tools: update offsets tool to work with go versions 1.7 - 1.10

Older go versions (1.7.x) specify a fixed page size (_PageSize const) as
part of their runtime whereas newer go versions populate the page size at
runtime.

The kernel asm bootstrap code was written with go 1.8 in mind. As a
result it attempts to populate the page size manually which obviously
breaks compilation in go 1.7.

The offsets tool has been updated to emit the special def
"SKIP_PAGESIZE_SETUP" when running under go 1.7 which allows us to
perform conditional compilation of the page setup code inside the
bootstrap asm code.

fixup

Makefile

@@ -22,7 +22,6 @@ FUZZ_PKG_LIST := src/gopheros/device/acpi/aml
 ifeq ($(OS), Linux)
 export SHELL := /bin/bash -o pipefail
 
-
 LD := ld
 AS := nasm
 
@@ -105,7 +104,7 @@ $(BUILD_DIR)/go_asm_offsets.inc:
 	@mkdir -p $(BUILD_DIR)
 
 	@echo "[tools:offsets] calculating OS/arch-specific offsets for g, m and stack structs"
-	@GOPATH=$(GOPATH) $(GO) run tools/offsets/offsets.go -target-os $(GOOS) -target-arch $(GOARCH) -go-binary $(GO) -out $@
+	@GOROOT=$(GOROOT) GOPATH=$(GOPATH) $(GO) run tools/offsets/offsets.go -target-os $(GOOS) -target-arch $(GOARCH) -go-binary $(GO) -out $@
 
 $(BUILD_DIR)/arch/$(ARCH)/asm/%.o: src/arch/$(ARCH)/asm/%.s
 	@mkdir -p $(shell dirname $@)

src/arch/x86_64/asm/rt0_64.s

@@ -17,17 +17,17 @@ _rt0_idt_desc:
 	resw 1
 	resq 1
 
-; Allocates space for the IRQ handlers pointers registered by the IRQ package 
+; Allocates space for the IRQ handlers pointers registered by the IRQ package
 _rt0_irq_handlers resq IDT_ENTRIES
 
 ; According to the "ELF handling for TLS" document section 3.4.6
 ; (https://www.akkadia.org/drepper/tls.pdf) for the GNU variant for x86-64,
-; fs:0x00 contains a pointer to the TCB. Variables in the TLS are stored 
+; fs:0x00 contains a pointer to the TCB. Variables in the TLS are stored
 ; before the TCB and are accessed using negative offsets from the TCB address.
-r0_g_ptr:  resq 1 
+r0_g_ptr:  resq 1
-tcb_ptr:   resq 1 
+tcb_ptr:   resq 1
 
-section .text 
+section .text
 
 ;------------------------------------------------------------------------------
 ; Kernel 64-bit entry point
@@ -36,7 +36,7 @@ section .text
 ; - it has entered long mode and enabled paging
 ; - it has loaded a 64bit GDT
 ; - it has set up identity paging for the physical 0-8M region and the
-;   PAGE_OFFSET to PAGE_OFFSET+8M region. 
+;   PAGE_OFFSET to PAGE_OFFSET+8M region.
 ;------------------------------------------------------------------------------
 global _rt0_64_entry
 _rt0_64_entry:
@@ -50,7 +50,7 @@ _rt0_64_entry:
 	extern _kernel_start
 	extern _kernel_end
 	extern kernel.Kmain
-	
+
 	mov rax, PAGE_OFFSET
 	push rax
 	mov rax, _kernel_end - PAGE_OFFSET
@@ -60,7 +60,7 @@ _rt0_64_entry:
 	mov rax, multiboot_data
 	push rax
 	call kernel.Kmain
-	
+
 	; Main should never return; halt the CPU
 	mov rdi, err_kmain_returned
 	call write_string
@@ -75,13 +75,15 @@ _rt0_64_entry:
 _rt0_64_setup_go_runtime_structs:
 	%include "go_asm_offsets.inc" ; generated by tools/offsets
 
