target/arm/arm-semi: fix SYS_OPEN to return nonzero filehandle
According to the specification "Semihosting for AArch32 and Aarch64", the SYS_OPEN operation should return: - A nonzero handle if the call is successful - -1 if the call is not successful So, it should never return 0. Prior to commit35e9a0a8ce
("target/arm/arm-semi: Make semihosting code hand out its own file descriptors"), the guest fd matched to the host fd. It returned a nonzero handle on success since the fd 0 is already used for stdin. Now that the guest fd is the index of guestfd_array, it starts from 0. I noticed this issue particularly because Trusted Firmware-A built with PLAT=qemu is no longer working. Its io_semihosting driver only handles a positive return value as a valid filehandle. Basically, there are two ways to fix this: - Use (guestfd - 1) as the index of guestfs_arrary. We need to insert increment/decrement to convert the guestfd and the array index back and forth. - Keep using guestfd as the index of guestfs_array. The first entry of guestfs_array is left unused. I thought the latter is simpler. We end up with wasting a small piece of memory for the unused first entry of guestfd_array, but this is probably not a big deal. Fixes:35e9a0a8ce
("target/arm/arm-semi: Make semihosting code hand out its own file descriptors") Cc: qemu-stable@nongnu.org Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-id: 20200109041228.10131-1-masahiroy@kernel.org Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
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@ -144,7 +144,8 @@ static int alloc_guestfd(void)
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guestfd_array = g_array_new(FALSE, TRUE, sizeof(GuestFD));
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guestfd_array = g_array_new(FALSE, TRUE, sizeof(GuestFD));
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}
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}
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for (i = 0; i < guestfd_array->len; i++) {
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/* SYS_OPEN should return nonzero handle on success. Start guestfd from 1 */
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for (i = 1; i < guestfd_array->len; i++) {
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GuestFD *gf = &g_array_index(guestfd_array, GuestFD, i);
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GuestFD *gf = &g_array_index(guestfd_array, GuestFD, i);
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if (gf->type == GuestFDUnused) {
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if (gf->type == GuestFDUnused) {
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@ -168,7 +169,7 @@ static GuestFD *do_get_guestfd(int guestfd)
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return NULL;
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return NULL;
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}
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}
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if (guestfd < 0 || guestfd >= guestfd_array->len) {
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if (guestfd <= 0 || guestfd >= guestfd_array->len) {
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return NULL;
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return NULL;
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}
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}
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