Re: [PATCH 1/3] kexec_load: Use new kexec flag for hotplug support

[Aditya Gupta <adityag@xxxxxxxxxxxxx>]

Hello sourabh,


On 29/05/24 18:43, Sourabh Jain wrote:
> Hello Aditya,
>
>
> On 28/05/24 17:03, Aditya Gupta wrote:
> > > diff --git a/kexec/arch/arm/kexec-arm.c b/kexec/arch/arm/kexec-arm.c
> > > index 49f35b1..34531f9 100644
> > > --- a/kexec/arch/arm/kexec-arm.c
> > > +++ b/kexec/arch/arm/kexec-arm.c
> > > @@ -148,3 +148,8 @@ int have_sysfs_fdt(void)
> > >   {
> > >       return !access(SYSFS_FDT, F_OK);
> > >   }
> > > +
> > > +int arch_do_exclude_segment(struct kexec_segment *UNUSED(seg_ptr), 
> > > struct kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/arm64/kexec-arm64.c 
> > > b/kexec/arch/arm64/kexec-arm64.c
> > > index 4a67b0d..9d052b0 100644
> > > --- a/kexec/arch/arm64/kexec-arm64.c
> > > +++ b/kexec/arch/arm64/kexec-arm64.c
> > > @@ -1363,3 +1363,7 @@ void arch_reuse_initrd(void)
> > >   void arch_update_purgatory(struct kexec_info *UNUSED(info))
> > >   {
> > >   }
> > > +int arch_do_exclude_segment(struct kexec_segment *UNUSED(seg_ptr), 
> > > struct kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/cris/kexec-cris.c 
> > > b/kexec/arch/cris/kexec-cris.c
> > > index 3b69709..7f09121 100644
> > > --- a/kexec/arch/cris/kexec-cris.c
> > > +++ b/kexec/arch/cris/kexec-cris.c
> > > @@ -109,3 +109,7 @@ unsigned long add_buffer(struct kexec_info 
> > > *info, const void *buf,
> > >                                       buf_min, buf_max, buf_end, 1);
> > >   }
> > >   +int arch_do_exclude_segment(struct kexec_segment 
> > > *UNUSED(seg_ptr), struct kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/hppa/kexec-hppa.c 
> > > b/kexec/arch/hppa/kexec-hppa.c
> > > index 77c9739..a64dc3d 100644
> > > --- a/kexec/arch/hppa/kexec-hppa.c
> > > +++ b/kexec/arch/hppa/kexec-hppa.c
> > > @@ -146,3 +146,8 @@ unsigned long virt_to_phys(unsigned long addr)
> > >   {
> > >       return addr - phys_offset;
> > >   }
> > > +
> > > +int arch_do_exclude_segment(struct kexec_segment *UNUSED(seg_ptr), 
> > > struct kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/i386/kexec-x86.c b/kexec/arch/i386/kexec-x86.c
> > > index 444cb69..b4947a0 100644
> > > --- a/kexec/arch/i386/kexec-x86.c
> > > +++ b/kexec/arch/i386/kexec-x86.c
> > > @@ -208,3 +208,11 @@ void arch_update_purgatory(struct kexec_info 
> > > *info)
> > >       elf_rel_set_symbol(&info->rhdr, "panic_kernel",
> > >           &panic_kernel, sizeof(panic_kernel));
> > >   }
> > > +
> > > +int arch_do_exclude_segment(struct kexec_segment *seg_ptr, struct 
> > > kexec_info *info)
> > > +{
> > > +    if (info->elfcorehdr == (unsigned long) seg_ptr->mem)
> > > +        return 1;
> > > +
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/ia64/kexec-ia64.c 
> > > b/kexec/arch/ia64/kexec-ia64.c
> > > index 418d997..8d9c1f3 100644
> > > --- a/kexec/arch/ia64/kexec-ia64.c
> > > +++ b/kexec/arch/ia64/kexec-ia64.c
> > > @@ -245,3 +245,7 @@ void arch_update_purgatory(struct kexec_info 
> > > *UNUSED(info))
> > >   {
> > >   }
> > >   +int arch_do_exclude_segment(struct kexec_segment 
> > > *UNUSED(seg_ptr), struct kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/loongarch/kexec-loongarch.c 
