[PATCH 0/2] Add semihosting support in opensbi

[PATCH 0/2] Add semihosting support in opensbi

[Kautuk Consul]

Semihosting is a mechanism that enables code running on
a target to communicate and use the Input/Output
facilities on a host computer that is running a debugger.
This patchset adds support for semihosting in opensbi
for RISCV64 targets.

Kautuk Consul (2):
  include: types: add noinline macro
  lib: utils/serial: add semihosting support

 include/sbi/sbi_types.h                |   1 +
 include/sbi_utils/serial/semihosting.h |  47 +++++++
 lib/utils/serial/Kconfig               |   4 +
 lib/utils/serial/objects.mk            |   1 +
 lib/utils/serial/semihosting.c         | 176 +++++++++++++++++++++++++
 platform/generic/configs/defconfig     |   1 +
 platform/generic/platform.c            |  11 +-
 7 files changed, 240 insertions(+), 1 deletion(-)
 create mode 100644 include/sbi_utils/serial/semihosting.h
 create mode 100644 lib/utils/serial/semihosting.c

-- 
2.34.1

[PATCH 1/2] include: types: add __noinline macro

[Kautuk Consul]

Add noinline macro to sbi_types.h similar to the Linux kernel.

Signed-off-by: Kautuk Consul <kconsul@ventanamicro.com>
---
 include/sbi/sbi_types.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/sbi/sbi_types.h b/include/sbi/sbi_types.h
index 7fb1af7..b1efed7 100644
--- a/include/sbi/sbi_types.h
+++ b/include/sbi/sbi_types.h
@@ -64,6 +64,7 @@ typedef unsigned long		physical_size_t;
 #define __packed		__attribute__((packed))
 #define __noreturn		__attribute__((noreturn))
 #define __aligned(x)		__attribute__((aligned(x)))
+#define __noinline		__attribute__((__noinline__))
 
 #define likely(x) __builtin_expect((x), 1)
 #define unlikely(x) __builtin_expect((x), 0)
-- 
2.34.1

[PATCH 2/2] lib: utils/serial: add semihosting support

[Kautuk Consul]

We add RISC-V semihosting based serial console for JTAG based early
debugging.

The RISC-V semihosting specification is available at:
https://github.com/riscv/riscv-semihosting-spec/blob/main/riscv-semihosting-spec.adoc

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Signed-off-by: Kautuk Consul <kconsul@ventanamicro.com>
---
 include/sbi_utils/serial/semihosting.h |  47 +++++++
 lib/utils/serial/Kconfig               |   4 +
 lib/utils/serial/objects.mk            |   1 +
 lib/utils/serial/semihosting.c         | 176 +++++++++++++++++++++++++
 platform/generic/configs/defconfig     |   1 +
 platform/generic/platform.c            |  11 +-
 6 files changed, 239 insertions(+), 1 deletion(-)
 create mode 100644 include/sbi_utils/serial/semihosting.h
 create mode 100644 lib/utils/serial/semihosting.c

