The set_swi_errno() function is called to capture the errno
from a host system call, so that we can return -1 from the
semihosting function and later allow the guest to get a more
specific error code with the SYS_ERRNO function. It comes in
two versions, one for user-only and one for softmmu. We forgot
to capture the errno in the softmmu version; fix the error.

(Semihosting calls directed to gdb are unaffected because
they go through a different code path that captures the
error return from the gdbstub call in arm_semi_cb() or
arm_semi_flen_cb().)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
NB that a later commit will put in some cleanup of TaskState
that will let us reduce the duplication between the two
implementations of this function.
---
 target/arm/arm-semi.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/target/arm/arm-semi.c b/target/arm/arm-semi.c
index 90423a35deb..03e60105c05 100644
--- a/target/arm/arm-semi.c
+++ b/target/arm/arm-semi.c
@@ -114,8 +114,13 @@ static inline uint32_t set_swi_errno(TaskState *ts, uint32_t code)
     return code;
 }
 #else
+static target_ulong syscall_err;
+
 static inline uint32_t set_swi_errno(CPUARMState *env, uint32_t code)
 {
+    if (code == (uint32_t)-1) {
+        syscall_err = errno;
+    }
     return code;
 }
 
@@ -124,10 +129,6 @@ static inline uint32_t set_swi_errno(CPUARMState *env, uint32_t code)
 
 static target_ulong arm_semi_syscall_len;
 
-#if !defined(CONFIG_USER_ONLY)
-static target_ulong syscall_err;
-#endif
-
 static void arm_semi_cb(CPUState *cs, target_ulong ret, target_ulong err)
 {
     ARMCPU *cpu = ARM_CPU(cs);
-- 
2.20.1

On 9/16/19 7:15 AM, Peter Maydell wrote:
> The set_swi_errno() function is called to capture the errno
> from a host system call, so that we can return -1 from the
> semihosting function and later allow the guest to get a more
> specific error code with the SYS_ERRNO function. It comes in
> two versions, one for user-only and one for softmmu. We forgot
> to capture the errno in the softmmu version; fix the error.
> 
> (Semihosting calls directed to gdb are unaffected because
> they go through a different code path that captures the
> error return from the gdbstub call in arm_semi_cb() or
> arm_semi_flen_cb().)
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> NB that a later commit will put in some cleanup of TaskState
> that will let us reduce the duplication between the two
> implementations of this function.
> ---

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

On 9/16/19 4:15 PM, Peter Maydell wrote:
> The set_swi_errno() function is called to capture the errno
> from a host system call, so that we can return -1 from the
> semihosting function and later allow the guest to get a more
> specific error code with the SYS_ERRNO function. It comes in
> two versions, one for user-only and one for softmmu. We forgot
> to capture the errno in the softmmu version; fix the error.
> 
> (Semihosting calls directed to gdb are unaffected because
> they go through a different code path that captures the
> error return from the gdbstub call in arm_semi_cb() or
> arm_semi_flen_cb().)
> 

Fixes: 8e71621f784
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> NB that a later commit will put in some cleanup of TaskState
> that will let us reduce the duplication between the two
> implementations of this function.
> ---
>   target/arm/arm-semi.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/target/arm/arm-semi.c b/target/arm/arm-semi.c
> index 90423a35deb..03e60105c05 100644
> --- a/target/arm/arm-semi.c
> +++ b/target/arm/arm-semi.c
> @@ -114,8 +114,13 @@ static inline uint32_t set_swi_errno(TaskState *ts, uint32_t code)
>       return code;
>   }
>   #else
> +static target_ulong syscall_err;
> +
>   static inline uint32_t set_swi_errno(CPUARMState *env, uint32_t code)
>   {
> +    if (code == (uint32_t)-1) {
> +        syscall_err = errno;
> +    }
>       return code;
>   }
>   
> @@ -124,10 +129,6 @@ static inline uint32_t set_swi_errno(CPUARMState *env, uint32_t code)
>   
>   static target_ulong arm_semi_syscall_len;
>   
> -#if !defined(CONFIG_USER_ONLY)
> -static target_ulong syscall_err;
> -#endif
> -
>   static void arm_semi_cb(CPUState *cs, target_ulong ret, target_ulong err)
>   {
>       ARMCPU *cpu = ARM_CPU(cs);
> 

On Fri, 4 Oct 2019 at 00:24, Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>
> On 9/16/19 4:15 PM, Peter Maydell wrote:
> > The set_swi_errno() function is called to capture the errno
> > from a host system call, so that we can return -1 from the
> > semihosting function and later allow the guest to get a more
> > specific error code with the SYS_ERRNO function. It comes in
> > two versions, one for user-only and one for softmmu. We forgot
> > to capture the errno in the softmmu version; fix the error.
> >
> > (Semihosting calls directed to gdb are unaffected because
> > they go through a different code path that captures the
> > error return from the gdbstub call in arm_semi_cb() or
> > arm_semi_flen_cb().)
> >
>
> Fixes: 8e71621f784

That was the commit that added support for semihosting
to softmmu in 2007, so I don't think suggesting that this
is a 'fix' to that makes much sense. This has just been
broken forever. (It's also pretty unimportant as a bug because
the semihosting 'errno' is so ill-defined as to be unused,
I think.)

thanks
-- PMM