> > > b/kexec/arch/loongarch/kexec-loongarch.c
> > > index 32a42d2..9a50ff6 100644
> > > --- a/kexec/arch/loongarch/kexec-loongarch.c
> > > +++ b/kexec/arch/loongarch/kexec-loongarch.c
> > > @@ -378,3 +378,8 @@ unsigned long add_buffer(struct kexec_info 
> > > *info, const void *buf,
> > >       return add_buffer_phys_virt(info, buf, bufsz, memsz, buf_align,
> > >                       buf_min, buf_max, buf_end, 1);
> > >   }
> > > +
> > > +int arch_do_exclude_segment(struct kexec_segment *UNUSED(seg_ptr), 
> > > struct kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/m68k/kexec-m68k.c 
> > > b/kexec/arch/m68k/kexec-m68k.c
> > > index cb54927..0c7dbaf 100644
> > > --- a/kexec/arch/m68k/kexec-m68k.c
> > > +++ b/kexec/arch/m68k/kexec-m68k.c
> > > @@ -108,3 +108,8 @@ void add_segment(struct kexec_info *info, const 
> > > void *buf, size_t bufsz,
> > >   {
> > >       add_segment_phys_virt(info, buf, bufsz, base, memsz, 1);
> > >   }
> > > +
> > > +int arch_do_exclude_segment(struct kexec_segment *UNUSED(seg_ptr), 
> > > struct kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/mips/kexec-mips.c 
> > > b/kexec/arch/mips/kexec-mips.c
> > > index d8cbea8..94224ee 100644
> > > --- a/kexec/arch/mips/kexec-mips.c
> > > +++ b/kexec/arch/mips/kexec-mips.c
> > > @@ -189,3 +189,7 @@ unsigned long add_buffer(struct kexec_info 
> > > *info, const void *buf,
> > >                       buf_min, buf_max, buf_end, 1);
> > >   }
> > >   +int arch_do_exclude_segment(const void *UNUSED(seg_ptr), struct 
> > > kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/ppc/kexec-ppc.c b/kexec/arch/ppc/kexec-ppc.c
> > > index 03bec36..c8af870 100644
> > > --- a/kexec/arch/ppc/kexec-ppc.c
> > > +++ b/kexec/arch/ppc/kexec-ppc.c
> > > @@ -966,3 +966,7 @@ void arch_update_purgatory(struct kexec_info 
> > > *UNUSED(info))
> > >   {
> > >   }
> > >   +int arch_do_exclude_segment(struct kexec_segment 
> > > *UNUSED(seg_ptr), struct kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/ppc64/kexec-ppc64.c 
> > > b/kexec/arch/ppc64/kexec-ppc64.c
> > > index bd5274c..fb27b6b 100644
> > > --- a/kexec/arch/ppc64/kexec-ppc64.c
> > > +++ b/kexec/arch/ppc64/kexec-ppc64.c
> > > @@ -967,3 +967,8 @@ int arch_compat_trampoline(struct kexec_info 
> > > *UNUSED(info))
> > >   void arch_update_purgatory(struct kexec_info *UNUSED(info))
> > >   {
> > >   }
> > > +
> > > +int arch_do_exclude_segment(struct kexec_segment *UNUSED(seg_ptr), 
> > > struct kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/s390/kexec-s390.c 
> > > b/kexec/arch/s390/kexec-s390.c
> > > index 33ba6b9..0561ee7 100644
> > > --- a/kexec/arch/s390/kexec-s390.c
> > > +++ b/kexec/arch/s390/kexec-s390.c
> > > @@ -267,3 +267,8 @@ int get_crash_kernel_load_range(uint64_t *start, 
> > > uint64_t *end)
> > >   {
> > >       return parse_iomem_single("Crash kernel\n", start, end);
> > >   }
> > > +
> > > +int arch_do_exclude_segment(struct kexec_segment *UNUSED(seg_ptr), 
> > > struct kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/sh/kexec-sh.c b/kexec/arch/sh/kexec-sh.c
> > > index ce341c8..f84c40c 100644
> > > --- a/kexec/arch/sh/kexec-sh.c
> > > +++ b/kexec/arch/sh/kexec-sh.c
> > > @@ -257,3 +257,8 @@ unsigned long add_buffer(struct kexec_info 
