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[PATCH] arch: arm64: fix KERNEL_SEGMENT_COUNT error

zhaoyang.huang posted 1 patch 1 month, 2 weeks ago
There is a newer version of this series
arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
[PATCH] arch: arm64: fix KERNEL_SEGMENT_COUNT error
Posted by zhaoyang.huang 1 month, 2 weeks ago 
From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>

During debug of a kernel panic, we find that the pte_t of the final
part of [data, end] segment got overflow to the next page of
init_pg_end[1] which is the gap page before early_init_stack[2].
This should be introduced by the KERNEL_SEGMENT_COUNT's value is 5
which should be 6 as map_segment are called 6 times for the segments
of (text, stext, rodata, inittext, initdata, data+bss)

[1]
crash_arm64_v9.0.1> vtop ffffffed00601000
VIRTUAL           PHYSICAL
ffffffed00601000  83401000

PAGE DIRECTORY: ffffffecffd62000
   PGD: ffffffecffd62da0 => 10000000833fb003
   PMD: ffffff80033fb018 => 10000000833fe003
   PTE: ffffff80033fe008 => 68000083401f03
  PAGE: 83401000

     PTE        PHYSICAL  FLAGS
68000083401f03  83401000  (VALID|SHARED|AF|NG|PXN|UXN)

      PAGE       PHYSICAL      MAPPING       INDEX CNT FLAGS
fffffffec00d0040 83401000                0        0  1 4000 reserved

[2]
ffffffed002c8000 (r) __pi__data
ffffffed0054e000 (d) __pi___bss_start
ffffffed005f5000 (b) __pi_init_pg_dir
ffffffed005fe000 (b) __pi_init_pg_end
ffffffed005ff000 (B) early_init_stack
ffffffed00608000 (b) __pi__end

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
 arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 74a4f738c5f5..14dd1c52552a 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -64,8 +64,8 @@
 #define INIT_IDMAP_FDT_PAGES	(EARLY_PAGES(INIT_IDMAP_PGTABLE_LEVELS, 0UL, UL(MAX_FDT_SIZE), 1) - 1)
 #define INIT_IDMAP_FDT_SIZE	((INIT_IDMAP_FDT_PAGES + EARLY_IDMAP_EXTRA_FDT_PAGES) * PAGE_SIZE)
 
-/* The number of segments in the kernel image (text, rodata, inittext, initdata, data+bss) */
-#define KERNEL_SEGMENT_COUNT	5
+/* The number of segments in the kernel image (text, stext, rodata, inittext, initdata, data+bss) */
+#define KERNEL_SEGMENT_COUNT	6
 
 #if SWAPPER_BLOCK_SIZE > SEGMENT_ALIGN
 #define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 1)
-- 
2.25.1
Re: [PATCH] arch: arm64: fix KERNEL_SEGMENT_COUNT error
Posted by Ard Biesheuvel 1 month, 2 weeks ago 
Hello Zhaoyang,

