Convert llvm_asm to asm

Summary:
The `llvm_asm` nightly feature was removed in Rust 1.59 and `asm!()` was simultaneously stabilized, so we need to make the switch so things continue compiling.

This retains the `llvm_asm` code so that it can continue compiling on old llvm versions. This will be removed when that is updated.

Reviewed By: johnhurt

Differential Revision: D34561246

fbshipit-source-id: 42cd2c7e83cea9a5c21bd5871463bb1a42be139d

reverie-ptrace/src/lib.rs

@@ -36,7 +36,7 @@
 #![feature(async_closure)]
 #![feature(internal_output_capture)]
 #![feature(never_type)]
-#![feature(llvm_asm)]
+#![cfg_attr(feature = "llvm_asm", feature(llvm_asm))]
 #![feature(map_first_last)]
 #![feature(bench_black_box)]
 

reverie-ptrace/src/perf.rs

@@ -569,10 +569,30 @@ macro_rules! ret_without_perf {
 /// Perform exactly `count+1` conditional branch instructions. Useful for
 /// testing timer-related code.
 #[cfg(target_arch = "x86_64")]
+#[cfg(not(feature = "llvm_asm"))]
+#[inline(never)]
+pub fn do_branches(mut count: u64) {
+    // Anything but assembly is unreliable between debug and release
+    unsafe {
+        // Loop until carry flag is set, indicating underflow
+        core::arch::asm!(
+            "2:",
+            "sub {0}, 1",
+            "jnc 2b",
+            inout(reg) count,
+        )
+    }
+
+    assert_eq!(count, u64::MAX);
+}
+
+/// Perform exactly `count+1` conditional branch instructions. Useful for
+/// testing timer-related code.
+#[cfg(target_arch = "x86_64")]
+#[cfg(feature = "llvm_asm")]
 #[inline(never)]
 pub fn do_branches(count: u64) {
     // Anything but assembly is unreliable between debug and release
-    // TODO: Switch to `asm!()` when our LLVM version supports it.
     #[allow(deprecated)]
     unsafe {
         // Loop until carry flag is set, indicating underflow

reverie-ptrace/src/validation.rs

@@ -13,7 +13,6 @@ use core::mem;
 use perf_event_open_sys::bindings as perf;
 use raw_cpuid::{CpuId, FeatureInfo};
 use reverie::Errno;
-use std::hint::black_box;
 use thiserror::Error;
 use tracing::{error, warn};
 
@@ -68,6 +67,7 @@ pub(crate) enum PmuValidationError {
     #[error("Intel Kvm-In-Txcp bug found")]
     IntelKvmInTxcpBugDetected,
 
+    #[cfg(feature = "llvm_asm")]
     #[error("Overcount triggered by PMU interrupts detected due to Xen PMU virtualization bug")]
     IntelXenPmiBugDetected,
 }
@@ -361,7 +361,7 @@ fn is_amd_zen(cpu_feature: FeatureInfo) -> bool {
 
 /// This is a transcription of the function with the same name in Mozilla-RR it will
 /// check for bugs specific to cpu architectures
-fn check_for_arch_bugs(precise_ip: bool) -> Result<(), PmuValidationError> {
+fn check_for_arch_bugs(_precise_ip: bool) -> Result<(), PmuValidationError> {
     let c = CpuId::new();
     let vendor = c.get_vendor_info().unwrap();
     let feature_info = c
@@ -371,7 +371,12 @@ fn check_for_arch_bugs(precise_ip: bool) -> Result<(), PmuValidationError> {
 
     match vendor_str {
         AMD_VENDOR if is_amd_zen(feature_info) => check_for_zen_speclockmap(),
-        INTEL_VENDOR => check_for_kvm_in_txcp_bug().and(check_for_xen_pmi_bug(precise_ip)),
+        INTEL_VENDOR => {
+            check_for_kvm_in_txcp_bug()?;
+            #[cfg(feature = "llvm_asm")]
+            check_for_xen_pmi_bug(_precise_ip)?;
+            Ok(())
+        }
         s => panic!("Unknown CPU vendor: {}", s),
     }
 }
@@ -395,6 +400,18 @@ fn check_for_zen_speclockmap() -> Result<(), PmuValidationError> {
     let count = read_counter(&fd)?;
 
     // A lock add is known to increase the perf counter we're looking at.
+    #[cfg(not(feature = "llvm_asm"))]
+    unsafe {
+        let _prev: usize;
+        core::arch::asm!(
+            "lock",
+            "xadd [{}], {}",
+            in(reg) val,
+            inout(reg) to_add => _prev,
+        )
+    }
+
+    #[cfg(feature = "llvm_asm")]
     #[allow(deprecated)]
     unsafe {
         let _prev: usize;
@@ -437,6 +454,8 @@ fn check_for_kvm_in_txcp_bug() -> Result<(), PmuValidationError> {
     }
 }
 
+// FIXME: Convert this big block of llvm_asm over to the new asm syntax.
+#[cfg(feature = "llvm_asm")]
 fn check_for_xen_pmi_bug(precise_ip: bool) -> Result<(), PmuValidationError> {
     #[allow(unused_assignments)]
     let mut count: i32 = -1;
@@ -451,7 +470,7 @@ fn check_for_xen_pmi_bug(precise_ip: bool) -> Result<(), PmuValidationError> {
         20764791
     }
 
-    let mut accumulator = black_box(make_accumulator_seed());
+    let mut accumulator = core::hint::black_box(make_accumulator_seed());
     let mut expected_accumulator = accumulator;
 
     // reproduce the assembly here to calculate what the final accumulator value should be

tests/basics.rs

@@ -6,7 +6,7 @@
  * This source code is licensed under the BSD-style license found in the
  * LICENSE file in the root directory of this source tree.
  */
-#![feature(llvm_asm)]
+#![cfg_attr(feature = "llvm_asm", feature(llvm_asm))]
 
 //! Basic tests that don't fall into some other category.
 