> > > *info, const void *buf,
> > >       return add_buffer_phys_virt(info, buf, bufsz, memsz, buf_align,
> > >                       buf_min, buf_max, buf_end, 1);
> > >   }
> > > +
> > > +int arch_do_exclude_segment(struct kexec_segment *UNUSED(seg_ptr), 
> > > struct kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > > diff --git a/kexec/arch/x86_64/kexec-x86_64.c 
> > > b/kexec/arch/x86_64/kexec-x86_64.c
> > > index ffd84f0..42af90a 100644
> > > --- a/kexec/arch/x86_64/kexec-x86_64.c
> > > +++ b/kexec/arch/x86_64/kexec-x86_64.c
> > > @@ -188,3 +188,8 @@ void arch_update_purgatory(struct kexec_info *info)
> > >       elf_rel_set_symbol(&info->rhdr, "panic_kernel",
> > >                   &panic_kernel, sizeof(panic_kernel));
> > >   }
> > > +
> > > +int arch_do_exclude_segment(struct kexec_segment *UNUSED(seg_ptr), 
> > > struct kexec_info *UNUSED(info))
> > > +{
> > > +    return 0;
> > > +}
> > Should all arch_do_exclude_segment return 1 for elfcorehdr ? Please
> > refer my below comment.
>
> No they shouldn't until they have CRASH_HTOPLUG support in the kernel.
>
>
> > > diff --git a/kexec/kexec-syscall.h b/kexec/kexec-syscall.h
> > > index 73e5254..4675c46 100644
> > > --- a/kexec/kexec-syscall.h
> > > +++ b/kexec/kexec-syscall.h
> > > @@ -112,7 +112,7 @@ static inline long kexec_file_load(int 
> > > kernel_fd, int initrd_fd,
> > >     #define KEXEC_ON_CRASH        0x00000001
> > >   #define KEXEC_PRESERVE_CONTEXT    0x00000002
> > > -#define KEXEC_UPDATE_ELFCOREHDR    0x00000004
> > > +#define KEXEC_CRASH_HOTPLUG_SUPPORT    0x00000008
> > >   #define KEXEC_ARCH_MASK        0xffff0000
> > >     /* Flags for kexec file based system call */
> > > diff --git a/kexec/kexec.c b/kexec/kexec.c
> > > index 222f79e..034cea6 100644
> > > --- a/kexec/kexec.c
> > > +++ b/kexec/kexec.c
> > > @@ -701,10 +701,13 @@ static void update_purgatory(struct kexec_info 
> > > *info)
> > >               continue;
> > >           }
> > >   -        /* Don't include elfcorehdr in the checksum, if hotplug
> > > -         * support enabled.
> > > +        /*
> > > +         * Let architecture decide which segments to exclude from 
> > > checksum
> > > +         * if hotplug support is enabled.
> > >            */
> > > -        if (do_hotplug && (info->segment[i].mem == (void 
> > > *)info->elfcorehdr)) {
> > > +        if (do_hotplug && 
> > > arch_do_exclude_segment(&info->segment[i], info)) {
> > > +            dbgprintf("Skipping segment mem: 0x%lx from SHA 
> > > calculation\n",
> > > +                  (unsigned long)info->segment[i].mem);
> > >               continue;
> > >           }
> > Current behaviour seems to skip elfcorehdr segment in all architectures.
> >
> > But now as all architectures are returning 0 in arch_do_exclude_segment,
> > will elfcorehdr still be skipped ?
>
> Skipping elfcorehdr for architectures that don't support CRASH_HOTPLUG 
> is, I think, incorrect.
> Therefore, I believe the proposed approach in this patch, which asks 
> the architecture which
> segments to exclude, is better.
Got it, makes sense to me. Thanks for the explanation sourabh.


- Aditya Gupta


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