diff options
| -rw-r--r-- | cortex-m-rt/Cargo.toml | 1 | ||||
| -rw-r--r-- | cortex-m-rt/link.x.in | 4 | ||||
| -rw-r--r-- | cortex-m-rt/src/lib.rs | 29 |
3 files changed, 25 insertions, 9 deletions
diff --git a/cortex-m-rt/Cargo.toml b/cortex-m-rt/Cargo.toml index f8438fb..3305d34 100644 --- a/cortex-m-rt/Cargo.toml +++ b/cortex-m-rt/Cargo.toml @@ -45,6 +45,7 @@ required-features = ["device"] device = [] set-sp = [] set-vtor = [] +zero-init-ram = [] [package.metadata.docs.rs] features = ["device"] diff --git a/cortex-m-rt/link.x.in b/cortex-m-rt/link.x.in index 551f576..f699dec 100644 --- a/cortex-m-rt/link.x.in +++ b/cortex-m-rt/link.x.in @@ -60,7 +60,9 @@ PROVIDE(__pre_init = DefaultPreInit); /* # Sections */ SECTIONS { - PROVIDE(_stack_start = ORIGIN(RAM) + LENGTH(RAM)); + PROVIDE(_ram_start = ORIGIN(RAM) + LENGTH(RAM)); + PROVIDE(_ram_end = ORIGIN(RAM)); + PROVIDE(_stack_start = _ram_start); /* ## Sections in FLASH */ /* ### Vector table */ diff --git a/cortex-m-rt/src/lib.rs b/cortex-m-rt/src/lib.rs index 2070efa..96d89dd 100644 --- a/cortex-m-rt/src/lib.rs +++ b/cortex-m-rt/src/lib.rs @@ -514,6 +514,19 @@ cfg_global_asm! { "ldr r0, =_stack_start msr msp, r0", + // If enabled, initialize RAM with zeros. This is normally not necessary but might be required + // on custom hardware. + #[cfg(feature = "zero-init-ram")] + "ldr r0, =_ram_end + ldr r1, =_ram_start + movs r2, #0 + 0: + cmp r1, r0 + beq 1f + stm r0!, {{r2}} + b 0b + 1:", + // If enabled, initialise VTOR to the start of the vector table. This is normally initialised // by a bootloader when the non-reset value is required, but some bootloaders do not set it, // leading to frustrating issues where everything seems to work but interrupts are never @@ -533,24 +546,24 @@ cfg_global_asm! { "ldr r0, =__sbss ldr r1, =__ebss movs r2, #0 - 0: + 2: cmp r1, r0 - beq 1f + beq 3f stm r0!, {{r2}} - b 0b - 1:", + b 2b + 3:", // Initialise .data memory. `__sdata`, `__sidata`, and `__edata` come from the linker script. "ldr r0, =__sdata ldr r1, =__edata ldr r2, =__sidata - 2: + 4: cmp r1, r0 - beq 3f + beq 5f ldm r2!, {{r3}} stm r0!, {{r3}} - b 2b - 3:", + b 4b + 5:", // Potentially enable an FPU. // SCB.CPACR is 0xE000_ED88. |