From: Ard Biesheuvel <ardb@kernel.org>
To: linux-efi@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Michael Roth <michael.roth@amd.com>
Subject: [PATCH v2 03/16] x86/compressed: efi-mixed: move bootargs parsing out of 32-bit startup code
Date: Wed, 21 Sep 2022 16:54:09 +0200 [thread overview]
Message-ID: <20220921145422.437618-4-ardb@kernel.org> (raw)
In-Reply-To: <20220921145422.437618-1-ardb@kernel.org>
Move the logic that chooses between the different EFI entrypoints out of
the 32-bit boot path, and into a 64-bit helper that can perform the same
task much more cleanly. While at it, document the mixed mode boot flow
in a code comment.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/boot/compressed/efi_mixed.S | 43 ++++++++++++++++++++
arch/x86/boot/compressed/head_64.S | 24 ++---------
2 files changed, 47 insertions(+), 20 deletions(-)
diff --git a/arch/x86/boot/compressed/efi_mixed.S b/arch/x86/boot/compressed/efi_mixed.S
index 67e7edcdfea8..77e77c3ea393 100644
--- a/arch/x86/boot/compressed/efi_mixed.S
+++ b/arch/x86/boot/compressed/efi_mixed.S
@@ -22,6 +22,49 @@
.code64
.text
+/*
+ * When booting in 64-bit mode on 32-bit EFI firmware, startup_64_mixedmode()
+ * is the first thing that runs after switching to long mode. Depending on
+ * whether the EFI handover protocol or the compat entry point was used to
+ * enter the kernel, it will either branch to the 64-bit EFI handover
+ * entrypoint at offset 0x390 in the image, or to the 64-bit EFI PE/COFF
+ * entrypoint efi_pe_entry(). In the former case, the bootloader must provide a
+ * struct bootparams pointer as the third argument, so the presence of such a
+ * pointer is used to disambiguate.
+ *
+ * +--------------+
+ * +------------------+ +------------+ +------>| efi_pe_entry |
+ * | efi32_pe_entry |---->| | | +-----------+--+
+ * +------------------+ | | +------+---------------+ |
+ * | startup_32 |---->| startup_64_mixedmode | |
+ * +------------------+ | | +------+---------------+ V
+ * | efi32_stub_entry |---->| | | +------------------+
+ * +------------------+ +------------+ +---->| efi64_stub_entry |
+ * +-------------+----+
+ * +------------+ +----------+ |
+ * | startup_64 |<----| efi_main |<--------------+
+ * +------------+ +----------+
+ */
+SYM_FUNC_START(startup_64_mixedmode)
+ lea efi32_boot_args(%rip), %rdx
+ mov 0(%rdx), %edi
+ mov 4(%rdx), %esi
+ mov 8(%rdx), %edx // saved bootparams pointer
+ test %edx, %edx
+ jnz efi64_stub_entry
+ /*
+ * efi_pe_entry uses MS calling convention, which requires 32 bytes of
+ * shadow space on the stack even if all arguments are passed in
+ * registers. We also need an additional 8 bytes for the space that
+ * would be occupied by the return address, and this also results in
+ * the correct stack alignment for entry.
+ */
+ sub $40, %rsp
+ mov %rdi, %rcx // MS calling convention
+ mov %rsi, %rdx
+ jmp efi_pe_entry
+SYM_FUNC_END(startup_64_mixedmode)
+
SYM_FUNC_START(__efi64_thunk)
push %rbp
push %rbx
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 1ba2fc2357e6..b51f0e107c2e 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -261,25 +261,9 @@ SYM_FUNC_START(startup_32)
*/
leal rva(startup_64)(%ebp), %eax
#ifdef CONFIG_EFI_MIXED
- movl rva(efi32_boot_args)(%ebp), %edi
- testl %edi, %edi
- jz 1f
- leal rva(efi64_stub_entry)(%ebp), %eax
- movl rva(efi32_boot_args+4)(%ebp), %esi
- movl rva(efi32_boot_args+8)(%ebp), %edx // saved bootparams pointer
- testl %edx, %edx
- jnz 1f
- /*
- * efi_pe_entry uses MS calling convention, which requires 32 bytes of
- * shadow space on the stack even if all arguments are passed in
- * registers. We also need an additional 8 bytes for the space that
- * would be occupied by the return address, and this also results in
- * the correct stack alignment for entry.
