RE: X86 fpu registers in a signal handler's ucontext

[Warlich, Christof]

Mikael Pettersson <mikpe@xxxxxxxx> writes:
> Write to the fpstate ->mxcsr and ->swd fields in the sigaction handler's uc_mcontext.

To me, "sigaction handler's uc_mcontext" sounds like userspace, which really confuses me:
Even in most recent glibc-2.17, uc_mcontext is of type mcontext_t, which us defined as:

typedef struct {
  gregset_t gregs;
  fpregset_t fpregs;
} mcontext_t;

typedef struct fpregset {
    union {
	struct fpchip_state {
	    int state[27];
	    int status;
	} fpchip_state;
	struct fp_emul_space {
	    char fp_emul[246];
	    char fp_epad[2];
	} fp_emul_space;
	int f_fpregs[62];
    } fp_reg_set;
    long int f_wregs[33];
} fpregset_t;

So there is no fpstate whatsoever.

However, these elements seem to be available in the uc_mcontext definition of the
kernel, but I can't have a sigaction handler there, can I? Then, how does the
kernel's uc_mcontext definition help me in my (userspace) signal handler?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/