lib: Add common semihosting library

We factor out the arch-independent parts of the ARM semihosting
implementation as a common library so that it can be shared
with RISC-V.

Signed-off-by: Kautuk Consul <kconsul@ventanamicro.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

arch/arm/Kconfig

@@ -413,52 +413,6 @@ config ARM_SMCCC
 	  This should be enabled if U-Boot needs to communicate with system
 	  firmware (for example, PSCI) according to SMCCC.
 
-config SEMIHOSTING
-	bool "Support ARM semihosting"
-	help
-	  Semihosting is a method for a target to communicate with a host
-	  debugger. It uses special instructions which the debugger will trap
-	  on and interpret. This allows U-Boot to read/write files, print to
-	  the console, and execute arbitrary commands on the host system.
-
-	  Enabling this option will add support for reading and writing files
-	  on the host system. If you don't have a debugger attached then trying
-	  to do this will likely cause U-Boot to hang. Say 'n' if you are unsure.
-
-config SEMIHOSTING_FALLBACK
-	bool "Recover gracefully when semihosting fails"
-	depends on SEMIHOSTING && ARM64
-	default y
-	help
-	  Normally, if U-Boot makes a semihosting call and no debugger is
-	  attached, then it will panic due to a synchronous abort
-	  exception. This config adds an exception handler which will allow
-	  U-Boot to recover. Say 'y' if unsure.
-
-config SPL_SEMIHOSTING
-	bool "Support ARM semihosting in SPL"
-	depends on SPL
-	help
-	  Semihosting is a method for a target to communicate with a host
-	  debugger. It uses special instructions which the debugger will trap
-	  on and interpret. This allows U-Boot to read/write files, print to
-	  the console, and execute arbitrary commands on the host system.
-
-	  Enabling this option will add support for reading and writing files
-	  on the host system. If you don't have a debugger attached then trying
-	  to do this will likely cause U-Boot to hang. Say 'n' if you are unsure.
-
-config SPL_SEMIHOSTING_FALLBACK
-	bool "Recover gracefully when semihosting fails in SPL"
-	depends on SPL_SEMIHOSTING && ARM64
-	select ARMV8_SPL_EXCEPTION_VECTORS
-	default y
-	help
-	  Normally, if U-Boot makes a semihosting call and no debugger is
-	  attached, then it will panic due to a synchronous abort
-	  exception. This config adds an exception handler which will allow
-	  U-Boot to recover. Say 'y' if unsure.
-
 config SYS_THUMB_BUILD
 	bool "Build U-Boot using the Thumb instruction set"
 	depends on !ARM64

arch/arm/lib/semihosting.c

@@ -5,20 +5,6 @@
  */
 
 #include <common.h>
-#include <log.h>
-#include <semihosting.h>
-
-#define SYSOPEN		0x01
-#define SYSCLOSE	0x02
-#define SYSWRITEC	0x03
-#define SYSWRITE0	0x04
-#define SYSWRITE	0x05
-#define SYSREAD		0x06
-#define SYSREADC	0x07
-#define SYSISERROR	0x08
-#define SYSSEEK		0x0A
-#define SYSFLEN		0x0C
-#define SYSERRNO	0x13
 
 /*
  * Macro to force the compiler to *populate* memory (for an array or struct)
@@ -39,7 +25,7 @@
 /*
  * Call the handler
  */
-static long smh_trap(unsigned int sysnum, void *addr)
+long smh_trap(unsigned int sysnum, void *addr)
 {
 	register long result asm("r0");
 	register void *_addr asm("r1") = addr;
@@ -59,168 +45,3 @@ static long smh_trap(unsigned int sysnum, void *addr)
 
