ARM: 9198/1: spectre-bhb: simplify BPIALL vector macro

The BPIALL mitigation for Spectre-BHB adds a single instruction to the
handler sequence that doesn't clobber any registers. Given that these
sequences are 10 instructions long, they don't fit neatly into a
cacheline anyway, so we can simply move that single instruction to the
start of the unmitigated one, and rearrange the symbol names accordingly.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 6e7dfb4..87cb063 100644 (file)
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -1078,6 +1078,12 @@ __kuser_helper_end:
  */
        .macro  vector_stub, name, mode, correction=0
        .align  5
+#ifdef CONFIG_HARDEN_BRANCH_HISTORY
+vector_bhb_bpiall_\name:
+       mcr     p15, 0, r0, c7, c5, 6   @ BPIALL
+       @ isb not needed due to "movs pc, lr" in the vector stub
+       @ which gives a "context synchronisation".
+#endif
 
 vector_\name:
        .if \correction
@@ -1129,21 +1135,6 @@ vector_bhb_loop8_\name:
        isb
        b       2b
 ENDPROC(vector_bhb_loop8_\name)
-
-vector_bhb_bpiall_\name:
-       .if \correction
-       sub     lr, lr, #\correction
-       .endif
-
-       @ Save r0, lr_<exception> (parent PC)
-       stmia   sp, {r0, lr}
-
-       @ bhb workaround
-       mcr     p15, 0, r0, c7, c5, 6   @ BPIALL
-       @ isb not needed due to "movs pc, lr" in the vector stub
-       @ which gives a "context synchronisation".
-       b       2b
-ENDPROC(vector_bhb_bpiall_\name)
        .previous
 #endif