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include: riscv_asm: Optimize csr_xyz() macros to reduce stack usage

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When using debug builds, aka., DEBUG=1, csr_write_num() function can
trigger stack overflow. This is caused by the large amount of macro
expansion of csr_write(...), which, under debug builds, will generate
massive amount of stack variables (tested with GCC 13.2.0). The issue
is masked previously as we didn't have too many csr_write()'s before
commit 55296fd27c, but now, it does overflow the default 4KB stack.

The csr_read(relaxed) macros already use the "register" modifier to
optimize stack usage (perhaps unknowingly?), so this patch just
follows suit.

Fixes: 55296fd27c ("lib: Allow custom CSRs in csr_read_num() and csr_write_num()")
Signed-off-by: Bo Gan <ganboing@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20251216052528.18896-1-ganboing@gmail.com
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Bo Gan
2025-12-15 21:25:28 -08:00
committed by Anup Patel
parent f7b81034aa
commit 4c1c77e085
1 changed files with 6 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
include/sbi/riscv_asm.h
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@@ -83,7 +83,7 @@
#define csr_swap(csr, val) \
({ \
unsigned long __v = (unsigned long)(val); \
register unsigned long __v = (unsigned long)(val); \
__asm__ __volatile__("csrrw %0, " __ASM_STR(csr) ", %1" \
: "=r"(__v) \
: "rK"(__v) \
@@ -111,7 +111,7 @@
#define csr_write(csr, val) \
({ \
unsigned long __v = (unsigned long)(val); \
register unsigned long __v = (unsigned long)(val); \
__asm__ __volatile__("csrw " __ASM_STR(csr) ", %0" \
: \
: "rK"(__v) \
@@ -120,7 +120,7 @@
#define csr_read_set(csr, val) \
({ \
unsigned long __v = (unsigned long)(val); \
register unsigned long __v = (unsigned long)(val); \
__asm__ __volatile__("csrrs %0, " __ASM_STR(csr) ", %1" \
: "=r"(__v) \
: "rK"(__v) \
@@ -130,7 +130,7 @@
#define csr_set(csr, val) \
({ \
unsigned long __v = (unsigned long)(val); \
register unsigned long __v = (unsigned long)(val); \
__asm__ __volatile__("csrs " __ASM_STR(csr) ", %0" \
: \
: "rK"(__v) \
@@ -139,7 +139,7 @@
#define csr_read_clear(csr, val) \
({ \
unsigned long __v = (unsigned long)(val); \
register unsigned long __v = (unsigned long)(val); \
__asm__ __volatile__("csrrc %0, " __ASM_STR(csr) ", %1" \
: "=r"(__v) \
: "rK"(__v) \
@@ -149,7 +149,7 @@
#define csr_clear(csr, val) \
({ \
unsigned long __v = (unsigned long)(val); \
register unsigned long __v = (unsigned long)(val); \
__asm__ __volatile__("csrc " __ASM_STR(csr) ", %0" \
: \
: "rK"(__v) \