Only add CFI instructions for panic=unwind build

src/unwinder/arch/aarch64.rs

@@ -2,6 +2,8 @@ use core::fmt;
 use core::ops;
 use gimli::{AArch64, Register};
 
+use super::maybe_cfi;
+
 // Match DWARF_FRAME_REGISTERS in libgcc
 pub const MAX_REG_RULES: usize = 97;
 
@@ -61,13 +63,15 @@ macro_rules! save {
     (gp$(, $fp:ident)?) => {
         // No need to save caller-saved registers here.
         core::arch::naked_asm!(
-            "
-            stp x29, x30, [sp, -16]!
+            "stp x29, x30, [sp, -16]!",
+            maybe_cfi!("
             .cfi_def_cfa_offset 16
             .cfi_offset x29, -16
             .cfi_offset x30, -8
-            sub sp, sp, 512
-            .cfi_def_cfa_offset 528
+            "),
+            "sub sp, sp, 512",
+            maybe_cfi!(".cfi_def_cfa_offset 528"),
+            "
             mov x8, x0
             mov x0, sp
             ",
@@ -85,13 +89,15 @@ macro_rules! save {
             blr x8
 
             add sp, sp, 512
-            .cfi_def_cfa_offset 16
-            ldp x29, x30, [sp], 16
+            ",
+            maybe_cfi!(".cfi_def_cfa_offset 16"),
+            "ldp x29, x30, [sp], 16",
+            maybe_cfi!("
             .cfi_def_cfa_offset 0
             .cfi_restore x29
             .cfi_restore x30
-            ret
-            ",
+            "),
+            "ret",
         );
     };
     (maybesavefp(fp)) => {

src/unwinder/arch/mod.rs

@@ -31,3 +31,21 @@ pub use aarch64::*;
     target_arch = "aarch64"
 )))]
 compile_error!("Current architecture is not supported");
+
+// CFI directives cannot be used if neither debuginfo nor panic=unwind is enabled.
+// We don't have an easy way to check the former, so just check based on panic strategy.
+#[cfg(panic = "abort")]
+macro_rules! maybe_cfi {
+    ($x: literal) => {
+        ""
+    };
+}
+
+#[cfg(panic = "unwind")]
+macro_rules! maybe_cfi {
+    ($x: literal) => {
+        $x
+    };
+}
+
+pub(crate) use maybe_cfi;

src/unwinder/arch/riscv32.rs

@@ -2,6 +2,8 @@ use core::fmt;
 use core::ops;
 use gimli::{Register, RiscV};
 
+use super::maybe_cfi;
+
 // Match DWARF_FRAME_REGISTERS in libgcc
 pub const MAX_REG_RULES: usize = 65;
 
@@ -176,10 +178,10 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
             "
             mv t0, sp
             add sp, sp, -0x190
-            .cfi_def_cfa_offset 0x190
-            sw ra, 0x180(sp)
-            .cfi_offset ra, -16
             ",
+            maybe_cfi!(".cfi_def_cfa_offset 0x190"),
+            "sw ra, 0x180(sp)",
+            maybe_cfi!(".cfi_offset ra, -16"),
             code!(save_gp),
             code!(save_fp),
             "
@@ -188,10 +190,10 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
             jalr t0
             lw ra, 0x180(sp)
             add sp, sp, 0x190
-            .cfi_def_cfa_offset 0
-            .cfi_restore ra
-            ret
             ",
+            maybe_cfi!(".cfi_def_cfa_offset 0"),
+            maybe_cfi!(".cfi_restore ra"),
+            "ret",
         );
     }
     #[cfg(not(target_feature = "d"))]
@@ -200,10 +202,10 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
             "
             mv t0, sp
             add sp, sp, -0x90
-            .cfi_def_cfa_offset 0x90
-            sw ra, 0x80(sp)
-            .cfi_offset ra, -16
             ",
+            maybe_cfi!(".cfi_def_cfa_offset 0x90"),
+            "sw ra, 0x80(sp)",
+            maybe_cfi!(".cfi_offset ra, -16"),
             code!(save_gp),
             "
             mv t0, a0
@@ -211,10 +213,10 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
             jalr t0
             lw ra, 0x80(sp)
             add sp, sp, 0x90
-            .cfi_def_cfa_offset 0
-            .cfi_restore ra
-            ret
             ",
+            maybe_cfi!(".cfi_def_cfa_offset 0"),
+            maybe_cfi!(".cfi_restore ra"),
+            "ret",
         );
     }
 }

src/unwinder/arch/riscv64.rs

@@ -2,6 +2,8 @@ use core::fmt;
 use core::ops;
 use gimli::{Register, RiscV};
 