+	%ifndef SKIP_PAGESIZE_SETUP
 	; The Go allocator expects this symbol to be set to the system page size
-	; As the kernel bypass osinit() this needs to be set here.
+	; As the kernel bypasses osinit() this needs to be manually set here.
 	extern runtime.physPageSize
 	mov rax, runtime.physPageSize
 	mov qword [rax], 0x1000 ; 4096
-	
+	%endif
-	; Setup r0_g stack limits using the reserved stack 
+
+	; Setup r0_g stack limits using the reserved stack
 	extern stack_top
 	extern stack_bottom
 	extern runtime.g0
@@ -99,21 +101,21 @@ _rt0_64_setup_go_runtime_structs:
 	mov qword [rbx+GO_M_G0], rsi       ; m.g0 = g0
 	mov qword [rsi+GO_G_M], rbx        ; g.m = m
 
-	; Store the address of g0 in r0_g_ptr 
+	; Store the address of g0 in r0_g_ptr
 	mov rax, r0_g_ptr
 	mov qword [rax], rsi
 
-	; According to the x86-64 ABI requirements fs:0x0 should point to the 
+	; According to the x86-64 ABI requirements fs:0x0 should point to the
 	; TCB.
 	mov rax, tcb_ptr
 	mov qword [rax], rax
 
-	; Load 64-bit FS register address 
+	; Load 64-bit FS register address
-	; eax -> lower 32 bits 
+	; eax -> lower 32 bits
 	; edx -> upper 32 bits
 	mov ecx, 0xc0000100  ; fs_base
 	mov rsi, tcb_ptr
-	mov rax, rsi         ; lower 32 bits 
+	mov rax, rsi         ; lower 32 bits
 	shr rsi, 32
 	mov rdx, rsi         ; high 32 bits
 	wrmsr
@@ -122,26 +124,26 @@ _rt0_64_setup_go_runtime_structs:
 
 
 ;------------------------------------------------------------------------------
-; Setup and load IDT. We preload each IDT entry with a pointer to a gate handler 
+; Setup and load IDT. We preload each IDT entry with a pointer to a gate handler
-; but set it as inactive. The code in irq_amd64 is responsible for enabling 
+; but set it as inactive. The code in irq_amd64 is responsible for enabling
 ; individual IDT entries when handlers are installed.
 ;------------------------------------------------------------------------------
 _rt0_64_load_idt:
 	mov rax, _rt0_idt_start
 
-%assign gate_num 0 
+%assign gate_num 0
 %rep    IDT_ENTRIES
 	mov rbx, _rt0_64_gate_entry_%+ gate_num
 	mov word [rax], bx        ; gate entry bits 0-15
 	mov word [rax+2], 0x8     ; GDT descriptor
-	mov byte [rax+5], 0x0     ; Mark the entry as NOT present 
+	mov byte [rax+5], 0x0     ; Mark the entry as NOT present
 	shr rbx, 16
 	mov word [rax+6], bx      ; gate entry bits 16-31
 	shr rbx, 16
 	mov dword [rax+8], ebx    ; gate entry bits 32-63
 
 	add rax, 16		  ; size of IDT entry
-%assign gate_num gate_num+1 
+%assign gate_num gate_num+1
 %endrep
 	mov rax, _rt0_idt_desc
 	mov word [rax], _rt0_idt_end - _rt0_idt_start - 1 ; similar to GDT this must be len(IDT) - 1
@@ -152,15 +154,15 @@ ret
 
 
 ;------------------------------------------------------------------------------
-; Generate gate entries. Each gate handler pushes the address of the registered 
+; Generate gate entries. Each gate handler pushes the address of the registered
 ; handler to the stack before jumping to a dispatcher function.
 ;
 ; Some exceptions push an error code to the stack after the stack frame. This
-; code must be popped off the stack before calling iretq. The generated handlers 
+; code must be popped off the stack before calling iretq. The generated handlers
-; are aware whether they need to deal with the code or not and jump to the 
+; are aware whether they need to deal with the code or not and jump to the
 ; appropriate get dispatcher.
 ;------------------------------------------------------------------------------
-%assign gate_num 0 
+%assign gate_num 0
 %rep    IDT_ENTRIES
 extern _rt0_interrupt_handlers
 _rt0_64_gate_entry_%+ gate_num:
@@ -177,13 +179,13 @@ _rt0_64_gate_entry_%+ gate_num:
 	%else
 		jmp _rt0_64_gate_dispatcher_without_code
 	%endif
-%assign gate_num gate_num+1 
+%assign gate_num gate_num+1
 %endrep
 
