lib: utils: fdt: fix "ranges" translation

According to the Device Tree Spec, Chapter 2.3.8 "ranges" [1]:
The parent address size will be determined from the #address-cells
property of the node that defines the parent’s address space.

In fdt_translate_address(), which considered the parent address size
is the child address size, this commit fix the two address sizes
and parsing the address independently.

Signed-off-by: Max Hsu <max.hsu@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20250711-dev-maxh-master_fdt_helper-v2-1-9579e1f02ee1@sifive.com
Signed-off-by: Anup Patel <anup@brainfault.org>

firmware/Kconfig

@@ -1 +1,28 @@
 # SPDX-License-Identifier: BSD-2-Clause
+
+menu "Stack Protector Support"
+
+config STACK_PROTECTOR
+	bool "Stack Protector buffer overflow detection"
+	default n
+	help
+	  This option turns on the "stack-protector" compiler feature.
+
+config STACK_PROTECTOR_STRONG
+	bool "Strong Stack Protector"
+	depends on STACK_PROTECTOR
+	default n
+	help
+	  Turn on the "stack-protector" with "-fstack-protector-strong" option.
+	  Like -fstack-protector but includes additional functions to be
+	  protected.
+
+config STACK_PROTECTOR_ALL
+	bool "Almighty Stack Protector"
+	depends on STACK_PROTECTOR
+	default n
+	help
+	  Turn on the "stack-protector" with "-fstack-protector-all" option.
+	  Like -fstack-protector except that all functions are protected.
+
+endmenu

firmware/fw_base.S

@@ -76,21 +76,21 @@ _sc_fail:
 	li	t0, FW_TEXT_START	/* link start */
 	lla	t1, _fw_start		/* load start */
 	sub	t2, t1, t0		/* load offset */
-	lla	t0, __rel_dyn_start
-	lla	t1, __rel_dyn_end
+	lla	t0, __rela_dyn_start
+	lla	t1, __rela_dyn_end
 	beq	t0, t1, _relocate_done
 2:
-	REG_L	t5, REGBYTES(t0)	/* t5 <-- relocation info:type */
+	REG_L	t5, __SIZEOF_LONG__(t0)	/* t5 <-- relocation info:type */
 	li	t3, R_RISCV_RELATIVE	/* reloc type R_RISCV_RELATIVE */
 	bne	t5, t3, 3f
 	REG_L	t3, 0(t0)
-	REG_L	t5, (REGBYTES * 2)(t0)	/* t5 <-- addend */
+	REG_L	t5, (__SIZEOF_LONG__ * 2)(t0)	/* t5 <-- addend */
 	add	t5, t5, t2
 	add	t3, t3, t2
 	REG_S	t5, 0(t3)		/* store runtime address to the GOT entry */
 
 3:
-	addi	t0, t0, (REGBYTES * 3)
+	addi	t0, t0, (__SIZEOF_LONG__ * 3)
 	blt	t0, t1, 2b
 _relocate_done:
 	/* At this point we are running from link address */
@@ -736,6 +736,27 @@ _reset_regs:
 
 	ret
 
+	.section .rodata
+.Lstack_corrupt_msg:
+	.string "stack smashing detected\n"
+
+	/* This will be called when the stack corruption is detected */
+	.section .text
+	.align 3
+	.globl __stack_chk_fail
+	.type __stack_chk_fail, %function
+__stack_chk_fail:
+	la	a0, .Lstack_corrupt_msg
+	call	sbi_panic
+
+	/* Initial value of the stack guard variable */
+	.section .data
+	.align 3
+	.globl __stack_chk_guard
+	.type __stack_chk_guard, %object
+__stack_chk_guard:
+	RISCV_PTR	0x95B5FF5A
+
 #ifdef FW_FDT_PATH
 	.section .rodata
 	.align 4

firmware/fw_base.ldS

@@ -47,9 +47,9 @@
 	. = ALIGN(0x1000); /* Ensure next section is page aligned */
 
 	.rela.dyn : {
-		PROVIDE(__rel_dyn_start = .);
+		PROVIDE(__rela_dyn_start = .);
 		*(.rela*)
-		PROVIDE(__rel_dyn_end = .);
+		PROVIDE(__rela_dyn_end = .);
 	}
 