- */
- subl $40, %esp
- leal rva(efi_pe_entry)(%ebp), %eax
- movl %edi, %ecx // MS calling convention
- movl %esi, %edx
+ cmpb $1, rva(efi_is64)(%ebp)
+ je 1f
+ leal rva(startup_64_mixedmode)(%ebp), %eax
1:
#endif
/* Check if the C-bit position is correct when SEV is active */
@@ -766,7 +750,7 @@ SYM_DATA_END_LABEL(boot32_idt, SYM_L_GLOBAL, boot32_idt_end)
SYM_DATA(image_offset, .long 0)
#endif
#ifdef CONFIG_EFI_MIXED
-SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0, 0)
+SYM_DATA(efi32_boot_args, .long 0, 0, 0)
SYM_DATA(efi_is64, .byte 1)
#define ST32_boottime 60 // offsetof(efi_system_table_32_t, boottime)
--
2.35.1
next prev parent reply other threads:[~2022-09-21 14:54 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 14:54 [PATCH v2 00/16] x86: head_64.S spring cleaning Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 01/16] x86/compressed: efi-mixed: rename efi_thunk_64.S to efi-mixed.S Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 02/16] x86/compressed: efi-mixed: move 32-bit entrypoint code into .text section Ard Biesheuvel
2022-10-06 10:42 ` Borislav Petkov
2022-10-06 10:56 ` Ard Biesheuvel
2022-10-06 11:13 ` Borislav Petkov
2022-10-06 11:19 ` Ard Biesheuvel
2022-10-06 12:27 ` Ard Biesheuvel
2022-10-07 8:56 ` Borislav Petkov
2022-09-21 14:54 ` Ard Biesheuvel [this message]
2022-10-06 11:03 ` [PATCH v2 03/16] x86/compressed: efi-mixed: move bootargs parsing out of 32-bit startup code Borislav Petkov
2022-10-06 11:29 ` Ard Biesheuvel
2022-10-07 9:30 ` Borislav Petkov
2022-09-21 14:54 ` [PATCH v2 04/16] x86/compressed: efi-mixed: move efi32_pe_entry into .text section Ard Biesheuvel
2022-11-17 15:57 ` Borislav Petkov
2022-11-17 16:06 ` Ard Biesheuvel
2022-11-17 17:08 ` Borislav Petkov
2022-09-21 14:54 ` [PATCH v2 05/16] x86/compressed: efi-mixed: move efi32_entry out of head_64.S Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 06/16] x86/compressed: efi-mixed: move efi32_pe_entry() " Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 07/16] x86/compressed: efi: merge multiple definitions of image_offset into one Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 08/16] x86/compressed: efi-mixed: simplify IDT/GDT preserve/restore Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 09/16] x86/compressed: avoid touching ECX in startup32_set_idt_entry() Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 10/16] x86/compressed: pull global variable ref up into startup32_load_idt() Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 11/16] x86/compressed: move startup32_load_idt() into .text section Ard Biesheuvel
2022-11-18 16:44 ` Borislav Petkov
2022-09-21 14:54 ` [PATCH v2 12/16] x86/compressed: move startup32_load_idt() out of head_64.S Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 13/16] x86/compressed: move startup32_check_sev_cbit() into .text Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 14/16] x86/compressed: move startup32_check_sev_cbit() out of head_64.S Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 15/16] x86/compressed: adhere to calling convention in get_sev_encryption_bit() Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 16/16] x86/compressed: only build mem_encrypt.S if AMD_MEM_ENCRYPT=y Ard Biesheuvel
2022-11-18 18:26 ` [PATCH v2 00/16] x86: head_64.S spring cleaning Borislav Petkov
2022-11-18 23:31 ` Ard Biesheuvel
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