 %macro save_regs 0
-	push r15 
+	push r15
 	push r14
-	push r13 
+	push r13
 	push r12
 	push r11
 	push r10
@@ -191,10 +193,10 @@ _rt0_64_gate_entry_%+ gate_num:
 	push r8
 	push rbp
 	push rdi
-	push rsi 
+	push rsi
-	push rdx 
+	push rdx
-	push rcx 
+	push rcx
-	push rbx 
+	push rbx
 	push rax
 %endmacro
 
@@ -203,13 +205,13 @@ _rt0_64_gate_entry_%+ gate_num:
 	pop rbx
 	pop rcx
 	pop rdx
-	pop rsi 
+	pop rsi
 	pop rdi
-	pop rbp 
+	pop rbp
 	pop r8
 	pop r9
 	pop r10
-	pop r11 
+	pop r11
 	pop r12
 	pop r13
 	pop r14
@@ -217,14 +219,14 @@ _rt0_64_gate_entry_%+ gate_num:
 %endmacro
 
 ;------------------------------------------------------------------------------
-; This dispatcher is invoked by gate entries that expect a code to be pushed 
+; This dispatcher is invoked by gate entries that expect a code to be pushed
 ; by the CPU to the stack. It performs the following functions:
 ; - save registers
-; - push pointer to saved regs 
+; - push pointer to saved regs
-; - push pointer to stack frame 
+; - push pointer to stack frame
-; - read and push exception code 
+; - read and push exception code
 ; - invoke handler(code, &frame, &regs)
-; - restore registers 
+; - restore registers
 ; - pop exception code from stack so rsp points to the stack frame
 ;------------------------------------------------------------------------------
 _rt0_64_gate_dispatcher_with_code:
@@ -236,7 +238,7 @@ _rt0_64_gate_dispatcher_with_code:
 	;-----------------|
 	; Exception code  | <- needs to be removed from stack before calling iretq
 	;-----------------|
-	; RIP             | <- exception frame             
+	; RIP             | <- exception frame
 	; CS              |
 	; RFLAGS          |
 	; RSP             |
@@ -244,12 +246,12 @@ _rt0_64_gate_dispatcher_with_code:
 	;-----------------
 	cld
 
-	; save regs and push a pointer to them 
+	; save regs and push a pointer to them
 	save_regs
 	mov rax, rsp   ; rax points to saved rax
 	push rax       ; push pointer to saved regs
 
-	; push pointer to exception stack frame (we have used 15 qwords for the 
+	; push pointer to exception stack frame (we have used 15 qwords for the
 	; saved registers plus one qword for the data pushed by the gate entry
 	; plus one extra qword to jump over the exception code)
 	add rax, 17*8
@@ -261,7 +263,7 @@ _rt0_64_gate_dispatcher_with_code:
 
 	call [rsp + 18*8] ; call registered irq handler
 
-	add rsp, 3 * 8    ; unshift the pushed arguments so rsp points to the saved regs 
+	add rsp, 3 * 8    ; unshift the pushed arguments so rsp points to the saved regs
 	restore_regs
 
 	add rsp, 16	  ; pop handler address and exception code off the stack before returning
@@ -271,10 +273,10 @@ _rt0_64_gate_dispatcher_with_code:
 ; This dispatcher is invoked by gate entries that do not use exception codes.
 ; It performs the following functions:
 ; - save registers
-; - push pointer to saved regs 
+; - push pointer to saved regs
-; - push pointer to stack frame 
+; - push pointer to stack frame
 ; - invoke handler(&frame, &regs)
-; - restore registers 
+; - restore registers
 ;------------------------------------------------------------------------------
 _rt0_64_gate_dispatcher_without_code:
 	; This is how the stack looks like when entering this function:
@@ -283,7 +285,7 @@ _rt0_64_gate_dispatcher_without_code:
 	;------------------
 	; handler address | <- pushed by gate_entry_xxx (RSP points here)
 	;-----------------|
-	; RIP             | <- exception frame             
+	; RIP             | <- exception frame
 	; CS              |
 	; RFLAGS          |
 	; RSP             |
@@ -291,21 +293,21 @@ _rt0_64_gate_dispatcher_without_code:
 	;-----------------
 	cld
 
-	; save regs and push a pointer to them 
+	; save regs and push a pointer to them
 	save_regs
 	mov rax, rsp   ; rax points to saved rax
 	push rax       ; push pointer to saved regs
 
