Add symbols for start and end of embedded linker
Add __dlwrap_linker and __dlwrap_linker_end symbols for use by the
embedded linker trampoline to determine which load segments are
part of the embedded linker and should not be exposed to the
executable.
Use flags to name the sections to avoid colliding with __dlwrap_linker
when no section name can be determined.
Bug: 190084016
Test: build with musl
Change-Id: I51ccbf9c15a65c6194fa263b7504a598dbf4ad18
diff --git a/cmd/extract_linker/main.go b/cmd/extract_linker/main.go
index f1f7bc7..1280553 100644
--- a/cmd/extract_linker/main.go
+++ b/cmd/extract_linker/main.go
@@ -26,7 +26,7 @@
"io/ioutil"
"log"
"os"
- "strings"
+ "strconv"
)
func main() {
@@ -59,20 +59,16 @@
fmt.Fprintln(script, "ENTRY(__dlwrap__start)")
fmt.Fprintln(script, "SECTIONS {")
+ progsWithFlagsCount := make(map[string]int)
+
for _, prog := range ef.Progs {
if prog.Type != elf.PT_LOAD {
continue
}
- var progName string
- progSection := progToFirstSection(prog, ef.Sections)
- if progSection != nil {
- progName = progSection.Name
- } else {
- progName = fmt.Sprintf(".sect%d", load)
- }
- sectionName := ".linker" + progName
- symName := "__dlwrap_linker" + strings.ReplaceAll(progName, ".", "_")
+ progName := progNameFromFlags(prog.Flags, progsWithFlagsCount)
+ sectionName := ".linker_" + progName
+ symName := "__dlwrap_linker_" + progName
flags := ""
if prog.Flags&elf.PF_W != 0 {
@@ -83,6 +79,12 @@
}
fmt.Fprintf(asm, ".section %s, \"a%s\"\n", sectionName, flags)
+ if load == 0 {
+ fmt.Fprintln(asm, ".globl __dlwrap_linker")
+ fmt.Fprintln(asm, "__dlwrap_linker:")
+ fmt.Fprintln(asm)
+ }
+
fmt.Fprintf(asm, ".globl %s\n%s:\n\n", symName, symName)
fmt.Fprintf(script, " %s 0x%x : {\n", sectionName, baseLoadAddr+prog.Vaddr)
@@ -106,6 +108,10 @@
load += 1
}
+ fmt.Fprintln(asm, ".globl __dlwrap_linker_end")
+ fmt.Fprintln(asm, "__dlwrap_linker_end:")
+ fmt.Fprintln(asm)
+
fmt.Fprintln(asm, `.section .note.android.embedded_linker,"a",%note`)
fmt.Fprintln(script, "}")
@@ -139,11 +145,25 @@
fmt.Fprintln(asm)
}
-func progToFirstSection(prog *elf.Prog, sections []*elf.Section) *elf.Section {
- for _, section := range sections {
- if section.Addr == prog.Vaddr {
- return section
- }
+func progNameFromFlags(flags elf.ProgFlag, progsWithFlagsCount map[string]int) string {
+ s := ""
+ if flags&elf.PF_R != 0 {
+ s += "r"
}
- return nil
+ if flags&elf.PF_W != 0 {
+ s += "w"
+ }
+ if flags&elf.PF_X != 0 {
+ s += "x"
+ }
+
+ count := progsWithFlagsCount[s]
+ count++
+ progsWithFlagsCount[s] = count
+
+ if count > 1 {
+ s += strconv.Itoa(count)
+ }
+
+ return s
}