Re: [Minios-devel] [UNIKRAFT PATCH 4/4] lib/ukcontext: add {get, set, swap, make, start}context implementation

[Costin Lupu <costin.lup@xxxxxxxxx>]

On 8/22/19 7:51 PM, Costin Lupu wrote:
> Hi Charalampos,
> 
> I'm wondering if we should use the original libucontext as an external
> library instead. Of course this depends on the number of changes you are
> mentioning in the commit message. But we will end up adding more
> architectures support as well, so we will use more code from this library.
> 
> Please see my other comments inline.
> 
> On 8/22/19 7:06 PM, Charalampos Mainas wrote:
>> Copied from https://github.com/AdelieLinux/libucontext with some small
>> changes.
> 
> Which small changes is it about? I would suggest making the changes in a
> different commit and this patch should only import the original code
> without any changes.
> 
>>
>> Commits:
>> getcontext.S:        6046eb4
>> setcontext.S:        6046eb4
>> startcontext.S:      0622245
>> swapcontext.S:       790ed28
>> makecontext.c:       da10e5a

And another one: why are the commits different instead of using one
single commit?

>>
>> Signed-off by: Charalampos Mainas <charalampos.mainas@xxxxxxxxx>
> 
> s/Signed-off by/Signed-off-by/g
> 
>> ---
>>  lib/ukucontext/Makefile.uk    |  6 ++-
>>  lib/ukucontext/exportsyms.uk  |  4 ++
>>  lib/ukucontext/getcontext.S   | 49 ++++++++++++++++++++++
>>  lib/ukucontext/makecontext.c  | 78 +++++++++++++++++++++++++++++++++++
>>  lib/ukucontext/setcontext.S   | 45 ++++++++++++++++++++
>>  lib/ukucontext/startcontext.S | 33 +++++++++++++++
>>  lib/ukucontext/swapcontext.S  | 75 +++++++++++++++++++++++++++++++++
>>  7 files changed, 289 insertions(+), 1 deletion(-)
>>  create mode 100644 lib/ukucontext/getcontext.S
>>  create mode 100644 lib/ukucontext/makecontext.c
>>  create mode 100644 lib/ukucontext/setcontext.S
>>  create mode 100644 lib/ukucontext/startcontext.S
>>  create mode 100644 lib/ukucontext/swapcontext.S
> 
> We should keep the original structure, in order to support multiple
> architectures.
> 
>>
>> diff --git a/lib/ukucontext/Makefile.uk b/lib/ukucontext/Makefile.uk
>> index 0f92b6ca..e42f9bb9 100644
>> --- a/lib/ukucontext/Makefile.uk
>> +++ b/lib/ukucontext/Makefile.uk
>> @@ -44,4 +44,8 @@ $(eval $(call addlib_s,libucontext,$(CONFIG_LIBUCONTEXT)))
>>  CINCLUDES-$(CONFIG_LIBUCONTEXT)    += -I$(LIBUCONTEXT_BASE)/include      
>>  CXXINCLUDES-$(CONFIG_LIBUCONTEXT)  += -I$(LIBUCONTEXT_BASE)/include      
>>  
>> -
>> +LIBUCONTEXT_SRCS-y += $(LIBUCONTEXT_BASE)/getcontext.S
>> +LIBUCONTEXT_SRCS-y += $(LIBUCONTEXT_BASE)/swapcontext.S
>> +LIBUCONTEXT_SRCS-y += $(LIBUCONTEXT_BASE)/setcontext.S
>> +LIBUCONTEXT_SRCS-y += $(LIBUCONTEXT_BASE)/startcontext.S
>> +LIBUCONTEXT_SRCS-y += $(LIBUCONTEXT_BASE)/makecontext.c
>> diff --git a/lib/ukucontext/exportsyms.uk b/lib/ukucontext/exportsyms.uk
>> index e69de29b..ade29ee7 100644
>> --- a/lib/ukucontext/exportsyms.uk
>> +++ b/lib/ukucontext/exportsyms.uk
>> @@ -0,0 +1,4 @@
>> +makecontext
>> +setcontext
>> +swapcontext
>> +getcontext
>> diff --git a/lib/ukucontext/getcontext.S b/lib/ukucontext/getcontext.S
>> new file mode 100644
>> index 00000000..ee4c9af1
>> --- /dev/null
>> +++ b/lib/ukucontext/getcontext.S
>> @@ -0,0 +1,49 @@
>> +// Taken from https://github.com/AdelieLinux/libucontext
>> +/*
>> + * Copyright (c) 2018 William Pitcock <nenolod@xxxxxxxxxxxxxxxx>
>> + *
>> + * Permission to use, copy, modify, and/or distribute this software for any
>> + * purpose with or without fee is hereby granted, provided that the above
>> + * copyright notice and this permission notice appear in all copies.
