Fix flip-link, make SSP configurable (#3203)

* Test flip-link

* Add todo

* Rebuild if linker files change

* Let espsegs show .stack

* Try to fix flip_link

* Changelog

* Make SSP configurable

* Substitute config values

Author: bugadani

esp-hal/CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Support for `rand_core` 0.9 (#3211)
+- `ESP_HAL_CONFIG_STACK_GUARD_OFFSET` and `ESP_HAL_CONFIG_STACK_GUARD_VALUE` to configure Rust's [Stack smashing protection](https://doc.rust-lang.org/rustc/exploit-mitigations.html#stack-smashing-protection) (#3203)
 
 ### Changed
 
@@ -22,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - ESP32-S2: Fixed PSRAM initialization (#3196)
 - `Uart::{with_tx, with_rx}` can now be called on the async driver as well (#3212)
 - ESP32: Fixed SPI3 QSPI signals (#3201)
+- ESP32-C6/H2: The `flip_link` feature should no longer crash (#3203)
 
 ### Removed
 

esp-hal/build.rs

@@ -1,4 +1,5 @@
 use std::{
+    collections::HashMap,
     env,
     error::Error,
     fs::{self, File},
@@ -122,6 +123,19 @@ fn main() -> Result<(), Box<dyn Error>> {
             Some(Validator::Enumeration(
                 vec![String::from("quad"), String::from("octal")]
             )),
+        ),
+        // Rust's stack smashing protection configuration
+        (
+            "stack-guard-offset",
+            "The stack guard variable will be placed this many bytes from the stack's end.",
+            Value::Integer(4096),
+            None
+        ),
+        (
+            "stack-guard-value",
+            "The value to be written to the stack guard variable.",
+            Value::Integer(0xDEED_BAAD),
+            None
         )
     ], true);
 
@@ -166,19 +180,30 @@ fn main() -> Result<(), Box<dyn Error>> {
     } else {
         // RISC-V devices:
 
-        preprocess_file(&config_symbols, "ld/riscv/asserts.x", out.join("asserts.x"))?;
-        preprocess_file(&config_symbols, "ld/riscv/debug.x", out.join("debug.x"))?;
         preprocess_file(
             &config_symbols,
+            &cfg,
+            "ld/riscv/asserts.x",
+            out.join("asserts.x"),
+        )?;
+        preprocess_file(
+            &config_symbols,
+            &cfg,
+            "ld/riscv/debug.x",
+            out.join("debug.x"),
+        )?;
+        preprocess_file(
+            &config_symbols,
+            &cfg,
             "ld/riscv/hal-defaults.x",
             out.join("hal-defaults.x"),
         )?;
     }
 
     // With the architecture-specific linker scripts taken care of, we can copy all
     // remaining linker scripts which are common to all devices:
-    copy_dir_all(&config_symbols, "ld/sections", &out)?;
-    copy_dir_all(&config_symbols, format!("ld/{device_name}"), &out)?;
+    copy_dir_all(&config_symbols, &cfg, "ld/sections", &out)?;
+    copy_dir_all(&config_symbols, &cfg, format!("ld/{device_name}"), &out)?;
 
     Ok(())
 }
@@ -188,6 +213,7 @@ fn main() -> Result<(), Box<dyn Error>> {
 
 fn copy_dir_all(
     config_symbols: &[&str],
+    cfg: &HashMap<String, Value>,
     src: impl AsRef<Path>,
     dst: impl AsRef<Path>,
 ) -> std::io::Result<()> {
@@ -198,12 +224,14 @@ fn copy_dir_all(
         if ty.is_dir() {
             copy_dir_all(
                 config_symbols,
+                cfg,
                 entry.path(),
                 dst.as_ref().join(entry.file_name()),
             )?;
         } else {
             preprocess_file(
                 config_symbols,
+                cfg,
                 entry.path(),
                 dst.as_ref().join(entry.file_name()),
             )?;
@@ -215,17 +243,20 @@ fn copy_dir_all(
 /// A naive pre-processor for linker scripts
 fn preprocess_file(
     config: &[&str],
+    cfg: &HashMap<String, Value>,
     src: impl AsRef<Path>,
     dst: impl AsRef<Path>,
 ) -> std::io::Result<()> {
+    println!("cargo:rerun-if-changed={}", src.as_ref().display());
+
     let file = File::open(src)?;
     let mut out_file = File::create(dst)?;
 