diff --git a/include/sbi_utils/serial/semihosting.h b/include/sbi_utils/serial/semihosting.h
new file mode 100644
index 0000000..8cc4a86
--- /dev/null
+++ b/include/sbi_utils/serial/semihosting.h
@@ -0,0 +1,47 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2022 Ventana Micro Systems Inc.
+ *
+ * Authors:
+ *   Anup Patel <apatel@ventanamicro.com>
+ *   Kautuk Consul <kconsul@ventanamicro.com>
+ */
+
+#ifndef __SERIAL_SEMIHOSTING_H__
+#define __SERIAL_SEMIHOSTING_H__
+
+#include <sbi/sbi_types.h>
+
+/**
+ * enum semihosting_open_mode - Numeric file modes for use with semihosting_open()
+ * MODE_READ: 'r'
+ * MODE_BINARY: 'b'
+ * MODE_PLUS: '+'
+ * MODE_WRITE: 'w'
+ * MODE_APPEND: 'a'
+ *
+ * These modes represent the mode string used by fopen(3) in a form which can
+ * be passed to semihosting_open(). These do NOT correspond directly to %O_RDONLY,
+ * %O_CREAT, etc; see fopen(3) for details. In particular, @MODE_PLUS
+ * effectively results in adding %O_RDWR, and @MODE_WRITE will add %O_TRUNC.
+ * For compatibility, @MODE_BINARY should be added when opening non-text files
+ * (such as images).
+ */
+enum semihosting_open_mode {
+	MODE_READ	= 0x0,
+	MODE_BINARY	= 0x1,
+	MODE_PLUS	= 0x2,
+	MODE_WRITE	= 0x4,
+	MODE_APPEND	= 0x8,
+};
+
+#ifdef CONFIG_SERIAL_SEMIHOSTING
+int semihosting_init(void);
+int semihosting_enabled(void);
+#else
+static inline int semihosting_init(void) { return SBI_ENODEV; }
+static inline int semihosting_enabled(void) { return 0; }
+#endif
+
+#endif
diff --git a/lib/utils/serial/Kconfig b/lib/utils/serial/Kconfig
index 6e425f2..da549a7 100644
--- a/lib/utils/serial/Kconfig
+++ b/lib/utils/serial/Kconfig
@@ -79,4 +79,8 @@ config SERIAL_XILINX_UARTLITE
 	bool "Xilinx UART Lite support"
 	default n
 
