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authorgVisor bot <gvisor-bot@google.com>2020-04-13 21:22:36 +0000
committergVisor bot <gvisor-bot@google.com>2020-04-13 21:22:36 +0000
commit4ecfb10d3489c33de488eebf1b4d7f72b96c8800 (patch)
treee01d940661dfcf480d64602985261649f7f56ac3 /pkg
parent177e29429d0118710eee48f77f7dbc7eb9c9f4e7 (diff)
parent7e5d67ee90867ba3a2cc0bf1abc59a6c0a47203b (diff)
Merge release-20200323.0-144-g7e5d67e (automated)
Diffstat (limited to 'pkg')
-rw-r--r--pkg/sentry/arch/arch.go3
-rw-r--r--pkg/sentry/arch/syscalls_amd64.go7
-rwxr-xr-xpkg/sentry/arch/syscalls_arm64.go13
-rw-r--r--pkg/sentry/kernel/task_syscall.go14
4 files changed, 36 insertions, 1 deletions
diff --git a/pkg/sentry/arch/arch.go b/pkg/sentry/arch/arch.go
index 1d11cc472..a903d031c 100644
--- a/pkg/sentry/arch/arch.go
+++ b/pkg/sentry/arch/arch.go
@@ -88,6 +88,9 @@ type Context interface {
// SyscallNo returns the syscall number.
SyscallNo() uintptr
+ // SyscallSaveOrig save orignal register value.
+ SyscallSaveOrig()
+
// SyscallArgs returns the syscall arguments in an array.
SyscallArgs() SyscallArguments
diff --git a/pkg/sentry/arch/syscalls_amd64.go b/pkg/sentry/arch/syscalls_amd64.go
index 8b4f23007..3859f41ee 100644
--- a/pkg/sentry/arch/syscalls_amd64.go
+++ b/pkg/sentry/arch/syscalls_amd64.go
@@ -18,6 +18,13 @@ package arch
const restartSyscallNr = uintptr(219)
+// SyscallSaveOrig save the value of the register which is clobbered in
+// syscall handler(doSyscall()).
+//
+// Noop on x86.
+func (c *context64) SyscallSaveOrig() {
+}
+
// SyscallNo returns the syscall number according to the 64-bit convention.
func (c *context64) SyscallNo() uintptr {
return uintptr(c.Regs.Orig_rax)
diff --git a/pkg/sentry/arch/syscalls_arm64.go b/pkg/sentry/arch/syscalls_arm64.go
index dc13b6124..92d062513 100755
--- a/pkg/sentry/arch/syscalls_arm64.go
+++ b/pkg/sentry/arch/syscalls_arm64.go
@@ -18,6 +18,17 @@ package arch
const restartSyscallNr = uintptr(128)
+// SyscallSaveOrig save the value of the register R0 which is clobbered in
+// syscall handler(doSyscall()).
+//
+// In linux, at the entry of the syscall handler(el0_svc_common()), value of R0
+// is saved to the pt_regs.orig_x0 in kernel code. But currently, the orig_x0
+// was not accessible to the user space application, so we have to do the same
+// operation in the sentry code to save the R0 value into the App context.
+func (c *context64) SyscallSaveOrig() {
+ c.OrigR0 = c.Regs.Regs[0]
+}
+
// SyscallNo returns the syscall number according to the 64-bit convention.
func (c *context64) SyscallNo() uintptr {
return uintptr(c.Regs.Regs[8])
@@ -40,7 +51,7 @@ func (c *context64) SyscallNo() uintptr {
// R30: the link register.
func (c *context64) SyscallArgs() SyscallArguments {
return SyscallArguments{
- SyscallArgument{Value: uintptr(c.Regs.Regs[0])},
+ SyscallArgument{Value: uintptr(c.OrigR0)},
SyscallArgument{Value: uintptr(c.Regs.Regs[1])},
SyscallArgument{Value: uintptr(c.Regs.Regs[2])},
SyscallArgument{Value: uintptr(c.Regs.Regs[3])},
diff --git a/pkg/sentry/kernel/task_syscall.go b/pkg/sentry/kernel/task_syscall.go
index d555d69a8..3d7a734ef 100644
--- a/pkg/sentry/kernel/task_syscall.go
+++ b/pkg/sentry/kernel/task_syscall.go
@@ -194,6 +194,19 @@ func (t *Task) executeSyscall(sysno uintptr, args arch.SyscallArguments) (rval u
//
// The syscall path is very hot; avoid defer.
func (t *Task) doSyscall() taskRunState {
+ // Save value of the register which is clobbered in the following
+ // t.Arch().SetReturn(-ENOSYS) operation. This is dedicated to arm64.
+ //
+ // On x86, register rax was shared by syscall number and return
+ // value, and at the entry of the syscall handler, the rax was
+ // saved to regs.orig_rax which was exposed to user space.
+ // But on arm64, syscall number was passed through X8, and the X0
+ // was shared by the first syscall argument and return value. The
+ // X0 was saved to regs.orig_x0 which was not exposed to user space.
+ // So we have to do the same operation here to save the X0 value
+ // into the task context.
+ t.Arch().SyscallSaveOrig()
+
sysno := t.Arch().SyscallNo()
args := t.Arch().SyscallArgs()
@@ -269,6 +282,7 @@ func (*runSyscallAfterSyscallEnterStop) execute(t *Task) taskRunState {
return (*runSyscallExit)(nil)
}
args := t.Arch().SyscallArgs()
+
return t.doSyscallInvoke(sysno, args)
}