 	PROVIDE(_rodata_end = .);

firmware/objects.mk

@@ -66,3 +66,12 @@ endif
 ifdef FW_OPTIONS
 firmware-genflags-y += -DFW_OPTIONS=$(FW_OPTIONS)
 endif
+
+ifeq ($(CONFIG_STACK_PROTECTOR),y)
+stack-protector-cflags-$(CONFIG_STACK_PROTECTOR) := -fstack-protector
+stack-protector-cflags-$(CONFIG_STACK_PROTECTOR_STRONG) := -fstack-protector-strong
+stack-protector-cflags-$(CONFIG_STACK_PROTECTOR_ALL) := -fstack-protector-all
+else
+stack-protector-cflags-y := -fno-stack-protector
+endif
+firmware-cflags-y += $(stack-protector-cflags-y)

firmware/payloads/test_head.S

@@ -97,3 +97,18 @@ _boot_a0:
 	RISCV_PTR	0
 _boot_a1:
 	RISCV_PTR	0
+
+	/* This will be called when the stack corruption is detected */
+	.section .text
+	.align 3
+	.globl __stack_chk_fail
+	.type __stack_chk_fail, %function
+	.equ  __stack_chk_fail, _start_hang
+
+	/* Initial value of the stack guard variable */
+	.section .data
+	.align 3
+	.globl __stack_chk_guard
+	.type __stack_chk_guard, %object
+__stack_chk_guard:
+	RISCV_PTR	0x95B5FF5A

firmware/payloads/test_main.c

@@ -46,6 +46,13 @@ static inline void sbi_ecall_console_puts(const char *str)
 		  sbi_strlen(str), (unsigned long)str, 0, 0, 0, 0);
 }
 
+static inline void sbi_ecall_shutdown(void)
+{
+	sbi_ecall(SBI_EXT_SRST, SBI_EXT_SRST_RESET,
+		  SBI_SRST_RESET_TYPE_SHUTDOWN, SBI_SRST_RESET_REASON_NONE,
+		  0, 0, 0, 0);
+}
+
 #define wfi()                                             \
 	do {                                              \
 		__asm__ __volatile__("wfi" ::: "memory"); \
@@ -54,7 +61,6 @@ static inline void sbi_ecall_console_puts(const char *str)
 void test_main(unsigned long a0, unsigned long a1)
 {
 	sbi_ecall_console_puts("\nTest payload running\n");
-
-	while (1)
-		wfi();
+	sbi_ecall_shutdown();
+	sbi_ecall_console_puts("sbi_ecall_shutdown failed to execute.\n");
 }

include/sbi/riscv_encoding.h

@@ -1291,6 +1291,8 @@
 #define SHIFT_FUNCT3			12
 
 #define MASK_RS1			0xf8000
+#define MASK_RS2			0x1f00000
+#define MASK_RD				0xf80
 
 #define MASK_CSR			0xfff00000
 #define SHIFT_CSR			20
@@ -1315,13 +1317,6 @@
 
 #define INSN_LEN(insn)			(INSN_IS_16BIT(insn) ? 2 : 4)
 
-#if __riscv_xlen == 64
-#define LOG_REGBYTES			3
-#else
-#define LOG_REGBYTES			2
-#endif
-#define REGBYTES			(1 << LOG_REGBYTES)
-
 #define SH_VSEW			3
 #define SH_VIEW			12
 #define SH_VD				7
@@ -1356,28 +1351,17 @@
 #define SHIFT_RIGHT(x, y)		\
 	((y) < 0 ? ((x) << -(y)) : ((x) >> (y)))
 
-#define REG_MASK			\
-	((1 << (5 + LOG_REGBYTES)) - (1 << LOG_REGBYTES))
-
-#define REG_OFFSET(insn, pos)		\
-	(SHIFT_RIGHT((insn), (pos) - LOG_REGBYTES) & REG_MASK)
-
-#define REG_PTR(insn, pos, regs)	\
-	(ulong *)((ulong)(regs) + REG_OFFSET(insn, pos))
-
 #define GET_FUNC3(insn)			((insn & MASK_FUNCT3) >> SHIFT_FUNCT3)
 #define GET_RM(insn)			GET_FUNC3(insn)
-#define GET_RS1_NUM(insn)		((insn & MASK_RS1) >> 15)
+#define GET_RS1_NUM(insn)		((insn & MASK_RS1) >> SH_RS1)
+#define GET_RS2_NUM(insn)		((insn & MASK_RS2) >> SH_RS2)
+#define GET_RS1S_NUM(insn)		RVC_RS1S(insn)
+#define GET_RS2S_NUM(insn)		RVC_RS2S(insn)
+#define GET_RS2C_NUM(insn)		RVC_RS2(insn)
+#define GET_RD_NUM(insn)		((insn & MASK_RD) >> SH_RD)
 #define GET_CSR_NUM(insn)		((insn & MASK_CSR) >> SHIFT_CSR)
 #define GET_AQRL(insn)			((insn & MASK_AQRL) >> SHIFT_AQRL)
 