+use super::maybe_cfi;
+
 // Match DWARF_FRAME_REGISTERS in libgcc
 pub const MAX_REG_RULES: usize = 65;
 
@@ -176,10 +178,10 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
             "
             mv t0, sp
             add sp, sp, -0x210
-            .cfi_def_cfa_offset 0x210
-            sd ra, 0x200(sp)
-            .cfi_offset ra, -16
             ",
+            maybe_cfi!(".cfi_def_cfa_offset 0x210"),
+            "sd ra, 0x200(sp)",
+            maybe_cfi!(".cfi_offset ra, -16"),
             code!(save_gp),
             code!(save_fp),
             "
@@ -188,10 +190,10 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
             jalr t0
             ld ra, 0x200(sp)
             add sp, sp, 0x210
-            .cfi_def_cfa_offset 0
-            .cfi_restore ra
-            ret
             ",
+            maybe_cfi!(".cfi_def_cfa_offset 0"),
+            maybe_cfi!(".cfi_restore ra"),
+            "ret",
         );
     }
     #[cfg(not(target_feature = "d"))]
@@ -200,10 +202,10 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
             "
             mv t0, sp
             add sp, sp, -0x110
-            .cfi_def_cfa_offset 0x110
-            sd ra, 0x100(sp)
-            .cfi_offset ra, -16
             ",
+            maybe_cfi!(".cfi_def_cfa_offset 0x110"),
+            "sd ra, 0x100(sp)",
+            maybe_cfi!(".cfi_offset ra, -16"),
             code!(save_gp),
             "
             mv t0, a0
@@ -211,10 +213,10 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
             jalr t0
             ld ra, 0x100(sp)
             add sp, sp, 0x110
-            .cfi_def_cfa_offset 0
-            .cfi_restore ra
-            ret
             ",
+            maybe_cfi!(".cfi_def_cfa_offset 0"),
+            maybe_cfi!(".cfi_restore ra"),
+            "ret",
         );
     }
 }

src/unwinder/arch/x86.rs

@@ -2,6 +2,8 @@ use core::fmt;
 use core::ops;
 use gimli::{Register, X86};
 
+use super::maybe_cfi;
+
 // Match DWARF_FRAME_REGISTERS in libgcc
 pub const MAX_REG_RULES: usize = 17;
 
@@ -59,10 +61,9 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
     // No need to save caller-saved registers here.
     unsafe {
         core::arch::naked_asm!(
+            "sub esp, 52",
+            maybe_cfi!(".cfi_def_cfa_offset 56"),
             "
-            sub esp, 52
-            .cfi_def_cfa_offset 56
-
             mov [esp + 4], ecx
             mov [esp + 8], edx
             mov [esp + 12], ebx
@@ -85,15 +86,17 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
             mov eax, [esp + 60]
             mov ecx, esp
             push eax
-            .cfi_adjust_cfa_offset 4
-            push ecx
-            .cfi_adjust_cfa_offset 4
+            ",
+            maybe_cfi!(".cfi_adjust_cfa_offset 4"),
+            "push ecx",
+            maybe_cfi!(".cfi_adjust_cfa_offset 4"),
+            "
             call [esp + 64]
 
             add esp, 60
-            .cfi_def_cfa_offset 4
-            ret
             ",
+            maybe_cfi!(".cfi_def_cfa_offset 4"),
+            "ret",
         );
     }
 }

src/unwinder/arch/x86_64.rs

@@ -2,6 +2,8 @@ use core::fmt;
 use core::ops;
 use gimli::{Register, X86_64};
 
+use super::maybe_cfi;
+
 // Match DWARF_FRAME_REGISTERS in libgcc
 pub const MAX_REG_RULES: usize = 17;
 
@@ -61,9 +63,9 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
     // No need to save caller-saved registers here.
     unsafe {
         core::arch::naked_asm!(
+            "sub rsp, 0x98",
+            maybe_cfi!(".cfi_def_cfa_offset 0xA0"),
             "
-            sub rsp, 0x98
-            .cfi_def_cfa_offset 0xA0
             mov [rsp + 0x18], rbx
             mov [rsp + 0x30], rbp
 
@@ -87,9 +89,9 @@ pub extern "C-unwind" fn save_context(f: extern "C" fn(&mut Context, *mut ()), p
             mov rdi, rsp
             call rax
             add rsp, 0x98
-            .cfi_def_cfa_offset 8
-            ret
-            "
+            ",
+            maybe_cfi!(".cfi_def_cfa_offset 8"),
+            "ret"
         );
     }
 }