From 4ee379569c84a9c0931c23e3fd22a4391cec7070 Mon Sep 17 00:00:00 2001
From: Viet Anh Duong <anh.duong@kyber.network>
Date: Wed, 15 Nov 2023 11:05:38 +0000
Subject: [PATCH] Add load /proc/kallsyms function

Signed-off-by: Viet Anh Duong <anh.duong@kyber.network>
---
 bcc/symbol.go                | 33 +++++++++++++++--
 bcc/symbol_utils.go          | 71 ++++++++++++++++++++++++++++++++++++
 examples/bcc/ksymbol/main.go | 19 ++++++++++
 3 files changed, 119 insertions(+), 4 deletions(-)
 create mode 100644 bcc/symbol_utils.go
 create mode 100644 examples/bcc/ksymbol/main.go

diff --git a/bcc/symbol.go b/bcc/symbol.go
index a523332..eefaedd 100644
--- a/bcc/symbol.go
+++ b/bcc/symbol.go
@@ -62,9 +62,23 @@ func (s *Symbolizer) SymbolOrAddrIfUnknown(pid int, addr uintptr) string {
 	}
 
 	if module := C.GoString(symbol.module); module != "" {
-		return s.formatModuleName(C.GoString(symbol.module), uintptr(symbol.offset))
+		return formatModuleName(C.GoString(symbol.module), uintptr(symbol.offset))
 	}
-	return s.formatAddress(addr)
+	return formatAddress(addr)
+}
+
+func (s *Symbolizer) ResolveName(pid int, module, name string) (uintptr, error) {
+	cmodule := C.CString(module)
+	defer C.free(unsafe.Pointer(cmodule))
+	cname := C.CString(name)
+	defer C.free(unsafe.Pointer(cname))
+
+	var addr C.ulong
+	ret := C.bcc_symcache_resolve_name(s.getBCCSymbolCache(pid), cmodule, cname, &addr)
+	if ret < 0 {
+		return 0, fmt.Errorf("unable to resolve symbol name %q", name)
+	}
+	return uintptr(addr), nil
 }
 
 func (s *Symbolizer) ReleasePidSymCache(pid int) {
@@ -86,11 +100,11 @@ func (s *Symbolizer) getBCCSymbolCache(pid int) unsafe.Pointer {
 	return cache
 }
 
-func (s *Symbolizer) formatAddress(addr uintptr) string {
+func formatAddress(addr uintptr) string {
 	return fmt.Sprintf("0x%016x", addr)
 }
 
-func (s *Symbolizer) formatModuleName(module string, offset uintptr) string {
+func formatModuleName(module string, offset uintptr) string {
 	return fmt.Sprintf("[m] %s + 0x%08x", module, offset)
 }
 
@@ -124,6 +138,17 @@ type bccSymbolOption struct {
 	useSymbolType     uint32
 }
 
+// Ksymname Translate a kernel name into an address. This is the reverse of
+// ksym. Returns -1 when the function name is unknown.
+// TODO(vietanhduong): Implement symnol cache
+func Ksymname(name string) (uint64, error) {
+	addr, err := bccResolveName("", name, -1)
+	if err != nil {
+		return 0, err
+	}
+	return addr, nil
+}
+
 // resolveSymbolPath returns the file and offset to locate symname in module
 func resolveSymbolPath(module string, symname string, addr uint64, pid int) (string, uint64, error) {
 	if pid == -1 {
diff --git a/bcc/symbol_utils.go b/bcc/symbol_utils.go
new file mode 100644
index 0000000..0c9304e
--- /dev/null
+++ b/bcc/symbol_utils.go
@@ -0,0 +1,71 @@
+package bcc
+
+import (
+	"bufio"
+	"fmt"
+	"math"
+	"os"
+	"strconv"
+	"strings"
+)
+
+const KernelAddressSpace = 0x00ffffffffffffff
+
+type Symbol struct {
+	Name    string
+	Module  string
+	Address uint64
+}
+
+func (k *Symbol) String() string {
+	if k == nil {
+		return ""
+	}
+	return fmt.Sprintf("module=%s symbol=%s address=0x%016x", k.Module, k.Name, k.Address)
+}
+
+func LoadProcKallsym() ([]*Symbol, error) {
+	var ret []*Symbol
+	LoadProcKallsymWithCallback(func(sym *Symbol) { ret = append(ret, sym) })
+	return ret, nil
+}
+
+func LoadProcKallsymWithCallback(callback func(sym *Symbol)) error {
+	f, err := os.Open("/proc/kallsyms")
+	if err != nil {
+		return fmt.Errorf("open /proc/kallsyms: %w", err)
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		parts := strings.Fields(scanner.Text())
+		if len(parts) < 3 { // This should never happen
+			continue
+		}
+		sym := &Symbol{Name: parts[2], Module: "kernel"}
+
+		if parts[1][0] == 'b' || parts[1][0] == 'B' ||
+			parts[1][0] == 'd' || parts[1][0] == 'D' ||
+			parts[1][0] == 'r' || parts[1][0] == 'R' {
+			continue
+		}
+
+		sym.Address, _ = strconv.ParseUint(parts[0], 16, 0)
+		if sym.Address == 0 || sym.Address == math.MaxUint64 || sym.Address < KernelAddressSpace {
+			continue
+		}
+
+		parts = append(parts, "")
+		if len(parts[3]) > 0 && parts[3][0] == '[' && parts[3][len(parts[3])-1] == ']' {
+			sym.Module = parts[3][1 : len(parts[3])-1]
+		}
+
+		callback(sym)
+	}
+
+	if err = scanner.Err(); err != nil {
+		return fmt.Errorf("scanner error: %w", err)
+	}
+	return nil
+}
diff --git a/examples/bcc/ksymbol/main.go b/examples/bcc/ksymbol/main.go
new file mode 100644
index 0000000..8ef67fb
--- /dev/null
+++ b/examples/bcc/ksymbol/main.go
@@ -0,0 +1,19 @@
+package main
+
+import (
+	"log"
+	"os"
+
+	"github.com/vietanhduong/go-bpf/bcc"
+)
+
+func main() {
+	ksyms, err := bcc.LoadProcKallsym()
+	if err != nil {
+		log.Printf("Failed to load Kallsyms: %v", err)
+		os.Exit(1)
+	}
+	for _, sym := range ksyms {
+		log.Println(sym.String())
+	}
+}