 	return result;
 }
-
-#if CONFIG_IS_ENABLED(SEMIHOSTING_FALLBACK)
-static bool _semihosting_enabled = true;
-static bool try_semihosting = true;
-
-bool semihosting_enabled(void)
-{
-	if (try_semihosting) {
-		smh_trap(SYSERRNO, NULL);
-		try_semihosting = false;
-	}
-
-	return _semihosting_enabled;
-}
-
-void disable_semihosting(void)
-{
-	_semihosting_enabled = false;
-}
-#endif
-
-/**
- * smh_errno() - Read the host's errno
- *
- * This gets the value of the host's errno and negates it. The host's errno may
- * or may not be set, so only call this function if a previous semihosting call
- * has failed.
- *
- * Return: a negative error value
- */
-static int smh_errno(void)
-{
-	long ret = smh_trap(SYSERRNO, NULL);
-
-	if (ret > 0 && ret < INT_MAX)
-		return -ret;
-	return -EIO;
-}
-
-long smh_open(const char *fname, enum smh_open_mode mode)
-{
-	long fd;
-	struct smh_open_s {
-		const char *fname;
-		unsigned long mode;
-		size_t len;
-	} open;
-
-	debug("%s: file \'%s\', mode \'%u\'\n", __func__, fname, mode);
-
-	open.fname = fname;
-	open.len = strlen(fname);
-	open.mode = mode;
-
-	/* Open the file on the host */
-	fd = smh_trap(SYSOPEN, &open);
-	if (fd == -1)
-		return smh_errno();
-	return fd;
-}
-
-/**
- * struct smg_rdwr_s - Arguments for read and write
- * @fd: A file descriptor returned from smh_open()
- * @memp: Pointer to a buffer of memory of at least @len bytes
- * @len: The number of bytes to read or write
- */
-struct smh_rdwr_s {
-	long fd;
-	void *memp;
-	size_t len;
-};
-
-long smh_read(long fd, void *memp, size_t len)
-{
-	long ret;
-	struct smh_rdwr_s read;
-
-	debug("%s: fd %ld, memp %p, len %zu\n", __func__, fd, memp, len);
-
-	read.fd = fd;
-	read.memp = memp;
-	read.len = len;
-
-	ret = smh_trap(SYSREAD, &read);
-	if (ret < 0)
-		return smh_errno();
-	return len - ret;
-}
-
-long smh_write(long fd, const void *memp, size_t len, ulong *written)
-{
-	long ret;
-	struct smh_rdwr_s write;
-
-	debug("%s: fd %ld, memp %p, len %zu\n", __func__, fd, memp, len);
-
-	write.fd = fd;
-	write.memp = (void *)memp;
-	write.len = len;
-
-	ret = smh_trap(SYSWRITE, &write);
-	*written = len - ret;
-	if (ret)
-		return smh_errno();
-	return 0;
-}
-
-long smh_close(long fd)
-{
-	long ret;
-
-	debug("%s: fd %ld\n", __func__, fd);
-
-	ret = smh_trap(SYSCLOSE, &fd);
-	if (ret == -1)
-		return smh_errno();
-	return 0;
-}
-
-long smh_flen(long fd)
-{
-	long ret;
-
-	debug("%s: fd %ld\n", __func__, fd);
-
-	ret = smh_trap(SYSFLEN, &fd);
-	if (ret == -1)
-		return smh_errno();
-	return ret;
-}
-
-long smh_seek(long fd, long pos)
-{
-	long ret;
-	struct smh_seek_s {
-		long fd;
-		long pos;
-	} seek;
-
-	debug("%s: fd %ld pos %ld\n", __func__, fd, pos);
-
-	seek.fd = fd;
-	seek.pos = pos;
-
-	ret = smh_trap(SYSSEEK, &seek);
-	if (ret)
-		return smh_errno();
-	return 0;
-}
-
-int smh_getc(void)
-{
-	return smh_trap(SYSREADC, NULL);
-}
-
-void smh_putc(char ch)
-{
-	smh_trap(SYSWRITEC, &ch);
-}
-
-void smh_puts(const char *s)
-{
-	smh_trap(SYSWRITE0, (char *)s);
-}