+config SERIAL_SEMIHOSTING
+	bool "Semihosting support"
+	default n
+
 endmenu
diff --git a/lib/utils/serial/objects.mk b/lib/utils/serial/objects.mk
index efb1d9e..98f3f9a 100644
--- a/lib/utils/serial/objects.mk
+++ b/lib/utils/serial/objects.mk
@@ -41,3 +41,4 @@ libsbiutils-objs-$(CONFIG_SERIAL_SIFIVE) += serial/sifive-uart.o
 libsbiutils-objs-$(CONFIG_SERIAL_LITEX) += serial/litex-uart.o
 libsbiutils-objs-$(CONFIG_SERIAL_UART8250) += serial/uart8250.o
 libsbiutils-objs-$(CONFIG_SERIAL_XILINX_UARTLITE) += serial/xlnx-uartlite.o
+libsbiutils-objs-$(CONFIG_SERIAL_SEMIHOSTING) += serial/semihosting.o
diff --git a/lib/utils/serial/semihosting.c b/lib/utils/serial/semihosting.c
new file mode 100644
index 0000000..aa1bb16
--- /dev/null
+++ b/lib/utils/serial/semihosting.c
@@ -0,0 +1,176 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2022 Ventana Micro Systems Inc.
+ *
+ * Authors:
+ *   Anup Patel <apatel@ventanamicro.com>
+ *   Kautuk Consul <kconsul@ventanamicro.com>
+ */
+
+#include <sbi/sbi_console.h>
+#include <limits.h>
+#include <sbi/sbi_string.h>
+#include <sbi/sbi_error.h>
+#include <sbi_utils/serial/semihosting.h>
+
+#define SYSOPEN     0x01
+#define SYSWRITEC   0x03
+#define SYSREAD     0x06
+#define SYSREADC    0x07
+#define SYSERRNO	0x13
+
+/*
+ * Note: This function is intentionally noinline and 256 bytes aligned to
+ * ensure that semihosting instruction sequence is within same 4K page.
+ */
+static __noinline __aligned(256) long semihosting_trap(int sysnum, void *addr)
+{
+	register int ret asm ("a0") = sysnum;
+	register void *param0 asm ("a1") = addr;
+
+	asm volatile (
+		"\t.option push\n"
+		"\t.option norvc\n"
+		"\tslli zero, zero, 0x1f\n"
+		"\tebreak\n"
+		"\tsrai zero, zero, 7\n"
+		"\t.option pop\n"
+		: "+r" (ret) : "r" (param0) : "memory");
+
+	return ret;
+}
+
+static bool _semihosting_enabled = true;
+static bool try_semihosting = true;
+
+bool __aligned(256) semihosting_enabled(void)
+{
+	register int ret asm ("a0") = SYSERRNO;
+	register void *param0 asm ("a1") = NULL;
+	unsigned long tmp = 0;
+
+	if (!try_semihosting)
+		return _semihosting_enabled;
+
+	asm volatile (
+		"\t.option push\n"
+		"\t.option norvc\n"
+
+		"\tj _semihost_test_vector_next\n"
+		"\t.align 4\n"
+		"\t_semihost_test_vector:\n"
+		"\t\tcsrr %[en], mepc\n"
+		"\t\taddi %[en], %[en], 4\n"
+		"\t\tcsrw mepc, %[en]\n"
+		"\t\tadd %[en], zero, zero\n"
+		"\t\tmret\n"
+		"\t_semihost_test_vector_next:\n"
+
+		"\tla %[tmp], _semihost_test_vector\n"
+		"\tcsrrw %[tmp], mtvec, %[tmp]\n"
+		"\tslli zero, zero, 0x1f\n"
+		"\tebreak\n"
+		"\tsrai zero, zero, 7\n"
+		"\tcsrw mtvec, %[tmp]\n"
+
+		"\t.option pop\n"
