[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Wed, 25 May 2022 18:08:23 +0800
From: 王洪亮 <wanghongliang@...ngson.cn>
To: musl@...ts.openwall.com
Subject: Re: add loongarch64 port v3
在 2022/5/24 下午8:32, Rich Felker 写道:
> What we've been trying to say is that there are several cases, none of
> which seem to need it:
>
> 1. You create an object with declared type struct sigcontext. In this
> case, the flexible array member at the end is not present at all
> (because that's how C works) which means there's no extended
> context which needs additional alignment and probably also means
> this is not a usable way of creating sigcontext structs.
>
> 2. You malloc storage for the object with space for the flexible array
> member. In this case the allocation has alignment max_align_t and
> everything is fine.
>
> 3. You get the object from the kernel pushing it onto the stack in a
> signal frame. This is probably actually the only case the type is
> usable in, and of course it has whatever alignment the kernel gave
> it.
Specify the __attribute__((__aligned__(16))) in musl,is used to be
consistent with kernel.if I removed the __attribute__((__aligned__(16))),
there is a libc-test fail in pthread_cancel.exe.the reason is that the
offset of uc->uc_mcontext from the start of uc obtained in cancel_handler
is inconsistent with kernel pushing it onto the stack in a signal frame.
so I understand the __attribute__((__aligned__(16))) is necessary in musl.
src/thread/pthread_cancel.c
static void cancel_handler(int sig, siginfo_t *si, void *ctx)
{
pthread_t self = __pthread_self();
ucontext_t *uc = ctx;
uintptr_t pc = uc->uc_mcontext.MC_PC;
...
}
musl/arch/loongarch64/bits/signal.h:
typedef unsigned long greg_t, gregset_t[32];
typedef struct sigcontext {
unsigned long pc;
gregset_t gregs;
unsigned int flags;
unsigned long extcontext[];
}mcontext_t;
linux/arch/loongarch/include/uapi/asm/sigcontext.h:
struct sigcontext {
__u64 sc_pc;
__u64 sc_regs[32];
__u32 sc_flags;
__u64 sc_extcontext[0] __attribute__((__aligned__(16)));
};
>
> Rich
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
