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authorMasahiro Yamada <masahiroy@kernel.org>2020-01-17 14:09:30 +0000
committerPeter Maydell <peter.maydell@linaro.org>2020-01-17 14:09:30 +0000
commitf89db8778f1c2c472584524ac1f10f01ba03aa93 (patch)
tree905a6779a38861191c7c60ac6aa5ffb6a779fbd8
parentaf4ba4ed13b2bbfd2d33527741810a5905a11310 (diff)
downloadqemu-arm-f89db8778f1c2c472584524ac1f10f01ba03aa93.tar.gz
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 commit 35e9a0a8ce4b ("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: 35e9a0a8ce4b ("target/arm/arm-semi: Make semihosting code hand out its own file descriptors") 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>
-rw-r--r--target/arm/arm-semi.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/target/arm/arm-semi.c b/target/arm/arm-semi.c
index 47d61f6fe1..788fe61b51 100644
--- a/target/arm/arm-semi.c
+++ b/target/arm/arm-semi.c
@@ -144,7 +144,8 @@ static int alloc_guestfd(void)
guestfd_array = g_array_new(FALSE, TRUE, sizeof(GuestFD));
}
- for (i = 0; i < guestfd_array->len; i++) {
+ /* SYS_OPEN should return nonzero handle on success. Start guestfd from 1 */
+ for (i = 1; i < guestfd_array->len; i++) {
GuestFD *gf = &g_array_index(guestfd_array, GuestFD, i);
if (gf->type == GuestFDUnused) {
@@ -168,7 +169,7 @@ static GuestFD *do_get_guestfd(int guestfd)
return NULL;
}
- if (guestfd < 0 || guestfd >= guestfd_array->len) {
+ if (guestfd <= 0 || guestfd >= guestfd_array->len) {
return NULL;
}