-	; push pointer to exception stack frame (we have used 15 qwords for the 
+	; push pointer to exception stack frame (we have used 15 qwords for the
 	; saved registers plus one qword for the data pushed by the gate entry)
 	add rax, 16*8
 	push rax
 
 	call [rsp + 17*8] ; call registered irq handler
 
-	add rsp, 2 * 8    ; unshift the pushed arguments so rsp points to the saved regs 
+	add rsp, 2 * 8    ; unshift the pushed arguments so rsp points to the saved regs
 	restore_regs
-	
+
 	add rsp, 8	  ; pop handler address off the stack before returning
 	iretq
 
@@ -340,13 +342,13 @@ write_string:
 ; runtime functions to the kernel's own implementation without the need to
 ; export/globalize any symbols. This works by first setting up a redirect table
 ; (populated by a post-link step) that contains the addresses of the symbol to
-; hook and the address where calls to that symbol should be redirected. 
+; hook and the address where calls to that symbol should be redirected.
 ;
 ; This function iterates the redirect table entries and for each entry it
 ; sets up a trampoline to the dst symbol and overwrites the code in src with
-; the 14-byte long _rt0_redirect_trampoline code. 
+; the 14-byte long _rt0_redirect_trampoline code.
 ;
-; Note: this code modification is only possible because we are currently 
+; Note: this code modification is only possible because we are currently
 ; operating in supervisor mode with no memory protection enabled. Under normal
 ; conditions the .text section should be flagged as read-only.
 ;------------------------------------------------------------------------------
@@ -355,7 +357,7 @@ _rt0_install_redirect_trampolines:
 	mov rdx, NUM_REDIRECTS
 
 _rt0_install_redirect_rampolines.next:
-	mov rdi, [rax]	 ; the symbol address to hook 
+	mov rdi, [rax]	 ; the symbol address to hook
 	mov rbx, [rax+8] ; the symbol to redirect to
 
 	; setup trampoline target and copy it to the hooked symbol
@@ -364,15 +366,15 @@ _rt0_install_redirect_rampolines.next:
 	mov rcx, 14
 	rep movsb ; copy rcx bytes from rsi to rdi
 
-	add rax, 16 
+	add rax, 16
-	dec rdx 
+	dec rdx
 	jnz _rt0_install_redirect_rampolines.next
 
 	ret
 
 ;------------------------------------------------------------------------------
-; This trampoline exploits rip-relative addressing to allow a jump to a 
+; This trampoline exploits rip-relative addressing to allow a jump to a
-; 64-bit address without the need to touch any registers. The generated 
+; 64-bit address without the need to touch any registers. The generated
 ; code is equivalent to:
 ;
 ; jmp [rip+0]
@@ -380,14 +382,14 @@ _rt0_install_redirect_rampolines.next:
 ;------------------------------------------------------------------------------
 _rt0_redirect_trampoline:
 	db 0xff ; the first 6 bytes encode a "jmp [rip+0]" instruction
-	db 0x25 
+	db 0x25
-	dd 0x00   
+	dd 0x00
 	dq 0x00 ; the absolute address to jump to
 
 ;------------------------------------------------------------------------------
-; The redirect table is placed in a dedicated section allowing us to easily 
+; The redirect table is placed in a dedicated section allowing us to easily
 ; find its offset in the kernel image file. As the VMA addresses of the src
-; and target symbols for the redirect are now known in advance we just reserve 
+; and target symbols for the redirect are now known in advance we just reserve
 ; enough space space for the src and dst addresses using the NUM_REDIRECTS
 ; define which is calculated by the Makefile and passed to nasm.
 ;------------------------------------------------------------------------------
@@ -395,7 +397,7 @@ section .goredirectstbl
 
