cli: Port upstream Busybox hush to U-Boot

Adds new file cli_hush_upstream.c, it is a copy of Busybox hush file as it was of
time to commit 37460f5da.
This commit modifies Busybox hush to not compile some part specific to Busybox
and adds some code needed by U-Boot.
The modifications consists mainly on adding code #if(n)def guards.

For the moment, this refurbished flavor of hush only permits running command
without any keywords (i.e., if and for are not recognized) or variable expansion
(i.e., echo $foo prints foo and not value stored in variable foo).

A new file was also added to define some functions specific to U-Boot.

Signed-off-by: Francis Laniel <francis.laniel@amarulasolutions.com>
Signed-off-by: Harald Seiler <hws@denx.de>

common/cli_hush_modern.c

@@ -0,0 +1,274 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * This file defines the compilation unit for the new hush shell version.  The
+ * actual implementation from upstream BusyBox can be found in
+ * `cli_hush_upstream.c` which is included at the end of this file.
+ *
+ * This "wrapper" technique is used to keep the changes to the upstream version
+ * as minmal as possible.  Instead, all defines and redefines necessary are done
+ * here, outside the upstream sources.  This will hopefully make upgrades to
+ * newer revisions much easier.
+ *
+ * Copyright (c) 2021, Harald Seiler, DENX Software Engineering, hws@denx.de
+ */
+
+#include <common.h>         /* readline */
+#include <env.h>
+#include <malloc.h>         /* malloc, free, realloc*/
+#include <linux/ctype.h>    /* isalpha, isdigit */
+#include <console.h>
+#include <bootretry.h>
+#include <cli.h>
+#include <cli_hush.h>
+#include <command.h>        /* find_cmd */
+#include <asm/global_data.h>
+
+/*
+ * BusyBox Version: UPDATE THIS WHEN PULLING NEW UPSTREAM REVISION!
+ */
+#define BB_VER			"1.34.0.git37460f5daff9"
+
+/*
+ * Define hush features by the names used upstream.
+ */
+#define ENABLE_HUSH_INTERACTIVE	1
+#define ENABLE_FEATURE_EDITING	1
+/* No MMU in U-Boot */
+#define BB_MMU			0
+#define USE_FOR_NOMMU(...)	__VA_ARGS__
+#define USE_FOR_MMU(...)
+
+/*
+ * Size-saving "small" ints (arch-dependent)
+ */
+#if CONFIG_IS_ENABLED(X86) || CONFIG_IS_ENABLED(X86_64) || CONFIG_IS_ENABLED(MIPS)
+/* add other arches which benefit from this... */
+typedef signed char smallint;
+typedef unsigned char smalluint;
+#else
+/* for arches where byte accesses generate larger code: */
+typedef int smallint;
+typedef unsigned smalluint;
+#endif
+
+/*
+ * Alignment defines used by BusyBox.
+ */
+#define ALIGN1			__attribute__((aligned(1)))
+#define ALIGN2			__attribute__((aligned(2)))
+#define ALIGN4			__attribute__((aligned(4)))
+#define ALIGN8			__attribute__((aligned(8)))
+#define ALIGN_PTR		__attribute__((aligned(sizeof(void*))))
+
+/*
+ * Miscellaneous compiler/platform defines.
+ */
+#define FAST_FUNC /* not used in U-Boot */
+#define UNUSED_PARAM		__always_unused
+#define ALWAYS_INLINE		__always_inline
+#define NOINLINE		noinline
+
+/*
+ * Defines to provide equivalents to what libc/BusyBox defines.
+ */
+#define EOF			(-1)
+#define EXIT_SUCCESS		0
+#define EXIT_FAILURE		1
+
+/*
+ * Stubs to provide libc/BusyBox functions based on U-Boot equivalents where it
+ * makes sense.
+ */
+#define utoa			simple_itoa
+
+static void __noreturn xfunc_die(void)
+{
+	panic("HUSH died!");
+}
+
+#define bb_error_msg_and_die(format, ...) do { \
+panic("HUSH: " format, __VA_ARGS__); \
+} while (0);
+
+#define bb_simple_error_msg_and_die(msg) do { \
+panic_str("HUSH: " msg); \
+} while (0);
+
+/* fdprintf() is used for debug output. */
