Modify hostenv and use execv instead of execve.

This is needed so that the gentoo sandbox picks up
changes to the SANDBOX_WRITE env variable correctly,
which we update for ccache.

BUG=chromium:773875
TEST=emerge-kevin sci-libs/tensorflow

Change-Id: I6377c109f30071182b5af6948f320c7c53df4062
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/1792228
Reviewed-by: George Burgess <gbiv@chromium.org>
Tested-by: Tobias Bosch <tbosch@google.com>

2 files changed, 17 insertions, 7 deletions

diff --git a/compiler_wrapper/env.go b/compiler_wrapper/env.go
index 71e4c7ef..588441dd 100644
--- a/compiler_wrapper/env.go
+++ b/compiler_wrapper/env.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"os/exec"
 	"strings"
 )
 
@@ -71,8 +72,18 @@ func (env *processEnv) stderr() io.Writer {
 }
 
 func (env *processEnv) exec(cmd *command) error {
-	execCmd := newExecCmd(env, cmd)
-	return libcExecve(execCmd.Path, execCmd.Args, execCmd.Env)
+	execCmd := exec.Command(cmd.Path, cmd.Args...)
+	// Note: We are not using execve and pass the new environment here
+	// as that sometimes doesn't work well with the gentoo sandbox to
+	// pick update changes to SANDBOX_WRITE env variable (needed for ccache).
+	// Instead, we are updating our own environment and call execv.
+	// This update of global state is ok as we won't execute anything else
+	// after the exec.
+	for _, update := range cmd.EnvUpdates {
+		parts := strings.Split(update, "=")
+		os.Setenv(parts[0], parts[1])
+	}
+	return libcExecv(execCmd.Path, execCmd.Args)
 }
 
 func (env *processEnv) run(cmd *command, stdin io.Reader, stdout io.Writer, stderr io.Writer) error {
diff --git a/compiler_wrapper/libc_execve.go b/compiler_wrapper/libc_execv.go
index 53160695..19c40ef0 100644
--- a/compiler_wrapper/libc_execve.go
+++ b/compiler_wrapper/libc_execv.go
@@ -7,9 +7,8 @@ package main
 // #include <stdlib.h>
 // #include <unistd.h>
 // #include <errno.h>
-// int libc_execve(const char *pathname, char *const argv[],
-//   char *const envp[]) {
-//   if (execve(pathname, argv, envp) != 0) {
+// int libc_execv(const char *pathname, char *const argv[]) {
+//   if (execv(pathname, argv) != 0) {
 //	   return errno;
 //   }
 //   return 0;
@@ -24,7 +23,7 @@ import (
 // LD_PRELOAD to work properly (e.g. gentoo sandbox).
 // Note that this changes the go binary to be a dynamically linked one.
 // See crbug.com/1000863 for details.
-func libcExecve(argv0 string, argv []string, envv []string) error {
+func libcExecv(argv0 string, argv []string) error {
 	freeList := []unsafe.Pointer{}
 	defer func() {
 		for _, ptr := range freeList {
@@ -55,7 +54,7 @@ func libcExecve(argv0 string, argv []string, envv []string) error {
 		return (**C.char)(cArray)
 	}
 
-	if errno := C.libc_execve(goStrToC(argv0), goSliceToC(argv), goSliceToC(envv)); errno != 0 {
+	if errno := C.libc_execv(goStrToC(argv0), goSliceToC(argv)); errno != 0 {
 		return newErrorwithSourceLocf("exec error: %d", errno)
 	}