On Wed, 29 Apr 2026, at 08:17, zhaoyang.huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
>
> During debug of a kernel panic, we find that the pte_t of the final
> part of [data, end] segment got overflow to the next page of
> init_pg_end[1] which is the gap page before early_init_stack[2].
> This should be introduced by the KERNEL_SEGMENT_COUNT's value is 5
> which should be 6 as map_segment are called 6 times for the segments
> of (text, stext, rodata, inittext, initdata, data+bss)
>
> [1]
> crash_arm64_v9.0.1> vtop ffffffed00601000
> VIRTUAL           PHYSICAL
> ffffffed00601000  83401000
>
> PAGE DIRECTORY: ffffffecffd62000
>    PGD: ffffffecffd62da0 => 10000000833fb003
>    PMD: ffffff80033fb018 => 10000000833fe003
>    PTE: ffffff80033fe008 => 68000083401f03
>   PAGE: 83401000
>
>      PTE        PHYSICAL  FLAGS
> 68000083401f03  83401000  (VALID|SHARED|AF|NG|PXN|UXN)
>
>       PAGE       PHYSICAL      MAPPING       INDEX CNT FLAGS
> fffffffec00d0040 83401000                0        0  1 4000 reserved
>
> [2]
> ffffffed002c8000 (r) __pi__data
> ffffffed0054e000 (d) __pi___bss_start
> ffffffed005f5000 (b) __pi_init_pg_dir
> ffffffed005fe000 (b) __pi_init_pg_end
> ffffffed005ff000 (B) early_init_stack
> ffffffed00608000 (b) __pi__end
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> ---
>  arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kernel-pgtable.h 
> b/arch/arm64/include/asm/kernel-pgtable.h
> index 74a4f738c5f5..14dd1c52552a 100644
> --- a/arch/arm64/include/asm/kernel-pgtable.h
> +++ b/arch/arm64/include/asm/kernel-pgtable.h
> @@ -64,8 +64,8 @@
>  #define INIT_IDMAP_FDT_PAGES	(EARLY_PAGES(INIT_IDMAP_PGTABLE_LEVELS, 
> 0UL, UL(MAX_FDT_SIZE), 1) - 1)
>  #define INIT_IDMAP_FDT_SIZE	((INIT_IDMAP_FDT_PAGES + 
> EARLY_IDMAP_EXTRA_FDT_PAGES) * PAGE_SIZE)
> 
> -/* The number of segments in the kernel image (text, rodata, inittext, 
> initdata, data+bss) */
> -#define KERNEL_SEGMENT_COUNT	5
> +/* The number of segments in the kernel image (text, stext, rodata, 
> inittext, initdata, data+bss) */
> +#define KERNEL_SEGMENT_COUNT	6
> 
>  #if SWAPPER_BLOCK_SIZE > SEGMENT_ALIGN
>  #define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 1)

I think the better fix would be

--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -68,7 +68,7 @@
 #define KERNEL_SEGMENT_COUNT   5
 
 #if SWAPPER_BLOCK_SIZE > SEGMENT_ALIGN
-#define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 1)
+#define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 2)
 /*
  * The initial ID map consists of the kernel image, mapped as two separate
  * segments, and may appear misaligned wrt the swapper block size. This means