-#define GET_RS1(insn, regs)		(*REG_PTR(insn, SH_RS1, regs))
-#define GET_RS2(insn, regs)		(*REG_PTR(insn, SH_RS2, regs))
-#define GET_RS1S(insn, regs)		(*REG_PTR(RVC_RS1S(insn), 0, regs))
-#define GET_RS2S(insn, regs)		(*REG_PTR(RVC_RS2S(insn), 0, regs))
-#define GET_RS2C(insn, regs)		(*REG_PTR(insn, SH_RS2C, regs))
-#define GET_SP(regs)			(*REG_PTR(2, 0, regs))
-#define SET_RD(insn, regs, val)		(*REG_PTR(insn, SH_RD, regs) = (val))
 #define IMM_I(insn)			((s32)(insn) >> 20)
 #define IMM_S(insn)			(((s32)(insn) >> 25 << 5) | \
 					 (s32)(((insn) >> 7) & 0x1f))

include/sbi/sbi_byteorder.h

@@ -14,13 +14,13 @@
 # define _conv_cast(type, val) ((type)(val))
 #endif
 
-#define BSWAP16(x)	((((x) & 0x00ff) << 8) | \
+#define __BSWAP16(x)	((((x) & 0x00ff) << 8) | \
 			 (((x) & 0xff00) >> 8))
-#define BSWAP32(x)	((((x) & 0x000000ff) << 24) | \
+#define __BSWAP32(x)	((((x) & 0x000000ff) << 24) | \
 			 (((x) & 0x0000ff00) << 8) | \
 			 (((x) & 0x00ff0000) >> 8) | \
 			 (((x) & 0xff000000) >> 24))
-#define BSWAP64(x)	((((x) & 0x00000000000000ffULL) << 56) | \
+#define __BSWAP64(x)	((((x) & 0x00000000000000ffULL) << 56) | \
 			 (((x) & 0x000000000000ff00ULL) << 40) | \
 			 (((x) & 0x0000000000ff0000ULL) << 24) | \
 			 (((x) & 0x00000000ff000000ULL) << 8) | \
@@ -29,6 +29,10 @@
 			 (((x) & 0x00ff000000000000ULL) >> 40) | \
 			 (((x) & 0xff00000000000000ULL) >> 56))
 
+#define BSWAP64(x) ({ uint64_t _sv = (x); __BSWAP64(_sv); })
+#define BSWAP32(x) ({ uint32_t _sv = (x); __BSWAP32(_sv); })
+#define BSWAP16(x) ({ uint16_t _sv = (x); __BSWAP16(_sv); })
+
 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__  /* CPU(little-endian) */
 #define cpu_to_be16(x)		_conv_cast(uint16_t, BSWAP16(x))
 #define cpu_to_be32(x)		_conv_cast(uint32_t, BSWAP32(x))

include/sbi/sbi_csr_detect.h

@@ -18,7 +18,7 @@
 	({								\
 	register ulong tinfo asm("a3") = (ulong)trap;			\
 	register ulong ttmp asm("a4");					\
-	register ulong mtvec = sbi_hart_expected_trap_addr();		\
+	register ulong mtvec = (ulong)sbi_hart_expected_trap;		\
 	register ulong ret = 0;						\
 	((struct sbi_trap_info *)(trap))->cause = 0;			\
 	asm volatile(							\
@@ -37,7 +37,7 @@
 	({								\
 	register ulong tinfo asm("a3") = (ulong)trap;			\
 	register ulong ttmp asm("a4");					\
-	register ulong mtvec = sbi_hart_expected_trap_addr();		\
+	register ulong mtvec = (ulong)sbi_hart_expected_trap;		\
 	((struct sbi_trap_info *)(trap))->cause = 0;			\
 	asm volatile(							\
 		"add %[ttmp], %[tinfo], zero\n"				\

