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Fix "Out of range pc-relative fixup value" with dcache asm. #685

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Merged
adamgreig merged 1 commit into from
Aug 13, 2026
+15 −2
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Fix "Out of range pc-relative fixup value" with dcache asm. #685

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5 changes: 5 additions & 0 deletions cortex-m/CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/).

## [Unreleased]

### Fixed
- `SCB::enable_icache` and `SCB::enable_dcache` now build the CCR address with
`movw`/`movt` instead of `ldr =`, fixing "out of range pc-relative fixup value"
errors when the asm block is inlined into a large function.

## [v0.7.8] - 2026-07-21

### Deprecated
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12 changes: 10 additions & 2 deletions cortex-m/src/peripheral/scb.rs
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Expand Up @@ -368,7 +368,11 @@ impl SCB {
// its own, and is only `unsafe` here because it's asm.
unsafe {
asm!(
"ldr {0}, =0xE000ED14", // CCR
// Build the CCR address (0xE000ED14) with movw/movt instead of `ldr =`, as the
// latter emits a PC-relative load from a literal pool which can end up out of
// range when this asm block is inlined into a large function.
"movw {0}, #0xED14", // CCR address, lower half
"movt {0}, #0xE000", // CCR address, upper half
"mrs {2}, PRIMASK", // save critical nesting info
"cpsid i", // mask interrupts
"ldr {1}, [{0}]", // read CCR
Expand Down Expand Up @@ -454,7 +458,11 @@ impl SCB {
unsafe {
asm!(
// Should this be replaced with a register modify?
"ldr {0}, =0xE000ED14", // CCR
// Build the CCR address (0xE000ED14) with movw/movt instead of `ldr =`, as the
// latter emits a PC-relative load from a literal pool which can end up out of
// range when this asm block is inlined into a large function.
"movw {0}, #0xED14", // CCR address, lower half
"movt {0}, #0xE000", // CCR address, upper half
"mrs {2}, PRIMASK", // save critical nesting info
"cpsid i", // mask interrupts
"ldr {1}, [{0}]", // read CCR
Expand Down