include/semihosting.h

@@ -17,6 +17,17 @@
 #define SMH_T32_SVC 0xDFAB
 #define SMH_T32_HLT 0xBABC
 
+/**
+ * smh_trap() - ARCH-specific semihosting call.
+ *
+ * Semihosting library/driver can use this function to do the
+ * actual semihosting calls.
+ *
+ * Return: Error code defined by semihosting spec.
+ */
+
+long smh_trap(unsigned int sysnum, void *addr);
+
 #if CONFIG_IS_ENABLED(SEMIHOSTING_FALLBACK)
 /**
  * semihosting_enabled() - Determine whether semihosting is supported

lib/Kconfig

@@ -71,6 +71,53 @@ config HAVE_PRIVATE_LIBGCC
 config LIB_UUID
 	bool
 
+config SEMIHOSTING
+	bool "Support semihosting"
+	depends on ARM
+	help
+	  Semihosting is a method for a target to communicate with a host
+	  debugger. It uses special instructions which the debugger will trap
+	  on and interpret. This allows U-Boot to read/write files, print to
+	  the console, and execute arbitrary commands on the host system.
+
+	  Enabling this option will add support for reading and writing files
+	  on the host system. If you don't have a debugger attached then trying
+	  to do this will likely cause U-Boot to hang. Say 'n' if you are unsure.
+
+config SEMIHOSTING_FALLBACK
+	bool "Recover gracefully when semihosting fails"
+	depends on SEMIHOSTING && ARM64
+	default y
+	help
+	  Normally, if U-Boot makes a semihosting call and no debugger is
+	  attached, then it will panic due to a synchronous abort
+	  exception. This config adds an exception handler which will allow
+	  U-Boot to recover. Say 'y' if unsure.
+
+config SPL_SEMIHOSTING
+	bool "Support semihosting in SPL"
+	depends on SPL && ARM
+	help
+	  Semihosting is a method for a target to communicate with a host
+	  debugger. It uses special instructions which the debugger will trap
+	  on and interpret. This allows U-Boot to read/write files, print to
+	  the console, and execute arbitrary commands on the host system.
+
+	  Enabling this option will add support for reading and writing files
+	  on the host system. If you don't have a debugger attached then trying
+	  to do this will likely cause U-Boot to hang. Say 'n' if you are unsure.
+
+config SPL_SEMIHOSTING_FALLBACK
+	bool "Recover gracefully when semihosting fails in SPL"
+	depends on SPL_SEMIHOSTING && ARM64
+	select ARMV8_SPL_EXCEPTION_VECTORS
+	default y
+	help
+	  Normally, if U-Boot makes a semihosting call and no debugger is
+	  attached, then it will panic due to a synchronous abort
+	  exception. This config adds an exception handler which will allow
+	  U-Boot to recover. Say 'y' if unsure.
+
 config PRINTF
 	bool
 	default y

lib/Makefile

@@ -146,6 +146,8 @@ obj-y += date.o
 obj-y += rtc-lib.o
 obj-$(CONFIG_LIB_ELF) += elf.o
 
+obj-$(CONFIG_$(SPL_TPL_)SEMIHOSTING) += semihosting.o
+
 #
 # Build a fast OID lookup registry from include/linux/oid_registry.h
 #

