diff options
| author |  Josh Poimboeuf <jpoimboe@kernel.org>
| 2024-01-03 19:36:26 +0100 |
|---|---|---|
| committer |  Borislav Petkov (AMD) <bp@alien8.de>
| 2024-02-12 11:42:15 +0100 |
| commit | 4461438a8405e800f90e0e40409e5f3d07eed381 (patch) | |
| tree | 1c660616f321919a56e80cac4fd9e0e980065a68 /arch/x86/entry/calling.h | |
| parent | x86/bugs: Rename CONFIG_RETHUNK => CONFIG_MITIGATION_RETHUNK (diff) | |
| download | linux-4461438a8405e800f90e0e40409e5f3d07eed381.tar.gz linux-4461438a8405e800f90e0e40409e5f3d07eed381.tar.bz2 linux-4461438a8405e800f90e0e40409e5f3d07eed381.zip | |
x86/retpoline: Ensure default return thunk isn't used at runtime
Make sure the default return thunk is not used after all return
instructions have been patched by the alternatives because the default
return thunk is insufficient when it comes to mitigating Retbleed or
SRSO.
Fix based on an earlier version by David Kaplan <david.kaplan@amd.com>.
[ bp: Fix the compilation error of warn_thunk_thunk being an invisible
symbol, hoist thunk macro into calling.h ]
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Co-developed-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231010171020.462211-4-david.kaplan@amd.com
Link: https://lore.kernel.org/r/20240104132446.GEZZaxnrIgIyat0pqf@fat_crate.local
Diffstat (limited to 'arch/x86/entry/calling.h')
| -rw-r--r-- | arch/x86/entry/calling.h | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index 39e069b68c6e..bd31b2534053 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -426,3 +426,63 @@ For 32-bit we have the following conventions - kernel is built with .endm #endif /* CONFIG_SMP */ + +#ifdef CONFIG_X86_64 + +/* rdi: arg1 ... normal C conventions. rax is saved/restored. */ +.macro THUNK name, func +SYM_FUNC_START(\name) + pushq %rbp + movq %rsp, %rbp + + pushq %rdi + pushq %rsi + pushq %rdx + pushq %rcx + pushq %rax + pushq %r8 + pushq %r9 + pushq %r10 + pushq %r11 + + call \func + + popq %r11 + popq %r10 + popq %r9 + popq %r8 + popq %rax + popq %rcx + popq %rdx + popq %rsi + popq %rdi + popq %rbp + RET +SYM_FUNC_END(\name) + _ASM_NOKPROBE(\name) +.endm + +#else /* CONFIG_X86_32 */ + +/* put return address in eax (arg1) */ +.macro THUNK name, func, put_ret_addr_in_eax=0 +SYM_CODE_START_NOALIGN(\name) + pushl %eax + pushl %ecx + pushl %edx + + .if \put_ret_addr_in_eax + /* Place EIP in the arg1 */ + movl 3*4(%esp), %eax + .endif + + call \func + popl %edx + popl %ecx + popl %eax + RET + _ASM_NOKPROBE(\name) +SYM_CODE_END(\name) + .endm + +#endif |