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e8dc73c9f9
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Link: https://lore.kernel.org/r/20200226212612.GA4663@embeddedor
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
52 lines
1.7 KiB
C
52 lines
1.7 KiB
C
/******************************************************************************
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* tpmif.h
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*
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* TPM I/O interface for Xen guest OSes, v2
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*
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* This file is in the public domain.
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*
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*/
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#ifndef __XEN_PUBLIC_IO_TPMIF_H__
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#define __XEN_PUBLIC_IO_TPMIF_H__
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/*
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* Xenbus state machine
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*
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* Device open:
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* 1. Both ends start in XenbusStateInitialising
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* 2. Backend transitions to InitWait (frontend does not wait on this step)
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* 3. Frontend populates ring-ref, event-channel, feature-protocol-v2
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* 4. Frontend transitions to Initialised
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* 5. Backend maps grant and event channel, verifies feature-protocol-v2
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* 6. Backend transitions to Connected
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* 7. Frontend verifies feature-protocol-v2, transitions to Connected
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*
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* Device close:
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* 1. State is changed to XenbusStateClosing
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* 2. Frontend transitions to Closed
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* 3. Backend unmaps grant and event, changes state to InitWait
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*/
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enum vtpm_shared_page_state {
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VTPM_STATE_IDLE, /* no contents / vTPM idle / cancel complete */
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VTPM_STATE_SUBMIT, /* request ready / vTPM working */
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VTPM_STATE_FINISH, /* response ready / vTPM idle */
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VTPM_STATE_CANCEL, /* cancel requested / vTPM working */
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};
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/* The backend should only change state to IDLE or FINISH, while the
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* frontend should only change to SUBMIT or CANCEL. */
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struct vtpm_shared_page {
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uint32_t length; /* request/response length in bytes */
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uint8_t state; /* enum vtpm_shared_page_state */
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uint8_t locality; /* for the current request */
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uint8_t pad;
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uint8_t nr_extra_pages; /* extra pages for long packets; may be zero */
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uint32_t extra_pages[]; /* grant IDs; length in nr_extra_pages */
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};
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#endif
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