From aba82eaacb7b59ba297a108d3b46f8098a3c6611 Mon Sep 17 00:00:00 2001
From: Curle <curle@gemwire.uk>
Date: Thu, 27 Aug 2020 01:39:56 +0100
Subject: [PATCH] Add support for C++

This was a doozy. I had to recompile gcc with a custom target to get it to output the CRT{BEGIN/END}.o files with proper 64 bit relocations.

The CMakeLists.txt file was also edited to allow these files to be linked (thereby actually adding the support) as well as to automatically create the boot image upon build.
---
 CMakeLists.txt             |  46 ++++++++++++++++++++++++++-----------
 chroma/inc/kernel/chroma.h |   4 ++++
 chroma/kernel.c            |  14 ++++++++++-
 global/a.out               | Bin 0 -> 720 bytes
 global/crt0.c              |  11 +++++++++
 global/crt0.o              | Bin 0 -> 1360 bytes
 global/crt0.s              |  10 ++++++++
 global/crtbegin.o          | Bin 0 -> 3584 bytes
 global/crtend.o            | Bin 0 -> 1800 bytes
 global/crti.o              | Bin 0 -> 912 bytes
 global/crti.s              |  13 +++++++++++
 global/crtn.o              | Bin 0 -> 856 bytes
 global/crtn.s              |   9 ++++++++
 linker.ld                  |   8 ++++++-
 14 files changed, 100 insertions(+), 15 deletions(-)
 create mode 100644 global/a.out
 create mode 100644 global/crt0.c
 create mode 100644 global/crt0.o
 create mode 100644 global/crt0.s
 create mode 100644 global/crtbegin.o
 create mode 100644 global/crtend.o
 create mode 100644 global/crti.o
 create mode 100644 global/crti.s
 create mode 100644 global/crtn.o
 create mode 100644 global/crtn.s

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6686564..7fad308 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,26 +9,46 @@ project(chroma)
 
 
 SET(src_files
-    chroma/kernel.c
-    chroma/video/draw.c
-    chroma/video/print.c
-    chroma/system/cpu.c
-    chroma/system/rw.c
-    chroma/system/serial.c
-    chroma/system/memory/paging.c
-    chroma/system/memory/physmem.c
-    chroma/system/drivers/keyboard.c
+    ${CMAKE_SOURCE_DIR}/chroma/kernel.c
+    ${CMAKE_SOURCE_DIR}/chroma/video/draw.c
+    ${CMAKE_SOURCE_DIR}/chroma/video/print.c
+    ${CMAKE_SOURCE_DIR}/chroma/system/cpu.c
+    ${CMAKE_SOURCE_DIR}/chroma/system/rw.c
+    ${CMAKE_SOURCE_DIR}/chroma/system/serial.c
+    ${CMAKE_SOURCE_DIR}/chroma/system/pci.c
+    ${CMAKE_SOURCE_DIR}/chroma/system/memory/paging.c
+    ${CMAKE_SOURCE_DIR}/chroma/system/memory/physmem.c
+    ${CMAKE_SOURCE_DIR}/chroma/system/drivers/keyboard.c
 )
 
 include_directories("chroma/inc")
 
 SET(src_no_sse
-    chroma/system/interrupts.c
+    ${CMAKE_SOURCE_DIR}/chroma/system/interrupts.c
+)
+
+SET(src_preamble
+    ${CMAKE_SOURCE_DIR}/global/crt0.o
+    ${CMAKE_SOURCE_DIR}/global/crti.o
+    ${CMAKE_SOURCE_DIR}/global/crtbegin.o
+)
+
+set(src_epilogue
+    ${CMAKE_SOURCE_DIR}/global/crtend.o
+    ${CMAKE_SOURCE_DIR}/global/crtn.o
 )
 
 set_property(SOURCE ${src_no_sse} PROPERTY COMPILE_FLAGS -mgeneral-regs-only)
 
-add_executable(kernel.elf ${src_files} ${src_no_sse} font.o)
-target_compile_options(kernel.elf PRIVATE -ffreestanding -O2 -Wall -Wextra -Wall -Werror -pedantic -fPIC)
-target_link_options(kernel.elf PRIVATE -T linker.ld -ffreestanding -O2 -nostdlib -lgcc)
+add_executable(kernel)
 
