> So something clearly changed…
Compiler output, most probably. I cannot reproduce it. I tried:
struct xid_command
{
int syscall_no;
long int id[3];
volatile int cntr;
volatile int error; /* -1: no call yet, 0: success seen, >0: error
seen. */
};
extern void a_barrier(int *);
# define REGISTERS_CLOBBERED_BY_SYSCALL "cc", "r11", "cx"
/* NB: This also works when X is an array. For an array X, type of
(X) - (X) is ptrdiff_t, which is signed, since size of ptrdiff_t
== size of pointer, cast is a NOP. */
#define TYPEFY1(X) __typeof__ ((X) - (X))
/* Explicit cast the argument. */
#define ARGIFY(X) ((TYPEFY1 (X)) (X))
/* Create a variable 'name' based on type of variable 'X' to avoid
explicit types. */
#define TYPEFY(X, name) __typeof__ (ARGIFY (X)) name
#undef INTERNAL_SYSCALL_NCS
#define INTERNAL_SYSCALL_NCS(number, err, nr, args...)
\
internal_syscall##nr (number, err, args)
#undef internal_syscall3
#define internal_syscall3(number, err, arg1, arg2, arg3)
\
({
\
unsigned long int resultvar;
\
TYPEFY (arg3, __arg3) = ARGIFY (arg3);
\
TYPEFY (arg2, __arg2) = ARGIFY (arg2);
\
TYPEFY (arg1, __arg1) = ARGIFY (arg1);
\
register TYPEFY (arg3, _a3) asm ("rdx") = __arg3;
\
register TYPEFY (arg2, _a2) asm ("rsi") = __arg2;
\
register TYPEFY (arg1, _a1) asm ("rdi") = __arg1;
\
asm volatile (
\
"syscall\n\t"
\
: "=a" (resultvar)
\
: "0" (number), "r" (_a1), "r" (_a2), "r" (_a3)
\
: "memory", REGISTERS_CLOBBERED_BY_SYSCALL);
\
(long int) resultvar;
\
})
int
foo(struct xid_command *cmdp)
{
int result;
asm volatile ("xor rsi,rsi\n\txor rdi,rdi" : : : "rsi", "rdi");
result = INTERNAL_SYSCALL_NCS (cmdp->syscall_no, err, 3,
cmdp->id[0], cmdp->id[1], cmdp->id[2]);
a_barrier(&result);
return result;
}
Save as x.c then:
x86_64-linux-gnux32-gcc-10 -c -std=gnu11 -fgnu89-inline -pipe -O2 -g -Wall
-Wwrite-strings -Wundef -Werror -fmerge-all-constants -frounding-math
-fstack-protector-strong -Wstrict-prototypes -Wold-style-definition
-fmath-errno -fpie -ftls-model=initial-exec -D_LIBC_REENTRANT -DPIC -S
-masm=intel x.c -Wno-error
This doesn’t yield any “movsxd” in the output, like in glibc, though:
b32: 67 48 63 73 08 movsxd rsi,DWORD PTR [ebx+0x8]
b37: 67 48 63 7b 04 movsxd rdi,DWORD PTR [ebx+0x4]
b3c: 67 48 63 53 0c movsxd rdx,DWORD PTR [ebx+0xc]
b41: 67 8b 03 mov eax,DWORD PTR [ebx]
b44: 0f 05 syscall
(disassembly of pthread_create.o from libpthread.a 2.31)
I’m unsure whether this is a glibc or gcc issue… without a reproducer
I’m stuck.
I’ll have to downgrade to 2.30 for now, to keep the system ssh-in-able…
bye,
//mirabilos
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