include/sbi/sbi_hart.h

@@ -134,10 +134,6 @@ int sbi_hart_reinit(struct sbi_scratch *scratch);
 int sbi_hart_init(struct sbi_scratch *scratch, bool cold_boot);
 
 extern void (*sbi_hart_expected_trap)(void);
-static inline ulong sbi_hart_expected_trap_addr(void)
-{
-	return (ulong)sbi_hart_expected_trap;
-}
 
 unsigned int sbi_hart_mhpm_mask(struct sbi_scratch *scratch);
 void sbi_hart_delegation_dump(struct sbi_scratch *scratch,

include/sbi/sbi_list.h

@@ -160,4 +160,17 @@ static inline void sbi_list_del_init(struct sbi_dlist *entry)
 	     &pos->member != (head); 	\
 	     pos = sbi_list_entry(pos->member.next, typeof(*pos), member))
 
+/**
+ * Iterate over list of given type safe against removal of list entry
+ * @param pos the type * to use as a loop cursor.
+ * @param n another type * to use as temporary storage.
+ * @param head the head for your list.
+ * @param member the name of the list_struct within the struct.
+ */
+#define sbi_list_for_each_entry_safe(pos, n, head, member) \
+	for (pos = sbi_list_entry((head)->next, typeof(*pos), member),	\
+	     n = sbi_list_entry(pos->member.next, typeof(*pos), member);	\
+	     &pos->member != (head);	\
+	     pos = n, n = sbi_list_entry(pos->member.next, typeof(*pos), member))
+
 #endif

include/sbi/sbi_trap.h

@@ -127,70 +127,75 @@
 
 /** Representation of register state at time of trap/interrupt */
 struct sbi_trap_regs {
-	/** zero register state */
-	unsigned long zero;
-	/** ra register state */
-	unsigned long ra;
-	/** sp register state */
-	unsigned long sp;
-	/** gp register state */
-	unsigned long gp;
-	/** tp register state */
-	unsigned long tp;
-	/** t0 register state */
-	unsigned long t0;
-	/** t1 register state */
-	unsigned long t1;
-	/** t2 register state */
-	unsigned long t2;
-	/** s0 register state */
-	unsigned long s0;
-	/** s1 register state */
-	unsigned long s1;
-	/** a0 register state */
-	unsigned long a0;
-	/** a1 register state */
-	unsigned long a1;
-	/** a2 register state */
-	unsigned long a2;
-	/** a3 register state */
-	unsigned long a3;
-	/** a4 register state */
-	unsigned long a4;
-	/** a5 register state */
-	unsigned long a5;
-	/** a6 register state */
-	unsigned long a6;
-	/** a7 register state */
-	unsigned long a7;
-	/** s2 register state */
-	unsigned long s2;
-	/** s3 register state */
-	unsigned long s3;
-	/** s4 register state */
-	unsigned long s4;
-	/** s5 register state */
-	unsigned long s5;
-	/** s6 register state */
-	unsigned long s6;
-	/** s7 register state */
-	unsigned long s7;
-	/** s8 register state */
-	unsigned long s8;
-	/** s9 register state */
-	unsigned long s9;
-	/** s10 register state */
-	unsigned long s10;
-	/** s11 register state */
-	unsigned long s11;
-	/** t3 register state */
-	unsigned long t3;
-	/** t4 register state */
-	unsigned long t4;
-	/** t5 register state */
-	unsigned long t5;
-	/** t6 register state */
-	unsigned long t6;
+	union {
+		unsigned long gprs[32];
+		struct {
+			/** zero register state */
+			unsigned long zero;
+			/** ra register state */
+			unsigned long ra;
+			/** sp register state */
+			unsigned long sp;
+			/** gp register state */
+			unsigned long gp;
+			/** tp register state */
+			unsigned long tp;
+			/** t0 register state */
+			unsigned long t0;
+			/** t1 register state */
+			unsigned long t1;
+			/** t2 register state */
+			unsigned long t2;
+			/** s0 register state */
+			unsigned long s0;
+			/** s1 register state */
+			unsigned long s1;
+			/** a0 register state */
+			unsigned long a0;
+			/** a1 register state */
+			unsigned long a1;
+			/** a2 register state */
+			unsigned long a2;
+			/** a3 register state */
+			unsigned long a3;
+			/** a4 register state */
+			unsigned long a4;
+			/** a5 register state */
+			unsigned long a5;
+			/** a6 register state */
+			unsigned long a6;
+			/** a7 register state */
+			unsigned long a7;
+			/** s2 register state */
+			unsigned long s2;
+			/** s3 register state */
+			unsigned long s3;
+			/** s4 register state */
+			unsigned long s4;
+			/** s5 register state */
+			unsigned long s5;
+			/** s6 register state */
+			unsigned long s6;
+			/** s7 register state */
+			unsigned long s7;
+			/** s8 register state */
+			unsigned long s8;
+			/** s9 register state */
+			unsigned long s9;
+			/** s10 register state */
+			unsigned long s10;
+			/** s11 register state */
+			unsigned long s11;
+			/** t3 register state */
+			unsigned long t3;
+			/** t4 register state */
+			unsigned long t4;
+			/** t5 register state */
+			unsigned long t5;
+			/** t6 register state */
+			unsigned long t6;
+		};
+	};
 	/** mepc register state */
 	unsigned long mepc;
 	/** mstatus register state */
@@ -199,6 +204,21 @@ struct sbi_trap_regs {
 	unsigned long mstatusH;
 };
 
