hw/char/riscv_htif: Fix the console syscall on big endian hosts

Values that have been read via cpu_physical_memory_read() from the
guest's memory have to be swapped in case the host endianess differs
from the guest.

Fixes: a6e13e3 ("riscv_htif: Support console output via proxy syscall")
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-Id: <20230721094720.902454-3-thuth@redhat.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
(cherry picked from commit 058096f)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
(Mjt: context fix in hw/char/riscv_htif.c for #include)

hw/char/riscv_htif.c

@@ -29,6 +29,7 @@
 #include "chardev/char-fe.h"
 #include "qemu/timer.h"
 #include "qemu/error-report.h"
+#include "exec/tswap.h"
 
 #define RISCV_DEBUG_HTIF 0
 #define HTIF_DEBUG(fmt, ...)                                                   \
@@ -167,11 +168,11 @@ static void htif_handle_tohost_write(HTIFState *s, uint64_t val_written)
             } else {
                 uint64_t syscall[8];
                 cpu_physical_memory_read(payload, syscall, sizeof(syscall));
-                if (syscall[0] == PK_SYS_WRITE &&
-                    syscall[1] == HTIF_DEV_CONSOLE &&
-                    syscall[3] == HTIF_CONSOLE_CMD_PUTC) {
+                if (tswap64(syscall[0]) == PK_SYS_WRITE &&
+                    tswap64(syscall[1]) == HTIF_DEV_CONSOLE &&
+                    tswap64(syscall[3]) == HTIF_CONSOLE_CMD_PUTC) {
                     uint8_t ch;
-                    cpu_physical_memory_read(syscall[2], &ch, 1);
+                    cpu_physical_memory_read(tswap64(syscall[2]), &ch, 1);
                     qemu_chr_fe_write(&s->chr, &ch, 1);
                     resp = 0x100 | (uint8_t)payload;
                 } else {