+target_sources(kernel PUBLIC ${src_preamble} PUBLIC ${src_files} PUBLIC ${src_no_sse} PUBLIC ${CMAKE_SOURCE_DIR}/font.o PUBLIC ${src_epilogue})
+target_compile_options(kernel PRIVATE -ffreestanding -O2 -Wall -Wextra -Wall -Werror -pedantic -fPIC -fno-exceptions)
+target_link_options(kernel PRIVATE -T linker.ld -ffreestanding -O2 -nostdlib -nostartfiles -lgcc)
+
+add_custom_command(
+    TARGET kernel
+    POST_BUILD
+    COMMAND cp ${CMAKE_SOURCE_DIR}/kernel ${CMAKE_SOURCE_DIR}/img/boot/exe
+    COMMAND ${CMAKE_SOURCE_DIR}/mkbootimg chroma.json chroma.img
+)
\ No newline at end of file
diff --git a/chroma/inc/kernel/chroma.h b/chroma/inc/kernel/chroma.h
index b9e1eb7..e22fa31 100644
--- a/chroma/inc/kernel/chroma.h
+++ b/chroma/inc/kernel/chroma.h
@@ -58,3 +58,7 @@ void InitPrint();
 
 void SetupInitialGDT();
 void SetupIDT();
+
+int Main();
+
+void Exit();
diff --git a/chroma/kernel.c b/chroma/kernel.c
index 9205766..b82b5c2 100644
--- a/chroma/kernel.c
+++ b/chroma/kernel.c
@@ -16,12 +16,16 @@ size_t KernelAddr = (size_t) &LoadAddr;
 size_t KernelEnd = (size_t) &end;
 
 
-void _start(void) {
+int Main(void) {
 
 
     SerialPrintf("\r\nBooting Chroma..\r\n");
     SerialPrintf("Kernel loaded at 0x%p, ends at 0x%p, is %d bytes long.\r\n", KernelAddr, KernelEnd, KernelEnd - KernelAddr);
 
+    SerialPrintf("The bootloader has put the paging tables at 0x%p.\r\n", ReadControlRegister(3));
+
+    TraversePageTables();
+
     ListMemoryMap();
 
     InitPrint();
@@ -41,5 +45,13 @@ void _start(void) {
 
 
     for(;;) { }
+
+    return 0;
     
 }
+
+
+void Exit(int ExitCode) {
+    SerialPrintf("Kernel stopped with code %x\r\n", ExitCode);
+
+}
\ No newline at end of file
diff --git a/global/a.out b/global/a.out
new file mode 100644
index 0000000000000000000000000000000000000000..ee9c26914d985091e07c2fc7c7435255276cfac9
GIT binary patch
literal 720
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zck*uTO%rmP&Sze!1Q{O2(A^aiBiRZp-WFOJk!OMm0^<#gQ;H-kGnR!w*C^35dh*g&
z__X_(&rvk_@bdGCu8$Xzo?$7HVf~BVWc}{=5yz`EjZ>AJ6ynV~Q3>I=28QY7ppq3)
zoh)}U+aLD|!!6<C-~Tin3hBF4I4t)+bMG+)g=aBRk7_Y5?|9|Fue{E>9v!{wLgQh9
mGSR26%6*GjW1ZU^As@7zD|W(it~O|<_jSjBjeTdq&A$M1g(cAd

literal 0
HcmV?d00001

diff --git a/global/crt0.c b/global/crt0.c
new file mode 100644
index 0000000..5f3ba44
--- /dev/null
+++ b/global/crt0.c
@@ -0,0 +1,11 @@
+
+extern void Exit(int code);
+extern int Main();
+
+extern void _init();
+
+void _start() {
+    _init();
+    int ex = Main();
+    Exit(ex);
+}
\ No newline at end of file
diff --git a/global/crt0.o b/global/crt0.o
new file mode 100644
index 0000000000000000000000000000000000000000..af9b40e1fa048808a004c3fbddf009ab9d5896bb
GIT binary patch
literal 1360
zcmbu9Jxc>Y5QgUxKjT*v1yR8?ih>+kDHeJXVj`%8U>(kQY9NVl*&^B~2tu&Q&#@FN
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literal 0
HcmV?d00001

