fix(esp_system): fixes build failure with XIP PSRAM + BSS/NoInit in external memory

Declare ext_ram_xip_seg as a distinct region overlapping drom_seg at the
same origin (the esp32s3/c5/c61/h4 pattern) instead of aliasing drom_seg,
so .ext_ram.dummy has its own location counter and .ext_ram.bss reclaims
the VMA space of NOLOAD rodata (.rodata_wlog_*), saving up to one MMU
page of PSRAM on esp32s31. No layout change on esp32p4.

Closes https://github.com/espressif/esp-idf/issues/18791
Related https://github.com/espressif/esp-idf/issues/14992

components/esp_system/ld/esp32p4/memory.ld.in

@@ -163,6 +163,15 @@ MEMORY
 
   /* PSRAM seg */
   extern_ram_seg(RWX) :        org = 0x48000000, len = IDROM_SEG_SIZE
+
+#if CONFIG_SPIRAM_XIP_FROM_PSRAM
+  /**
+   * Distinct region overlapping `drom_seg` at the same origin, so `.ext_ram.dummy`
+   * gets its own location counter and `.ext_ram.bss` can reclaim the space of
+   * NOLOAD rodata (e.g. `.rodata_wlog_*`).
+   */
+  ext_ram_xip_seg(RWX) :       org = 0x48000020, len = IDROM_SEG_SIZE - 0x20
+#endif // CONFIG_SPIRAM_XIP_FROM_PSRAM
 }
 
 /* Heap ends at top of dram0_0_seg */
@@ -212,7 +221,7 @@ REGION_ALIAS("rtc_reserved_seg", lp_reserved_seg );
 #endif // CONFIG_APP_BUILD_USE_FLASH_SECTIONS
 
 #if CONFIG_SPIRAM_XIP_FROM_PSRAM
-  REGION_ALIAS("ext_ram_seg", drom_seg);
+  REGION_ALIAS("ext_ram_seg", ext_ram_xip_seg);
 #else
   REGION_ALIAS("ext_ram_seg", extern_ram_seg);
 #endif //#if CONFIG_SPIRAM_XIP_FROM_PSRAM

components/esp_system/ld/esp32s31/memory.ld.in

@@ -85,6 +85,15 @@ MEMORY
 
   /* PSRAM seg */
   extern_ram_seg(RWX) :        org = 0x50000000, len = IDROM_SEG_SIZE
+
+#if CONFIG_SPIRAM_XIP_FROM_PSRAM
+  /**
+   * Distinct region overlapping `drom_seg` at the same origin, so `.ext_ram.dummy`
+   * gets its own location counter and `.ext_ram.bss` can reclaim the space of
+   * NOLOAD rodata (e.g. `.rodata_wlog_*`).
+   */
+  ext_ram_xip_seg(RWX) :       org = 0x50000020, len = IDROM_SEG_SIZE - 0x20
+#endif // CONFIG_SPIRAM_XIP_FROM_PSRAM
 }
 
 /* Heap ends at top of dram0_0_seg */
@@ -114,7 +123,7 @@ REGION_ALIAS("rtc_reserved_seg", lp_reserved_seg);
 #endif // CONFIG_APP_BUILD_USE_FLASH_SECTIONS
 
 #if CONFIG_SPIRAM_XIP_FROM_PSRAM
-  REGION_ALIAS("ext_ram_seg", drom_seg);
+  REGION_ALIAS("ext_ram_seg", ext_ram_xip_seg);
 #else
   REGION_ALIAS("ext_ram_seg", extern_ram_seg);
 #endif //#if CONFIG_SPIRAM_XIP_FROM_PSRAM

components/esp_system/ld/ld.ext_ram.sections

@@ -9,6 +9,13 @@
   .ext_ram.dummy (NOLOAD) :
   {
     HIDDEN(_ext_ram_on_same_bus = ORIGIN(ext_ram_seg) == ORIGIN(flash_rodata_seg));
+    /**
+     * This must be the first section placed in `ext_ram_seg`, and `ext_ram_seg` must be
+     * a distinct region (not a REGION_ALIAS of `flash_rodata_seg`) so it has its own
+     * location counter. Otherwise NOLOAD rodata (e.g. .rodata_wlog_*) placed after
+     * `_rodata_reserved_end` leaves the counter past the skip target, and moving it
+     * backwards here is a hard linker error.
+     */
     . = _ext_ram_on_same_bus ? ORIGIN(ext_ram_seg) + (_rodata_reserved_end - _flash_rodata_dummy_start) : 0;
     . = ALIGN(_ext_ram_on_same_bus ? _esp_mmu_page_size : 0);
   } > ext_ram_seg