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From: Christoph Hellwig <hch@lst.de>
To: Palmer Dabbelt <palmer@sifive.com>,
	Paul Walmsley <paul.walmsley@sifive.com>
Cc: linux-mm@kvack.org, Damien Le Moal <damien.lemoal@wdc.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH 16/17] riscv: clear the instruction cache and all registers when booting
Date: Mon, 24 Jun 2019 07:43:10 +0200	[thread overview]
Message-ID: <20190624054311.30256-17-hch@lst.de> (raw)
In-Reply-To: <20190624054311.30256-1-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/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>
 
 __INIT
 ENTRY(_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
+	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
-- 
2.20.1


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  parent reply	other threads:[~2019-06-24  5:44 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-24  5:42 RISC-V nommu support v2 Christoph Hellwig
2019-06-24  5:42 ` [PATCH 01/17] mm: provide a print_vma_addr stub for !CONFIG_MMU Christoph Hellwig
2019-06-24  5:42 ` [PATCH 02/17] mm: stub out all of swapops.h " Christoph Hellwig
2019-06-24  5:42 ` [PATCH 03/17] mm/nommu: fix the MAP_UNINITIALIZED flag Christoph Hellwig
2019-06-24  5:42 ` [PATCH 04/17] irqchip/sifive-plic: set max threshold for ignored handlers Christoph Hellwig
2019-06-24  5:42 ` [PATCH 05/17] riscv: use CSR_SATP instead of the legacy sptbr name in switch_mm Christoph Hellwig
2019-07-01 18:53   ` Atish Patra
2019-06-24  5:43 ` [PATCH 06/17] riscv: refactor the IPI code Christoph Hellwig
2019-06-24  5:43 ` [PATCH 07/17] riscv: abstract out CSR names for supervisor vs machine mode Christoph Hellwig
2019-07-01 18:37   ` Atish Patra
2019-06-24  5:43 ` [PATCH 08/17] riscv: improve the default power off implementation Christoph Hellwig
2019-07-01 21:07   ` Atish Patra
2019-06-24  5:43 ` [PATCH 09/17] riscv: provide a flat entry loader Christoph Hellwig
2019-06-24  5:43 ` [PATCH 10/17] riscv: read the hart ID from mhartid on boot Christoph Hellwig
2019-07-01 21:15   ` Atish Patra
2019-06-24  5:43 ` [PATCH 11/17] riscv: provide native clint access for M-mode Christoph Hellwig
2019-06-24  5:43 ` [PATCH 12/17] riscv: implement remote sfence.i natively " Christoph Hellwig
2019-06-24  5:43 ` [PATCH 13/17] riscv: poison SBI calls " Christoph Hellwig
2019-06-24  5:43 ` [PATCH 14/17] riscv: don't allow selecting SBI-based drivers " Christoph Hellwig
2019-06-24  5:43 ` [PATCH 15/17] riscv: use the correct interrupt levels " Christoph Hellwig
2019-06-24  5:43 ` Christoph Hellwig [this message]
2019-07-01 21:26   ` [PATCH 16/17] riscv: clear the instruction cache and all registers when booting Atish Patra
2019-07-08  8:26     ` Palmer Dabbelt
2019-08-13 15:40       ` Christoph Hellwig
2019-08-13 15:37     ` hch
2019-06-24  5:43 ` [PATCH 17/17] riscv: add nommu support Christoph Hellwig
2019-07-12 14:52   ` Vladimir Murzin
2019-06-24 11:47 ` RISC-V nommu support v2 Vladimir Murzin
2019-06-24 11:54   ` Christoph Hellwig
2019-06-24 13:08     ` Vladimir Murzin
2019-06-24 13:16       ` Christoph Hellwig
2019-06-25  7:31       ` Palmer Dabbelt
2019-06-25 12:37         ` Vladimir Murzin
2019-07-01  6:56 ` Christoph Hellwig
2019-07-01 16:06   ` Paul Walmsley

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