Hi yang, On Mon, Oct 21, 2024 at 3:51 PM yang li <yang.li85200@xxxxxxxxx> wrote: > > Hi Guo Ren: > In C language, your conclusion is correct, but in assembly language, > global_symbol != &global_symbol > I did the following experiment: > > liyang@liyang-virtual-machine:~/Desktop/test$ ls > main.c test.s > liyang@liyang-virtual-machine:~/Desktop/test$ cat test.s > > .globl test_symbol > test_symbol: > nop > liyang@liyang-virtual-machine:~/Desktop/test$ cat main.c > #include <stdio.h> > > extern unsigned long test_symbol; > int main(void) > { > printf("test_symbol = 0x%lx\n",(unsigned long)test_symbol); > printf("&test_symbol = 0x%lx\n",(unsigned long)&test_symbol); > > printf("main = 0x%lx\n",(unsigned long)main); > printf("&main = 0x%lx\n",(unsigned long)&main); > } > liyang@liyang-virtual-machine:~/Desktop/test$ gcc main.c test.s --static -o test > liyang@liyang-virtual-machine:~/Desktop/test$ ls > main.c test test.s > liyang@liyang-virtual-machine:~/Desktop/test$ readelf test -s | grep test_symbol > 884: 000000000040170c 0 NOTYPE GLOBAL DEFAULT 7 test_symbol > liyang@liyang-virtual-machine:~/Desktop/test$ readelf test -s | grep main -w > 1605: 0000000000401685 135 FUNC GLOBAL DEFAULT 7 main > liyang@liyang-virtual-machine:~/Desktop/test$ ./test > test_symbol = 0x4b853001f0f90 > &test_symbol = 0x40170c > main = 0x401685 > &main = 0x401685 > > The above test can lead to the conclusion that: > Both c_symbol and &c_symbol represent the address of a symbol, but > &ASM_symbol represents the address of a symbol while ASM_symbol > represents the opcode stored at that address. > > On Thu, Oct 17, 2024 at 2:05 PM Guo Ren <guoren@xxxxxxxxxx> wrote: > > > > On Wed, Oct 16, 2024 at 5:56 PM Yang Li <yang.li85200@xxxxxxxxx> wrote: > > > > > > In the csky_cmpxchg_fixup function, it is incorrect to use the global > > > variable csky_cmpxchg_stw to determine the address where the exception > > > occurred.The global variable csky_cmpxchg_stw stores the opcode at the > > > time of the exception, while &csky_cmpxchg_stw shows the address where > > > the exception occurred. > > > > > > Signed-off-by: Yang Li <yang.li85200@xxxxxxxxx> You convinced me. Applied to csky/linux-next, thanks! > > > --- > > > V1 -> V2:Eliminate compilation warnings > > > > > > arch/csky/mm/fault.c | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/arch/csky/mm/fault.c b/arch/csky/mm/fault.c > > > index a885518ce1dd..5226bc08c336 100644 > > > --- a/arch/csky/mm/fault.c > > > +++ b/arch/csky/mm/fault.c > > > @@ -45,8 +45,8 @@ static inline void csky_cmpxchg_fixup(struct pt_regs *regs) > > > if (trap_no(regs) != VEC_TLBMODIFIED) > > > return; > > > > > > - if (instruction_pointer(regs) == csky_cmpxchg_stw) > > > - instruction_pointer_set(regs, csky_cmpxchg_ldw); > > > + if (instruction_pointer(regs) == (unsigned long)&csky_cmpxchg_stw) > > > + instruction_pointer_set(regs, (unsigned long)&csky_cmpxchg_ldw); > > csky_cmpxchg_ldw(stw) is a label symbol, not a variable. > > > > arch/csky/kernel/atomic.S: > > GLOBAL(csky_cmpxchg_ldw) > > GLOBAL(csky_cmpxchg_stw) > > > > Your modification does not affect the ASM output. > > > > (gdb) p main > > $1 = {void (void)} 0x5fa <main> > > (gdb) p &main > > $2 = (void (*)(void)) 0x5fa <main> > > > > > return; > > > } > > > #endif > > > -- > > > 2.34.1 > > > > > > > > > -- > > Best Regards > > Guo Ren -- Best Regards Guo Ren