linux-kernel - Re: [PATCH -next] efi/tpm: fix a compilation warning

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Date:   Thu, 13 Jun 2019 10:55:33 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Qian Cai <cai@....pw>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>, mjg59@...gle.com,
        linux-efi <linux-efi@...r.kernel.org>, bsz@...ihalf.com,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] efi/tpm: fix a compilation warning

On Tue, Jun 11, 2019 at 3:59 PM Qian Cai <cai@....pw> wrote:
>
> The linux-next "tpm: Reserve the TPM final events table" [1] introduced
> a compilation warning,
>
> drivers/firmware/efi/tpm.c: In function 'efi_tpm_eventlog_init':
> drivers/firmware/efi/tpm.c:80:10: warning: passing argument 1 of
> 'tpm2_calc_event_log_size' makes pointer from integer without a cast
> [-Wint-conversion]
>   tbl_size = tpm2_calc_event_log_size(efi.tpm_final_log
> drivers/firmware/efi/tpm.c:19:43: note: expected 'void *' but argument
> is of type 'long unsigned int'
>
> Fix it by making a necessary cast for the argument 1 of
> tpm2_calc_event_log_size().
>
> [1] https://lore.kernel.org/linux-efi/20190520205501.177637-3-matthewgarrett@google.com/
>
> Signed-off-by: Qian Cai <cai@....pw>

I see the same build warning, but I don't think adding a cast here
solves the problem:

- efi.tpm_final_log is a physical address that gets passed into
  memremap() to return a pointer
- tpm2_calc_event_log_size() takes a pointer argument and
  dereferences it.

My best guess is that we should pass the output of memremap()
here rather than the input:

--- a/drivers/firmware/efi/tpm.c
+++ b/drivers/firmware/efi/tpm.c
@@ -75,7 +75,7 @@ int __init efi_tpm_eventlog_init(void)
                goto out;
        }

-       tbl_size = tpm2_calc_event_log_size(efi.tpm_final_log
+       tbl_size = tpm2_calc_event_log_size(final_tbl
                                            + sizeof(final_tbl->version)
                                            + sizeof(final_tbl->nr_events),
                                            final_tbl->nr_events,

No idea if that is actually what was intended here, but it makes
the code look more plausible.

        Arnd