+static int __maybe_unused fdprintf(int fd, const char *format, ...)
+{
+	va_list args;
+	uint i;
+
+	assert(fd == 2);
+
+	va_start(args, format);
+	i = vprintf(format, args);
+	va_end(args);
+
+	return i;
+}
+
+static void bb_verror_msg(const char *s, va_list p, const char* strerr)
+{
+	/* TODO: what to do with strerr arg? */
+	vprintf(s, p);
+}
+
+static void bb_error_msg(const char *s, ...)
+{
+	va_list p;
+
+	va_start(p, s);
+	bb_verror_msg(s, p, NULL);
+	va_end(p);
+}
+
+static void *xmalloc(size_t size)
+{
+	void *p = NULL;
+	if (!(p = malloc(size)))
+		panic("out of memory");
+	return p;
+}
+
+static void *xzalloc(size_t size)
+{
+	void *p = xmalloc(size);
+	memset(p, 0, size);
+	return p;
+}
+
+static void *xrealloc(void *ptr, size_t size)
+{
+	void *p = NULL;
+	if (!(p = realloc(ptr, size)))
+		panic("out of memory");
+	return p;
+}
+
+#define xstrdup		strdup
+#define xstrndup	strndup
+
+static void *mempcpy(void *dest, const void *src, size_t len)
+{
+	return memcpy(dest, src, len) + len;
+}
+
+/* Like strcpy but can copy overlapping strings. */
+static void overlapping_strcpy(char *dst, const char *src)
+{
+	/*
+	 * Cheap optimization for dst == src case -
+	 * better to have it here than in many callers.
+	 */
+	if (dst != src) {
+		while ((*dst = *src) != '\0') {
+			dst++;
+			src++;
+		}
+	}
+}
+
+static char* skip_whitespace(const char *s)
+{
+	/*
+	 * In POSIX/C locale (the only locale we care about: do we REALLY want
+	 * to allow Unicode whitespace in, say, .conf files? nuts!)
+	 * isspace is only these chars: "\t\n\v\f\r" and space.
+	 * "\t\n\v\f\r" happen to have ASCII codes 9,10,11,12,13.
+	 * Use that.
+	 */
+	while (*s == ' ' || (unsigned char)(*s - 9) <= (13 - 9))
+		s++;
+
+	return (char *) s;
+}
+
+static char* skip_non_whitespace(const char *s)
+{
+	while (*s != '\0' && *s != ' ' && (unsigned char)(*s - 9) > (13 - 9))
+		s++;
+
+	return (char *) s;
+}
+
+#define is_name(c)	((c) == '_' || isalpha((unsigned char)(c)))
+#define is_in_name(c)	((c) == '_' || isalnum((unsigned char)(c)))
+
+static const char* endofname(const char *name)
+{
+	if (!is_name(*name))
+		return name;
+	while (*++name) {
+		if (!is_in_name(*name))
+			break;
+	}
+	return name;
+}
+
+struct in_str;
+static int u_boot_cli_readline(struct in_str *i);
+
+struct in_str;
+static int u_boot_cli_readline(struct in_str *i);
+
+/*
+ * BusyBox globals which are needed for hush.
+ */
+static uint8_t xfunc_error_retval;
+
+static const char defifsvar[] __aligned(1) = "IFS= \t\n";
+#define defifs (defifsvar + 4)
+
+/*
+ * This define is used for changes that need be done directly in the upstream
+ * sources still. Ideally, its use should be minimized as much as possible.
+ */
+#define __U_BOOT__
+
+/*
+ *
+ * +-- Include of the upstream sources --+ *
+ * V                                     V
+ */
+#include "cli_hush_upstream.c"
+/*
+ * A                                     A
+ * +-- Include of the upstream sources --+ *
+ *
+ */
+
+int u_boot_hush_start_modern(void)
+{
+	INIT_G();
+	return 0;
+}
+
+static int u_boot_cli_readline(struct in_str *i)
+{
+	char *prompt;
+	char __maybe_unused *ps_prompt = NULL;
+
+	if (!G.promptmode)
+		prompt = CONFIG_SYS_PROMPT;
+#ifdef CONFIG_SYS_PROMPT_HUSH_PS2
+	else
+		prompt = CONFIG_SYS_PROMPT_HUSH_PS2;
+#else
+	/* TODO: default value? */
+	#error "SYS_PROMPT_HUSH_PS2 is not defined!"
+#endif
+
+	if (CONFIG_IS_ENABLED(CMDLINE_PS_SUPPORT)) {
+		if (!G.promptmode)
+			ps_prompt = env_get("PS1");
+		else
+			ps_prompt = env_get("PS2");
+
+		if (ps_prompt)
+			prompt = ps_prompt;
+	}
+
+	return cli_readline(prompt);
+}