From 0d2ddecc9aeb232746b76b4eebdb1381053a8951 Mon Sep 17 00:00:00 2001
From: Ada Christine <adachristine18@gmail.com>
Date: Mon, 27 Jan 2025 02:05:07 +0000
Subject: checkpoint. we can fake syscall with the dummy gdt

---
 service/Makefile    |  4 ++--
 service/kjarna.c    | 14 +++++---------
 service/lib/posix.c | 19 +++++++++++++++++++
 3 files changed, 26 insertions(+), 11 deletions(-)
 create mode 100644 service/lib/posix.c

(limited to 'service')

diff --git a/service/Makefile b/service/Makefile
index 09ff0be..b78cac3 100644
--- a/service/Makefile
+++ b/service/Makefile
@@ -4,7 +4,7 @@ LDFLAGS += -z max-page-size=4096 --export-dynamic -pic \
 	   -z separate-code -pie -Bsymbolic -shared \
 	   -z noexecstack -g
 
-VPATH := ../lib arch/x86_64/
+VPATH := ../lib arch/x86_64/ lib
 
 TARGET := kjarna.os
 .DEFAULT: $(TARGET)
@@ -15,7 +15,7 @@ CFLAGS += -fPIC -fvisibility=hidden -mgeneral-regs-only
 
 LDSCRIPT := kjarna.ld
 
-CRT_OBJS := start.o rtld_link.o dynamic.o elf64.o kjarna.o
+CRT_OBJS := start.o rtld_link.o dynamic.o elf64.o kjarna.o posix.o
 LIB_OBJS := memcmp.o memcpy.o memmove.o memset.o string.o stdio.o \
 			printf.o heap.o
 APP_OBJS := main.o
diff --git a/service/kjarna.c b/service/kjarna.c
index 1240c97..ce9ec54 100644
--- a/service/kjarna.c
+++ b/service/kjarna.c
@@ -4,19 +4,15 @@ struct kjarna_entry_params *entry_params;
 
 extern int main(int argc, char **argv);
 
-int kjarna_entry(struct kjarna_entry_params *params)
+int kjarna_entry()
 {
-	entry_params = params;
-
-	__asm__ ("leaq kc_image_base(%%rip), %%rax" ::: "rax");
+	uint64_t image_base;
+	__asm__ ("leaq kc_image_base(%%rip), %0" : "=r"(image_base) :: );
 
 	bool wait = true;
 
-	while(wait)
-	{
-		__asm__ volatile("hlt");
-	}
+	while(wait);
 
-	return main(params->argc, params->argv);
+	return main(0, nullptr);
 }
 
diff --git a/service/lib/posix.c b/service/lib/posix.c
new file mode 100644
index 0000000..a912977
--- /dev/null
+++ b/service/lib/posix.c
@@ -0,0 +1,19 @@
+#include <unistd.h>
+
+ssize_t write(int fd, const void *buffer, size_t length)
+{
+	ssize_t result;
+
+	__asm__ (
+		"movq %0, %%rdi\n"
+		"movq %1, %%rsi\n"
+		"movq %2, %%rdx\n"
+		"movq $1, %%rax\n"
+		"syscall"
+		: "=a"(result)
+		: "g"(fd), "g"(buffer), "g"(length)
+		: "rdi", "rsi","rdx");
+
+	return result;
+}
+
-- 
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