+_Static_assert(
+	sizeof(((struct sbi_trap_regs *)0)->gprs) ==
+	offsetof(struct sbi_trap_regs, t6) +
+	sizeof(((struct sbi_trap_regs *)0)->t6),
+	"struct sbi_trap_regs's layout differs between gprs and named members");
+
+#define REG_VAL(idx, regs)		((regs)->gprs[(idx)])
+
+#define GET_RS1(insn, regs)		REG_VAL(GET_RS1_NUM(insn), regs)
+#define GET_RS2(insn, regs)		REG_VAL(GET_RS2_NUM(insn), regs)
+#define GET_RS1S(insn, regs)		REG_VAL(GET_RS1S_NUM(insn), regs)
+#define GET_RS2S(insn, regs)		REG_VAL(GET_RS2S_NUM(insn), regs)
+#define GET_RS2C(insn, regs)		REG_VAL(GET_RS2C_NUM(insn), regs)
+#define SET_RD(insn, regs, val)		(REG_VAL(GET_RD_NUM(insn), regs) = (val))
+
 /** Representation of trap details */
 struct sbi_trap_info {
 	/** cause Trap exception cause */

include/sbi/sbi_visibility.h

@@ -7,10 +7,12 @@
 #ifndef __SBI_VISIBILITY_H__
 #define __SBI_VISIBILITY_H__
 
+#ifndef __DTS__
 /*
  * Declare all global objects with hidden visibility so access is PC-relative
  * instead of going through the GOT.
  */
 #pragma GCC visibility push(hidden)
+#endif
 
 #endif

lib/sbi/sbi_hart.c

@@ -49,10 +49,10 @@ static void mstatus_init(struct sbi_scratch *scratch)
 
 	csr_write(CSR_MSTATUS, mstatus_val);
 
-	/* Disable user mode usage of all perf counters except default ones (CY, TM, IR) */
+	/* Disable user mode usage of all perf counters except TM */
 	if (misa_extension('S') &&
 	    sbi_hart_priv_version(scratch) >= SBI_HART_PRIV_VER_1_10)
-		csr_write(CSR_SCOUNTEREN, 7);
+		csr_write(CSR_SCOUNTEREN, 0x02);
 
 	/**
 	 * OpenSBI doesn't use any PMU counters in M-mode.

lib/sbi/sbi_illegal_atomic.c

@@ -30,7 +30,7 @@ int sbi_illegal_atomic(ulong insn, struct sbi_trap_regs *regs)
 	{									\
 		register ulong tinfo asm("a3");					\
 		register ulong mstatus = 0;					\
-		register ulong mtvec = sbi_hart_expected_trap_addr();		\
+		register ulong mtvec = (ulong)sbi_hart_expected_trap;		\
 		type ret = 0;							\
 		trap->cause = 0;						\
 		asm volatile(							\
@@ -57,7 +57,7 @@ int sbi_illegal_atomic(ulong insn, struct sbi_trap_regs *regs)
 	{									\
 		register ulong tinfo asm("a3");					\
 		register ulong mstatus = 0;					\
-		register ulong mtvec = sbi_hart_expected_trap_addr();		\
+		register ulong mtvec = (ulong)sbi_hart_expected_trap;		\
 		type ret = 0;							\
 		trap->cause = 0;						\
 		asm volatile(							\