+		: [tmp] "+r" (tmp), [en] "+r" (_semihosting_enabled),
+		  [ret] "+r" (ret)
+		: "r" (param0) : "memory");
+
+	try_semihosting = false;
+	return _semihosting_enabled;
+}
+
+static int semihosting_errno(void)
+{
+	long ret = semihosting_trap(SYSERRNO, NULL);
+
+	if (ret > 0 && ret < INT_MAX)
+		return -ret;
+	return SBI_EIO;
+}
+
+static int infd = SBI_ENODEV;
+
+static long semihosting_open(const char *fname, enum semihosting_open_mode mode)
+{
+	long fd;
+	struct semihosting_open_s {
+		const char *fname;
+		unsigned long mode;
+		size_t len;
+	} open;
+
+	open.fname = fname;
+	open.len = sbi_strlen(fname);
+	open.mode = mode;
+
+	/* Open the file on the host */
+	fd = semihosting_trap(SYSOPEN, &open);
+	if (fd == -1)
+		return semihosting_errno();
+	return fd;
+}
+
+/**
+ * struct semihosting_rdwr_s - Arguments for read and write
+ * @fd: A file descriptor returned from semihosting_open()
+ * @memp: Pointer to a buffer of memory of@least @len bytes
+ * @len: The number of bytes to read or write
+ */
+struct semihosting_rdwr_s {
+	long fd;
+	void *memp;
+	size_t len;
+};
+
+static long semihosting_read(long fd, void *memp, size_t len)
+{
+	long ret;
+	struct semihosting_rdwr_s read;
+
+	read.fd = fd;
+	read.memp = memp;
+	read.len = len;
+
+	ret = semihosting_trap(SYSREAD, &read);
+	if (ret < 0)
+		return semihosting_errno();
+	return len - ret;
+}
+
+/* clang-format on */
+
+static void semihosting_putc(char ch)
+{
+	semihosting_trap(SYSWRITEC, &ch);
+}
+
+static int semihosting_getc(void)
+{
+	char ch = 0;
+
+	if (infd < 0)
+		return semihosting_trap(SYSREADC, NULL);
+
+	semihosting_read(infd, &ch, sizeof(ch));
+
+	return ch;
+}
+
+static struct sbi_console_device semihosting_console = {
+	.name = "semihosting",
+	.console_putc = semihosting_putc,
+	.console_getc = semihosting_getc
+};
+
+int semihosting_init(void)
+{
+	infd = semihosting_open(":tt", MODE_READ);
+
+	sbi_console_set_device(&semihosting_console);
+
+	return 0;
+}
diff --git a/platform/generic/configs/defconfig b/platform/generic/configs/defconfig
index e324173..c95b7fa 100644
--- a/platform/generic/configs/defconfig
+++ b/platform/generic/configs/defconfig
@@ -28,3 +28,4 @@ CONFIG_FDT_SERIAL_UART8250=y
 CONFIG_FDT_SERIAL_XILINX_UARTLITE=y
 CONFIG_FDT_TIMER=y
 CONFIG_FDT_TIMER_MTIMER=y
+CONFIG_SERIAL_SEMIHOSTING=y
diff --git a/platform/generic/platform.c b/platform/generic/platform.c
index cc3620f..bf51aba 100644
--- a/platform/generic/platform.c
+++ b/platform/generic/platform.c
@@ -23,6 +23,7 @@
 #include <sbi_utils/timer/fdt_timer.h>
 #include <sbi_utils/ipi/fdt_ipi.h>
 #include <sbi_utils/reset/fdt_reset.h>
+#include <sbi_utils/serial/semihosting.h>
 
