Hi, Fangrui Thank you for your time :) On 11/6/2023 4:50 AM, Fangrui Song wrote: > On Fri, Nov 3, 2023 at 9:01 AM Yuan Tan <tanyuan@xxxxxxxxxxx> wrote: > > > > .size directive fails in some functions with SHF_GROUP, this is not > > really required for normal building, inhibit it to silence the compiling > > failures with SHF_GROUP. > > > > Signed-off-by: Yuan Tan <tanyuan@xxxxxxxxxxx> > > Signed-off-by: Zhangjin Wu <falcon@xxxxxxxxxxx> > > --- > > Makefile | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/Makefile b/Makefile > > index a4e522b747cb..f67b6e8d2c45 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -936,6 +936,9 @@ endif > > # `rustc`'s `-Zfunction-sections` applies to data too (as of 1.59.0). > > ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION > > KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections > > +ifdef CONFIG_SECTION_SHF_GROUP_SUPPORT > > +KBUILD_CFLAGS_KERNEL += -finhibit-size-directive > > +endif > > KBUILD_RUSTFLAGS_KERNEL += -Zfunction-sections=y > > LDFLAGS_vmlinux += --gc-sections > > ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION_DEBUG > > -- > > 2.34.1 > > > > Clang doesn't support -finhibit-size-directive, so this would break > Clang builds. Currently, Clang doesn't support LD_DEAD_CODE_DATA_ELIMINATION. So in this patch series I didn't take much thought about clang. > > GCC has had this option since 1992, but it is not used in the wild. > https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html#index-finhibit-size-directive > says > > > ... This option is used when compiling crtstuff.c; you should not need to use it for anything else. > > What problem have you seen with .size directives (st_size field in > symbol table entries)? $ make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- fs/ioctl.o /tmp/ccy5E3wN.s: Error: .size expression for __riscv_sys_ioctl does not evaluate to a constant make[3]: *** [scripts/Makefile.build:243: fs/ioctl.o] Error 1 make[2]: *** [scripts/Makefile.build:480: fs] Error 2 make[1]: *** [/home/tanyuan/projects/linux/Makefile:1916: .] Error 2 make: *** [Makefile:234: __sub-make] Error 2 And the fs/ioctl.s is like .section .text.__riscv_sys_ioctl,"ax",@progbits .align 1 .globl __riscv_sys_ioctl .type __riscv_sys_ioctl, @function __riscv_sys_ioctl: ... ... .size __riscv_sys_ioctl, .-__riscv_sys_ioctl I cannot understand this error and this option just solve the problem :) > > % cat a.c > int v; > void f() {} > % diff -u0 <(gcc -S a.c -o -) <(gcc -S -finhibit-size-directive a.c -o -) > --- /proc/self/fd/11 2023-11-05 12:42:51.298618475 -0800 > +++ /proc/self/fd/15 2023-11-05 12:42:51.298618475 -0800 > @@ -7 +6,0 @@ > - .size v, 4 > @@ -27 +25,0 @@ > - .size f, .-f > >
