Re: [PATCH 2/4 v2] efi/libstub: x86/mixed: increase supported argument count

[Ilias Apalodimas <ilias.apalodimas@linaro.org>]

Hi Ard, 

On Thu, Sep 02, 2021 at 10:27:19AM +0200, Ard Biesheuvel wrote:
> On Thu, 2 Sept 2021 at 10:04, Ilias Apalodimas
> <ilias.apalodimas@linaro.org> wrote:
> >
> > From: Ard Biesheuvel <ardb@kernel.org>
> >
> > Increase the number of arguments supported by mixed mode calls, so that
> > we will be able to call into the TCG2 protocol to measure the initrd
> > and extend the associated PCR. This involves the TCG2 protocol's
> > hash_log_extend_event() method, which takes five arguments, three of
> > which are u64 and need to be split, producing a total of 8 outgoing
> > arguments.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
> 
> Does this still apply cleanly? There was a last minute fix that went
> into v5.14 that looked like it would conflict with this.

Not sure, I just rebased this on on top of net-next.  The last commit I can
see in there is 9d31d2338950.  I'll give it a try and send a v3 if that
fails.

> 
> > ---
> >  arch/x86/boot/compressed/efi_thunk_64.S | 17 ++++++++++++-----
> >  arch/x86/include/asm/efi.h              | 10 ++++++----
> >  arch/x86/platform/efi/efi_thunk_64.S    | 14 ++++++++++++--
> >  3 files changed, 30 insertions(+), 11 deletions(-)
> >
> > diff --git a/arch/x86/boot/compressed/efi_thunk_64.S b/arch/x86/boot/compressed/efi_thunk_64.S
> > index 95a223b3e56a..fec6c48d6b30 100644
> > --- a/arch/x86/boot/compressed/efi_thunk_64.S
> > +++ b/arch/x86/boot/compressed/efi_thunk_64.S
> > @@ -27,8 +27,6 @@ SYM_FUNC_START(__efi64_thunk)
> >         push    %rbp
> >         push    %rbx
> >
> > -       leaq    1f(%rip), %rbp
> > -
> >         movl    %ds, %eax
> >         push    %rax
> >         movl    %es, %eax
> > @@ -36,19 +34,28 @@ SYM_FUNC_START(__efi64_thunk)
> >         movl    %ss, %eax
> >         push    %rax
> >
> > +       movq    0x30(%rsp), %rbp
> > +       movq    0x38(%rsp), %rbx
> > +       movq    0x40(%rsp), %rax
> > +
> >         /*
> >          * Convert x86-64 ABI params to i386 ABI
> >          */
> > -       subq    $32, %rsp
> > +       subq    $48, %rsp
> >         movl    %esi, 0x0(%rsp)
> >         movl    %edx, 0x4(%rsp)
> >         movl    %ecx, 0x8(%rsp)
> >         movl    %r8d, 0xc(%rsp)
> >         movl    %r9d, 0x10(%rsp)
> > +       movl    %ebp, 0x14(%rsp)
> > +       movl    %ebx, 0x18(%rsp)
> > +       movl    %eax, 0x1c(%rsp)
> >
> > -       leaq    0x14(%rsp), %rbx
> > +       leaq    0x20(%rsp), %rbx
> >         sgdt    (%rbx)
> >
> > +       leaq    1f(%rip), %rbp
> > +
> >         /*
> >          * Switch to gdt with 32-bit segments. This is the firmware GDT
> >          * that was installed when the kernel started executing. This
> > @@ -67,7 +74,7 @@ SYM_FUNC_START(__efi64_thunk)
> >         pushq   %rax
> >         lretq
> >
> > -1:     addq    $32, %rsp
> > +1:     addq    $48, %rsp
> >         movq    %rdi, %rax
> >
> >         pop     %rbx
> > diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
> > index 85f156f8ef81..a323dbac9182 100644