 /* List of platform override modules generated at compile time */
 extern const struct platform_override *platform_override_modules[];
@@ -242,6 +243,14 @@ static uint64_t generic_pmu_xlate_to_mhpmevent(uint32_t event_idx,
 	return evt_val;
 }
 
+static int generic_console_init(void)
+{
+	if (semihosting_enabled())
+		return semihosting_init();
+	else
+		return fdt_serial_init();
+}
+
 const struct sbi_platform_operations platform_ops = {
 	.nascent_init		= generic_nascent_init,
 	.early_init		= generic_early_init,
@@ -249,7 +258,7 @@ const struct sbi_platform_operations platform_ops = {
 	.early_exit		= generic_early_exit,
 	.final_exit		= generic_final_exit,
 	.domains_init		= generic_domains_init,
-	.console_init		= fdt_serial_init,
+	.console_init		= generic_console_init,
 	.irqchip_init		= fdt_irqchip_init,
 	.irqchip_exit		= fdt_irqchip_exit,
 	.ipi_init		= fdt_ipi_init,
-- 
2.34.1

[PATCH 2/2] lib: utils/serial: add semihosting support

[Jessica Clarke]

On 8 Sept 2022, at 09:42, Kautuk Consul <kconsul@ventanamicro.com> wrote:
> 
> We add RISC-V semihosting based serial console for JTAG based early
> debugging.
> 
> The RISC-V semihosting specification is available at:
> https://github.com/riscv/riscv-semihosting-spec/blob/main/riscv-semihosting-spec.adoc
> 
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> Signed-off-by: Kautuk Consul <kconsul@ventanamicro.com>
> ---
> include/sbi_utils/serial/semihosting.h |  47 +++++++
> lib/utils/serial/Kconfig               |   4 +
> lib/utils/serial/objects.mk            |   1 +
> lib/utils/serial/semihosting.c         | 176 +++++++++++++++++++++++++
> platform/generic/configs/defconfig     |   1 +
> platform/generic/platform.c            |  11 +-
> 6 files changed, 239 insertions(+), 1 deletion(-)
> create mode 100644 include/sbi_utils/serial/semihosting.h
> create mode 100644 lib/utils/serial/semihosting.c
> 
> diff --git a/include/sbi_utils/serial/semihosting.h b/include/sbi_utils/serial/semihosting.h
> new file mode 100644
> index 0000000..8cc4a86
> --- /dev/null
> +++ b/include/sbi_utils/serial/semihosting.h
> @@ -0,0 +1,47 @@
> +/*
> + * SPDX-License-Identifier: BSD-2-Clause
> + *
> + * Copyright (c) 2022 Ventana Micro Systems Inc.
> + *
> + * Authors:
> + *   Anup Patel <apatel@ventanamicro.com>
> + *   Kautuk Consul <kconsul@ventanamicro.com>
> + */
> +
> +#ifndef __SERIAL_SEMIHOSTING_H__
> +#define __SERIAL_SEMIHOSTING_H__
> +
> +#include <sbi/sbi_types.h>
> +
> +/**
> + * enum semihosting_open_mode - Numeric file modes for use with semihosting_open()
> + * MODE_READ: 'r'
> + * MODE_BINARY: 'b'
> + * MODE_PLUS: '+'
> + * MODE_WRITE: 'w'
> + * MODE_APPEND: 'a'
> + *
> + * These modes represent the mode string used by fopen(3) in a form which can
> + * be passed to semihosting_open(). These do NOT correspond directly to %O_RDONLY,
> + * %O_CREAT, etc; see fopen(3) for details. In particular, @MODE_PLUS
> + * effectively results in adding %O_RDWR, and @MODE_WRITE will add %O_TRUNC.
> + * For compatibility, @MODE_BINARY should be added when opening non-text files
> + * (such as images).
> + */
> +enum semihosting_open_mode {
> +	MODE_READ	= 0x0,
> +	MODE_BINARY	= 0x1,
> +	MODE_PLUS	= 0x2,
> +	MODE_WRITE	= 0x4,
> +	MODE_APPEND	= 0x8,
> +};
> +
> +#ifdef CONFIG_SERIAL_SEMIHOSTING
> +int semihosting_init(void);
> +int semihosting_enabled(void);
> +#else
> +static inline int semihosting_init(void) { return SBI_ENODEV; }
> +static inline int semihosting_enabled(void) { return 0; }
> +#endif
> +
> +#endif
> diff --git a/lib/utils/serial/Kconfig b/lib/utils/serial/Kconfig
> index 6e425f2..da549a7 100644
> --- a/lib/utils/serial/Kconfig
> +++ b/lib/utils/serial/Kconfig
> @@ -79,4 +79,8 @@ config SERIAL_XILINX_UARTLITE
> 	bool "Xilinx UART Lite support"
> 	default n
> 
> +config SERIAL_SEMIHOSTING
> +	bool "Semihosting support"
> +	default n
> +
> endmenu
> diff --git a/lib/utils/serial/objects.mk b/lib/utils/serial/objects.mk
> index efb1d9e..98f3f9a 100644
> --- a/lib/utils/serial/objects.mk
> +++ b/lib/utils/serial/objects.mk
> @@ -41,3 +41,4 @@ libsbiutils-objs-$(CONFIG_SERIAL_SIFIVE) += serial/sifive-uart.o
> libsbiutils-objs-$(CONFIG_SERIAL_LITEX) += serial/litex-uart.o
> libsbiutils-objs-$(CONFIG_SERIAL_UART8250) += serial/uart8250.o
> libsbiutils-objs-$(CONFIG_SERIAL_XILINX_UARTLITE) += serial/xlnx-uartlite.o
> +libsbiutils-objs-$(CONFIG_SERIAL_SEMIHOSTING) += serial/semihosting.o
> diff --git a/lib/utils/serial/semihosting.c b/lib/utils/serial/semihosting.c
> new file mode 100644
> index 0000000..aa1bb16
> --- /dev/null
> +++ b/lib/utils/serial/semihosting.c
> @@ -0,0 +1,176 @@
> +/*
> + * SPDX-License-Identifier: BSD-2-Clause
> + *
> + * Copyright (c) 2022 Ventana Micro Systems Inc.
> + *
> + * Authors:
> + *   Anup Patel <apatel@ventanamicro.com>
> + *   Kautuk Consul <kconsul@ventanamicro.com>
> + */
> +
> +#include <sbi/sbi_console.h>
> +#include <limits.h>
> +#include <sbi/sbi_string.h>
> +#include <sbi/sbi_error.h>
> +#include <sbi_utils/serial/semihosting.h>
> +
> +#define SYSOPEN     0x01
> +#define SYSWRITEC   0x03
> +#define SYSREAD     0x06
> +#define SYSREADC    0x07
> +#define SYSERRNO	0x13
> +
> +/*
> + * Note: This function is intentionally noinline and 256 bytes aligned to
> + * ensure that semihosting instruction sequence is within same 4K page.
> + */

I don?t think this is relevant for M-mode, and really the spec is
inaccurate. The point is that it must be able to look before and after
the ebreak to check that it?s a semihosting sequence but that there?s a
risk of a page fault if you straddle a page boundary. However, in
M-mode we don?t have paging enabled, even though this is a system that
supports (and, at less-privileged modes, uses) paging.

