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Message-ID: <886145d3-a9f2-41f3-a754-253decdb1b4f@oracle.com>
Date: Mon, 31 Mar 2025 11:29:08 -0700
From: ross.philipson@...cle.com
To: "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
x86@...nel.org, linux-integrity@...r.kernel.org,
linux-doc@...r.kernel.org, linux-crypto@...r.kernel.org,
kexec@...ts.infradead.org, linux-efi@...r.kernel.org,
iommu@...ts.linux.dev
Cc: dpsmith@...rtussolutions.com, tglx@...utronix.de, mingo@...hat.com,
bp@...en8.de, dave.hansen@...ux.intel.com, ardb@...nel.org,
mjg59@...f.ucam.org, James.Bottomley@...senpartnership.com,
peterhuewe@....de, jarkko@...nel.org, jgg@...pe.ca,
luto@...capital.net, nivedita@...m.mit.edu,
herbert@...dor.apana.org.au, davem@...emloft.net, corbet@....net,
ebiederm@...ssion.com, dwmw2@...radead.org, baolu.lu@...ux.intel.com,
kanth.ghatraju@...cle.com, andrew.cooper3@...rix.com,
trenchboot-devel@...glegroups.com
Subject: Re: [PATCH v13 19/19] x86/efi: EFI stub DRTM launch support for
Secure Launch
On 3/29/25 6:13 PM, H. Peter Anvin wrote:
> On March 28, 2025 4:08:14 PM PDT, Ross Philipson <ross.philipson@...cle.com> wrote:
>> This support allows the DRTM launch to be initiated after an EFI stub
>> launch of the Linux kernel is done. This is accomplished by providing
>> a handler to jump to when a Secure Launch is in progress. This has to be
>> called after the EFI stub does Exit Boot Services.
>>
>> Signed-off-by: Ross Philipson <ross.philipson@...cle.com>
>> Reviewed-by: Ard Biesheuvel <ardb@...nel.org>
>> ---
>> drivers/firmware/efi/libstub/efistub.h | 8 +++
>> drivers/firmware/efi/libstub/x86-stub.c | 94 +++++++++++++++++++++++++
>> 2 files changed, 102 insertions(+)
>>
>> diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
>> index d96d4494070d..bbbc4b327ce1 100644
>> --- a/drivers/firmware/efi/libstub/efistub.h
>> +++ b/drivers/firmware/efi/libstub/efistub.h
>> @@ -135,6 +135,14 @@ void efi_set_u64_split(u64 data, u32 *lo, u32 *hi)
>> *hi = upper_32_bits(data);
>> }
>>
>> +static inline
>> +void efi_set_u64_form(u32 lo, u32 hi, u64 *data)
>> +{
>> + u64 upper = hi;
>> +
>> + *data = lo | upper << 32;
>> +}
>> +
>> /*
>> * Allocation types for calls to boottime->allocate_pages.
>> */
>> diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
>> index 863910e9eefc..033133e7d953 100644
>> --- a/drivers/firmware/efi/libstub/x86-stub.c
>> +++ b/drivers/firmware/efi/libstub/x86-stub.c
>> @@ -9,6 +9,8 @@
>> #include <linux/efi.h>
>> #include <linux/pci.h>
>> #include <linux/stddef.h>
>> +#include <linux/slr_table.h>
>> +#include <linux/slaunch.h>
>>
>> #include <asm/efi.h>
>> #include <asm/e820/types.h>
>> @@ -798,6 +800,93 @@ static efi_status_t efi_decompress_kernel(unsigned long *kernel_entry)
>> return efi_adjust_memory_range_protection(addr, kernel_text_size);
>> }
>>
>> +#if (IS_ENABLED(CONFIG_SECURE_LAUNCH))
>> +static bool efi_secure_launch_update_boot_params(struct slr_table *slrt,
>> + struct boot_params *boot_params)
>> +{
>> + struct slr_entry_intel_info *txt_info;
>> + struct slr_entry_policy *policy;
>> + bool updated = false;
>> + int i;
>> +
>> + txt_info = slr_next_entry_by_tag(slrt, NULL, SLR_ENTRY_INTEL_INFO);
>> + if (!txt_info)
>> + return false;
>> +
>> + txt_info->boot_params_addr = (u64)boot_params;
>> +
>> + policy = slr_next_entry_by_tag(slrt, NULL, SLR_ENTRY_ENTRY_POLICY);
>> + if (!policy)
>> + return false;
>> +
>> + for (i = 0; i < policy->nr_entries; i++) {
>> + if (policy->policy_entries[i].entity_type == SLR_ET_BOOT_PARAMS) {
>> + policy->policy_entries[i].entity = (u64)boot_params;
>> + updated = true;
>> + break;
>> + }
>> + }
>> +
>> + /*
>> + * If this is a PE entry into EFI stub the mocked up boot params will
>> + * be missing some of the setup header data needed for the second stage
>> + * of the Secure Launch boot.