@@ -221,12 +221,27 @@ fn i_should_segfault() {
 fn i_should_segfault_2() {
     use nix::sys::signal::Signal::SIGSEGV;
     use reverie_ptrace::testing::test_fn;
-    let (output, _) = test_fn::<NoopTool, _>(|| unsafe {
+
+    #[inline]
+    #[cfg(not(feature = "llvm_asm"))]
+    unsafe fn do_segfault() {
+        let null_ptr: *const usize = core::ptr::null();
+        asm!(
+            "jmp {0}",
+            in(reg) null_ptr,
+        )
+    }
+
+    #[inline]
+    #[cfg(feature = "llvm_asm")]
+    #[allow(deprecated)]
+    unsafe fn do_segfault() {
         llvm_asm!(r#"mov $$0, %rax
                 jmpq *%rax
                 "#:::"rax")
-    })
-    .unwrap();
+    }
+
+    let (output, _) = test_fn::<NoopTool, _>(|| unsafe { do_segfault() }).unwrap();
     assert_eq!(output.status, ExitStatus::Signaled(SIGSEGV, true),);
 }
 

tests/convert.rs

@@ -6,7 +6,7 @@
  * This source code is licensed under the BSD-style license found in the
  * LICENSE file in the root directory of this source tree.
  */
-#![feature(llvm_asm)]
+#![cfg_attr(feature = "llvm_asm", feature(llvm_asm))]
 
 // when we convert syscall, such as open -> openat, the old syscall
 // args should not be clobbered, even with the conversion.
@@ -61,7 +61,64 @@ mod tests {
     use reverie_ptrace::testing::check_fn;
 
     #[cfg(target_arch = "x86_64")]
+    #[cfg(not(feature = "llvm_asm"))]
     #[allow(unused_mut)]
+    unsafe fn open_syscall_sanity_check() -> i32 {
+        let path = b"/dev/null\0".as_ptr() as usize;
+        let flags: usize = 0x8000; // O_LARGEFILE
+        let mode: usize = 0o644;
+
+        let mut ret: usize;
+
+        // // The following asm block does this:
+        // let ret = open("/dev/null", 0x8000, 0644);
+        // if ret >= -4095 as u64 { exit_group(1) }
+        // // Sanity check input registers to ensure they didn't change.
+        // if %rsi != 0x8000 { exit_group(1) }
+        // if %rdx != 0644 { exit_roup(1) }
+        // return fd
+        core::arch::asm!(
+            "mov r8, {arg1}",
+            "syscall",
+            // if (ret >= -4095 as u64) goto 1
+            "cmp 0xfffffffffffff001"
+            "jae 2f",
+            // if (rax != r8) goto label1;
+            "cmp rdi, r8",
+            "jne 2f",
+            // if (rsi != 0x8000) goto label1;
+            "cmp rsi, 0x8000",
+            "jne 2f",
+            // if (rdx != 0644) goto label1;
+            "cmp rdx, 0x1a4",
+            "jne 2f",
+            // Otherwise, we're successful.
+            "jmp 3f",
+            "2:",
+            // Set syscall arg1 to label1
+            "mov rdi, 0x1",
+            // Set syscall to exit_group
+            "mov rax, {sys_exit_group}",
+            // Do the syscall
+            "syscall",
+            "3:",
+            lateout("rax") ret,
+            in("rax") n,
+            arg1 = inlateout("rdi") path, // Reused for the exit_group syscall.
+            in("rsi") flags,
+            in("rdx") mode,
+            out("r8") _, // Clobbered
+            out("rcx") _, // rcx is used to store old rip
+            out("r11") _, // r11 is used to store old rflags
+        );
+
+        ret
+    }
+
+    #[cfg(target_arch = "x86_64")]
+    #[cfg(feature = "llvm_asm")]
+    #[allow(unused_mut)]
+    #[allow(deprecated)]
     unsafe fn open_syscall_sanity_check() -> i32 {
         let mut ret;
         let path = b"/dev/null\0";

tests/timer_semantics.rs

@@ -12,8 +12,7 @@
 //! Syscalls are abused to communicate from the guest to the tool instructions
 //! necessary to carry out the test, such as setting timers or reading clocks.
 
-#![feature(llvm_asm)]
-
+#![cfg_attr(feature = "llvm_asm", feature(llvm_asm))]
 use core::arch::x86_64::{__cpuid, __rdtscp, _rdtsc};
 use libc;
 use reverie::{
@@ -189,7 +188,25 @@ async fn raise_sigwinch<T: Guest<LocalState>>(guest: &mut T) -> Tgkill {
         .with_sig(libc::SIGWINCH)
 }
 
+// FIXME: Use the syscalls crate for doing this when it switches to using the
+// `asm!()` macro instead of asm inside of a C file.
 #[cfg(all(target_os = "linux", target_arch = "x86_64"))]
+#[cfg(not(feature = "llvm_asm"))]
+unsafe fn syscall_no_branches(no: libc::c_long, arg1: libc::c_long) {
+    let mut ret: u64;
+    core::arch::asm!(
+        "syscall",
+        lateout("rax") ret,
+        in("rax") no,
+        in("rdi") arg1,
+        out("rcx") _, // rcx is used to store old rip
+        out("r11") _, // r11 is used to store old rflags
+    );
+}
+
+#[cfg(all(target_os = "linux", target_arch = "x86_64"))]
+#[cfg(feature = "llvm_asm")]
+#[allow(deprecated)]
 unsafe fn syscall_no_branches(no: libc::c_long, arg1: libc::c_long) {
     llvm_asm!("
         mov $0, %rax