Even if the sequence were required to not cross a page boundary, this
is not a good way to do it, as aligning the function to 256 bytes is
rather overkill in practice (whilst not strictly guaranteed to even be
sufficient). If you want to take the non-inlineable function approach
it should be written in raw assembly, not C with inline assembly in the
function, so that you can be much more precise with the alignment. That
or don?t make the function inlineable and instead put the align
directive in the inline assembly snippet.

Jess

> +static __noinline __aligned(256) long semihosting_trap(int sysnum, void *addr)
> +{
> +	register int ret asm ("a0") = sysnum;
> +	register void *param0 asm ("a1") = addr;
> +
> +	asm volatile (
> +		"\t.option push\n"
> +		"\t.option norvc\n"
> +		"\tslli zero, zero, 0x1f\n"
> +		"\tebreak\n"
> +		"\tsrai zero, zero, 7\n"
> +		"\t.option pop\n"
> +		: "+r" (ret) : "r" (param0) : "memory");
> +
> +	return ret;
> +}
> +
> +static bool _semihosting_enabled = true;
> +static bool try_semihosting = true;
> +
> +bool __aligned(256) semihosting_enabled(void)
> +{
> +	register int ret asm ("a0") = SYSERRNO;
> +	register void *param0 asm ("a1") = NULL;
> +	unsigned long tmp = 0;
> +
> +	if (!try_semihosting)
> +		return _semihosting_enabled;
> +
> +	asm volatile (
> +		"\t.option push\n"
> +		"\t.option norvc\n"
> +
> +		"\tj _semihost_test_vector_next\n"
> +		"\t.align 4\n"
> +		"\t_semihost_test_vector:\n"
> +		"\t\tcsrr %[en], mepc\n"
> +		"\t\taddi %[en], %[en], 4\n"
> +		"\t\tcsrw mepc, %[en]\n"
> +		"\t\tadd %[en], zero, zero\n"
> +		"\t\tmret\n"
> +		"\t_semihost_test_vector_next:\n"
> +
> +		"\tla %[tmp], _semihost_test_vector\n"
> +		"\tcsrrw %[tmp], mtvec, %[tmp]\n"
> +		"\tslli zero, zero, 0x1f\n"
> +		"\tebreak\n"
> +		"\tsrai zero, zero, 7\n"
> +		"\tcsrw mtvec, %[tmp]\n"
> +
> +		"\t.option pop\n"
> +		: [tmp] "+r" (tmp), [en] "+r" (_semihosting_enabled),
> +		  [ret] "+r" (ret)
> +		: "r" (param0) : "memory");
> +
> +	try_semihosting = false;
> +	return _semihosting_enabled;
> +}
> +
> +static int semihosting_errno(void)
> +{
> +	long ret = semihosting_trap(SYSERRNO, NULL);
> +
> +	if (ret > 0 && ret < INT_MAX)
> +		return -ret;
> +	return SBI_EIO;
> +}
> +
> +static int infd = SBI_ENODEV;
> +
> +static long semihosting_open(const char *fname, enum semihosting_open_mode mode)
> +{
> +	long fd;
> +	struct semihosting_open_s {
> +		const char *fname;
> +		unsigned long mode;
> +		size_t len;
> +	} open;
> +
> +	open.fname = fname;
> +	open.len = sbi_strlen(fname);
> +	open.mode = mode;
> +
> +	/* Open the file on the host */
> +	fd = semihosting_trap(SYSOPEN, &open);
> +	if (fd == -1)
> +		return semihosting_errno();
> +	return fd;
> +}
> +
> +/**
> + * struct semihosting_rdwr_s - Arguments for read and write
> + * @fd: A file descriptor returned from semihosting_open()
> + * @memp: Pointer to a buffer of memory of at least @len bytes