>> + *
>> + * This software is provided 'as is' and without any warranty, express or
>> + * implied.  In no event shall the authors be liable for any damages arising
>> + * from the use of this software.
>> + */
>> +
>> +.globl __getcontext;
>> +__getcontext:
>> +    /* copy all of the current registers into the ucontext structure */
>> +    movq    %r8, 40(%rdi)
>> +    movq    %r9, 48(%rdi)
>> +    movq    %r10, 56(%rdi)
>> +    movq    %r11, 64(%rdi)
>> +    movq    %r12, 72(%rdi)
>> +    movq    %r13, 80(%rdi)
>> +    movq    %r14, 88(%rdi)
>> +    movq    %r15, 96(%rdi)
>> +    movq    %rdi, 104(%rdi)
>> +    movq    %rsi, 112(%rdi)
>> +    movq    %rbp, 120(%rdi)
>> +    movq    %rbx, 128(%rdi)
>> +    movq    %rdx, 136(%rdi)
>> +    movq    $1, 144(%rdi)           /* $1 is %rax */
>> +    movq    %rcx, 152(%rdi)
>> +
>> +    /* the first argument on the stack is the jump target (%rip), so we 
>> store it in the RIP
>> +       register in the ucontext structure. */
>> +    movq    (%rsp), %rcx
>> +    movq    %rcx, 168(%rdi)
>> +
>> +    /* finally take the stack pointer address (%rsp) offsetting by 8 to 
>> skip over the jump
>> +       target. */
>> +    leaq    8(%rsp), %rcx
>> +    movq    %rcx, 160(%rdi)
>> +
>> +    /* we're all done here, return 0 */
>> +    xorl    %eax, %eax
>> +    ret
>> +
>> +
>> +.weak getcontext;
>> +getcontext = __getcontext;
>> diff --git a/lib/ukucontext/makecontext.c b/lib/ukucontext/makecontext.c
>> new file mode 100644
>> index 00000000..b5a32eee
>> --- /dev/null
>> +++ b/lib/ukucontext/makecontext.c
>> @@ -0,0 +1,78 @@
>> +// Taken from https://github.com/AdelieLinux/libucontext
>> +/*
>> + * Copyright (c) 2018 William Pitcock <nenolod@xxxxxxxxxxxxxxxx>
>> + *
>> + * Permission to use, copy, modify, and/or distribute this software for any
>> + * purpose with or without fee is hereby granted, provided that the above
>> + * copyright notice and this permission notice appear in all copies.
>> + *
>> + * This software is provided 'as is' and without any warranty, express or
>> + * implied.  In no event shall the authors be liable for any damages arising
>> + * from the use of this software.
>> + */
>> +
>> +#define _GNU_SOURCE
>> +#include <stddef.h>
>> +#include <stdarg.h>
>> +#include <ucontext.h>
>> +#include <string.h>
>> +#include <stdint.h>
>> +
>> +
>> +extern void __start_context(void);
>> +
>> +
>> +void
>> +__makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
>> +{
>> +    greg_t *sp;
>> +    va_list va;
>> +    int i;
>> +    unsigned int uc_link;
>> +
>> +    uc_link = (argc > 6 ? argc - 6 : 0) + 1;
>> +
>> +    sp = (greg_t *) ((uintptr_t) ucp->uc_stack.ss_sp + 
>> ucp->uc_stack.ss_size);
>> +    sp -= uc_link;
>> +    sp = (greg_t *) (((uintptr_t) sp & -16L) - 8);
>> +
>> +    ucp->uc_mcontext.gregs[REG_RIP] = (uintptr_t) func;
>> +    ucp->uc_mcontext.gregs[REG_RBX] = (uintptr_t) &sp[uc_link];
>> +    ucp->uc_mcontext.gregs[REG_RSP] = (uintptr_t) sp;
>> +
>> +    sp[0] = (uintptr_t) &__start_context;
>> +    sp[uc_link] = (uintptr_t) ucp->uc_link;
>> +
>> +    va_start(va, argc);
>> +
>> +    for (i = 0; i < argc; i++)
>> +            switch (i)
>> +            {
>> +            case 0:
>> +                    ucp->uc_mcontext.gregs[REG_RDI] = va_arg (va, greg_t);
>> +                    break;
>> +            case 1:
>> +                    ucp->uc_mcontext.gregs[REG_RSI] = va_arg (va, greg_t);