lib/sbi/sbi_unpriv.c

@@ -24,7 +24,7 @@
 	{                                                                     \
 		register ulong tinfo asm("a3");                               \
 		register ulong mstatus = 0;                                   \
-		register ulong mtvec = sbi_hart_expected_trap_addr();         \
+		register ulong mtvec = (ulong)sbi_hart_expected_trap;         \
 		type ret = 0;                                                 \
 		trap->cause = 0;                                              \
 		asm volatile(                                                 \
@@ -51,7 +51,7 @@
 	{                                                                     \
 		register ulong tinfo asm("a3") = (ulong)trap;                 \
 		register ulong mstatus = 0;                                   \
-		register ulong mtvec = sbi_hart_expected_trap_addr();         \
+		register ulong mtvec = (ulong)sbi_hart_expected_trap;         \
 		trap->cause = 0;                                              \
 		asm volatile(                                                 \
 			"add %[tinfo], %[taddr], zero\n"                      \
@@ -121,7 +121,7 @@ ulong sbi_get_insn(ulong mepc, struct sbi_trap_info *trap)
 	register ulong tinfo asm("a3");
 	register ulong ttmp asm("a4");
 	register ulong mstatus = 0;
-	register ulong mtvec = sbi_hart_expected_trap_addr();
+	register ulong mtvec = (ulong)sbi_hart_expected_trap;
 	ulong insn = 0;
 
 	trap->cause = 0;

lib/utils/fdt/fdt_helper.c

@@ -84,23 +84,27 @@ static int fdt_translate_address(const void *fdt, uint64_t reg, int parent,
 				 uint64_t *addr)
 {
 	int i, rlen;
-	int cell_addr, cell_size;
+	int cell_parent_addr, cell_child_addr, cell_size;
 	const fdt32_t *ranges;
 	uint64_t offset, caddr = 0, paddr = 0, rsize = 0;
 
-	cell_addr = fdt_address_cells(fdt, parent);
-	if (cell_addr < 1)
-		return SBI_ENODEV;
-
-	cell_size = fdt_size_cells(fdt, parent);
-	if (cell_size < 0)
-		return SBI_ENODEV;
-
 	ranges = fdt_getprop(fdt, parent, "ranges", &rlen);
 	if (ranges && rlen > 0) {
-		for (i = 0; i < cell_addr; i++)
+		cell_child_addr = fdt_address_cells(fdt, parent);
+		if (cell_child_addr < 1)
+			return SBI_ENODEV;
+
+		cell_parent_addr = fdt_address_cells(fdt, fdt_parent_offset(fdt, parent));
+		if (cell_parent_addr < 1)
+			return SBI_ENODEV;
+
+		cell_size = fdt_size_cells(fdt, parent);
+		if (cell_size < 0)
+			return SBI_ENODEV;
+
+		for (i = 0; i < cell_child_addr; i++)
 			caddr = (caddr << 32) | fdt32_to_cpu(*ranges++);
-		for (i = 0; i < cell_addr; i++)
+		for (i = 0; i < cell_parent_addr; i++)
 			paddr = (paddr << 32) | fdt32_to_cpu(*ranges++);
 		for (i = 0; i < cell_size; i++)
 			rsize = (rsize << 32) | fdt32_to_cpu(*ranges++);

lib/utils/serial/uart8250.c

@@ -133,10 +133,9 @@ int uart8250_init(unsigned long base, u32 in_freq, u32 baudrate, u32 reg_shift,
 	set_reg(UART_FCR_OFFSET, 0x01);
 	/* No modem control DTR RTS */
 	set_reg(UART_MCR_OFFSET, 0x00);
-	/* Clear line status */
-	get_reg(UART_LSR_OFFSET);
-	/* Read receive buffer */
-	get_reg(UART_RBR_OFFSET);
+	/* Clear line status and read receive buffer */
+	if (get_reg(UART_LSR_OFFSET) & UART_LSR_DR)
+		get_reg(UART_RBR_OFFSET);
 	/* Set scratchpad */
 	set_reg(UART_SCR_OFFSET, 0x00);
 

platform/fpga/openpiton/platform.c

@@ -79,7 +79,7 @@ static int openpiton_early_init(bool cold_boot)
 {
 	const void *fdt;
 	struct platform_uart_data uart_data = { 0 };
-	struct plic_data plic_data;
+	struct plic_data plic_data = plic;
 	unsigned long aclint_freq;
 	uint64_t clint_addr;
 	int rc;