> + * @len: The number of bytes to read or write
> + */
> +struct semihosting_rdwr_s {
> +	long fd;
> +	void *memp;
> +	size_t len;
> +};
> +
> +static long semihosting_read(long fd, void *memp, size_t len)
> +{
> +	long ret;
> +	struct semihosting_rdwr_s read;
> +
> +	read.fd = fd;
> +	read.memp = memp;
> +	read.len = len;
> +
> +	ret = semihosting_trap(SYSREAD, &read);
> +	if (ret < 0)
> +		return semihosting_errno();
> +	return len - ret;
> +}
> +
> +/* clang-format on */
> +
> +static void semihosting_putc(char ch)
> +{
> +	semihosting_trap(SYSWRITEC, &ch);
> +}
> +
> +static int semihosting_getc(void)
> +{
> +	char ch = 0;
> +
> +	if (infd < 0)
> +		return semihosting_trap(SYSREADC, NULL);
> +
> +	semihosting_read(infd, &ch, sizeof(ch));
> +
> +	return ch;
> +}
> +
> +static struct sbi_console_device semihosting_console = {
> +	.name = "semihosting",
> +	.console_putc = semihosting_putc,
> +	.console_getc = semihosting_getc
> +};
> +
> +int semihosting_init(void)
> +{
> +	infd = semihosting_open(":tt", MODE_READ);
> +
> +	sbi_console_set_device(&semihosting_console);
> +
> +	return 0;
> +}
> diff --git a/platform/generic/configs/defconfig b/platform/generic/configs/defconfig
> index e324173..c95b7fa 100644
> --- a/platform/generic/configs/defconfig
> +++ b/platform/generic/configs/defconfig
> @@ -28,3 +28,4 @@ CONFIG_FDT_SERIAL_UART8250=y
> CONFIG_FDT_SERIAL_XILINX_UARTLITE=y
> CONFIG_FDT_TIMER=y
> CONFIG_FDT_TIMER_MTIMER=y
> +CONFIG_SERIAL_SEMIHOSTING=y
> diff --git a/platform/generic/platform.c b/platform/generic/platform.c
> index cc3620f..bf51aba 100644
> --- a/platform/generic/platform.c
> +++ b/platform/generic/platform.c
> @@ -23,6 +23,7 @@
> #include <sbi_utils/timer/fdt_timer.h>
> #include <sbi_utils/ipi/fdt_ipi.h>
> #include <sbi_utils/reset/fdt_reset.h>
> +#include <sbi_utils/serial/semihosting.h>
> 
> /* List of platform override modules generated at compile time */
> extern const struct platform_override *platform_override_modules[];
> @@ -242,6 +243,14 @@ static uint64_t generic_pmu_xlate_to_mhpmevent(uint32_t event_idx,
> 	return evt_val;
> }
> 
> +static int generic_console_init(void)
> +{
> +	if (semihosting_enabled())
> +		return semihosting_init();
> +	else
> +		return fdt_serial_init();
> +}
> +
> const struct sbi_platform_operations platform_ops = {
> 	.nascent_init		= generic_nascent_init,
> 	.early_init		= generic_early_init,
> @@ -249,7 +258,7 @@ const struct sbi_platform_operations platform_ops = {
> 	.early_exit		= generic_early_exit,
> 	.final_exit		= generic_final_exit,
> 	.domains_init		= generic_domains_init,
> -	.console_init		= fdt_serial_init,
> +	.console_init		= generic_console_init,
> 	.irqchip_init		= fdt_irqchip_init,
> 	.irqchip_exit		= fdt_irqchip_exit,
> 	.ipi_init		= fdt_ipi_init,
> -- 
> 2.34.1
> 
> 
> -- 
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