>> +                    break;
>> +            case 2:
>> +                    ucp->uc_mcontext.gregs[REG_RDX] = va_arg (va, greg_t);
>> +                    break;
>> +            case 3:
>> +                    ucp->uc_mcontext.gregs[REG_RCX] = va_arg (va, greg_t);
>> +                    break;
>> +            case 4:
>> +                    ucp->uc_mcontext.gregs[REG_R8] = va_arg (va, greg_t);
>> +                    break;
>> +            case 5:
>> +                    ucp->uc_mcontext.gregs[REG_R9] = va_arg (va, greg_t);
>> +                    break;
>> +            default:
>> +                    sp[i - 5] = va_arg (va, greg_t);
>> +                    break;
>> +            }
>> +
>> +    va_end(va);
>> +}
>> +
>> +
>> +extern __typeof(__makecontext) makecontext __attribute__((weak, 
>> __alias__("__makecontext")));
>> diff --git a/lib/ukucontext/setcontext.S b/lib/ukucontext/setcontext.S
>> new file mode 100644
>> index 00000000..d1807e21
>> --- /dev/null
>> +++ b/lib/ukucontext/setcontext.S
>> @@ -0,0 +1,45 @@
>> +// Taken from https://github.com/AdelieLinux/libucontext
>> +/*
>> + * Copyright (c) 2018 William Pitcock <nenolod@xxxxxxxxxxxxxxxx>
>> + *
>> + * Permission to use, copy, modify, and/or distribute this software for any
>> + * purpose with or without fee is hereby granted, provided that the above
>> + * copyright notice and this permission notice appear in all copies.
>> + *
>> + * This software is provided 'as is' and without any warranty, express or
>> + * implied.  In no event shall the authors be liable for any damages arising
>> + * from the use of this software.
>> + */
>> +
>> +.globl __setcontext;
>> +__setcontext:
>> +    /* set all of the registers */
>> +    movq    40(%rdi), %r8
>> +    movq    48(%rdi), %r9
>> +    movq    56(%rdi), %r10
>> +    movq    64(%rdi), %r11
>> +    movq    72(%rdi), %r12
>> +    movq    80(%rdi), %r13
>> +    movq    88(%rdi), %r14
>> +    movq    96(%rdi), %r15
>> +    movq    112(%rdi), %rsi
>> +    movq    120(%rdi), %rbp
>> +    movq    128(%rdi), %rbx
>> +    movq    136(%rdi), %rdx
>> +    movq    144(%rdi), %rax
>> +    movq    152(%rdi), %rcx
>> +    movq    160(%rdi), %rsp
>> +
>> +    /* set the jump target by pushing it to the stack.
>> +       ret will pop the new %rip from the stack, causing us to jump there. 
>> */
>> +    pushq   168(%rdi)
>> +
>> +    /* finally, set %rdi correctly. */
>> +    movq    104(%rdi), %rdi
>> +
>> +    /* we're all done here, return 0 */
>> +    xorl    %eax, %eax
>> +    ret
>> +
>> +.weak setcontext;
>> +setcontext = __setcontext;
>> diff --git a/lib/ukucontext/startcontext.S b/lib/ukucontext/startcontext.S
>> new file mode 100644
>> index 00000000..26cccbac
>> --- /dev/null
>> +++ b/lib/ukucontext/startcontext.S
>> @@ -0,0 +1,33 @@
>> +// Taken from https://github.com/AdelieLinux/libucontext
>> +/*
>> + * Copyright (c) 2018 William Pitcock <nenolod@xxxxxxxxxxxxxxxx>
>> + *
>> + * Permission to use, copy, modify, and/or distribute this software for any
>> + * purpose with or without fee is hereby granted, provided that the above
>> + * copyright notice and this permission notice appear in all copies.
>> + *
>> + * This software is provided 'as is' and without any warranty, express or
>> + * implied.  In no event shall the authors be liable for any damages arising
>> + * from the use of this software.
