From: Christoph Hellwig <hch@lst.de>
To: Palmer Dabbelt <palmer@sifive.com>,
Paul Walmsley <paul.walmsley@sifive.com>
Cc: Damien Le Moal <damien.lemoal@wdc.com>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH 12/15] riscv: clear the instruction cache and all registers when booting
Date: Thu, 17 Oct 2019 19:37:40 +0200 [thread overview]
Message-ID: <20191017173743.5430-13-hch@lst.de> (raw)
In-Reply-To: <20191017173743.5430-1-hch@lst.de>
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 <hch@lst.de>
---
arch/riscv/include/asm/csr.h | 1 +
arch/riscv/kernel/head.S | 88 +++++++++++++++++++++++++++++++++++-
2 files changed, 88 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index d0b5113e1a54..ee0101278608 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -83,6 +83,7 @@
/* symbolic CSR names: */
#define CSR_MHARTID 0xf14
#define CSR_MSTATUS 0x300
+#define CSR_MISA 0x301
#define CSR_MIE 0x304
#define CSR_MTVEC 0x305
#define CSR_MSCRATCH 0x340
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 583784cb3a32..25867b99cc95 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>
#include <asm/image.h>
__INIT
@@ -51,12 +52,18 @@ _start_kernel:
csrw CSR_XIP, zero
#ifdef CONFIG_RISCV_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.
*/
csrr a0, CSR_MHARTID
-#endif
+#endif /* CONFIG_RISCV_M_MODE */
/* Load the global pointer */
.option push
@@ -203,6 +210,85 @@ relocate:
j .Lsecondary_park
END(_start)
+#ifdef CONFIG_RISCV_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, CSR_MISA
+ andi t0, t0, (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)
+ bnez t0, .Lreset_regs_done
+
+ li t1, SR_FS
+ csrs CSR_XSTATUS, 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
+ /* note that the caller must clear SR_FS */
+#endif /* CONFIG_FPU */
+.Lreset_regs_done:
+ ret
+END(reset_regs)
+#endif /* CONFIG_RISCV_M_MODE */
+
__PAGE_ALIGNED_BSS
/* Empty zero page */
.balign PAGE_SIZE
--
2.20.1
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next prev parent reply other threads:[~2019-10-17 17:38 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-17 17:37 RISC-V nommu support v5 Christoph Hellwig
2019-10-17 17:37 ` [PATCH 01/15] riscv: cleanup <asm/bug.h> Christoph Hellwig
2019-10-18 2:50 ` Anup Patel
2019-10-23 22:04 ` Paul Walmsley
2019-10-17 17:37 ` [PATCH 02/15] riscv: cleanup do_trap_break Christoph Hellwig
2019-10-18 2:51 ` Anup Patel
2019-10-23 22:05 ` Paul Walmsley
2019-10-17 17:37 ` [PATCH 03/15] riscv: abstract out CSR names for supervisor vs machine mode Christoph Hellwig
2019-10-18 2:51 ` Anup Patel
2019-10-18 23:55 ` Paul Walmsley
2019-10-28 8:12 ` Christoph Hellwig
2019-10-17 17:37 ` [PATCH 04/15] riscv: don't allow selecting SBI based drivers for M-mode Christoph Hellwig
2019-10-18 2:52 ` Anup Patel
2019-10-17 17:37 ` [PATCH 05/15] riscv: poison SBI calls " Christoph Hellwig
2019-10-18 2:53 ` Anup Patel
2019-10-17 17:37 ` [PATCH 06/15] riscv: cleanup the default power off implementation Christoph Hellwig
2019-10-18 2:53 ` Anup Patel
2019-10-17 17:37 ` [PATCH 07/15] riscv: implement remote sfence.i using IPIs Christoph Hellwig
2019-10-18 2:55 ` Anup Patel
2019-10-17 17:37 ` [PATCH 08/15] riscv: add support for MMIO access to the timer registers Christoph Hellwig
2019-10-18 2:57 ` Anup Patel
2019-10-17 17:37 ` [PATCH 09/15] riscv: provide native clint access for M-mode Christoph Hellwig
2019-10-18 3:00 ` Anup Patel
2019-11-14 7:39 ` Paul Walmsley
2019-10-17 17:37 ` [PATCH 10/15] riscv: read the hart ID from mhartid on boot Christoph Hellwig
2019-10-18 3:01 ` Anup Patel
2019-11-14 7:40 ` Paul Walmsley
2019-10-17 17:37 ` [PATCH 11/15] riscv: use the correct interrupt levels for M-mode Christoph Hellwig
2019-10-18 3:01 ` Anup Patel
2019-10-17 17:37 ` Christoph Hellwig [this message]
2019-10-18 3:05 ` [PATCH 12/15] riscv: clear the instruction cache and all registers when booting Anup Patel
2019-10-17 17:37 ` [PATCH 13/15] riscv: add nommu support Christoph Hellwig
2019-10-18 3:04 ` Anup Patel
2019-10-17 17:37 ` [PATCH 14/15] riscv: provide a flat image loader Christoph Hellwig
2019-10-18 3:06 ` Anup Patel
2019-10-17 17:37 ` [PATCH 15/15] riscv: disable the EFI PECOFF header for M-mode Christoph Hellwig
2019-10-18 3:06 ` Anup Patel
2019-10-18 3:08 ` RISC-V nommu support v5 Anup Patel
2019-10-18 3:29 ` Paul Walmsley
2019-10-18 15:25 ` Christoph Hellwig
2019-10-18 23:46 ` Paul Walmsley
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