diff options
Diffstat (limited to 'target')
| -rw-r--r-- | target/arm/arm-semi.c | 19 |
1 files changed, 15 insertions, 4 deletions
diff --git a/target/arm/arm-semi.c b/target/arm/arm-semi.c index 51b55816fa..302529f227 100644 --- a/target/arm/arm-semi.c +++ b/target/arm/arm-semi.c @@ -217,10 +217,21 @@ static target_ulong arm_gdb_syscall(ARMCPU *cpu, gdb_syscall_complete_cb cb, gdb_do_syscallv(cb, fmt, va); va_end(va); - /* FIXME: we are implicitly relying on the syscall completing - * before this point, which is not guaranteed. We should - * put in an explicit synchronization between this and - * the callback function. + /* + * FIXME: in softmmu mode, the gdbstub will schedule our callback + * to occur, but will not actually call it to complete the syscall + * until after this function has returned and we are back in the + * CPU main loop. Therefore callers to this function must not + * do anything with its return value, because it is not necessarily + * the result of the syscall, but could just be the old value of X0. + * The only thing safe to do with this is that the callers of + * do_arm_semihosting() will write it straight back into X0. + * (In linux-user mode, the callback will have happened before + * gdb_do_syscallv() returns.) + * + * We should tidy this up so neither this function nor + * do_arm_semihosting() return a value, so the mistake of + * doing something with the return value is not possible to make. */ return is_a64(env) ? env->xregs[0] : env->regs[0]; |