6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ard Biesheuvel <ardb@xxxxxxxxxx> commit 8b63cba746f86a754d66e302c43209cc9b9b6e39 upstream. Instead of pushing and popping %RSI several times to preserve the struct boot_params pointer across the execution of the startup code, move it into a callee save register before the first call into C, and copy it back when needed. Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx> Link: https://lore.kernel.org/r/20230807162720.545787-8-ardb@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/boot/compressed/head_64.S | 42 ++++++++++++++----------------------- 1 file changed, 16 insertions(+), 26 deletions(-) --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -408,10 +408,14 @@ SYM_CODE_START(startup_64) lretq .Lon_kernel_cs: + /* + * RSI holds a pointer to a boot_params structure provided by the + * loader, and this needs to be preserved across C function calls. So + * move it into a callee saved register. + */ + movq %rsi, %r15 - pushq %rsi call load_stage1_idt - popq %rsi #ifdef CONFIG_AMD_MEM_ENCRYPT /* @@ -422,12 +426,10 @@ SYM_CODE_START(startup_64) * CPUID instructions being issued, so go ahead and do that now via * sev_enable(), which will also handle the rest of the SEV-related * detection/setup to ensure that has been done in advance of any dependent - * code. + * code. Pass the boot_params pointer as the first argument. */ - pushq %rsi - movq %rsi, %rdi /* real mode address */ + movq %r15, %rdi call sev_enable - popq %rsi #endif /* @@ -440,13 +442,10 @@ SYM_CODE_START(startup_64) * - Non zero RDX means trampoline needs to enable 5-level * paging. * - * RSI holds real mode data and needs to be preserved across - * this function call. + * Pass the boot_params pointer as the first argument. */ - pushq %rsi - movq %rsi, %rdi /* real mode address */ + movq %r15, %rdi call paging_prepare - popq %rsi /* Save the trampoline address in RCX */ movq %rax, %rcx @@ -459,9 +458,9 @@ SYM_CODE_START(startup_64) * because the architecture does not guarantee that GPRs will retain * their full 64-bit values across a 32-bit mode switch. */ + pushq %r15 pushq %rbp pushq %rbx - pushq %rsi /* * Push the 64-bit address of trampoline_return() onto the new stack. @@ -478,9 +477,9 @@ SYM_CODE_START(startup_64) lretq trampoline_return: /* Restore live 64-bit registers */ - popq %rsi popq %rbx popq %rbp + popq %r15 /* Restore the stack, the 32-bit trampoline uses its own stack */ leaq rva(boot_stack_end)(%rbx), %rsp @@ -490,14 +489,9 @@ trampoline_return: * * RDI is address of the page table to use instead of page table * in trampoline memory (if required). - * - * RSI holds real mode data and needs to be preserved across - * this function call. */ - pushq %rsi leaq rva(top_pgtable)(%rbx), %rdi call cleanup_trampoline - popq %rsi /* Zero EFLAGS */ pushq $0 @@ -507,7 +501,6 @@ trampoline_return: * Copy the compressed kernel to the end of our buffer * where decompression in place becomes safe. */ - pushq %rsi leaq (_bss-8)(%rip), %rsi leaq rva(_bss-8)(%rbx), %rdi movl $(_bss - startup_32), %ecx @@ -515,7 +508,6 @@ trampoline_return: std rep movsq cld - popq %rsi /* * The GDT may get overwritten either during the copy we just did or @@ -562,30 +554,28 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated shrq $3, %rcx rep stosq - pushq %rsi call load_stage2_idt /* Pass boot_params to initialize_identity_maps() */ - movq (%rsp), %rdi + movq %r15, %rdi call initialize_identity_maps - popq %rsi /* * Do the extraction, and jump to the new kernel.. */ - pushq %rsi /* Save the real mode argument */ - movq %rsi, %rdi /* real mode address */ + /* pass struct boot_params pointer */ + movq %r15, %rdi leaq boot_heap(%rip), %rsi /* malloc area for uncompression */ leaq input_data(%rip), %rdx /* input_data */ movl input_len(%rip), %ecx /* input_len */ movq %rbp, %r8 /* output target address */ movl output_len(%rip), %r9d /* decompressed length, end of relocs */ call extract_kernel /* returns kernel entry point in %rax */ - popq %rsi /* * Jump to the decompressed kernel. */ + movq %r15, %rsi jmp *%rax SYM_FUNC_END(.Lrelocated)
