[U-Boot] [PATCH v2 1/8] x86: Add implementations of setjmp() and longjmp()

[Alexander Graf]

On 26.09.16 09:00, Bin Meng wrote:
> Hi Simon,
> 
> On Mon, Sep 26, 2016 at 5:27 AM, Simon Glass <sjg at chromium.org> wrote:
>> Bring in these functions from Linux v4.4. They will be needed for EFI loader
>> support.
>>
>> Signed-off-by: Simon Glass <sjg at chromium.org>
>> ---
>>
>> Changes in v2:
>> - Drop irrelevant comment
>> - Add a comment about .size
>> - Drop unnecessary .text directive
>> - Make longjmp() always cause setjmp() to return 1
>>
>>  arch/x86/cpu/Makefile         |  2 +-
>>  arch/x86/cpu/setjmp.S         | 66 +++++++++++++++++++++++++++++++++++++++++++
>>  arch/x86/include/asm/setjmp.h | 24 ++++++++++++++++
>>  3 files changed, 91 insertions(+), 1 deletion(-)
>>  create mode 100644 arch/x86/cpu/setjmp.S
>>  create mode 100644 arch/x86/include/asm/setjmp.h
>>
>> diff --git a/arch/x86/cpu/Makefile b/arch/x86/cpu/Makefile
>> index 2667e0b..f5b8c9e 100644
>> --- a/arch/x86/cpu/Makefile
>> +++ b/arch/x86/cpu/Makefile
>> @@ -10,7 +10,7 @@
>>
>>  extra-y        = start.o
>>  obj-$(CONFIG_X86_RESET_VECTOR) += resetvec.o start16.o
>> -obj-y  += interrupts.o cpu.o cpu_x86.o call64.o
>> +obj-y  += interrupts.o cpu.o cpu_x86.o call64.o setjmp.o
>>
>>  AFLAGS_REMOVE_call32.o := -mregparm=3 \
>>         $(if $(CONFIG_EFI_STUB_64BIT),-march=i386 -m32)
>> diff --git a/arch/x86/cpu/setjmp.S b/arch/x86/cpu/setjmp.S
>> new file mode 100644
>> index 0000000..7443274
>> --- /dev/null
>> +++ b/arch/x86/cpu/setjmp.S
>> @@ -0,0 +1,66 @@
>> +/*
>> + * Written by H. Peter Anvin <hpa at zytor.com>
>> + * Brought in from Linux v4.4 and modified for U-Boot
>> + * From Linux arch/um/sys-i386/setjmp.S
>> + *
>> + * SPDX-License-Identifier:    GPL-2.0
>> + */
>> +
>> +#include <asm/global_data.h>
>> +#include <asm/msr-index.h>
>> +#include <asm/processor-flags.h>
>> +
> 
> I believe the above 3 includes are not needed.
> 
>> +#define _REGPARM
>> +
>> +/*
>> + * The jmp_buf is assumed to contain the following, in order:
>> + *     %ebx
>> + *     %esp
>> + *     %ebp
>> + *     %esi
>> + *     %edi
>> + *     <return address>
>> + */
>> +
>> +       .text
>> +       .align 4
>> +       .globl setjmp
>> +       .type setjmp, @function
>> +setjmp:
>> +#ifdef _REGPARM
>> +       movl %eax, %edx
>> +#else
>> +       movl 4(%esp), %edx
>> +#endif
>> +       popl %ecx               /* Return address, and adjust the stack */
>> +       xorl %eax, %eax         /* Return value */
>> +       movl %ebx, (%edx)
>> +       movl %esp, 4(%edx)      /* Post-return %esp! */
>> +       pushl %ecx              /* Make the call/return stack happy */
>> +       movl %ebp, 8(%edx)
>> +       movl %esi, 12(%edx)
>> +       movl %edi, 16(%edx)
>> +       movl %ecx, 20(%edx)     /* Return address */
>> +       ret
>> +
>> +       /* Provide function size if needed */
>> +       .size setjmp, .-setjmp
>> +
>> +       .align 4
>> +       .globl longjmp
>> +       .type longjmp, @function
>> +longjmp:
>> +#ifdef _REGPARM
>> +       xchgl %eax, %edx
>> +#else
>> +       movl 4(%esp), %edx      /* jmp_ptr address */
>> +#endif
>> +       movl 1, %eax
> 
> This should be $1.
> 
> But I still think the setjmp/longjump codes in efi_loader is wrong. We
> should have longjump() to pass the return value to setjmp().

Why? Where's the difference?


Alex