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X-Received-From: 2a00:1450:4864:20::443 Subject: Re: [Qemu-devel] [PATCH 12/13] target/arm/arm-semi: Implement SH_EXT_STDOUT_STDERR extension X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-arm@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Peter Maydell writes: > SH_EXT_STDOUT_STDERR is a v2.0 semihosting extension: the guest > can open ":tt" with a file mode requesting append access in > order to open stderr, in addition to the existing "open for > read for stdin or write for stdout". Implement this and > report it via the :semihosting-features data. > > Signed-off-by: Peter Maydell > --- > target/arm/arm-semi.c | 22 ++++++++++++++++++++-- > 1 file changed, 20 insertions(+), 2 deletions(-) > > diff --git a/target/arm/arm-semi.c b/target/arm/arm-semi.c > index 531084b7799..0df8d4d69d6 100644 > --- a/target/arm/arm-semi.c > +++ b/target/arm/arm-semi.c > @@ -476,12 +476,16 @@ static uint32_t gdb_flenfn(TaskState *ts, ARMCPU *c= pu, GuestFD *gf) > #define SHFB_MAGIC_2 0x46 > #define SHFB_MAGIC_3 0x42 > > +/* Feature bits reportable in feature byte 0 */ > +#define SH_EXT_EXIT_EXTENDED (1 << 0) If you swap 12/13 this could be kept with the related feature. I don't think one implies the other right? > +#define SH_EXT_STDOUT_STDERR (1 << 1) > + > static const uint8_t featurefile_data[] =3D { > SHFB_MAGIC_0, > SHFB_MAGIC_1, > SHFB_MAGIC_2, > SHFB_MAGIC_3, > - 0, /* Feature byte 0 */ > + SH_EXT_STDOUT_STDERR, /* Feature byte 0 */ > }; > > static void init_featurefile_guestfd(int guestfd) > @@ -674,7 +678,21 @@ target_ulong do_arm_semihosting(CPUARMState *env) > } > > if (strcmp(s, ":tt") =3D=3D 0) { > - int result_fileno =3D arg1 < 4 ? STDIN_FILENO : STDOUT_FILEN= O; > + int result_fileno; > + > + /* > + * We implement SH_EXT_STDOUT_STDERR, so: > + * open for read =3D=3D stdin > + * open for write =3D=3D stdout > + * open for append =3D=3D stderr > + */ I love the way the spec documents field2 as an ISO C fopen() mode and then an extension literally subverts the meaning to be something else. Where the designers worried about adding a SYS_OPEN_TTY function to the interface? Anyway it meets the spec however weird it might be: Reviewed-by: Alex Benn=C3=A9e > + if (arg1 < 4) { > + result_fileno =3D STDIN_FILENO; > + } else if (arg1 < 8) { > + result_fileno =3D STDOUT_FILENO; > + } else { > + result_fileno =3D STDERR_FILENO; > + } > associate_guestfd(guestfd, result_fileno); > unlock_user(s, arg0, 0); > return guestfd; -- Alex Benn=C3=A9e