>> + */
>> +
>> +.globl __start_context;
>> +__start_context:
>> +    /* get the proper context into position and test for NULL */
>> +    movq    %rbx, %rsp
>> +    movq    (%rsp), %rdi
>> +    testq   %rdi, %rdi
>> +
>> +    /* if we have no linked context, lets get out of here */
>> +    je      no_linked_context
>> +
>> +    /* call setcontext to switch to the linked context */
>> +    call    __setcontext@plt
>> +    movq    %rax, %rdi
>> +
>> +no_linked_context:
>> +    /* we are returning into a null context, it seems, so maybe we should 
>> exit */
>> +    call    ukplat_terminate@plt
>> +
>> +    /* something is really hosed, call hlt to force termination */
>> +    hlt
>> diff --git a/lib/ukucontext/swapcontext.S b/lib/ukucontext/swapcontext.S
>> new file mode 100644
>> index 00000000..c0e7bae3
>> --- /dev/null
>> +++ b/lib/ukucontext/swapcontext.S
>> @@ -0,0 +1,75 @@
>> +//Taken from https://github.com/AdelieLinux/libucontext
>> +/*
>> + * Copyright (c) 2018 William Pitcock <nenolod@xxxxxxxxxxxxxxxx>
>> + *
>> + * Permission to use, copy, modify, and/or distribute this software for any
>> + * purpose with or without fee is hereby granted, provided that the above
>> + * copyright notice and this permission notice appear in all copies.
>> + *
>> + * This software is provided 'as is' and without any warranty, express or
>> + * implied.  In no event shall the authors be liable for any damages arising
>> + * from the use of this software.
>> + */
>> +
>> +.globl __swapcontext;
>> +__swapcontext:
>> +    /* copy all of the current registers into the ucontext structure 
>> pointed by
>> +       the first argument */
>> +    movq    %r8, 40(%rdi)
>> +    movq    %r9, 48(%rdi)
>> +    movq    %r10, 56(%rdi)
>> +    movq    %r11, 64(%rdi)
>> +    movq    %r12, 72(%rdi)
>> +    movq    %r13, 80(%rdi)
>> +    movq    %r14, 88(%rdi)
>> +    movq    %r15, 96(%rdi)
>> +    movq    %rdi, 104(%rdi)
>> +    movq    %rsi, 112(%rdi)
>> +    movq    %rbp, 120(%rdi)
>> +    movq    %rbx, 128(%rdi)
>> +    movq    %rdx, 136(%rdi)
>> +    movq    $1, 144(%rdi)           /* $1 is %rax */
>> +    movq    %rcx, 152(%rdi)
>> +
>> +    /* the first argument on the stack is the jump target (%rip), so we 
>> store it in the RIP
>> +       register in the ucontext structure. */
>> +    movq    (%rsp), %rcx
>> +    movq    %rcx, 168(%rdi)
>> +
>> +    /* finally take the stack pointer address (%rsp) offsetting by 8 to 
>> skip over the jump
>> +       target. */
>> +    leaq    8(%rsp), %rcx
>> +    movq    %rcx, 160(%rdi)
>> +
>> +    /* set all of the registers to their new states, stored in the second
>> +       ucontext structure */        
>> +    movq    40(%rsi), %r8
>> +    movq    48(%rsi), %r9
>> +    movq    56(%rsi), %r10
>> +    movq    64(%rsi), %r11
>> +    movq    72(%rsi), %r12
>> +    movq    80(%rsi), %r13
>> +    movq    88(%rsi), %r14
>> +    movq    96(%rsi), %r15
>> +    movq    104(%rsi), %rdi
>> +    movq    120(%rsi), %rbp
>> +    movq    128(%rsi), %rbx
>> +    movq    136(%rsi), %rdx
>> +    movq    144(%rsi), %rax
>> +    movq    152(%rsi), %rcx
>> +    movq    160(%rsi), %rsp
>> +
>> +    /* set the jump target by pushing it to the stack.
>> +       ret will pop the new %rip from the stack, causing us to jump there. 
>> */
>> +    pushq   168(%rsi)
>> +
>> +    /* finally, set %rsi correctly since we do not need it anymore. */
>> +    movq    112(%rsi), %rsi
>> +
>> +    /* we're all done here, return 0 */
>> +    xorl    %eax, %eax
>> +    ret
>> +
>> +
>> +.weak swapcontext;
>> +swapcontext = __swapcontext;
>>

_______________________________________________
Minios-devel mailing list
Minios-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/minios-devel