Merge pull request #2168 from xiaobo55x:ptrace_test

PiperOrigin-RevId: 306306809

3 files changed, 22 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 100644
--- 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])},