and add a line

Fixes: 5973a62efa34 ("arm64: map [_text, _stext) virtual address range non-executable+read-only")
Re: [PATCH] arch: arm64: fix KERNEL_SEGMENT_COUNT error
Posted by Zhaoyang Huang 1 month, 2 weeks ago 
On Wed, Apr 29, 2026 at 5:28 PM Ard Biesheuvel <ardb@kernel.org> wrote:
>
> Hello Zhaoyang,
>
> On Wed, 29 Apr 2026, at 08:17, zhaoyang.huang wrote:
> > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> >
> > During debug of a kernel panic, we find that the pte_t of the final
> > part of [data, end] segment got overflow to the next page of
> > init_pg_end[1] which is the gap page before early_init_stack[2].
> > This should be introduced by the KERNEL_SEGMENT_COUNT's value is 5
> > which should be 6 as map_segment are called 6 times for the segments
> > of (text, stext, rodata, inittext, initdata, data+bss)
> >
> > [1]
> > crash_arm64_v9.0.1> vtop ffffffed00601000
> > VIRTUAL           PHYSICAL
> > ffffffed00601000  83401000
> >
> > PAGE DIRECTORY: ffffffecffd62000
> >    PGD: ffffffecffd62da0 => 10000000833fb003
> >    PMD: ffffff80033fb018 => 10000000833fe003
> >    PTE: ffffff80033fe008 => 68000083401f03
> >   PAGE: 83401000
> >
> >      PTE        PHYSICAL  FLAGS
> > 68000083401f03  83401000  (VALID|SHARED|AF|NG|PXN|UXN)
> >
> >       PAGE       PHYSICAL      MAPPING       INDEX CNT FLAGS
> > fffffffec00d0040 83401000                0        0  1 4000 reserved
> >
> > [2]
> > ffffffed002c8000 (r) __pi__data
> > ffffffed0054e000 (d) __pi___bss_start
> > ffffffed005f5000 (b) __pi_init_pg_dir
> > ffffffed005fe000 (b) __pi_init_pg_end
> > ffffffed005ff000 (B) early_init_stack
> > ffffffed00608000 (b) __pi__end
> >
> > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> > ---
> >  arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/kernel-pgtable.h
> > b/arch/arm64/include/asm/kernel-pgtable.h
> > index 74a4f738c5f5..14dd1c52552a 100644
> > --- a/arch/arm64/include/asm/kernel-pgtable.h
> > +++ b/arch/arm64/include/asm/kernel-pgtable.h
> > @@ -64,8 +64,8 @@
> >  #define INIT_IDMAP_FDT_PAGES (EARLY_PAGES(INIT_IDMAP_PGTABLE_LEVELS,
> > 0UL, UL(MAX_FDT_SIZE), 1) - 1)
> >  #define INIT_IDMAP_FDT_SIZE  ((INIT_IDMAP_FDT_PAGES +
> > EARLY_IDMAP_EXTRA_FDT_PAGES) * PAGE_SIZE)
> >
> > -/* The number of segments in the kernel image (text, rodata, inittext,
> > initdata, data+bss) */
> > -#define KERNEL_SEGMENT_COUNT 5
> > +/* The number of segments in the kernel image (text, stext, rodata,
> > inittext, initdata, data+bss) */
> > +#define KERNEL_SEGMENT_COUNT 6
> >
> >  #if SWAPPER_BLOCK_SIZE > SEGMENT_ALIGN
> >  #define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 1)
>
> I think the better fix would be
>
> --- a/arch/arm64/include/asm/kernel-pgtable.h
> +++ b/arch/arm64/include/asm/kernel-pgtable.h
> @@ -68,7 +68,7 @@
>  #define KERNEL_SEGMENT_COUNT   5
>
>  #if SWAPPER_BLOCK_SIZE > SEGMENT_ALIGN
> -#define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 1)
> +#define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 2)
Thanks for the comment. This makes sense since KERNEL_SEGMENT_COUNT is
also used for defining vmlinux_seg[] in declare_kernel_vmas.
>  /*
>   * The initial ID map consists of the kernel image, mapped as two separate
>   * segments, and may appear misaligned wrt the swapper block size. This means
>
> and add a line
>
> Fixes: 5973a62efa34 ("arm64: map [_text, _stext) virtual address range non-executable+read-only")
