Re: [PATCH v2 09/16] PM / hibernate: Reserve hibernation key and erase footprints

Matt Fleming
2015-08-21T13:27:58Z

On Tue, 11 Aug, at 02:16:29PM, Lee, Chun-Yi wrote:
> Add handler to parse the setup data that carrying hibernation key, it
> reserves hibernation key by memblock then copies key to a allocated page
> in later initcall stage.
>
> And for erasing footprints, the codes in this patch remove setup
> data that carried hibernation key, and clean the memory space that
> reserved by memblock.
>
> Reviewed-by: Jiri Kosina <jkosina@suse.com>
> Tested-by: Jiri Kosina <jkosina@suse.com>
> Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
> ---
> arch/x86/include/asm/suspend.h | 4 +++
> arch/x86/kernel/setup.c | 21 ++++++++++-
> arch/x86/power/Makefile | 1 +
> arch/x86/power/hibernate_keys.c | 78 +++++++++++++++++++++++++++++++++++++++++
> kernel/power/power.h | 5 +++
> 5 files changed, 108 insertions(+), 1 deletion(-)
> create mode 100644 arch/x86/power/hibernate_keys.c

[...]

> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 80f874b..b345359 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -112,6 +112,8 @@
> #include <asm/alternative.h>
> #include <asm/prom.h>
>
> +#include <asm/suspend.h>
> +
> /*
> * max_low_pfn_mapped: highest direct mapped pfn under 4GB
> * max_pfn_mapped: highest direct mapped pfn over 4GB
> @@ -425,10 +427,22 @@ static void __init reserve_initrd(void)
> }
> #endif /* CONFIG_BLK_DEV_INITRD */
>
> +static void __init remove_setup_data(u64 pa_prev, u64 pa_next)
> +{
> + struct setup_data *data;
> +
> + if (pa_prev) {
> + data = early_memremap(pa_prev, sizeof(*data));
> + data->next = pa_next;
> + early_iounmap(data, sizeof(*data));

This should be early_memunmap for consistency().

> diff --git a/arch/x86/power/hibernate_keys.c b/arch/x86/power/hibernate_keys.c
> new file mode 100644
> index 0000000..357dc0e
> --- /dev/null
> +++ b/arch/x86/power/hibernate_keys.c
> @@ -0,0 +1,78 @@
> +/* Hibernation keys handler
> + *
> + * Copyright (C) 2015 Lee, Chun-Yi <jlee@suse.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public Licence
> + * as published by the Free Software Foundation; either version
> + * 2 of the Licence, or (at your option) any later version.
> + */
> +
> +#include <linux/bootmem.h>
> +#include <linux/memblock.h>
> +#include <linux/suspend.h>
> +#include <asm/suspend.h>
> +
> +/* physical address of hibernation keys from boot params */
> +static u64 keys_phys_addr;
> +
> +/* A page used to keep hibernation keys */
> +static struct hibernation_keys *hibernation_keys;
> +
> +void __init parse_hibernation_keys(u64 phys_addr, u32 data_len)
> +{
> + struct setup_data *hibernation_setup_data;
> +
> + /* Reserve keys memory, will copy and erase in init_hibernation_keys() */
> + keys_phys_addr = phys_addr + sizeof(struct setup_data);
> + memblock_reserve(keys_phys_addr, sizeof(struct hibernation_keys));
> +
> + /* clear hibernation_data */
> + hibernation_setup_data = early_memremap(phys_addr, data_len);
> + if (!hibernation_setup_data)
> + return;
> +
> + memset(hibernation_setup_data, 0, sizeof(struct setup_data));

Why is this necessary? You're only clearing the struct setup_data
fields and you unlinked this setup_data entry in remove_setup_data()
anyway.

> + early_memunmap(hibernation_setup_data, data_len);
> +}
> +
> +int get_hibernation_key(u8 **hkey)
> +{
> + if (!hibernation_keys)
> + return -ENODEV;
> +
> + if (!hibernation_keys->hkey_status)
> + *hkey = hibernation_keys->hibernation_key;
> +
> + return hibernation_keys->hkey_status;
> +}

For global functions like this it's usually much preferred to prefix
the name with the subsystem, i.e. hibernation_get_key().

> +static int __init init_hibernation_keys(void)
> +{
> + struct hibernation_keys *keys;
> + int ret = 0;
> +
> + if (!keys_phys_addr)
> + return -ENODEV;
> +
> + keys = early_memremap(keys_phys_addr, sizeof(struct hibernation_keys));
> +
> + /* Copy hibernation keys to a allocated page */
> + hibernation_keys = (struct hibernation_keys *)get_zeroed_page(GFP_KERNEL);
> + if (hibernation_keys) {
> + *hibernation_keys = *keys;
> + } else {
> + pr_err("PM: Allocate hibernation keys page failed\n");
> + ret = -ENOMEM;
> + }

It seems overkill to allocate an entire page for 28 bytes of data.

--
Matt Fleming, Intel Open Source Technology Center