> > --- a/arch/x86/include/asm/efi.h
> > +++ b/arch/x86/include/asm/efi.h
> > @@ -46,13 +46,14 @@ extern unsigned long efi_mixed_mode_stack_pa;
> >
> >  #define __efi_nargs(...) __efi_nargs_(__VA_ARGS__)
> >  #define __efi_nargs_(...) __efi_nargs__(0, ##__VA_ARGS__,      \
> > +       __efi_arg_sentinel(9), __efi_arg_sentinel(8),           \
> >         __efi_arg_sentinel(7), __efi_arg_sentinel(6),           \
> >         __efi_arg_sentinel(5), __efi_arg_sentinel(4),           \
> >         __efi_arg_sentinel(3), __efi_arg_sentinel(2),           \
> >         __efi_arg_sentinel(1), __efi_arg_sentinel(0))
> > -#define __efi_nargs__(_0, _1, _2, _3, _4, _5, _6, _7, n, ...)  \
> > +#define __efi_nargs__(_0, _1, _2, _3, _4, _5, _6, _7, _8, _9, n, ...)  \
> >         __take_second_arg(n,                                    \
> > -               ({ BUILD_BUG_ON_MSG(1, "__efi_nargs limit exceeded"); 8; }))
> > +               ({ BUILD_BUG_ON_MSG(1, "__efi_nargs limit exceeded"); 10; }))
> >  #define __efi_arg_sentinel(n) , n
> >
> >  /*
> > @@ -176,8 +177,9 @@ extern u64 efi_setup;
> >  extern efi_status_t __efi64_thunk(u32, ...);
> >
> >  #define efi64_thunk(...) ({                                            \
> > -       __efi_nargs_check(efi64_thunk, 6, __VA_ARGS__);                 \
> > -       __efi64_thunk(__VA_ARGS__);                                     \
> > +       u64 __pad[3]; /* must have space for 3 args on the stack */     \
> > +       __efi_nargs_check(efi64_thunk, 9, __VA_ARGS__);                 \
> > +       __efi64_thunk(__VA_ARGS__, __pad);                              \
> >  })
> >
> >  static inline bool efi_is_mixed(void)
> > diff --git a/arch/x86/platform/efi/efi_thunk_64.S b/arch/x86/platform/efi/efi_thunk_64.S
> > index fd3dd1708eba..5b7c6e09954e 100644
> > --- a/arch/x86/platform/efi/efi_thunk_64.S
> > +++ b/arch/x86/platform/efi/efi_thunk_64.S
> > @@ -36,6 +36,17 @@ SYM_CODE_START(__efi64_thunk)
> >         movq    efi_mixed_mode_stack_pa(%rip), %rsp
> >         push    %rax
> >
> > +       /*
> > +        * Copy args passed via the stack
> > +        */
> > +       subq    $0x24, %rsp
> > +       movq    0x18(%rax), %rbp
> > +       movq    0x20(%rax), %rbx
> > +       movq    0x28(%rax), %rax
> > +       movl    %ebp, 0x18(%rsp)
> > +       movl    %ebx, 0x1c(%rsp)
> > +       movl    %eax, 0x20(%rsp)
> > +
> >         /*
> >          * Calculate the physical address of the kernel text.
> >          */
> > @@ -47,7 +58,6 @@ SYM_CODE_START(__efi64_thunk)
> >         subq    %rax, %rbp
> >         subq    %rax, %rbx
> >
> > -       subq    $28, %rsp
> >         movl    %ebx, 0x0(%rsp)         /* return address */
> >         movl    %esi, 0x4(%rsp)
> >         movl    %edx, 0x8(%rsp)
> > @@ -60,7 +70,7 @@ SYM_CODE_START(__efi64_thunk)
> >         pushq   %rdi                    /* EFI runtime service address */
> >         lretq
> >
> > -1:     movq    24(%rsp), %rsp
> > +1:     movq    0x20(%rsp), %rsp
> >         pop     %rbx
> >         pop     %rbp
> >         retq
> > --
> > 2.32.0.rc0
> >