diff --git a/global/crt0.s b/global/crt0.s
new file mode 100644
index 0000000..d50d2cd
--- /dev/null
+++ b/global/crt0.s
@@ -0,0 +1,10 @@
+.section .text
+.global _start
+.global _init
+.global main
+.global _fini
+.type _start, @function
+_start:
+	call _init
+	call main
+	call _fini
\ No newline at end of file
diff --git a/global/crtbegin.o b/global/crtbegin.o
new file mode 100644
index 0000000000000000000000000000000000000000..72d55319d5df8b1967e2c2fe34bd843dc05de6c1
GIT binary patch
literal 3584
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b-Q|lmDMSEC3{xR*Qv7u$S_`B09%lSMc)Q)_

literal 0
HcmV?d00001

diff --git a/global/crtend.o b/global/crtend.o
new file mode 100644
index 0000000000000000000000000000000000000000..1e31c40b1e83855e3496b309945a427da44d16ca
GIT binary patch
literal 1800
zcmbtU&ubGw6n>jk8&MmJ2#QE^@(0M!>ZKIalr-%swnA+M4?1j;jV<hEVRr)cq*4z`
z5PJ0J#s9&h(33Zh{sV%b2L%r~2=Tq$dE4xC1EMeNy!XBRzIiimCi}E;XQ^aaz-GY>
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literal 0
HcmV?d00001

diff --git a/global/crti.o b/global/crti.o
new file mode 100644
index 0000000000000000000000000000000000000000..440788727c348a40385be2b6dc3817db35190019
GIT binary patch
literal 912
zcmbVKEw2JG5S-)qI0S;1kdUBI7*c^kkrR&>1OkI5M}U9;!Bv1l^RM_b{ExTWYXjMq
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literal 0
HcmV?d00001

diff --git a/global/crti.s b/global/crti.s
new file mode 100644
index 0000000..e9ab988
--- /dev/null
+++ b/global/crti.s
@@ -0,0 +1,13 @@
+.section .init
+.global _init
+.type _init, @function
+_init:
+	push %rbp
+	movq %rsp, %rbp
+	
+.section .fini
+.global _fini
+.type _fini, @function
+_fini:
+	push %rbp
+	movq %rsp, %rbp
\ No newline at end of file
diff --git a/global/crtn.o b/global/crtn.o
new file mode 100644
index 0000000000000000000000000000000000000000..7223e2fce1bf0f859fc8d93b142cde2b66480973
GIT binary patch
literal 856
zcmb<-^>JfjWMqH=Mg}_u1P><4z#xGn=l~XWVBlonV2C{&dl;b#JBt~si3|+P3`|%x
zFau?<0cHjkY{Ed*tXRbLiYs$V5|bG8ic5+hbOwx7l3G#1pqG+ZlE|Q!R9wuUmzkFd
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literal 0
HcmV?d00001

diff --git a/global/crtn.s b/global/crtn.s
new file mode 100644
index 0000000..9c0665c
--- /dev/null
+++ b/global/crtn.s
@@ -0,0 +1,9 @@
+.section .init
+	
+	popq %rbp
+	ret
+	
+.section .fini
+
+	popq %rbp
+	ret
\ No newline at end of file
diff --git a/linker.ld b/linker.ld
index 6e0c8d4..b2b153f 100644
--- a/linker.ld
+++ b/linker.ld
@@ -26,7 +26,13 @@ SECTIONS
 		*(COMMON)
 	} :boot
 
-	/DISCARD/ : { *(.eh_frame) *(.comment) }
+	.eh_frame_hdr : {
+		*(.eh_frame_hdr)
+		*(.eh_frame)
+		*(.gcc_except_table)
+	} :boot
+
+	/DISCARD/ : {*(.comment) }
 
 	end = .;
 }