[Qemu-devel] [BUG] Inappropriate size of target_sigset_t

[Aleksandar Markovic]

Hello, Peter, Laurent,

While working on another problem yesterday, I think I discovered a 
long-standing bug in QEMU Linux user mode: our target_sigset_t structure is 
eight times smaller as it should be!

In this code segment from syscalls_def.h:

#ifdef TARGET_MIPS
#define TARGET_NSIG        128
#else
#define TARGET_NSIG        64
#endif
#define TARGET_NSIG_BPW    TARGET_ABI_BITS
#define TARGET_NSIG_WORDS  (TARGET_NSIG / TARGET_NSIG_BPW)

typedef struct {
    abi_ulong sig[TARGET_NSIG_WORDS];
} target_sigset_t;

... TARGET_ABI_BITS should be replaced by eight times smaller constant (in 
fact, semantically, we need TARGET_ABI_BYTES, but it is not defined) (what is 
needed is actually "a byte per signal" in target_sigset_t, and we allow "a bit 
per signal").

All this probably sounds to you like something impossible, since this code is 
in QEMU "since forever", but I checked everything, and the bug seems real. I 
wish you can prove me wrong.

I just wanted to let you know about this, given the sensitive timing of current 
softfreeze, and the fact that I won't be able to do more investigation on this 
in coming weeks, since I am busy with other tasks, but perhaps you can analyze 
and do something which you consider appropriate.

Yours,
Aleksandar