tpm: fix alignment issues

The new tpm-crb-test fails on sparc host:

TEST: tests/tpm-crb-test... (pid=230409)
  /i386/tpm-crb/test:
Broken pipe
FAIL
GTester: last random seed: R02S29cea50247fe1efa59ee885a26d51a85
(pid=230423)
FAIL: tests/tpm-crb-test

and generates a new clang sanitizer runtime warning:

/home/petmay01/linaro/qemu-for-merges/hw/tpm/tpm_util.h:36:24: runtime
error: load of misaligned address 0x7fdc24c00002 for type 'const
uint32_t' (aka 'const unsigned int'), which requires 4 byte alignment
0x7fdc24c00002: note: pointer points here
<memory cannot be printed>

The sparc architecture does not allow misaligned loads and will
segfault if you try them.  For example, this function:

static inline uint32_t tpm_cmd_get_size(const void *b)
{
    return be32_to_cpu(*(const uint32_t *)(b + 2));
}

Should read,
    return ldl_be_p(b + 2);

As a general rule you can't take an arbitrary pointer into a byte
buffer and try to interpret it as a structure or a pointer to a
larger-than-bytesize-data simply by casting the pointer.

Use this clean up as an opportunity to remove unnecessary temporary
buffers and casts.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>

1 files changed, 6 insertions, 8 deletions

diff --git a/hw/tpm/tpm_emulator.c b/hw/tpm/tpm_emulator.c
index 532d3e3c52..81bf7d1b01 100644
--- a/hw/tpm/tpm_emulator.c
+++ b/hw/tpm/tpm_emulator.c
@@ -120,7 +120,6 @@ static int tpm_emulator_unix_tx_bufs(TPMEmulator *tpm_emu,
 {
     ssize_t ret;
     bool is_selftest = false;
-    const struct tpm_resp_hdr *hdr = NULL;
 
     if (selftest_done) {
         *selftest_done = false;
@@ -132,22 +131,21 @@ static int tpm_emulator_unix_tx_bufs(TPMEmulator *tpm_emu,
         return -1;
     }
 
-    ret = qio_channel_read_all(tpm_emu->data_ioc, (char *)out, sizeof(*hdr),
-                               err);
+    ret = qio_channel_read_all(tpm_emu->data_ioc, (char *)out,
+              sizeof(struct tpm_resp_hdr), err);
     if (ret != 0) {
         return -1;
     }
 
-    hdr = (struct tpm_resp_hdr *)out;
-    out += sizeof(*hdr);
-    ret = qio_channel_read_all(tpm_emu->data_ioc, (char *)out,
-                               be32_to_cpu(hdr->len) - sizeof(*hdr) , err);
+    ret = qio_channel_read_all(tpm_emu->data_ioc,
+              (char *)out + sizeof(struct tpm_resp_hdr),
+              tpm_cmd_get_size(out) - sizeof(struct tpm_resp_hdr), err);
     if (ret != 0) {
         return -1;
     }
 
     if (is_selftest) {
-        *selftest_done = (be32_to_cpu(hdr->errcode) == 0);
+        *selftest_done = tpm_cmd_get_errcode(out) == 0;
     }
 
     return 0;