AArch64: Refactor GP register restore to separate function
At present, the function that restores general purpose registers also
does ERET. Refactor the restore code to restore general purpose
registers without ERET to complement the save function.
The macro save_x18_to_x29_sp_el0 was used only once, and is therefore
removed, and its contents expanded inline for readability.
No functional changes, but with this patch:
- The SMC return path will incur an branch-return and an additional
register load.
- The unknown SMC path restores registers x0 to x3.
Change-Id: I7a1a63e17f34f9cde810685d70a0ad13ca3b7c50
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
diff --git a/bl31/aarch64/runtime_exceptions.S b/bl31/aarch64/runtime_exceptions.S
index 1c3ed3f..e8cde54 100644
--- a/bl31/aarch64/runtime_exceptions.S
+++ b/bl31/aarch64/runtime_exceptions.S
@@ -154,25 +154,6 @@
.endm
- .macro save_x4_to_x29_sp_el0
- stp x4, x5, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X4]
- stp x6, x7, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X6]
- stp x8, x9, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X8]
- stp x10, x11, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X10]
- stp x12, x13, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X12]
- stp x14, x15, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X14]
- stp x16, x17, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X16]
- stp x18, x19, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X18]
- stp x20, x21, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X20]
- stp x22, x23, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X22]
- stp x24, x25, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X24]
- stp x26, x27, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X26]
- stp x28, x29, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X28]
- mrs x18, sp_el0
- str x18, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_SP_EL0]
- .endm
-
-
vector_base runtime_exceptions
/* ---------------------------------------------------------------------
@@ -345,7 +326,21 @@
*
* Save x4-x29 and sp_el0.
*/
- save_x4_to_x29_sp_el0
+ stp x4, x5, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X4]
+ stp x6, x7, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X6]
+ stp x8, x9, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X8]
+ stp x10, x11, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X10]
+ stp x12, x13, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X12]
+ stp x14, x15, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X14]
+ stp x16, x17, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X16]
+ stp x18, x19, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X18]
+ stp x20, x21, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X20]
+ stp x22, x23, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X22]
+ stp x24, x25, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X24]
+ stp x26, x27, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X26]
+ stp x28, x29, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X28]
+ mrs x18, sp_el0
+ str x18, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_SP_EL0]
mov x5, xzr
mov x6, sp
@@ -431,14 +426,12 @@
smc_unknown:
/*
- * Here we restore x4-x18 regardless of where we came from. AArch32
- * callers will find the registers contents unchanged, but AArch64
- * callers will find the registers modified (with stale earlier NS
- * content). Either way, we aren't leaking any secure information
- * through them.
+ * Unknown SMC call. Populate return value with SMC_UNK, restore
+ * GP registers, and return to caller.
*/
mov x0, #SMC_UNK
- b restore_gp_registers_callee_eret
+ str x0, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X0]
+ b restore_gp_registers_eret
smc_prohibited:
ldr x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]