Add generalized stack pointer access

Reviewed By: VladimirMakaev

Differential Revision: D40701834

fbshipit-source-id: 6cad4cedc0d22488117d3d991ae9a80b643ee037

reverie-ptrace/src/gdbstub/commands/mod.rs

@@ -49,6 +49,7 @@ use crate::gdbstub::Inferior;
 use crate::gdbstub::InferiorThreadId;
 use crate::gdbstub::ResumeInferior;
 use crate::gdbstub::StoppedInferior;
+use crate::regs::RegAccess;
 
 mod base;
 mod extended_mode;
@@ -363,9 +364,9 @@ pub struct ExpediatedRegs(BTreeMap<usize, u64>);
 impl From<libc::user_regs_struct> for ExpediatedRegs {
     fn from(regs: libc::user_regs_struct) -> Self {
         let mut exp_regs = BTreeMap::new();
-        exp_regs.insert(6, regs.rbp);
+        exp_regs.insert(6, regs.frame_ptr());
-        exp_regs.insert(7, regs.rsp);
+        exp_regs.insert(7, regs.stack_ptr());
-        exp_regs.insert(0x10, regs.rip);
+        exp_regs.insert(0x10, regs.ip());
         ExpediatedRegs(exp_regs)
     }
 }

reverie-ptrace/src/regs.rs

@@ -26,6 +26,22 @@ pub trait RegAccess {
     /// Mutable access to the instruction pointer (aka the program counter).
     fn ip_mut(&mut self) -> &mut Reg;
 
+    /// Returns the value of the stack pointer.
+    fn stack_ptr(&self) -> Reg;
+
+    /// Mutable access to the stack pointer.
+    fn stack_ptr_mut(&mut self) -> &mut Reg;
+
+    /// Returns the value of the stack frame pointer.
+    ///
+    /// NOTE: The frame pointer is not guaranteed to be available. For example,
+    /// if `-fomit-frame-pointer` was used (often the default), this will not
+    /// return the correct address.
+    fn frame_ptr(&self) -> Reg;
+
+    /// Mutable access to the stack frame pointer.
+    fn frame_ptr_mut(&mut self) -> &mut Reg;
+
     /// Returns the value of the register where the syscall number is stored.
     ///
     /// NOTE: Depending on the context, this may not actually be a syscall
@@ -76,6 +92,22 @@ impl RegAccess for libc::user_regs_struct {
         &mut self.rip
     }
 
+    fn stack_ptr(&self) -> Reg {
+        self.rsp
+    }
+
+    fn stack_ptr_mut(&mut self) -> &mut Reg {
+        &mut self.rsp
+    }
+
+    fn frame_ptr(&self) -> Reg {
+        self.rbp
+    }
+
+    fn frame_ptr_mut(&mut self) -> &mut Reg {
+        &mut self.rbp
+    }
+
     fn syscall(&self) -> Reg {
         self.rax
     }
@@ -126,6 +158,24 @@ impl RegAccess for libc::user_regs_struct {
         &mut self.pc
     }
 
+    fn stack_ptr(&self) -> Reg {
+        self.sp
+    }
+
+    fn stack_ptr_mut(&mut self) -> &mut Reg {
+        &mut self.sp
+    }
+
+    fn frame_ptr(&self) -> Reg {
+        // aarch64 uses x29 for the frame pointer (unless `-fomit-frame-pointer`
+        // is used).
+        self.regs[29]
+    }
+
+    fn frame_ptr_mut(&mut self) -> &mut Reg {
+        &mut self.regs[29]
+    }
+
     fn syscall(&self) -> Reg {
         self.regs[8]
     }

reverie-ptrace/src/stack.rs

@@ -19,6 +19,8 @@ use reverie::Stack;
 use safeptrace::Error as TraceError;
 use safeptrace::Stopped;
 
+use super::regs::RegAccess;
+
 // NB: leaf function can use redzone without explicit stack allocation, as
 // a result it is not safe to just adjust stack pointer. 128B of stack
 // space is mostly wasted -- to avoid the corner case when redzone is used.
@@ -49,7 +51,7 @@ impl GuestStack {
             );
         }
         let task = Stopped::new_unchecked(pid);
-        let rsp = task.getregs()?.rsp as usize;
+        let rsp = task.getregs()?.stack_ptr() as usize;
         let top = rsp - REDZONE_SIZE as usize;
         Ok(GuestStack {
             top,