tcg: Use correct trap number for page faults on *BSD systems

The trap number for a page fault on BSD systems is T_PAGEFLT not 0xe. 0xe is
used by Linux and represents the intel hardware trap vector. The BSD kernels,
however, translate this to T_PAGEFLT in their Xpage, Xtrap0e, Xtrap14, etc fault
handlers. This is true for i386 and x86_64, though the name of the trap hanlder
can very on the flavor of BSD. As far as I can tell, Linux doesn't provide a
avoid uglier #ifdefs.

Signed-off-by: Mark Johnston <markj@FreeBSD.org>
Signed-off-by: Juergen Lock <nox@FreeBSD.org>
[ Rework to avoid ifdefs and expand it to i386 ]
Signed-off-by: Warner Losh <imp@bsdimp.com>
---
 accel/tcg/user-exec.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

On Thu, May 6, 2021 at 10:43 AM Warner Losh <imp@bsdimp.com> wrote:

> The trap number for a page fault on BSD systems is T_PAGEFLT not 0xe. 0xe
> is
> used by Linux and represents the intel hardware trap vector. The BSD
> kernels,
> however, translate this to T_PAGEFLT in their Xpage, Xtrap0e, Xtrap14, etc
> fault
> handlers. This is true for i386 and x86_64, though the name of the trap
> hanlder
> can very on the flavor of BSD. As far as I can tell, Linux doesn't provide
> a
>

I've been burned by git's # comments in the commit message. This is missing
a line:

#define for this value. Invent a new one and use it instead to


> avoid uglier #ifdefs.
>

I'll amend and resend.


> Signed-off-by: Mark Johnston <markj@FreeBSD.org>
> Signed-off-by: Juergen Lock <nox@FreeBSD.org>
> [ Rework to avoid ifdefs and expand it to i386 ]
> Signed-off-by: Warner Losh <imp@bsdimp.com>
> ---
>  accel/tcg/user-exec.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
> index 0d8cc27b21..959fec1257 100644
> --- a/accel/tcg/user-exec.c
> +++ b/accel/tcg/user-exec.c
> @@ -260,6 +260,7 @@ void *probe_access(CPUArchState *env, target_ulong
> addr, int size,
>  #define TRAP_sig(context)    ((context)->uc_mcontext.__gregs[_REG_TRAPNO])
>  #define ERROR_sig(context)   ((context)->uc_mcontext.__gregs[_REG_ERR])
>  #define MASK_sig(context)    ((context)->uc_sigmask)
> +#define PAGE_FAULT_TRAP      T_PAGEFLT
>  #elif defined(__FreeBSD__) || defined(__DragonFly__)
>  #include <ucontext.h>
>
> @@ -267,16 +268,19 @@ void *probe_access(CPUArchState *env, target_ulong
> addr, int size,
>  #define TRAP_sig(context)    ((context)->uc_mcontext.mc_trapno)
>  #define ERROR_sig(context)   ((context)->uc_mcontext.mc_err)
>  #define MASK_sig(context)    ((context)->uc_sigmask)
> +#define PAGE_FAULT_TRAP      T_PAGEFLT
>  #elif defined(__OpenBSD__)
>  #define EIP_sig(context)     ((context)->sc_eip)
>  #define TRAP_sig(context)    ((context)->sc_trapno)
>  #define ERROR_sig(context)   ((context)->sc_err)
>  #define MASK_sig(context)    ((context)->sc_mask)
> +#define PAGE_FAULT_TRAP      T_PAGEFLT
>  #else
>  #define EIP_sig(context)     ((context)->uc_mcontext.gregs[REG_EIP])
>  #define TRAP_sig(context)    ((context)->uc_mcontext.gregs[REG_TRAPNO])
>  #define ERROR_sig(context)   ((context)->uc_mcontext.gregs[REG_ERR])
>  #define MASK_sig(context)    ((context)->uc_sigmask)
> +#define PAGE_FAULT_TRAP      0xe
>  #endif
>
>  int cpu_signal_handler(int host_signum, void *pinfo,
> @@ -302,7 +306,8 @@ int cpu_signal_handler(int host_signum, void *pinfo,
>      pc = EIP_sig(uc);
>      trapno = TRAP_sig(uc);
>      return handle_cpu_signal(pc, info,
> -                             trapno == 0xe ? (ERROR_sig(uc) >> 1) & 1 : 0,
> +                             trapno == PAGE_FAULT_TRAP ?
> +                             (ERROR_sig(uc) >> 1) & 1 : 0,
>                               &MASK_sig(uc));
>  }
>
> @@ -313,11 +318,13 @@ int cpu_signal_handler(int host_signum, void *pinfo,
>  #define TRAP_sig(context)
>  ((context)->uc_mcontext.__gregs[_REG_TRAPNO])
>  #define ERROR_sig(context)    ((context)->uc_mcontext.__gregs[_REG_ERR])
>  #define MASK_sig(context)     ((context)->uc_sigmask)
> +#define PAGE_FAULT_TRAP       T_PAGEFLT
>  #elif defined(__OpenBSD__)
>  #define PC_sig(context)       ((context)->sc_rip)
>  #define TRAP_sig(context)     ((context)->sc_trapno)
>  #define ERROR_sig(context)    ((context)->sc_err)
>  #define MASK_sig(context)     ((context)->sc_mask)
> +#define PAGE_FAULT_TRAP       T_PAGEFLT
>  #elif defined(__FreeBSD__) || defined(__DragonFly__)
>  #include <ucontext.h>
>
> @@ -325,11 +332,13 @@ int cpu_signal_handler(int host_signum, void *pinfo,
>  #define TRAP_sig(context)     ((context)->uc_mcontext.mc_trapno)
>  #define ERROR_sig(context)    ((context)->uc_mcontext.mc_err)
>  #define MASK_sig(context)     ((context)->uc_sigmask)
> +#define PAGE_FAULT_TRAP       T_PAGEFLT
>  #else
>  #define PC_sig(context)       ((context)->uc_mcontext.gregs[REG_RIP])
>  #define TRAP_sig(context)     ((context)->uc_mcontext.gregs[REG_TRAPNO])
>  #define ERROR_sig(context)    ((context)->uc_mcontext.gregs[REG_ERR])
>  #define MASK_sig(context)     ((context)->uc_sigmask)
> +#define PAGE_FAULT_TRAP       0xe
>  #endif
>
>  int cpu_signal_handler(int host_signum, void *pinfo,
> @@ -347,7 +356,8 @@ int cpu_signal_handler(int host_signum, void *pinfo,
>
>      pc = PC_sig(uc);
>      return handle_cpu_signal(pc, info,
> -                             TRAP_sig(uc) == 0xe ? (ERROR_sig(uc) >> 1) &
> 1 : 0,
> +                             TRAP_sig(uc) == PAGE_FAULT_TRAP ?
> +                             (ERROR_sig(uc) >> 1) & 1 : 0,
>                               &MASK_sig(uc));
>  }
>
> --
> 2.22.1
>
>