>> + */
>> + if (image) {
>> + struct setup_header *hdr = (struct setup_header *)((u8 *)image->image_base +
>> + offsetof(struct boot_params, hdr));
>> + u64 cmdline_ptr;
>> +
>> + boot_params->hdr.setup_sects = hdr->setup_sects;
>> + boot_params->hdr.syssize = hdr->syssize;
>> + boot_params->hdr.version = hdr->version;
>> + boot_params->hdr.loadflags = hdr->loadflags;
>> + boot_params->hdr.kernel_alignment = hdr->kernel_alignment;
>> + boot_params->hdr.min_alignment = hdr->min_alignment;
>> + boot_params->hdr.xloadflags = hdr->xloadflags;
>> + boot_params->hdr.init_size = hdr->init_size;
>> + boot_params->hdr.kernel_info_offset = hdr->kernel_info_offset;
>> + efi_set_u64_form(boot_params->hdr.cmd_line_ptr, boot_params->ext_cmd_line_ptr,
>> + &cmdline_ptr);
>> + boot_params->hdr.cmdline_size = strlen((const char *)cmdline_ptr);
>> + }
>> +
>> + return updated;
>> +}
>> +
>> +static void efi_secure_launch(struct boot_params *boot_params)
>> +{
>> + struct slr_entry_dl_info *dlinfo;
>> + efi_guid_t guid = SLR_TABLE_GUID;
>> + dl_handler_func handler_callback;
>> + struct slr_table *slrt;
>> +
>> + /*
>> + * The presence of this table indicated a Secure Launch
>> + * is being requested.
>> + */
>> + slrt = (struct slr_table *)get_efi_config_table(guid);
>> + if (!slrt || slrt->magic != SLR_TABLE_MAGIC)
>> + return;
>> +
>> + /*
>> + * Since the EFI stub library creates its own boot_params on entry, the
>> + * SLRT and TXT heap have to be updated with this version.
>> + */
>> + if (!efi_secure_launch_update_boot_params(slrt, boot_params))
>> + return;
>> +
>> + /* Jump through DL stub to initiate Secure Launch */
>> + dlinfo = slr_next_entry_by_tag(slrt, NULL, SLR_ENTRY_DL_INFO);
>> +
>> + handler_callback = (dl_handler_func)dlinfo->dl_handler;
>> +
>> + handler_callback(&dlinfo->bl_context);
>> +
>> + unreachable();
>> +}
>> +#endif
>> +
>> static void __noreturn enter_kernel(unsigned long kernel_addr,
>> struct boot_params *boot_params)
>> {
>> @@ -925,6 +1014,11 @@ void __noreturn efi_stub_entry(efi_handle_t handle,
>> goto fail;
>> }
>>
>> +#if (IS_ENABLED(CONFIG_SECURE_LAUNCH))
>> + /* If a Secure Launch is in progress, this never returns */
>> + efi_secure_launch(boot_params);
>> +#endif
>> +
>> /*
>> * Call the SEV init code while still running with the firmware's
>> * GDT/IDT, so #VC exceptions will be handled by EFI.
>
> efi_set_u64_form()?
>
> What the heck is that? If it actually involves two u32 packed into a 64 field, why not simply do two stores?
>
Well the story is this. The EFI maintainers asked me to use the
efi_set_u64_split() type functions (this one splits a u64 into 2 u32). I
went to look and there was no function that did the opposite action so I
added it. The original function was called efi_set_u64_split() so
efi_set_u64_form() was what I came up with. I can name it anything that
is desired.
Thanks
Ross
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