 _rt0_redirect_table:
 	%rep NUM_REDIRECTS
-	dq 0  ; src: address of the symbol we want to redirect 
+	dq 0  ; src: address of the symbol we want to redirect
 	dq 0  ; dst: address of the symbol where calls to src are redirected to
 	%endrep
 

tools/offsets/offsets.go

@@ -7,6 +7,8 @@ import (
 	"io/ioutil"
 	"os"
 	"os/exec"
+	"path/filepath"
+	"runtime"
 	"strconv"
 	"strings"
 	"time"
@@ -30,6 +32,7 @@ func genBuildScript(targetOS, targetArch, goBinary, workDir string) ([]byte, err
 	// rebuild the runtime packages.
 	cmd := exec.Command(goBinary, "build", "-a", "-n")
 	cmd.Dir = workDir
+	cmd.Env = append(cmd.Env, fmt.Sprintf("GOROOT=%s", os.Getenv("GOROOT")))
 	cmd.Env = append(cmd.Env, fmt.Sprintf("GOOS=%s", targetOS))
 	cmd.Env = append(cmd.Env, fmt.Sprintf("GOARCH=%s", targetArch))
 	out, err := cmd.CombinedOutput()
@@ -41,13 +44,18 @@ func genBuildScript(targetOS, targetArch, goBinary, workDir string) ([]byte, err
 }
 
 func patchBuildScript(script []byte, workDir, targetOS, targetArch, goBinary string) ([]byte, error) {
-	lines := strings.Split(string(script), "\n")
+	// Replace $WORK with the workDir location. This is required for executing
+	// build scripts generated by go 1.10
+	lines := strings.Split(
+		strings.Replace(string(script), "$WORK", workDir, -1),
+		"\n",
+	)
 
 	// Inject os/arch and workdir to the top of the build file
 	header := []string{
+		fmt.Sprintf("export GOROOT=%s", os.Getenv("GOROOT")),
 		fmt.Sprintf("export GOOS=%s", targetOS),
 		fmt.Sprintf("export GOARCH=%s", targetArch),
-		fmt.Sprintf("WORK=%q", workDir),
 		fmt.Sprintf("alias pack='%s tool pack'", goBinary),
 	}
 	lines = append(header, lines...)
@@ -58,7 +66,7 @@ func patchBuildScript(script []byte, workDir, targetOS, targetArch, goBinary str
 	var stopOnNextComment bool
 	for lineIndex := 0; lineIndex < len(lines); lineIndex++ {
 		// Ignore empty comments
-		if lines[lineIndex] == "#" {
+		if strings.TrimSpace(lines[lineIndex]) == "#" || strings.Contains(lines[lineIndex], "# import") {
 			continue
 		}
 
@@ -97,8 +105,32 @@ func execBuildScript(script []byte, workDir string) error {
 }
 
 func genAsmIncludes(workDir string) ([]byte, error) {
-	headers, err := ioutil.ReadFile(fmt.Sprintf("%s/runtime/_obj/go_asm.h", workDir))
+	// Find all generated go_asm.h files and concat their conentents
-	if err != nil {
+	var (
+		allHeaders, headers []byte
+	)
+
+	if err := filepath.Walk(workDir, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if info.IsDir() {
+			return nil
+		}
+
+		if filepath.Base(path) != "go_asm.h" {
+			return nil
+		}
+
+		if headers, err = ioutil.ReadFile(path); err != nil {
+			return err
+		}
+
+		allHeaders = append(allHeaders, '\n')
+		allHeaders = append(allHeaders, headers...)
+		return nil
+	}); err != nil {
 		return nil, err
 	}
 
@@ -106,7 +138,7 @@ func genAsmIncludes(workDir string) ([]byte, error) {
 	includes = append(includes, "; vim: set ft=nasm :\n")
 	includes = append(includes, fmt.Sprintf("; generated by tools/offsets at %v\n", time.Now()))
 
-	for _, line := range strings.Split(string(headers), "\n") {
+	for _, line := range strings.Split(string(allHeaders), "\n") {
 		line = strings.TrimPrefix(line, "#define ")
 
 		// We are only interested in the offsets for the g, m and stack structures
@@ -131,6 +163,16 @@ func genAsmIncludes(workDir string) ([]byte, error) {
 		}
 	}
 
+	// In go 1.7.x, the page size is given by the _PageSize constant whereas in
+	// newer go versions it is specified at runtime and needs to be manually set
+	// by our asm bootstrap code.
+	if strings.Contains(runtime.Version(), "go1.7") {
+		includes = append(includes,
+			"; go 1.7 runtime uses a fixed 4k page size for our target arch so our bootstrap code does not need to do any extra work to set it up",
+			"%define SKIP_PAGESIZE_SETUP 1",
+		)
+	}
+
 	return []byte(strings.Join(includes, "\n")), nil
 }