Remove flip link (#4295)

* Remove `flip-link`

* Changelog entry

* PR number

Author: bjoernQ

esp-hal/CHANGELOG.md

@@ -280,6 +280,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Removed the `FullDuplex` trait from the PARL_IO driver. (#3339)
 - Removed `Flex::{set_as_input, set_as_output, set_drive_strength, set_as_open_drain, pull_direction}` functions (#3387)
 - The `Efuse::read_field_be` function has been removed (#3440)
+- The config option (`ESP_HAL_CONFIG_FLIP_LINK`) got removed, `ESP_HAL_CONFIG_WRITE_VEC_TABLE_MONITORING` will yield equally good results (#4295)
 
 ## [v1.0.0-beta.0] - 2025-02-24
 

esp-hal/esp_config.yml

@@ -70,12 +70,6 @@ options:
     - value: true
   active: 'chip == "esp32"'
 
-- name: flip-link
-  description: Move the stack to start of RAM to get zero-cost stack overflow protection.
-  default:
-    - value: false
-  active: 'chip == "esp32c6" || chip == "esp32h2"'
-
 - name: psram-mode
   description: SPIRAM chip mode
   default:

esp-hal/ld/esp32c2/esp32c2.x

@@ -54,8 +54,4 @@ INCLUDE "metadata.x"
 INCLUDE "eh_frame.x"
 /* End of Shared sections */
 
-#IF ESP_HAL_CONFIG_FLIP_LINK
-  _dram_data_start = ORIGIN( DRAM );
-#ELSE
-  _dram_data_start = ORIGIN( DRAM ) + SIZEOF(.trap) + SIZEOF(.rwtext);
-#ENDIF
+_dram_data_start = ORIGIN( DRAM ) + SIZEOF(.trap) + SIZEOF(.rwtext);

esp-hal/ld/esp32c3/esp32c3.x

@@ -55,8 +55,4 @@ INCLUDE "metadata.x"
 INCLUDE "eh_frame.x"
 /* End of Shared sections */
 
-#IF ESP_HAL_CONFIG_FLIP_LINK
-  _dram_data_start = ORIGIN( DRAM );
-#ELSE
-  _dram_data_start = ORIGIN( DRAM ) + SIZEOF(.trap) + SIZEOF(.rwtext);
-#ENDIF
+_dram_data_start = ORIGIN( DRAM ) + SIZEOF(.trap) + SIZEOF(.rwtext);

esp-hal/ld/esp32c6/esp32c6.x

@@ -10,11 +10,6 @@ SECTIONS {
   INCLUDE "rwdata.x"
   /* End of Shared sections */
 }
-#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 {
   /**
@@ -39,8 +34,4 @@ INCLUDE "metadata.x"
 INCLUDE "eh_frame.x"
 /* End of Shared sections #2 */
 
-#IF ESP_HAL_CONFIG_FLIP_LINK
-  _dram_data_start = ORIGIN( RAM );
-#ELSE
-  _dram_data_start = ORIGIN( RAM ) + SIZEOF(.trap) + SIZEOF(.rwtext);
-#ENDIF
+_dram_data_start = ORIGIN( RAM ) + SIZEOF(.trap) + SIZEOF(.rwtext);

esp-hal/ld/esp32h2/esp32h2.x

@@ -9,11 +9,6 @@ SECTIONS {
   INCLUDE "rwdata.x"
   /* End of Shared sections */
 }
-#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 {
   /**
@@ -37,8 +32,4 @@ INCLUDE "metadata.x"
 INCLUDE "eh_frame.x"
 /* End of Shared sections #2 */
 
-#IF ESP_HAL_CONFIG_FLIP_LINK
-  _dram_data_start = ORIGIN( RAM );
-#ELSE
-  _dram_data_start = ORIGIN( RAM ) + SIZEOF(.trap) + SIZEOF(.rwtext);
-#ENDIF
+_dram_data_start = ORIGIN( RAM ) + SIZEOF(.trap) + SIZEOF(.rwtext);

esp-hal/ld/sections/stack.x

@@ -8,14 +8,8 @@ SECTIONS {
     /* The stack_guard for `stack-protector` mitigation - https://doc.rust-lang.org/rustc/exploit-mitigations.html#stack-smashing-protection */
     __stack_chk_guard = ABSOLUTE(_stack_end) + ${ESP_HAL_CONFIG_STACK_GUARD_OFFSET};
 
