On Mon, 01 Jul 2019 14:26:18 PDT (-0700), Atish Patra wrote:
On Mon, 2019-06-24 at 07:43 +0200, Christoph Hellwig wrote: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.That means it should be done for S-mode as well. Right ? I see the reset code is enabled only for M-mode only.Vaguely based on the concepts from opensbi. Signed-off-by: Christoph Hellwig <hch@xxxxxx> --- arch/riscv/kernel/head.S | 85 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index a4c170e41a34..74feb17737b4 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>__INITENTRY(_start) @@ -19,6 +20,12 @@ ENTRY(_start) csrw CSR_XIP, zero#ifdef CONFIG_M_MODE+ /* flush the instruction cache */ + fence.i + + /* Reset all registers except ra, a0, a1 */ + call reset_regs + /* * The hartid in a0 is expected later on, and we have no firmware * to hand it to us. @@ -168,6 +175,84 @@ relocate: j .Lsecondary_park END(_start)+#ifdef CONFIG_M_MODE+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
You need to check that the write stuck and branch around the FP instructions. Specifically, CONFIG_FPU means there may be an FPU, not there's definately an FPU. You should also turn the FPU back off after zeroing the state.
+ 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) +#endif /* CONFIG_M_MODE */ + __PAGE_ALIGNED_BSS /* Empty zero page */ .balign PAGE_SIZE-- Regards, Atish
