Stack protector adds extra mov, extra stack allocation and extra branch to save and validate the stack canary. While this feature could be useful to detect stack corruption in some scenarios, it is not really needed for liburing which is simple enough to review. Good code shouldn't corrupt the stack. We don't need this extra checking at the moment. Just for comparison, let's take a hot function __io_uring_get_cqe. Before this patch: ``` 0000000000002b80 <__io_uring_get_cqe>: 2b80: f3 0f 1e fa endbr64 2b84: 48 83 ec 28 sub $0x28,%rsp 2b88: 64 48 8b 04 25 28 00 mov %fs:0x28,%rax 2b8f: 00 00 2b91: 48 89 44 24 18 mov %rax,0x18(%rsp) 2b96: 31 c0 xor %eax,%eax 2b98: 89 14 24 mov %edx,(%rsp) 2b9b: 48 89 e2 mov %rsp,%rdx 2b9e: 48 b8 00 00 00 00 08 movabs $0x800000000,%rax 2ba5: 00 00 00 2ba8: 89 4c 24 04 mov %ecx,0x4(%rsp) 2bac: 48 89 44 24 08 mov %rax,0x8(%rsp) 2bb1: 4c 89 44 24 10 mov %r8,0x10(%rsp) 2bb6: e8 45 fe ff ff call 2a00 <_io_uring_get_cqe> 2bbb: 48 8b 54 24 18 mov 0x18(%rsp),%rdx 2bc0: 64 48 2b 14 25 28 00 sub %fs:0x28,%rdx 2bc7: 00 00 2bc9: 75 05 jne 2bd0 <__io_uring_get_cqe+0x50> 2bcb: 48 83 c4 28 add $0x28,%rsp 2bcf: c3 ret 2bd0: e8 9b f5 ff ff call 2170 <__stack_chk_fail@plt> 2bd5: 66 66 2e 0f 1f 84 00 data16 cs nopw 0x0(%rax,%rax,1) 2bdc: 00 00 00 00 ``` After this patch: ``` 0000000000002ab0 <__io_uring_get_cqe>: 2ab0: f3 0f 1e fa endbr64 2ab4: 48 b8 00 00 00 00 08 movabs $0x800000000,%rax 2abb: 00 00 00 2abe: 48 83 ec 28 sub $0x28,%rsp 2ac2: 89 14 24 mov %edx,(%rsp) 2ac5: 48 89 e2 mov %rsp,%rdx 2ac8: 89 4c 24 04 mov %ecx,0x4(%rsp) 2acc: 48 89 44 24 08 mov %rax,0x8(%rsp) 2ad1: 4c 89 44 24 10 mov %r8,0x10(%rsp) 2ad6: e8 55 fe ff ff call 2930 <_io_uring_get_cqe> 2adb: 48 83 c4 28 add $0x28,%rsp 2adf: c3 ret ``` Previously, we only use `-fno-stack-protector` for nolibc build as the stack protector needs to call `__stack_chk_fail@plt` function from the libc. Now, we always use `-fno-stack-protector` for both nolibc and libc builds to generate shorter Assembly code. Cc: Nugra <richiisei@xxxxxxxxx> Cc: Alviro Iskandar Setiawan <alviro.iskandar@xxxxxxxxxxx> Cc: GNU/Weeb Mailing List <gwml@xxxxxxxxxxxxxxxx> Cc: Tea Inside Mailing List <timl@xxxxxxxxxxxxxxxxxx> Cc: io-uring Mailing List <io-uring@xxxxxxxxxxxxxxx> Signed-off-by: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx> --- src/Makefile | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/src/Makefile b/src/Makefile index cc6c871..3e1192f 100644 --- a/src/Makefile +++ b/src/Makefile @@ -8,7 +8,7 @@ libdevdir ?= $(prefix)/lib CPPFLAGS ?= override CPPFLAGS += -D_GNU_SOURCE \ -Iinclude/ -include ../config-host.h -CFLAGS ?= -g -fomit-frame-pointer -O2 -Wall -Wextra +CFLAGS ?= -g -fomit-frame-pointer -O2 -Wall -Wextra -fno-stack-protector override CFLAGS += -Wno-unused-parameter -Wno-sign-compare -DLIBURING_INTERNAL SO_CFLAGS=-fPIC $(CFLAGS) L_CFLAGS=$(CFLAGS) @@ -36,8 +36,8 @@ liburing_srcs := setup.c queue.c register.c ifeq ($(CONFIG_NOLIBC),y) liburing_srcs += nolibc.c - override CFLAGS += -nostdlib -nodefaultlibs -ffreestanding -fno-stack-protector - override CPPFLAGS += -nostdlib -nodefaultlibs -ffreestanding -fno-stack-protector + override CFLAGS += -nostdlib -nodefaultlibs -ffreestanding + override CPPFLAGS += -nostdlib -nodefaultlibs -ffreestanding override LINK_FLAGS += -nostdlib -nodefaultlibs else liburing_srcs += syscall.c base-commit: 896a1d3ab14a8777a45db6e7b67cf557a44923fb -- 2.32.0
