Re: [PATCH v3] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel

Dave Young
2019-04-04T07:32:46Z

Hi Junichi,

While we are still debuggin the bug I reproduced, but for this patch
I have still some comments inline.

BTW, it would be good to start a new thread when you send V4 :)

On 04/02/19 at 10:25am, Junichi Nomura wrote:
> Commit 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in
> boot_params") broke kexec boot on EFI systems. efi_get_rsdp_addr()
> in the early parsing code tries to search RSDP from EFI table but
> that will crash because the table address is virtual when the kernel
> was booted by kexec.
>
> In the case of kexec, physical address of EFI tables is provided
> via efi_setup_data in boot_params, which is set up by kexec(1).
>
> Factor out the table parsing code and use different pointers depending
> on whether the kernel is booted by kexec or not.
>
> Fixes: 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in boot_params")
> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
> Acked-by: Baoquan He <bhe@redhat.com>
> Tested-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Dave Young <dyoung@redhat.com>
>
> --
> v2: Added comments above __efi_get_rsdp_addr() and kexec_get_rsdp_addr()
>
> v3: Properly ifdef out 64bit-only kexec code to avoid 32bit build warnings
>
> diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
> index 0ef4ad5..d9f9abd 100644
> --- a/arch/x86/boot/compressed/acpi.c
> +++ b/arch/x86/boot/compressed/acpi.c
> @@ -44,17 +44,114 @@ static acpi_physical_address get_acpi_rsdp(void)
> return addr;
> }
>
> -/* Search EFI system tables for RSDP. */
> -static acpi_physical_address efi_get_rsdp_addr(void)
> +#if defined(CONFIG_EFI) && defined(CONFIG_X86_64)
> +static unsigned long efi_get_kexec_setup_data_addr(void)
> +{
> + struct setup_data *data;
> + u64 pa_data;
> +
> + pa_data = boot_params->hdr.setup_data;
> + while (pa_data) {
> + data = (struct setup_data *) pa_data;
> + if (data->type == SETUP_EFI)
> + return pa_data + sizeof(struct setup_data);
> + pa_data = data->next;
> + }
> + return 0;
> +}
> +#endif
> +
> +#ifdef CONFIG_EFI
> +/*
> + * Search EFI system tables for RSDP. If both ACPI_20_TABLE_GUID and
> + * ACPI_TABLE_GUID are found, take the former, which has more features.
> + */
> +static acpi_physical_address
> +__efi_get_rsdp_addr(unsigned long config_tables, unsigned int nr_tables,
> + bool efi_64)
> {
> acpi_physical_address rsdp_addr = 0;
> + int i;
>
> + /* Get EFI tables from systab. */
> + for (i = 0; i < nr_tables; i++) {
> + acpi_physical_address table;
> + efi_guid_t guid;
> +
> + if (efi_64) {
> + efi_config_table_64_t *tbl = (efi_config_table_64_t *) config_tables + i;
> +
> + guid = tbl->guid;
> + table = tbl->table;
> +
> + if (!IS_ENABLED(CONFIG_X86_64) && table >> 32) {
> + debug_putstr("Error getting RSDP address: EFI config table located above 4GB.\n");
> + return 0;
> + }
> + } else {
> + efi_config_table_32_t *tbl = (efi_config_table_32_t *) config_tables + i;
> +
> + guid = tbl->guid;
> + table = tbl->table;
> + }
> +
> + if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
> + rsdp_addr = table;
> + else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
> + return table;
> + }
> +
> + return rsdp_addr;
> +}
> +#endif
> +
> +/*
> + * EFI/kexec support is only added for 64bit. So we don't have to
> + * care 32bit case.
> + */
> +static acpi_physical_address kexec_get_rsdp_addr(void)
> +{
> +#if defined(CONFIG_EFI) && defined(CONFIG_X86_64)
> + efi_system_table_64_t *systab;
> + struct efi_setup_data *esd;
> + struct efi_info *ei;
> + char *sig;
> +
> + esd = (struct efi_setup_data *) efi_get_kexec_setup_data_addr();
> + if (!esd)
> + return 0;
> +
> + if (!esd->tables) {
> + debug_putstr("Wrong kexec SETUP_EFI data.\n");
> + return 0;
> + }
> +
> + ei = &boot_params->efi_info;
> + sig = (char *)&ei->efi_loader_signature;
> + if (strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
> + debug_putstr("Wrong kexec EFI loader signature.\n");
> + return 0;
> + }
> +
> + /* Get systab from boot params. */
> + systab = (efi_system_table_64_t *) (ei->efi_systab | ((__u64)ei->efi_systab_hi << 32));
> + if (!systab)
> + error("EFI system table not found in kexec boot_params.");

Instead of hang the system, return 0 should be better

> +
> + return __efi_get_rsdp_addr((unsigned long) esd->tables,
> + systab->nr_tables, true);
> +#else
> + return 0;
> +#endif
> +}
> +
> +static acpi_physical_address efi_get_rsdp_addr(void)
> +{
> #ifdef CONFIG_EFI
> - unsigned long systab, systab_tables, config_tables;
> + unsigned long systab, config_tables;
> unsigned int nr_tables;
> struct efi_info *ei;
> bool efi_64;
> - int size, i;
> char *sig;
>
> ei = &boot_params->efi_info;
> @@ -88,49 +185,20 @@ static acpi_physical_address efi_get_rsdp_addr(void)
>
> config_tables = stbl->tables;
> nr_tables = stbl->nr_tables;
> - size = sizeof(efi_config_table_64_t);
> } else {
> efi_system_table_32_t *stbl = (efi_system_table_32_t *)systab;
>
> config_tables = stbl->tables;
> nr_tables = stbl->nr_tables;
> - size = sizeof(efi_config_table_32_t);
> }
>
> if (!config_tables)
> error("EFI config tables not found.");
>
> - /* Get EFI tables from systab. */
> - for (i = 0; i < nr_tables; i++) {
> - acpi_physical_address table;
> - efi_guid_t guid;
> -
> - config_tables += size;
> -
> - if (efi_64) {
> - efi_config_table_64_t *tbl = (efi_config_table_64_t *)config_tables;
> -
> - guid = tbl->guid;
> - table = tbl->table;
> -
> - if (!IS_ENABLED(CONFIG_X86_64) && table >> 32) {
> - debug_putstr("Error getting RSDP address: EFI config table located above 4GB.\n");
> - return 0;
> - }
> - } else {
> - efi_config_table_32_t *tbl = (efi_config_table_32_t *)config_tables;
> -
> - guid = tbl->guid;
> - table = tbl->table;
> - }
> -
> - if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
> - rsdp_addr = table;
> - else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
> - return table;
> - }
> + return __efi_get_rsdp_addr(config_tables, nr_tables, efi_64);
> +#else
> + return 0;
> #endif
> - return rsdp_addr;
> }
>
> static u8 compute_checksum(u8 *buffer, u32 length)
> @@ -221,6 +289,9 @@ acpi_physical_address get_rsdp_addr(void)
> pa = boot_params->acpi_rsdp_addr;
>
> if (!pa)
> + pa = kexec_get_rsdp_addr();
> +
> + if (!pa)
> pa = efi_get_rsdp_addr();

In case kexec_get_rsdp_addr failed, above code will try efi_get.. again,
but that will also fail for same issue this patch is fixing. In case
kexec we should avoid the efi_get_rsdp_addr.

>
> if (!pa)
>
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
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Thanks
Dave