     let mut take = Vec::new();
     take.push(true);
 
     for line in std::io::BufReader::new(file).lines() {
-        let line = line?;
+        let line = substitute_config(cfg, &line?);
         let trimmed = line.trim();
 
         if let Some(condition) = trimmed.strip_prefix("#IF ") {
@@ -252,6 +283,43 @@ fn preprocess_file(
     Ok(())
 }
 
+fn substitute_config(cfg: &HashMap<String, Value>, line: &str) -> String {
+    let mut result = String::new();
+    let mut chars = line.chars().peekable();
+
+    while let Some(c) = chars.next() {
+        if c != '$' {
+            result.push(c);
+            continue;
+        }
+
+        let Some('{') = chars.peek() else {
+            result.push(c);
+            continue;
+        };
+        chars.next();
+
+        let mut key = String::new();
+        for c in chars.by_ref() {
+            if c == '}' {
+                break;
+            }
+            key.push(c);
+        }
+        match cfg
+            .get(&key)
+            .unwrap_or_else(|| panic!("missing config key: {key}"))
+        {
+            Value::Bool(true) => result.push('1'),
+            Value::Bool(false) => result.push('0'),
+            Value::Integer(value) => result.push_str(&value.to_string()),
+            Value::String(value) => result.push_str(value),
+        }
+    }
+
+    result
+}
+
 #[cfg(feature = "esp32")]
 fn generate_memory_extras() -> Vec<u8> {
     let reserve_dram = if cfg!(feature = "bluetooth") {

esp-hal/ld/esp32/esp32.x

@@ -19,9 +19,11 @@ INCLUDE "fixups/rtc_fast_rwdata_dummy.x"
 /* END ESP32 fixups */
 
 /* Shared sections - ordering matters */
-INCLUDE "rwtext.x"
+SECTIONS {
+  INCLUDE "rwtext.x"
+  INCLUDE "rwdata.x"
+}
 INCLUDE "text.x"
-INCLUDE "rwdata.x"
 INCLUDE "rodata.x"
 INCLUDE "rtc_fast.x"
 INCLUDE "rtc_slow.x"

esp-hal/ld/esp32c2/esp32c2.x

@@ -80,9 +80,11 @@ PROVIDE(__global_pointer$ = _data_start + 0x800);
 /* end of esp32c2 fixups */
 
 /* Shared sections - ordering matters */
-INCLUDE "rwtext.x"
+SECTIONS {
+  INCLUDE "rwtext.x"
+  INCLUDE "rwdata.x"
+}
 INCLUDE "text.x"
-INCLUDE "rwdata.x"
 INCLUDE "rodata.x"
 INCLUDE "stack.x"
 INCLUDE "dram2.x"

esp-hal/ld/esp32c3/esp32c3.x

@@ -80,9 +80,11 @@ PROVIDE(__global_pointer$ = _data_start + 0x800);
 /* end of esp32c3 fixups */
 
 /* Shared sections - ordering matters */
-INCLUDE "rwtext.x"
+SECTIONS {
+  INCLUDE "rwtext.x"
+  INCLUDE "rwdata.x"
+}
 INCLUDE "text.x"
-INCLUDE "rwdata.x"
 INCLUDE "rodata.x"
 INCLUDE "rtc_fast.x"
 INCLUDE "stack.x"

esp-hal/ld/esp32c6/esp32c6.x

@@ -55,8 +55,17 @@ SECTIONS {
     KEEP(*(.trap));
     *(.trap.*);
   } > RWTEXT
+
+  /* Shared sections - ordering matters */
+  INCLUDE "rwtext.x"
+  INCLUDE "rwdata.x"
+  /* End of Shared sections */
 }
-INSERT BEFORE .rwtext;
+#IF ESP_HAL_CONFIG_FLIP_LINK
+/* INSERT BEFORE does not seem to work for the .stack section. Instead, we place every RAM
+  section after .stack if `flip_link` is enabled. */
+INSERT AFTER .stack;
+#ENDIF
 
