diff options
| author | Ard Biesheuvel <ardb@kernel.org> | 2024-01-29 21:05:06 +0300 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2024-01-31 20:31:21 +0300 |
| commit | 15675706241887ed7fdad9e91f4bf977b9896d0f (patch) | |
| tree | ba0f437fa50ee66c9049e0f0fbb46a76d110b8b2 /arch/x86/kernel/head_64.S | |
| parent | 41bccc98fb7931d63d03f326a746ac4d429c1dd3 (diff) | |
| download | linux-15675706241887ed7fdad9e91f4bf977b9896d0f.tar.xz | |
x86/startup_64: Drop long return to initial_code pointer
Since
866b556efa12 ("x86/head/64: Install startup GDT")
the primary startup sequence sets the code segment register (CS) to
__KERNEL_CS before calling into the startup code shared between primary
and secondary boot.
This means a simple indirect call is sufficient here.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240129180502.4069817-24-ardb+git@google.com
Diffstat (limited to 'arch/x86/kernel/head_64.S')
| -rw-r--r-- | arch/x86/kernel/head_64.S | 35 |
1 files changed, 3 insertions, 32 deletions
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index d4918d03efb4..bfbac50dbe69 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -428,39 +428,10 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) movq %r15, %rdi .Ljump_to_C_code: - /* - * Jump to run C code and to be on a real kernel address. - * Since we are running on identity-mapped space we have to jump - * to the full 64bit address, this is only possible as indirect - * jump. In addition we need to ensure %cs is set so we make this - * a far return. - * - * Note: do not change to far jump indirect with 64bit offset. - * - * AMD does not support far jump indirect with 64bit offset. - * AMD64 Architecture Programmer's Manual, Volume 3: states only - * JMP FAR mem16:16 FF /5 Far jump indirect, - * with the target specified by a far pointer in memory. - * JMP FAR mem16:32 FF /5 Far jump indirect, - * with the target specified by a far pointer in memory. - * - * Intel64 does support 64bit offset. - * Software Developer Manual Vol 2: states: - * FF /5 JMP m16:16 Jump far, absolute indirect, - * address given in m16:16 - * FF /5 JMP m16:32 Jump far, absolute indirect, - * address given in m16:32. - * REX.W + FF /5 JMP m16:64 Jump far, absolute indirect, - * address given in m16:64. - */ - pushq $.Lafter_lret # put return address on stack for unwinder xorl %ebp, %ebp # clear frame pointer - movq initial_code(%rip), %rax - pushq $__KERNEL_CS # set correct cs - pushq %rax # target address in negative space - lretq -.Lafter_lret: - ANNOTATE_NOENDBR + ANNOTATE_RETPOLINE_SAFE + callq *initial_code(%rip) + ud2 SYM_CODE_END(secondary_startup_64) #include "verify_cpu.S" |