>
>
Re: [PATCH] arch: arm64: fix KERNEL_SEGMENT_COUNT error
Posted by Zhaoyang Huang 1 month, 2 weeks ago 
On Thu, Apr 30, 2026 at 9:29 AM Zhaoyang Huang <huangzhaoyang@gmail.com> wrote:
>
> On Wed, Apr 29, 2026 at 5:28 PM Ard Biesheuvel <ardb@kernel.org> wrote:
> >
> > Hello Zhaoyang,
> >
> > On Wed, 29 Apr 2026, at 08:17, zhaoyang.huang wrote:
> > > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> > >
> > > During debug of a kernel panic, we find that the pte_t of the final
> > > part of [data, end] segment got overflow to the next page of
> > > init_pg_end[1] which is the gap page before early_init_stack[2].
> > > This should be introduced by the KERNEL_SEGMENT_COUNT's value is 5
> > > which should be 6 as map_segment are called 6 times for the segments
> > > of (text, stext, rodata, inittext, initdata, data+bss)
> > >
> > > [1]
> > > crash_arm64_v9.0.1> vtop ffffffed00601000
> > > VIRTUAL           PHYSICAL
> > > ffffffed00601000  83401000
> > >
> > > PAGE DIRECTORY: ffffffecffd62000
> > >    PGD: ffffffecffd62da0 => 10000000833fb003
> > >    PMD: ffffff80033fb018 => 10000000833fe003
> > >    PTE: ffffff80033fe008 => 68000083401f03
> > >   PAGE: 83401000
> > >
> > >      PTE        PHYSICAL  FLAGS
> > > 68000083401f03  83401000  (VALID|SHARED|AF|NG|PXN|UXN)
> > >
> > >       PAGE       PHYSICAL      MAPPING       INDEX CNT FLAGS
> > > fffffffec00d0040 83401000                0        0  1 4000 reserved
> > >
> > > [2]
> > > ffffffed002c8000 (r) __pi__data
> > > ffffffed0054e000 (d) __pi___bss_start
> > > ffffffed005f5000 (b) __pi_init_pg_dir
> > > ffffffed005fe000 (b) __pi_init_pg_end
> > > ffffffed005ff000 (B) early_init_stack
> > > ffffffed00608000 (b) __pi__end
> > >
> > > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> > > ---
> > >  arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/arm64/include/asm/kernel-pgtable.h
> > > b/arch/arm64/include/asm/kernel-pgtable.h
> > > index 74a4f738c5f5..14dd1c52552a 100644
> > > --- a/arch/arm64/include/asm/kernel-pgtable.h
> > > +++ b/arch/arm64/include/asm/kernel-pgtable.h
> > > @@ -64,8 +64,8 @@
> > >  #define INIT_IDMAP_FDT_PAGES (EARLY_PAGES(INIT_IDMAP_PGTABLE_LEVELS,
> > > 0UL, UL(MAX_FDT_SIZE), 1) - 1)
> > >  #define INIT_IDMAP_FDT_SIZE  ((INIT_IDMAP_FDT_PAGES +
> > > EARLY_IDMAP_EXTRA_FDT_PAGES) * PAGE_SIZE)
> > >
> > > -/* The number of segments in the kernel image (text, rodata, inittext,
> > > initdata, data+bss) */
> > > -#define KERNEL_SEGMENT_COUNT 5
> > > +/* The number of segments in the kernel image (text, stext, rodata,
> > > inittext, initdata, data+bss) */
> > > +#define KERNEL_SEGMENT_COUNT 6
> > >
> > >  #if SWAPPER_BLOCK_SIZE > SEGMENT_ALIGN
> > >  #define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 1)
> >
> > I think the better fix would be
> >
> > --- a/arch/arm64/include/asm/kernel-pgtable.h
> > +++ b/arch/arm64/include/asm/kernel-pgtable.h
> > @@ -68,7 +68,7 @@
> >  #define KERNEL_SEGMENT_COUNT   5
> >
> >  #if SWAPPER_BLOCK_SIZE > SEGMENT_ALIGN
> > -#define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 1)
> > +#define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 2)
> Thanks for the comment. This makes sense since KERNEL_SEGMENT_COUNT is
> also used for defining vmlinux_seg[] in declare_kernel_vmas.
Is the following fix more reasonable, since it makes both map_segment
and declare_kernel_vmas compatible with the value 6?