-/* no Xtensa chip is supported - so we can assume RISC-V */
-#IF ESP_HAL_CONFIG_FLIP_LINK
-    /* Since we cannot know how much the alignment padding of the sections will add we shrink the stack for "the worst case"
-    */
-    . = . + LENGTH(RWDATA) -  (SIZEOF(.trap) + SIZEOF(.rwtext) + SIZEOF(.rwtext.wifi) + SIZEOF(.data) + SIZEOF(.bss) + SIZEOF(.noinit) + SIZEOF(.data.wifi)) - 304;
-#ELSE
     . = ORIGIN(RWDATA) + LENGTH(RWDATA);
-#ENDIF
+
     . = ALIGN (4);
     _stack_start = ABSOLUTE(.);
     _stack_start_cpu0 = ABSOLUTE(.);

esp-hal/src/soc/mod.rs

@@ -261,39 +261,36 @@ pub(crate) fn enable_main_stack_guard_monitoring() {
 
 #[cfg(all(riscv, write_vec_table_monitoring))]
 pub(crate) fn setup_trap_section_protection() {
-    #[cfg(not(flip_link))]
+    if !cfg!(stack_guard_monitoring_with_debugger_connected)
+        && crate::debugger::debugger_connected()
     {
-        if !cfg!(stack_guard_monitoring_with_debugger_connected)
-            && crate::debugger::debugger_connected()
-        {
-            return;
-        }
+        return;
+    }
 
-        unsafe extern "C" {
-            static _rwtext_len: u32;
-            static _trap_section_origin: u32;
-        }
+    unsafe extern "C" {
+        static _rwtext_len: u32;
+        static _trap_section_origin: u32;
+    }
 
-        let rwtext_len = core::ptr::addr_of!(_rwtext_len) as usize;
+    let rwtext_len = core::ptr::addr_of!(_rwtext_len) as usize;
 
-        // protect as much as possible via NAPOT
-        let len = 1 << (usize::BITS - rwtext_len.leading_zeros() - 1) as usize;
-        if len == 0 {
-            warn!("No trap vector protection available");
-            return;
-        }
+    // protect as much as possible via NAPOT
+    let len = 1 << (usize::BITS - rwtext_len.leading_zeros() - 1) as usize;
+    if len == 0 {
+        warn!("No trap vector protection available");
+        return;
+    }
 
-        // protect MTVEC and trap handlers
-        // (probably plus some more bytes because of NAPOT)
-        // via watchpoint 1.
-        //
-        // Why not use PMP? On C2/C3 the bootloader locks all available PMP entries.
-        // And additionally we write to MTVEC for direct-vectoring and we write
-        // to __EXTERNAL_INTERRUPTS when setting an interrupt handler.
-        let addr = core::ptr::addr_of!(_trap_section_origin) as usize;
+    // protect MTVEC and trap handlers
+    // (probably plus some more bytes because of NAPOT)
+    // via watchpoint 1.
+    //
+    // Why not use PMP? On C2/C3 the bootloader locks all available PMP entries.
+    // And additionally we write to MTVEC for direct-vectoring and we write
+    // to __EXTERNAL_INTERRUPTS when setting an interrupt handler.
+    let addr = core::ptr::addr_of!(_trap_section_origin) as usize;
 
-        unsafe {
-            crate::debugger::set_watchpoint(1, addr, len);
-        }
+    unsafe {
+        crate::debugger::set_watchpoint(1, addr, len);
     }
 }

hil-test/Cargo.toml

@@ -36,10 +36,6 @@ harness = false
 name    = "dma_mem2mem"
 harness = false
 
-[[bin]]
-name    = "flip_link"
-harness = false
-
 [[bin]]
 name    = "gpio"
 harness = false