[PATCH 4.15 027/202] [Variant 3/Meltdown] arm64: entry: Hook up entry trampoline to exception vectors

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

--

From: Will Deacon 


Commit 4bf3286d29f3 upstream.

Hook up the entry trampoline to our exception vectors so that all
exceptions from and returns to EL0 go via the trampoline, which swizzles
the vector base register accordingly. Transitioning to and from the
kernel clobbers x30, so we use tpidrro_el0 and far_el1 as scratch
registers for native tasks.

Reviewed-by: Mark Rutland 
Tested-by: Laura Abbott 
Tested-by: Shanker Donthineni 
Signed-off-by: Will Deacon 
Signed-off-by: Greg Kroah-Hartman 
---
 arch/arm64/kernel/entry.S |   39 ---
 1 file changed, 36 insertions(+), 3 deletions(-)

--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -73,6 +73,17 @@
 
.macro kernel_ventry, el, label, regsize = 64
.align 7
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+   .if \el == 0
+   .if \regsize == 64
+   mrs x30, tpidrro_el0
+   msr tpidrro_el0, xzr
+   .else
+   mov x30, xzr
+   .endif
+   .endif
+#endif
+
sub sp, sp, #S_FRAME_SIZE
 #ifdef CONFIG_VMAP_STACK
/*
@@ -119,6 +130,11 @@
b   el\()\el\()_\label
.endm
 
+   .macro tramp_alias, dst, sym
+   mov_q   \dst, TRAMP_VALIAS
+   add \dst, \dst, #(\sym - .entry.tramp.text)
+   .endm
+
.macro  kernel_entry, el, regsize = 64
.if \regsize == 32
mov w0, w0  // zero upper 32 bits of x0
@@ -271,18 +287,20 @@ alternative_else_nop_endif
.if \el == 0
ldr x23, [sp, #S_SP]// load return stack pointer
msr sp_el0, x23
+   tst x22, #PSR_MODE32_BIT// native task?
+   b.eq3f
+
 #ifdef CONFIG_ARM64_ERRATUM_845719
 alternative_if ARM64_WORKAROUND_845719
-   tbz x22, #4, 1f
 #ifdef CONFIG_PID_IN_CONTEXTIDR
mrs x29, contextidr_el1
msr contextidr_el1, x29
 #else
msr contextidr_el1, xzr
 #endif
-1:
 alternative_else_nop_endif
 #endif
+3:
.endif
 
msr elr_el1, x21// set up the return data
@@ -304,7 +322,22 @@ alternative_else_nop_endif
ldp x28, x29, [sp, #16 * 14]
ldr lr, [sp, #S_LR]
add sp, sp, #S_FRAME_SIZE   // restore sp
-   eret// return to kernel
+
+#ifndef CONFIG_UNMAP_KERNEL_AT_EL0
+   eret
+#else
+   .if \el == 0
+   bne 4f
+   msr far_el1, x30
+   tramp_alias x30, tramp_exit_native
+   br  x30
+4:
+   tramp_alias x30, tramp_exit_compat
+   br  x30
+   .else
+   eret
+   .endif
+#endif
.endm
 
.macro  irq_stack_entry

[PATCH 4.15 027/202] [Variant 3/Meltdown] arm64: entry: Hook up entry trampoline to exception vectors

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

--

From: Will Deacon 


Commit 4bf3286d29f3 upstream.

Hook up the entry trampoline to our exception vectors so that all
exceptions from and returns to EL0 go via the trampoline, which swizzles
the vector base register accordingly. Transitioning to and from the
kernel clobbers x30, so we use tpidrro_el0 and far_el1 as scratch
registers for native tasks.

Reviewed-by: Mark Rutland 
Tested-by: Laura Abbott 
Tested-by: Shanker Donthineni 
Signed-off-by: Will Deacon 
Signed-off-by: Greg Kroah-Hartman 
---
 arch/arm64/kernel/entry.S |   39 ---
 1 file changed, 36 insertions(+), 3 deletions(-)

--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -73,6 +73,17 @@
 
.macro kernel_ventry, el, label, regsize = 64
.align 7
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+   .if \el == 0
+   .if \regsize == 64
+   mrs x30, tpidrro_el0
+   msr tpidrro_el0, xzr
+   .else
+   mov x30, xzr
+   .endif
+   .endif
+#endif
+
sub sp, sp, #S_FRAME_SIZE
 #ifdef CONFIG_VMAP_STACK
/*
@@ -119,6 +130,11 @@
b   el\()\el\()_\label
.endm
 
+   .macro tramp_alias, dst, sym
+   mov_q   \dst, TRAMP_VALIAS
+   add \dst, \dst, #(\sym - .entry.tramp.text)
+   .endm
+
.macro  kernel_entry, el, regsize = 64
.if \regsize == 32
mov w0, w0  // zero upper 32 bits of x0
@@ -271,18 +287,20 @@ alternative_else_nop_endif
.if \el == 0
ldr x23, [sp, #S_SP]// load return stack pointer
msr sp_el0, x23
+   tst x22, #PSR_MODE32_BIT// native task?
+   b.eq3f
+
 #ifdef CONFIG_ARM64_ERRATUM_845719
 alternative_if ARM64_WORKAROUND_845719
-   tbz x22, #4, 1f
 #ifdef CONFIG_PID_IN_CONTEXTIDR
mrs x29, contextidr_el1
msr contextidr_el1, x29
 #else
msr contextidr_el1, xzr
 #endif
-1:
 alternative_else_nop_endif
 #endif
+3:
.endif
 
msr elr_el1, x21// set up the return data
@@ -304,7 +322,22 @@ alternative_else_nop_endif
ldp x28, x29, [sp, #16 * 14]
ldr lr, [sp, #S_LR]
add sp, sp, #S_FRAME_SIZE   // restore sp
-   eret// return to kernel
+
+#ifndef CONFIG_UNMAP_KERNEL_AT_EL0
+   eret
+#else
+   .if \el == 0
+   bne 4f
+   msr far_el1, x30
+   tramp_alias x30, tramp_exit_native
+   br  x30
+4:
+   tramp_alias x30, tramp_exit_compat
+   br  x30
+   .else
+   eret
+   .endif
+#endif
.endm
 
.macro  irq_stack_entry