When we get booted we want a clear slate without any leaks from previous
supervisors or the firmware. Flush the instruction cache and then clear
all registers to known good values. This is really important for the
upcoming nommu support that runs on M-mode, but can't really harm when
running in S-mode either. Vaguely based on the concepts from opensbi.
Signed-off-by: Christoph Hellwig <h...@lst.de>
---
arch/riscv/kernel/head.S | 83 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 83 insertions(+)
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 4e46f31072da..5681179183d4 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -11,6 +11,7 @@
#include <asm/thread_info.h>
#include <asm/page.h>
#include <asm/csr.h>
+#include <asm/hwcap.h>
__INIT
ENTRY(_start)
@@ -18,6 +19,12 @@ ENTRY(_start)
csrw CSR_SIE, zero
csrw CSR_SIP, zero
+ /* flush the instruction cache */
+ fence.i
+
+ /* Reset all registers except ra, a0,a1 */
+ call reset_regs
+
/* Load the global pointer */
.option push
.option norelax
@@ -160,6 +167,82 @@ relocate:
j .Lsecondary_park
END(_start)
+ENTRY(reset_regs)
+ li sp, 0
+ li gp, 0
+ li tp, 0
+ li t0, 0
+ li t1, 0
+ li t2, 0
+ li s0, 0
+ li s1, 0
+ li a2, 0
+ li a3, 0
+ li a4, 0
+ li a5, 0
+ li a6, 0
+ li a7, 0
+ li s2, 0
+ li s3, 0
+ li s4, 0
+ li s5, 0
+ li s6, 0
+ li s7, 0
+ li s8, 0
+ li s9, 0
+ li s10, 0
+ li s11, 0
+ li t3, 0
+ li t4, 0
+ li t5, 0
+ li t6, 0
+ csrw sscratch, 0
+
+#ifdef CONFIG_FPU
+ csrr t0, misa
+ andi t0, t0, (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)
+ bnez t0, .Lreset_regs_done
+
+ li t1, SR_FS
+ csrs sstatus, t1
+ fmv.s.x f0, zero
+ fmv.s.x f1, zero
+ fmv.s.x f2, zero
+ fmv.s.x f3, zero
+ fmv.s.x f4, zero
+ fmv.s.x f5, zero
+ fmv.s.x f6, zero
+ fmv.s.x f7, zero
+ fmv.s.x f8, zero
+ fmv.s.x f9, zero
+ fmv.s.x f10, zero
+ fmv.s.x f11, zero
+ fmv.s.x f12, zero
+ fmv.s.x f13, zero
+ fmv.s.x f14, zero
+ fmv.s.x f15, zero
+ fmv.s.x f16, zero
+ fmv.s.x f17, zero
+ fmv.s.x f18, zero
+ fmv.s.x f19, zero
+ fmv.s.x f20, zero
+ fmv.s.x f21, zero
+ fmv.s.x f22, zero
+ fmv.s.x f23, zero
+ fmv.s.x f24, zero
+ fmv.s.x f25, zero
+ fmv.s.x f26, zero
+ fmv.s.x f27, zero
+ fmv.s.x f28, zero
+ fmv.s.x f29, zero
+ fmv.s.x f30, zero
+ fmv.s.x f31, zero
+ csrw fcsr, 0
+#endif /* CONFIG_FPU */
+.Lreset_regs_done:
+ ret
+END(reset_regs)
+
__PAGE_ALIGNED_BSS
/* Empty zero page */
.balign PAGE_SIZE
--
2.20.1
