riscv: Simplify payload handling

1. Simplify payload code and convert it to C
2. Save the FDT pointer to HLS (hart-local storage).
3. Don't use mscratch to pass FDT pointer as it is used for exception handling.

Change-Id: I32bf2a99e07a65358a7f19b899259f0816eb45e8
Signed-off-by: Xiang Wang <wxjstz@126.com>
Signed-off-by: Philipp Hug <philipp@hug.cx>
Reviewed-on: https://review.coreboot.org/c/31179
Reviewed-by: ron minnich <rminnich@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/arch/riscv/Makefile.inc

@@ -137,7 +137,7 @@ ramstage-y += misc.c
 ramstage-y += smp.c
 ramstage-y += boot.c
 ramstage-y += tables.c
-ramstage-y += payload.S
+ramstage-y += payload.c
 ramstage-$(ARCH_RISCV_PMP) += pmp.c
 ramstage-y += \
 	$(top)/src/lib/memchr.c \

src/arch/riscv/boot.c

@@ -19,6 +19,7 @@
 #include <arch/encoding.h>
 #include <console/console.h>
 #include <arch/smp/smp.h>
+#include <mcall.h>
 
 /*
  * A pointer to the Flattened Device Tree passed to coreboot by the boot ROM.
@@ -26,27 +27,29 @@
  *
  * This pointer is only used in ramstage!
  */
-const void *rom_fdt;
 
 static void do_arch_prog_run(struct prog *prog)
 {
-	void (*doit)(void *) = prog_entry(prog);
-	void riscvpayload(const void *fdt, void *payload);
+	void (*doit)(int hart_id, void *fdt);
+	int hart_id;
+	void *fdt = prog_entry_arg(prog);
+
+	/*
+	 * If prog_entry_arg is not set (e.g. by fit_payload), use fdt from HLS
+	 * instead.
+	 */
+	if (fdt == NULL)
+		fdt = HLS()->fdt;
 
 	if (ENV_RAMSTAGE && prog_type(prog) == PROG_PAYLOAD) {
-		/*
-		 * FIXME: This is wrong and will crash. Linux can't (in early
-		 * boot) access memory that's before its own loading address.
-		 * We need to copy the FDT to a place where Linux can access it.
-		 */
-		const void *fdt = rom_fdt;
-
-		printk(BIOS_SPEW, "FDT is at %p\n", fdt);
-		printk(BIOS_SPEW, "OK, let's go\n");
-		riscvpayload(fdt, doit);
+		run_payload(prog, fdt, RISCV_PAYLOAD_MODE_S);
+		return;
 	}
 
-	doit(prog_entry_arg(prog));
+	doit = prog_entry(prog);
+	hart_id = HLS()->hart_id;
+
+	doit(hart_id, fdt);
 }
 
 void arch_prog_run(struct prog *prog)

src/arch/riscv/bootblock.S

@@ -50,6 +50,7 @@ _start:
 
 	# initialize hart-local storage
 	csrr a0, mhartid
+	csrrw a1, mscratch, zero
 	call hls_init
 
 	li   a0, CONFIG_RISCV_WORKING_HARTID

src/arch/riscv/include/arch/boot.h

@@ -16,6 +16,12 @@
 #ifndef ARCH_RISCV_INCLUDE_ARCH_BOOT_H
 #define ARCH_RISCV_INCLUDE_ARCH_BOOT_H
 
-extern const void *rom_fdt;
+#include <program_loading.h>
+
+#define RISCV_PAYLOAD_MODE_U 0
+#define RISCV_PAYLOAD_MODE_S 1
+#define RISCV_PAYLOAD_MODE_M 3
+
+void run_payload(struct prog *prog, void *fdt, int payload_mode);
 
 #endif

src/arch/riscv/include/arch/stages.h

@@ -18,6 +18,7 @@
 
 #include <main_decl.h>
 
-void stage_entry(void) __attribute__((section(".text.stage_entry")));
+void stage_entry(int hart_id, void *fdt)
+	__attribute__((section(".text.stage_entry")));
 
 #endif

src/arch/riscv/include/mcall.h

@@ -52,9 +52,14 @@ typedef struct {
 	int ipi_pending;
 	uint64_t *timecmp;
 	uint64_t *time;
+	void *fdt;
 	struct blocker entry;
 } hls_t;
 
