119,4 +119,4 @@ ENTRY(privcmd_call)
 
        ldm sp!, {r4}
        ret lr
-ENDPROC(privcmd_call);
+ENDPROC(arch_privcmd_call);
diff --git a/arch/arm64/include/asm/xen/hypercall.h 
b/arch/arm64/include/asm/xen/hypercall.h
index 3522cbaed316..1a74fb28607f 100644
--- a/arch/arm64/include/asm/xen/hypercall.h
+++ b/arch/arm64/include/asm/xen/hypercall.h
@@ -1 +1,29 @@
+#ifndef _ASM_ARM64_XEN_HYPERCALL_H
+#define _ASM_ARM64_XEN_HYPERCALL_H
 #include <xen/arm/hypercall.h>
+#include <linux/uaccess.h>
+
+static inline long privcmd_call(unsigned int call, unsigned long a1,
+                               unsigned long a2, unsigned long a3,
+                               unsigned long a4, unsigned long a5)
+{
+       long rv;
+
+       /*
+        * Privcmd calls are issued by the userspace. The kernel needs to
+        * enable access to TTBR0_EL1 as the hypervisor would issue stage 1
+        * translations to user memory via AT instructions. Since AT
+        * instructions are not affected by the PAN bit (ARMv8.1), we only
+        * need the explicit uaccess_enable/disable if the TTBR0 PAN emulation
+        * is enabled (it implies that hardware UAO and PAN disabled).
+        */
+       uaccess_ttbr0_enable();
+       rv = arch_privcmd_call(call, a1, a2, a3, a4, a5);
+       /*
+        * Disable userspace access from kernel once the hyp call completed.
+        */
+       uaccess_ttbr0_disable();
+
+       return rv;
+}
+#endif /* _ASM_ARM64_XEN_HYPERCALL_H */
diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S
index c5f05c4a4d00..921611778d2a 100644
--- a/arch/arm64/xen/hypercall.S
+++ b/arch/arm64/xen/hypercall.S
@@ -49,7 +49,6 @@
 
 #include <linux/linkage.h>
 #include <asm/assembler.h>
-#include <asm/asm-uaccess.h>
 #include <xen/interface/xen.h>
 
 
@@ -86,27 +85,13 @@ HYPERCALL2(multicall);
 HYPERCALL2(vm_assist);
 HYPERCALL3(dm_op);
 
-ENTRY(privcmd_call)
+ENTRY(arch_privcmd_call)
        mov x16, x0
        mov x0, x1
        mov x1, x2
        mov x2, x3
        mov x3, x4
        mov x4, x5
-       /*
-        * Privcmd calls are issued by the userspace. The kernel needs to
-        * enable access to TTBR0_EL1 as the hypervisor would issue stage 1
-        * translations to user memory via AT instructions. Since AT
-        * instructions are not affected by the PAN bit (ARMv8.1), we only
-        * need the explicit uaccess_enable/disable if the TTBR0 PAN emulation
-        * is enabled (it implies that hardware UAO and PAN disabled).
-        */
-       uaccess_ttbr0_enable x6, x7, x8
        hvc XEN_IMM
-
-       /*
-        * Disable userspace access from kernel once the hyp call completed.
-        */
-       uaccess_ttbr0_disable x6, x7
        ret
-ENDPROC(privcmd_call);
+ENDPROC(arch_privcmd_call);
diff --git a/include/xen/arm/hypercall.h b/include/xen/arm/hypercall.h
index b40485e54d80..624c8ad7e42a 100644
--- a/include/xen/arm/hypercall.h
+++ b/include/xen/arm/hypercall.h
@@ -30,8 +30,8 @@
  * IN THE SOFTWARE.
  */
 
-#ifndef _ASM_ARM_XEN_HYPERCALL_H
-#define _ASM_ARM_XEN_HYPERCALL_H
+#ifndef _ARM_XEN_HYPERCALL_H
+#define _ARM_XEN_HYPERCALL_H
 
 #include <linux/bug.h>
 
@@ -41,9 +41,9 @@
 
 struct xen_dm_op_buf;
 
-long privcmd_call(unsigned call, unsigned long a1,
-               unsigned long a2, unsigned long a3,
-               unsigned long a4, unsigned long a5);
+long arch_privcmd_call(unsigned int call, unsigned long a1,
+                      unsigned long a2, unsigned long a3,
+                      unsigned long a4, unsigned long a5);
 int HYPERVISOR_xen_version(int cmd, void *arg);
 int HYPERVISOR_console_io(int cmd, int count, char *str);
 int HYPERVISOR_grant_table_op(unsigned int cmd, void *uop, unsigned int count);
@@ -88,4 +88,4 @@ MULTI_mmu_update(struct multicall_entry *mcl, struct 
mmu_update *req,
        BUG();
 }
 
-#endif /* _ASM_ARM_XEN_HYPERCALL_H */
+#endif /* _ARM_XEN_HYPERCALL_H */
-- 
2.24.0


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