Subject: Re: [PATCH V2 3/3] drivers/char/tpm: Add securityfs support for event log

From: Michael Ellerman <[email-masked]>
Date: Fri, 10 Aug 2012 17:23:21 +1000

On Thu, 2012-08-09 at 18:13 -0500, Ashley Lai wrote:
> This patch retrieves the event log data from the device tree
> during file open. The event log data will then displayed through
> securityfs.

Hi Ashley,

Comments inline ..

> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> index 547509d..b53da57 100644
> --- a/drivers/char/tpm/Makefile
> +++ b/drivers/char/tpm/Makefile
> @@ -2,9 +2,15 @@
>  # Makefile for the kernel tpm device drivers.
>  #
>  obj-$(CONFIG_TCG_TPM) += tpm.o
> +obj-$(CONFIG_TCG_TPM) += tpm_bios.o
>  ifdef CONFIG_ACPI
> -	obj-$(CONFIG_TCG_TPM) += tpm_bios.o
>  	tpm_bios-objs += tpm_eventlog.o tpm_acpi.o
> +else
> +ifdef CONFIG_TCG_IBMVTPM
> +	tpm_bios-objs += tpm_eventlog.o tpm_of.o
> +else
> +	tpm_bios-objs += tpm_eventlog.o tpm_noeventlog.o

What does it mean to build tpm_eventlog and tpm_noeventlog ?

> diff --git a/drivers/char/tpm/tpm_eventlog.h b/drivers/char/tpm/tpm_eventlog.h
> index 8e23ccd..21ac6af 100644
> --- a/drivers/char/tpm/tpm_eventlog.h
> +++ b/drivers/char/tpm/tpm_eventlog.h
> @@ -68,4 +68,18 @@ enum tcpa_pc_event_ids {
>  };
>  
>  int read_log(struct tpm_bios_log *log);
> +
> +extern struct dentry **tpm_bios_log_setup(char *);
> +extern void tpm_bios_log_teardown(struct dentry **);
> +
> +#ifdef CONFIG_PPC64
> +#define TPM_NO_EVENT_LOG !of_find_node_by_name(NULL, "ibm,vtpm")
> +#else
> +#ifdef CONFIG_ACPI
> +#define TPM_NO_EVENT_LOG 0
> +#else
> +#define TPM_NO_EVENT_LOG 1
> +#endif
> +#endif

This should be a static inline, with the ifdefs inside.

How often is this called? of_find_node_by_name() is not particularly
efficient. It might be better to search once and save a flag indicating
whether you found it.

Also you must call of_node_put() on the result of
of_find_node_by_name(), so at the least you must do:

struct device_node *np;
np = of_find_node_by_name(NULL, "ibm,vtpm");
of_node_put(np);
return (np != NULL);

>  #endif
> diff --git a/drivers/char/tpm/tpm_noeventlog.c b/drivers/char/tpm/tpm_noeventlog.c
> new file mode 100644
> index 0000000..f30a2bf
> --- /dev/null
> +++ b/drivers/char/tpm/tpm_noeventlog.c
> @@ -0,0 +1,21 @@
> +/*
> + * Copyright (C) 2012 IBM Corporation
                ^^
Don't use (C)

> + *
> + * Author: Ashley Lai <[email-masked]>
> + *
> + * Maintained by: <[email-masked]>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + *
> + */
> +
> +#include <linux/slab.h>
> +#include "tpm_eventlog.h"
> +
> +int read_log(struct tpm_bios_log *log)
> +{
> +	return -EINVAL;
> +}

Wouldn't it be simpler to put this in a header with the appropriate
ifdefs, and then you'd need less logic in the Makefile?

> diff --git a/drivers/char/tpm/tpm_of.c b/drivers/char/tpm/tpm_of.c
> new file mode 100644
> index 0000000..6d44adb
> --- /dev/null
> +++ b/drivers/char/tpm/tpm_of.c
> @@ -0,0 +1,68 @@
> +/*
> + * Copyright 2012 IBM Corporation
> + *
> + * Author: Ashley Lai <[email-masked]>
> + *
> + * Maintained by: <[email-masked]>
> + *
> + * Read the event log created by the firmware on PPC64
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + *
> + */
> +
> +#include <linux/slab.h>
> +#include <linux/of.h>
> +
> +#include "tpm.h"
> +#include "tpm_eventlog.h"
> +
> +int read_log(struct tpm_bios_log *log)
> +{
> +	struct device_node *np;
> +	const u32 *sizep;
> +	const __be64 *basep;
> +
> +	if (log->bios_event_log != NULL) {
> +		pr_err("%s: ERROR - Eventlog already initialized\n", __func__);
> +		return -EFAULT;
> +	}
> +
> +	np = of_find_node_by_name(NULL, "ibm,vtpm");
> +	if (!np) {
> +		pr_err("%s: ERROR - IBMVTPM not supported\n", __func__);
> +		return -ENODEV;
> +	}

All your return paths below here must call of_node_put(np).

> +	sizep = of_get_property(np, "linux,sml-size", NULL);
> +	if (sizep == NULL) {
> +		pr_err("%s: ERROR - SML size not found\n", __func__);
> +		return -EIO;
> +	}
> +	if (*sizep == 0) {
> +		pr_err("%s: ERROR - event log area empty\n", __func__);
> +		return -EIO;
> +	}
> +
> +	basep = of_get_property(np, "linux,sml-base", NULL);
> +	if (basep == NULL) {
> +		pr_err(KERN_ERR "%s: ERROR - SML not found\n", __func__);
> +		return -EIO;
> +	}
> +
> +	log->bios_event_log = kmalloc(*sizep, GFP_KERNEL);
> +	if (!log->bios_event_log) {
> +		pr_err("%s: ERROR - Not enough memory for BIOS measurements\n",
> +		       __func__);
> +		return -ENOMEM;
> +	}
> +
> +	log->bios_event_log_end = log->bios_event_log + *sizep;
> +
> +	memcpy(log->bios_event_log, __va(be64_to_cpup(basep)), *sizep);
> +
> +	return 0;
> +}

cheers