lib/semihosting.c

@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2022 Sean Anderson <sean.anderson@seco.com>
+ * Copyright 2014 Broadcom Corporation
+ */
+
+#include <common.h>
+#include <log.h>
+#include <semihosting.h>
+
+#define SYSOPEN		0x01
+#define SYSCLOSE	0x02
+#define SYSWRITEC	0x03
+#define SYSWRITE0	0x04
+#define SYSWRITE	0x05
+#define SYSREAD		0x06
+#define SYSREADC	0x07
+#define SYSISERROR	0x08
+#define SYSSEEK		0x0A
+#define SYSFLEN		0x0C
+#define SYSERRNO	0x13
+
+#if CONFIG_IS_ENABLED(SEMIHOSTING_FALLBACK)
+static bool _semihosting_enabled = true;
+static bool try_semihosting = true;
+
+bool semihosting_enabled(void)
+{
+	if (try_semihosting) {
+		smh_trap(SYSERRNO, NULL);
+		try_semihosting = false;
+	}
+
+	return _semihosting_enabled;
+}
+
+void disable_semihosting(void)
+{
+	_semihosting_enabled = false;
+}
+#endif
+
+/**
+ * smh_errno() - Read the host's errno
+ *
+ * This gets the value of the host's errno and negates it. The host's errno may
+ * or may not be set, so only call this function if a previous semihosting call
+ * has failed.
+ *
+ * Return: a negative error value
+ */
+static int smh_errno(void)
+{
+	long ret = smh_trap(SYSERRNO, NULL);
+
+	if (ret > 0 && ret < INT_MAX)
+		return -ret;
+	return -EIO;
+}
+
+long smh_open(const char *fname, enum smh_open_mode mode)
+{
+	long fd;
+	struct smh_open_s {
+		const char *fname;
+		unsigned long mode;
+		size_t len;
+	} open;
+
+	debug("%s: file \'%s\', mode \'%u\'\n", __func__, fname, mode);
+
+	open.fname = fname;
+	open.len = strlen(fname);
+	open.mode = mode;
+
+	/* Open the file on the host */
+	fd = smh_trap(SYSOPEN, &open);
+	if (fd == -1)
+		return smh_errno();
+	return fd;
+}
+
+/**
+ * struct smg_rdwr_s - Arguments for read and write
+ * @fd: A file descriptor returned from smh_open()
+ * @memp: Pointer to a buffer of memory of at least @len bytes
+ * @len: The number of bytes to read or write
+ */
+struct smh_rdwr_s {
+	long fd;
+	void *memp;
+	size_t len;
+};
+
+long smh_read(long fd, void *memp, size_t len)
+{
+	long ret;
+	struct smh_rdwr_s read;
+
+	debug("%s: fd %ld, memp %p, len %zu\n", __func__, fd, memp, len);
+
+	read.fd = fd;
+	read.memp = memp;
+	read.len = len;
+
+	ret = smh_trap(SYSREAD, &read);
+	if (ret < 0)
+		return smh_errno();
+	return len - ret;
+}
+
+long smh_write(long fd, const void *memp, size_t len, ulong *written)
+{
+	long ret;
+	struct smh_rdwr_s write;
+
+	debug("%s: fd %ld, memp %p, len %zu\n", __func__, fd, memp, len);
+
+	write.fd = fd;
+	write.memp = (void *)memp;
+	write.len = len;
+
+	ret = smh_trap(SYSWRITE, &write);
+	*written = len - ret;
+	if (ret)
+		return smh_errno();
+	return 0;
+}
+
+long smh_close(long fd)
+{
+	long ret;
+
+	debug("%s: fd %ld\n", __func__, fd);
+
+	ret = smh_trap(SYSCLOSE, &fd);
+	if (ret == -1)
+		return smh_errno();
+	return 0;
+}
+
+long smh_flen(long fd)
+{
+	long ret;
+
+	debug("%s: fd %ld\n", __func__, fd);
+
+	ret = smh_trap(SYSFLEN, &fd);
+	if (ret == -1)
+		return smh_errno();
+	return ret;
+}
+
+long smh_seek(long fd, long pos)
+{
+	long ret;
+	struct smh_seek_s {
+		long fd;
+		long pos;
+	} seek;
+
+	debug("%s: fd %ld pos %ld\n", __func__, fd, pos);
+
+	seek.fd = fd;
+	seek.pos = pos;
+
+	ret = smh_trap(SYSSEEK, &seek);
+	if (ret)
+		return smh_errno();
+	return 0;
+}
+
+int smh_getc(void)
+{
+	return smh_trap(SYSREADC, NULL);
+}
+
+void smh_putc(char ch)
+{
+	smh_trap(SYSWRITEC, &ch);
+}
+
+void smh_puts(const char *s)
+{
+	smh_trap(SYSWRITE0, (char *)s);
+}