4 files changed, 67 insertions, 17 deletions
diff --git a/compiler/elymasAsmLib.ey b/compiler/elymasAsmLib.ey
index 71a4cab..b830a48 100644
--- a/compiler/elymasAsmLib.ey
+++ b/compiler/elymasAsmLib.ey
@@ -12,12 +12,24 @@
 
     2 ==MAP_PRIVATE
     16 ==MAP_FIXED
-    32 ==MAP_ANONYMOUS
+
+    [
+      { sys .?linux }   { 32 }
+      { sys .?freebsd } { 4096 }
+    ] conds ==MAP_ANONYMOUS
   > ==MMAP
 
   <
-    1 ==write
-    9 ==mmap
+    [
+      { sys .?linux } {
+        1 ==write
+        9 ==mmap
+      }'
+      { sys .?freebsd } {
+        4 ==write
+        477 ==mmap
+      }'
+    ] conds
   > ==SYSCALL
 
   0 ==constantAllocBegin
diff --git a/compiler/elymasGlobalSys.ey b/compiler/elymasGlobalSys.ey
index e00009c..0ba45d8 100644
--- a/compiler/elymasGlobalSys.ey
+++ b/compiler/elymasGlobalSys.ey
@@ -138,6 +138,11 @@
   "elymasGlobalSysDyn.ey" include
   "elymasGlobalSysTyped.ey" include
 
+  [
+    { sys .?linux } { "linux" }
+    { sys .?freebsd } { "freebsd" }
+  ] conds enterSubScope leaveSubScope
+
   leaveSubScope
 > --
 
diff --git a/compiler/elymasGlobalSysAsm.ey b/compiler/elymasGlobalSysAsm.ey
index 14052f5..9fe2f2d 100644
--- a/compiler/elymasGlobalSysAsm.ey
+++ b/compiler/elymasGlobalSysAsm.ey
@@ -491,7 +491,15 @@
         8 /rax :addqImm8Reg
       } rep
 
-      /r8 /rsp :xchgqRegReg # swap to elymas stack to ensure correct GC behavior for what follows
+      [
+        { sys .?linux } {
+          /r8 /rsp :xchgqRegReg # swap to elymas stack to ensure correct GC behavior for what follows
+        }
+        { sys .?freebsd } {
+          /r8 /rsp :movqRegReg # swap to elymas stack to ensure correct GC behavior for what follows
+          /rdi /r8 :movqRegReg # FreeBSD passes argc stack location in rdi
+        }
+      ] conds
       
       # empty encoding buffer to ensure the GC does not follow residue from freeze into unallocated memory
       :quoteEncodingBufferObjects /rdi :movqImmReg
diff --git a/compiler/standardClient.ey b/compiler/standardClient.ey
index 367d978..8d73236 100644
--- a/compiler/standardClient.ey
+++ b/compiler/standardClient.ey
@@ -389,25 +389,47 @@
   2 _ ==:RDWR
       bor bor ==:RWMASK
 
-  64 ==:OCREAT
-  512 ==:OTRUNC
-  1024 ==:OAPPEND
-
   1 ==:PROTREAD
   2 ==:PROTWRITE
   4 ==:PROTEXEC
 
   2 ==:MAPPRIVATE
-  32 ==:MAPANONYMOUS
 
-  0 ==:READ
-  1 ==:WRITE
-  2 ==:OPEN
-  3 ==:CLOSE
+  [
+    { sys .?linux }   { 32 }
+    { sys .?freebsd } { 4096 }
+  ] conds ==:MAPANONYMOUS
 
-  9 ==:MMAP
-  11 ==:MUNMAP
-  60 ==:EXIT
+  [
+    { sys .?linux } {
+      64 ==:OCREAT
+      512 ==:OTRUNC
+      1024 ==:OAPPEND
+
+      0 ==:READ
+      1 ==:WRITE
+      2 ==:OPEN
+      3 ==:CLOSE
+
+      9 ==:MMAP
+      11 ==:MUNMAP
+      60 ==:EXIT
+    }'
+    { sys .?freebsd } {
+      512 ==:OCREAT
+      1024 ==:OTRUNC
+      8 ==:OAPPEND
+
+      3 ==:READ
+      4 ==:WRITE
+      5 ==:OPEN
+      6 ==:CLOSE
+
+      477 ==:MMAP
+      73 ==:MUNMAP
+      1 ==:EXIT
+    }'
+  ] conds
 
   { ==code
     code 0 0 0 0 0 EXIT sys .asm .syscall
@@ -964,7 +986,10 @@
       %02                         # elfclass64
       %01                         # elf version
       %01                         # little endian encoding
-      %00 %00                     # Sys-V ABI
+      [
+        { sys .?linux }   { %00 %00 } # Sys-V ABI
+        { sys .?freebsd } { %09 %00 } # FreeBSD ABI
+      ] conds
       %00 %00 %00 %00 %00 %00 %00 # padding
       # Elf64_Half    e_type;      /* Object file type */
       %02 %00                     # executable file