-/* The number of segments in the kernel image (text, rodata,
inittext, initdata, data+bss) */
-#define KERNEL_SEGMENT_COUNT   5
+/* The number of segments in the kernel image (text, stext, rodata,
inittext, initdata, data+bss) */
+#define KERNEL_SEGMENT_COUNT   6

 static void __init declare_kernel_vmas(void)
 {
-       static struct vm_struct vmlinux_seg[KERNEL_SEGMENT_COUNT];
+       /*
+        * [_text, _stext) is mapped in init_pg_dir seperatly while they got
+        * merged into one here
+        */
+       static struct vm_struct vmlinux_seg[KERNEL_SEGMENT_COUNT - 1];


> >  /*
> >   * The initial ID map consists of the kernel image, mapped as two separate
> >   * segments, and may appear misaligned wrt the swapper block size. This means
> >
> > and add a line
> >
> > Fixes: 5973a62efa34 ("arm64: map [_text, _stext) virtual address range non-executable+read-only")
> >
> >
Re: [PATCH] arch: arm64: fix KERNEL_SEGMENT_COUNT error
Posted by Zhaoyang Huang 1 month, 2 weeks ago 
On Wed, Apr 29, 2026 at 2:19 PM zhaoyang.huang
<zhaoyang.huang@unisoc.com> wrote:
>
> From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
>
> During debug of a kernel panic, we find that the pte_t of the final
> part of [data, end] segment got overflow to the next page of
> init_pg_end[1] which is the gap page before early_init_stack[2].
> This should be introduced by the KERNEL_SEGMENT_COUNT's value is 5
> which should be 6 as map_segment are called 6 times for the segments
> of (text, stext, rodata, inittext, initdata, data+bss)
>
> [1]
> crash_arm64_v9.0.1> vtop ffffffed00601000
> VIRTUAL           PHYSICAL
> ffffffed00601000  83401000
>
> PAGE DIRECTORY: ffffffecffd62000
>    PGD: ffffffecffd62da0 => 10000000833fb003
>    PMD: ffffff80033fb018 => 10000000833fe003
>    PTE: ffffff80033fe008 => 68000083401f03
>   PAGE: 83401000
>
>      PTE        PHYSICAL  FLAGS
> 68000083401f03  83401000  (VALID|SHARED|AF|NG|PXN|UXN)
>
>       PAGE       PHYSICAL      MAPPING       INDEX CNT FLAGS
> fffffffec00d0040 83401000                0        0  1 4000 reserved
>
> [2]
> ffffffed002c8000 (r) __pi__data
> ffffffed0054e000 (d) __pi___bss_start
> ffffffed005f5000 (b) __pi_init_pg_dir
> ffffffed005fe000 (b) __pi_init_pg_end
> ffffffed005ff000 (B) early_init_stack
> ffffffed00608000 (b) __pi__end
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> ---
>  arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
> index 74a4f738c5f5..14dd1c52552a 100644
> --- a/arch/arm64/include/asm/kernel-pgtable.h
> +++ b/arch/arm64/include/asm/kernel-pgtable.h
> @@ -64,8 +64,8 @@
>  #define INIT_IDMAP_FDT_PAGES   (EARLY_PAGES(INIT_IDMAP_PGTABLE_LEVELS, 0UL, UL(MAX_FDT_SIZE), 1) - 1)
>  #define INIT_IDMAP_FDT_SIZE    ((INIT_IDMAP_FDT_PAGES + EARLY_IDMAP_EXTRA_FDT_PAGES) * PAGE_SIZE)
>
> -/* The number of segments in the kernel image (text, rodata, inittext, initdata, data+bss) */
> -#define KERNEL_SEGMENT_COUNT   5
> +/* The number of segments in the kernel image (text, stext, rodata, inittext, initdata, data+bss) */
> +#define KERNEL_SEGMENT_COUNT   6
>
>  #if SWAPPER_BLOCK_SIZE > SEGMENT_ALIGN
>  #define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 1)
I just noticed that the page just behind init_pg_end which I called as
guard page is designed as early_init_stack in vmlinux.lds.s. That
could explain why I find the strings of aliases within
idreg-override.c present in this page.

ffffffed005fe000 (b) __pi_init_pg_end
...
ffffffed005fec50:  77735f34366d7261 726c3d656876682e   arm64_sw.hvhe=lr
ffffffed005fec60:  00003d633d723d3d 0000000000000000   ==r=c=..........
...
ffffffed005ff000 (B) early_init_stack

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