+_Static_assert(
+	sizeof(hls_t) == HLS_SIZE,
+	"HLS_SIZE must equal to sizeof(hls_t)");
+
 #define MACHINE_STACK_TOP() ({ \
 	/* coverity[uninit_use] : FALSE */ \
 	register uintptr_t sp asm ("sp"); \
@@ -66,7 +71,8 @@ typedef struct {
 
 #define MACHINE_STACK_SIZE RISCV_PGSIZE
 
-void hls_init(uint32_t hart_id); // need to call this before launching linux
+// need to call this before launching linux
+void hls_init(uint32_t hart_id, void *fdt);
 
 /* This function is used to initialize HLS()->time/HLS()->timecmp  */
 void mtime_init(void);

src/arch/riscv/mcall.c

@@ -34,10 +34,11 @@
 
 int mcalldebug; // set this interactively for copious debug.
 
-void hls_init(uint32_t hart_id)
+void hls_init(uint32_t hart_id, void *fdt)
 {
 	printk(BIOS_SPEW, "hart %d: HLS is %p\n", hart_id, HLS());
 	memset(HLS(), 0, sizeof(*HLS()));
+	HLS()->fdt = fdt;
 	HLS()->hart_id = hart_id;
 
 	mtime_init();

src/arch/riscv/payload.S

@@ -1,35 +0,0 @@
-/*
- * This file is part of the coreboot project.
- *
- * Copyright (C) 2016 Google Inc
- * Copyright (C) 2018 Jonathan Neuschäfer
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; version 2 of the License.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- */
-
-// "return" to a payload. a0: FDT, a1: entry point
-	.global riscvpayload
-riscvpayload:
-	/* Load the entry point */
-	mv	t0, a1
-	csrw	mepc, t0
-	csrr	t0, mstatus
-
-	/* Set mstatus.MPP (the previous privilege mode) to supervisor mode */
-	li	t1, ~(3<<11)
-	and	t0, t0, t1
-	li	t2,  (1<<11)
-	or	t0, t0, t2
-	csrw	mstatus, t0
-
-	/* Pass the right arguments and jump! */
-	mv	a1, a0
-	csrr	a0, mhartid
-	mret

src/arch/riscv/payload.c

@@ -0,0 +1,51 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2016 Google Inc
+ * Copyright (C) 2018 HardenedLinux
+ * Copyright (C) 2018 Jonathan Neuschäfer
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <stdint.h>
+#include <arch/boot.h>
+#include <arch/encoding.h>
+#include <console/console.h>
+
+void run_payload(struct prog *prog, void *fdt, int payload_mode)
+{
+	void (*doit)(int hart_id, void *fdt) = prog_entry(prog);
+	int hart_id = read_csr(mhartid);
+	uintptr_t status = read_csr(mstatus);
+	status &= ~MSTATUS_MPIE;
+	status &= ~MSTATUS_MPP;
+	switch (payload_mode) {
+	case RISCV_PAYLOAD_MODE_U:
+		break;
+	case RISCV_PAYLOAD_MODE_S:
+		status |= MSTATUS_SPP;
+		break;
+	case RISCV_PAYLOAD_MODE_M:
+		doit(hart_id, fdt);
+		return;
+	default:
+		die("wrong privilege level for payload");
+		break;
+	}
+	write_csr(mstatus, status);
+	write_csr(mepc, doit);
+	asm volatile(
+		"mv a0, %0\n\t"
+		"mv a1, %0\n\t"
+		"mret" ::"r"(hart_id),
+		"r"(fdt)
+		: "a0", "a1");
+}

src/arch/riscv/stages.c

@@ -28,18 +28,19 @@
 #include <arch/encoding.h>
 #include <arch/stages.h>
 #include <arch/smp/smp.h>
+#include <rules.h>
+#include <mcall.h>
 
-void stage_entry(void)
+void stage_entry(int hart_id, void *fdt)
 {
-	smp_pause(CONFIG_RISCV_WORKING_HARTID);
-
 	/*
 	 * Save the FDT pointer before entering ramstage, because mscratch
 	 * might be overwritten in the trap handler, and there is code in
 	 * ramstage that generates misaligned access faults.
 	 */
-	if (ENV_RAMSTAGE)
-		rom_fdt = (const void *)read_csr(mscratch);
+	HLS()->hart_id = hart_id;
+	HLS()->fdt = fdt;
+	smp_pause(CONFIG_RISCV_WORKING_HARTID);
 
 	main();
 }