From 4c1c77e085599f6f95df4b94714e1d7829ebefbf Mon Sep 17 00:00:00 2001 From: Bo Gan Date: Mon, 15 Dec 2025 21:25:28 -0800 Subject: [PATCH] include: riscv_asm: Optimize csr_xyz() macros to reduce stack usage 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 55296fd27c0c, 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: 55296fd27c0c ("lib: Allow custom CSRs in csr_read_num() and csr_write_num()") Signed-off-by: Bo Gan Reviewed-by: Anup Patel Link: https://lore.kernel.org/r/20251216052528.18896-1-ganboing@gmail.com Signed-off-by: Anup Patel --- include/sbi/riscv_asm.h | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/include/sbi/riscv_asm.h b/include/sbi/riscv_asm.h index ef48dc89..0cf3fc37 100644 --- a/include/sbi/riscv_asm.h +++ b/include/sbi/riscv_asm.h @@ -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) \