From c3ccee650604e6cd8d471a1d7b68a51b3a8f363c Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Sat, 4 Nov 2023 23:58:33 +0000
Subject: [PATCH] preinit: print errno (in hex, it's easier) for failures

---
 pkgs/preinit/parseopts.c | 39 +++++++++++++++++++++++++++++++++++++--
 pkgs/preinit/preinit.c   | 19 +++++++++++--------
 2 files changed, 48 insertions(+), 10 deletions(-)

diff --git a/pkgs/preinit/parseopts.c b/pkgs/preinit/parseopts.c
index d21255ae..0523924b 100644
--- a/pkgs/preinit/parseopts.c
+++ b/pkgs/preinit/parseopts.c
@@ -1,3 +1,5 @@
+#include <unistd.h>
+#include <stdint.h>
 #include <string.h>
 #include <unistd.h>
 
@@ -12,6 +14,33 @@ static int begins_with(char * str, char * prefix)
 	return 1;
 }
 
+char * pr_u32(int32_t input) {
+    static char buf[9];
+    const char *digits = "0123456789abcdef";
+    int i=0;
+
+    buf[i] = digits[(input & 0xf0000000) >> 28];
+    buf[i+1] = digits[(input & 0x0f000000) >> 24];
+    if(buf[i] != '0' || buf[i+1] != '0') i+=2;
+
+    buf[i] = digits[(input & 0x00f00000) >> 20];
+    buf[i+1] = digits[(input & 0x000f0000) >> 16];
+    if(buf[i] != '0' || buf[i+1] != '0') i+=2;
+
+    buf[i] = digits[(input & 0x0000f000) >> 12];
+    buf[i+1] = digits[(input & 0x00000f00) >> 8];
+    if(buf[i] != '0' || buf[i+1] != '0') i+=2;
+
+    buf[i] = digits[(input & 0x000000f0) >> 4];
+    buf[i+1] = digits[(input & 0x0000000f)];
+    i+=2;
+
+    buf[i] ='\0';
+    write(2, buf, i);
+
+    return buf;
+}
+
 
 void parseopts(char * cmdline, char **root, char **rootfstype) {
     *root = 0;
@@ -21,7 +50,7 @@ void parseopts(char * cmdline, char **root, char **rootfstype) {
 	if(begins_with(p, "root=")) {
 	    *root = p + strlen("root=");
 	    while(*p && (*p != ' ')) p++;
-	    
+
 	    if(*p) {
 		*p = '\0';
 		p++;
@@ -43,6 +72,8 @@ void parseopts(char * cmdline, char **root, char **rootfstype) {
 #include <stdio.h>
 #include <stdlib.h>
 
+// cc -DTESTS  -o parseopts parseopts.c && ./parseopts
+
 #define die(fmt, ...) do { printf(fmt, __VA_ARGS__); exit(1); } while(0)
 #define S(x) #x
 #define expect_equal(actual, expected) \
@@ -91,7 +122,11 @@ int main()
     if(strlen(rootfstype)) die("expected empty rootfstype, got \"%s\"", rootfstype);
     if(strlen(root)) die("expected null root, got \"%s\"", root);
 
+    expect_equal("01", pr_u32(1));
+    expect_equal("ab", pr_u32(0xab));
+    expect_equal("0abc", pr_u32(0xabc));
+    expect_equal("aabc", pr_u32(0xaabc));
+    expect_equal("deadcafe", pr_u32(0xdeadcafe));
 }
 
-
 #endif
diff --git a/pkgs/preinit/preinit.c b/pkgs/preinit/preinit.c
index 89afb97e..f6236ec6 100644
--- a/pkgs/preinit/preinit.c
+++ b/pkgs/preinit/preinit.c
@@ -13,7 +13,9 @@
 void parseopts(char * cmdline, char **root, char **rootfstype);
 
 #define ERR(x) write(2, x, strlen(x))
-#define AVER(c) do { if(c < 0) ERR("failed: "  #c); } while(0)
+#define AVER(c) do { if(c < 0) { ERR("failed: "  #c ": error=0x" ); pr_u32(errno); ERR("\n"); } } while(0)
+
+char * pr_u32(int32_t input);
 
 static void die() {
     /* if init exits, it causes a kernel panic. On the Turris
@@ -52,7 +54,7 @@ int main(int argc, char *argv[], char *envp[])
 
     write(1, banner, strlen(banner));
 
-    mount("none", "/proc", "proc", 0, NULL);
+    AVER(mount("none", "/proc", "proc", 0, NULL));
 
     int cmdline = open("/proc/cmdline", O_RDONLY, 0);
 
@@ -66,18 +68,19 @@ int main(int argc, char *argv[], char *envp[])
 	write(1, "cmdline: \"", 10);
 	write(1, buf, len);
 	write(1, "\"\n", 2);
-    };
-
+    } else {
+	ERR("failed: open(\"/proc/cmdline\")\n");
+	die();
+    }
     parseopts(buf, &rootdevice, &rootfstype);
-	
+
     if(rootdevice) {
 	if(!rootfstype) rootfstype = "jffs2"; /* backward compatibility */
 	write(1, "rootdevice ", 11);
 	write(1, rootdevice, strlen(rootdevice));
 	write(1, " (", 2);
 	write(1, rootfstype, strlen(rootfstype));
-	write(1, ")\n", 1);
-
+	write(1, ")\n", 2);
 	AVER(mount(rootdevice, "/target/persist", rootfstype, 0, NULL));
 	AVER(mount("/target/persist/nix", "/target/nix",
 		   "bind", MS_BIND, NULL));
@@ -87,7 +90,7 @@ int main(int argc, char *argv[], char *envp[])
 	AVER(chdir("/target"));
 
 	AVER(mount("/target", "/", "bind", MS_BIND | MS_REC, NULL));
-	AVER(chroot(".")); 
+	AVER(chroot("."));
 
 	argv[0] = "init";
 	argv[1] = NULL;