The linker scripts in esp-open-sdk/sdk/ld/ dictate how the GCC linker organizes code sections (.text, .data, .bss, .irom0.text) and maps them to physical flash offsets and memory addresses.
v6: Refers to the version of Espressif's SDK linker layout definitions.new vs. old: Refers to the Espressif bootloader structure version:old (v1.1 bootloader era): Used legacy flash mapping rules (limited irom0 size).new (v1.2+ bootloader era): Expanded the mapped irom0 size per application slot to support larger code bases.512 / 1024 / 2048: Refers to the target flash size in Kilobytes (512 KB, 1 MB, 2 MB).app1 vs. app2: Used in OTA (Over-The-Air) two-slot layouts (user1.bin and user2.bin). app1 links code to execute from the first flash partition, while app2 links code to execute from the second partition.eagle.app.v6.ld: Purpose:** Non-OTA (No-Bootloader) applications. Maps eagle.flash.bin directly to offset 0x00000 and eagle.irom0text.bin to offset 0x10000 or 0x20000. It assumes the internal hardware ROM boots the application directly without checking an OTA header or selecting between slots.eagle.app.v6.new.512.app1.ld / app2.ld : Purpose: 512 KB Flash using the “new” bootloader format. Split into two equal OTA partition slots (~236 KB max code size per app).eagle.app.v6.new.1024.app1.ld / app2.ld : Purpose: 1 MB (and larger) Flash using the “new” bootloader format. Split into two ~492 KB OTA slots (user1.bin / user2.bin).eagle.app.v6.new.2048.ld: Purpose: Single large application layout for 2 MB+ flash modules designed to work alongside special bootloaders or expanded static allocations.eagle.app.v6.old.*.ld: Purpose: Legacy backward-compatibility layouts for projects targeted at very early Espressif bootloader releases.eagle.rom.addr.v6.ld: Purpose: Hardware ROM symbol map. Behavior: Does not define flash partitions. Instead, it provides the physical memory addresses of functions pre-baked into the ESP8266 internal hardware ROM (such as axtls crypto functions, low-level SPI functions, printf, and malloc). This file is included by other linker scripts.