 SECTIONS {
   /**
@@ -71,15 +80,13 @@ SECTIONS {
 INSERT BEFORE .rodata;
 /* end of esp32c6 fixups */
 
-/* Shared sections - ordering matters */
-INCLUDE "rwtext.x"
+/* Shared sections #2 - ordering matters */
 INCLUDE "text.x"
-INCLUDE "rwdata.x"
 INCLUDE "rodata.x"
 INCLUDE "rtc_fast.x"
 INCLUDE "stack.x"
 INCLUDE "dram2.x"
-/* End of Shared sections */
+/* End of Shared sections #2 */
 
 INCLUDE "debug.x"
 

esp-hal/ld/esp32h2/esp32h2.x

@@ -43,14 +43,24 @@ PROVIDE(_start_trap = default_start_trap);
 /* Must be called __global_pointer$ for linker relaxations to work. */
 PROVIDE(__global_pointer$ = _data_start + 0x800);
 
+
 SECTIONS {
   .trap : ALIGN(4)
   {
     KEEP(*(.trap));
     *(.trap.*);
   } > RWTEXT
+
+  /* Shared sections - ordering matters */
+  INCLUDE "rwtext.x"
+  INCLUDE "rwdata.x"
+  /* End of Shared sections */
 }
-INSERT BEFORE .rwtext;
+#IF ESP_HAL_CONFIG_FLIP_LINK
+/* INSERT BEFORE does not seem to work for the .stack section. Instead, we place every RAM
+  section after .stack if `flip_link` is enabled. */
+INSERT AFTER .stack;
+#ENDIF
 
 SECTIONS {
   /**
@@ -64,15 +74,13 @@ SECTIONS {
 }
 INSERT BEFORE .rodata;
 
-/* Shared sections - ordering matters */
-INCLUDE "rwtext.x"
+/* Shared sections #2 - ordering matters */
 INCLUDE "text.x"
-INCLUDE "rwdata.x"
 INCLUDE "rodata.x"
 INCLUDE "rtc_fast.x"
 INCLUDE "stack.x"
 INCLUDE "dram2.x"
-/* End of Shared sections */
+/* End of Shared sections #2 */
 
 INCLUDE "debug.x"
 

esp-hal/ld/esp32s2/esp32s2.x

@@ -27,9 +27,11 @@ INCLUDE "fixups/rtc_fast_rwdata_dummy.x"
 /* End of fixups for esp32s2 */
 
 /* Shared sections - ordering matters */
-INCLUDE "rwtext.x"
+SECTIONS {
+  INCLUDE "rwtext.x"
+  INCLUDE "rwdata.x"
+}
 INCLUDE "text.x"
-INCLUDE "rwdata.x"
 INCLUDE "rodata.x"
 INCLUDE "rtc_fast.x"
 INCLUDE "rtc_slow.x"

esp-hal/ld/esp32s3/esp32s3.x

@@ -41,9 +41,11 @@ INCLUDE "fixups/rodata_dummy.x"
 /* End of ESP32S3 fixups */
 
 /* Shared sections - ordering matters */
-INCLUDE "rwtext.x"
+SECTIONS {
+  INCLUDE "rwtext.x"
+  INCLUDE "rwdata.x"
+}
 INCLUDE "text.x"
-INCLUDE "rwdata.x"
 INCLUDE "rodata.x"
 INCLUDE "rtc_fast.x"
 INCLUDE "rtc_slow.x"