From 177957dac462b6134c5134e6567019f73a401b8b Mon Sep 17 00:00:00 2001
From: Per Lundberg <perlun@gmail.com>
Date: Thu, 12 Oct 2017 00:19:29 +0300
Subject: [PATCH] Linker scripts: made it possible to override PROCESS_VM_BASE

This turned out to be crucial to be able to debug the issues I was having tonight, so I put the time into fixing this. It turned out to be quite trivial in the end, since a Stack Overflow user had done the vast majority of the work for us. Thanks Aravind!

Closes #104.
---
 libraries/chaos.ld               | 5 ++++-
 servers/file_system/fat/Rakefile | 1 +
 servers/network/ipv4/Rakefile    | 2 +-
 servers/servers.rake             | 6 ++++--
 4 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/libraries/chaos.ld b/libraries/chaos.ld
index 889feea5..4c936bc3 100644
--- a/libraries/chaos.ld
+++ b/libraries/chaos.ld
@@ -10,10 +10,13 @@ OUTPUT_ARCH(i386)
 ENTRY(startup)
 SEARCH_DIR(/mnt/chaos/programming/libraries/static);
 
+DEFAULT_PROCESS_VM_BASE = 0x40000000;
+PROCESS_VM_BASE = DEFINED(PROCESS_VM_BASE) ? PROCESS_VM_BASE : DEFAULT_PROCESS_VM_BASE;
+
 SECTIONS
 {
   /* Read-only sections, merged into text segment: */
-  . = 0x40000000 + SIZEOF_HEADERS;
+  . = PROCESS_VM_BASE + SIZEOF_HEADERS;
   .interp     : { *(.interp) 	}
   .hash          : { *(.hash)		}
   .dynsym        : { *(.dynsym)		}
diff --git a/servers/file_system/fat/Rakefile b/servers/file_system/fat/Rakefile
index 56e5a41a..59bd0cc2 100644
--- a/servers/file_system/fat/Rakefile
+++ b/servers/file_system/fat/Rakefile
@@ -22,5 +22,6 @@ LIBRARIES = %w(
 ).freeze
 
 OUTPUT = 'fat'.freeze
+EXTRA_LDFLAGS_PRE = '-Wl,--defsym=PROCESS_VM_BASE=0x50000000'
 
 load '../../servers.rake'
diff --git a/servers/network/ipv4/Rakefile b/servers/network/ipv4/Rakefile
index 7a427a63..8c76c11e 100644
--- a/servers/network/ipv4/Rakefile
+++ b/servers/network/ipv4/Rakefile
@@ -11,7 +11,7 @@ OBJECTS = %w(
   udp.o
 ).freeze
 
-EXTRA_LDFLAGS = '-lgcc'.freeze
+EXTRA_LIBS = '-lgcc'.freeze
 LIBRARIES = %w(
   ipc
   ipv4
diff --git a/servers/servers.rake b/servers/servers.rake
index 1227ecc8..25e2e2a0 100644
--- a/servers/servers.rake
+++ b/servers/servers.rake
@@ -38,14 +38,16 @@ CFLAGS = (COMMON_CFLAGS + %w(
   -Wstrict-prototypes
 )).join(' ')
 
-EXTRA_LDFLAGS ||= ''.freeze
+EXTRA_LDFLAGS_PRE ||= ''.freeze
+EXTRA_LIBS ||= ''.freeze
 LDFLAGS = %W(
+  #{EXTRA_LDFLAGS_PRE}
   #{LIBRARIES_DIR}/startup.o
   -nostdlib
   -Wl,-T,#{LIBRARIES_DIR}/chaos.ld
   -m32
   -L#{LIBRARIES_DIR}
-  #{EXTRA_LDFLAGS}
+  #{EXTRA_LIBS}
 ).freeze
 
 LIBRARY_FILES = LIBRARIES.map { |l| "#{LIBRARIES_DIR}/lib#{l}.a" }