[PATCH v2 0/1] fix p_align on PT_LOAD segment in DSO isn't honored

[PATCH v2 0/1] fix p_align on PT_LOAD segment in DSO isn't honored

[Rongwei Wang]

Hi

This patch mainly to fix a reported bug:

"p_align on PT_LOAD segment in DSO isn't honored"
https://sourceware.org/bugzilla/show_bug.cgi?id=28676

A testcase had been builded by H.J.Lu:
https://sourceware.org/bugzilla/attachment.cgi?id=13838

And in Patch 1/1, I also show a simple testcase which
modified from H.J.Lu.

And a similar bug in ELF binary was also reported:
https://bugzilla.kernel.org/show_bug.cgi?id=215275

A related fix patch could been found:
https://lore.kernel.org/linux-mm/20211009092658.59665-4-rongwei.wang@linux.alibaba.com/
Originally, we send this patch for introducing .text
hugepages, was not aware of it's bug. And now, I am
not sure whether kernel maintainer will regards it as
a bug. But it deserved try again.

Thanks.

Changelog:

RFC/v1 -> v2

- Patch "elf: align the mapping address of LOAD segments with p_align"
fix coding format and add testcase in commit.

RFC link:
https://patchwork.sourceware.org/project/glibc/patch/20211204045848.71105-2-rongwei.wang@linux.alibaba.com/

Rongwei Wang (1):
  elf: align the mapping address of LOAD segments with p_align

 elf/dl-load.c         |  1 +
 elf/dl-map-segments.h | 63 +++++++++++++++++++++++++++++++++++++++----
 include/link.h        |  3 +++
 3 files changed, 62 insertions(+), 5 deletions(-)

-- 
2.27.0

[PATCH v2 1/1] elf: align the mapping address of LOAD segments with p_align

[Rongwei Wang]

Now, ld.so always map the LOAD segments and aligned by base
page size (e.g. 4k in x86 or 4k, 16k and 64k in arm64). This
is a bug, and had been reported:

https://sourceware.org/bugzilla/show_bug.cgi?id=28676

This patch mainly to fix it. In this patch, ld.so can align
the mapping address of the first LOAD segment with p_align
when p_align is greater than the current base page size.

A testcase:
main.c:

extern void dso_test(void);
int main(void)
{
    dso_test();
    getchar();

    return 0;
}

load.c, used to generate libload.so:

int foo  __attribute__((aligned(0x200000))) = 1;
void dso_test(void)
{
    printf("dso test\n");
    printf("foo: %p\n", &foo);
}

The steps:
$ gcc -O2 -fPIC -c -o load.o load.c
$ gcc -shared -Wl,-z,max-page-size=0x200000 -o libload.so load.o
$ gcc -no-pie -Wl,-z,max-page-size=0x200000 -O2 -o dso main.c libload.so -Wl,-R,.

Before fixing:
$ ./dso
dso test
foo: 0xffff88ae2000

After fixed:
$ ./dso
dso test
foo: 0xffff9e000000

And this fix can help code segments use huge pages become
simple and available.

Signed-off-by: Xu Yu <xuyu@linux.alibaba.com>
Signed-off-by: Rongwei Wang <rongwei.wang@linux.alibaba.com>
---
 elf/dl-load.c         |  1 +
 elf/dl-map-segments.h | 63 +++++++++++++++++++++++++++++++++++++++----
 include/link.h        |  3 +++
 3 files changed, 62 insertions(+), 5 deletions(-)

diff --git a/elf/dl-load.c b/elf/dl-load.c
index e39980fb19..136cfe2fa8 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1154,6 +1154,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
 	  c->dataend = ph->p_vaddr + ph->p_filesz;
 	  c->allocend = ph->p_vaddr + ph->p_memsz;
 	  c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
+          l->l_load_align = ph->p_align;
 
 	  /* Determine whether there is a gap between the last segment
 	     and this one.  */
diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
index ac9f09ab4c..fad98eb984 100644
--- a/elf/dl-map-segments.h
+++ b/elf/dl-map-segments.h
@@ -18,6 +18,48 @@
 
 #include <dl-load.h>
 
+static __always_inline void *
+_dl_map_segments_align (const struct loadcmd *c,
+                        ElfW(Addr) mappref, int fd, size_t alignment,
+                        const size_t maplength)
+{
+  unsigned long map_start, map_start_align, map_end;
+  unsigned long maplen = (maplength >= alignment) ?
+                         (maplength + alignment) : (2 * alignment);
+
+  /* Allocate enough space to ensure that address aligned by
+     p_align is included. */
+  map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplen,
+                                   PROT_NONE,
+                                   MAP_ANONYMOUS | MAP_PRIVATE,
+                                   -1, 0);
+  if (__glibc_unlikely ((void *) map_start == MAP_FAILED))
+    {
+      /* If mapping a aligned address failed, then ... */
+      map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
+                                       c->prot,
+                                       MAP_COPY|MAP_FILE,
+                                       fd, c->mapoff);
+
+      return (void *) map_start;
+    }
+  map_start_align = ALIGN_UP(map_start, alignment);
+  map_end = map_start_align + maplength;
+
+  /* Remember which part of the address space this object uses.  */
+  map_start_align = (ElfW(Addr)) __mmap ((void *) map_start_align, maplength,
+                                         c->prot,
+                                         MAP_COPY|MAP_FILE|MAP_FIXED,
+                                         fd, c->mapoff);
+  if (__glibc_unlikely ((void *) map_start_align == MAP_FAILED))
+    return MAP_FAILED;
+  if (map_start_align > map_start)
+    __munmap((void *)map_start, map_start_align - map_start);
+  __munmap((void *)map_end, map_start + maplen - map_end);
+
+  return (void *) map_start_align;
+}
+
 /* This implementation assumes (as does the corresponding implementation
    of _dl_unmap_segments, in dl-unmap-segments.h) that shared objects
    are always laid out with all segments contiguous (or with gaps
@@ -52,11 +94,22 @@ _dl_map_segments (struct link_map *l, int fd,
                                   c->mapstart & GLRO(dl_use_load_bias))
            - MAP_BASE_ADDR (l));
 
-      /* Remember which part of the address space this object uses.  */
-      l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
-                                            c->prot,
-                                            MAP_COPY|MAP_FILE,
-                                            fd, c->mapoff);
+      /* During mapping, align the mapping address of the LOAD segments
+         according to own p_align. This helps OS map its code segment to
+         huge pages. */
+      if (l->l_load_align > GLRO(dl_pagesize))
+        {
+          l->l_map_start = (ElfW(Addr)) _dl_map_segments_align (c, mappref,
+                                       fd, l->l_load_align, maplength);
+        }
+      else
+        {
+          /* Remember which part of the address space this object uses.  */
+          l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
+                                                c->prot,
+                                                MAP_COPY|MAP_FILE,
+                                                fd, c->mapoff);
+        }
       if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED))
         return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
 
diff --git a/include/link.h b/include/link.h
index aea268439c..fc6ce29fab 100644
--- a/include/link.h
+++ b/include/link.h
@@ -298,6 +298,9 @@ struct link_map
 
     /* Thread-local storage related info.  */
 
+    /* Alignment requirement of the LOAD block.  */
+    size_t l_load_align;
+
     /* Start of the initialization image.  */
     void *l_tls_initimage;
     /* Size of the initialization image.  */
-- 
2.27.0

Re: [PATCH v2 0/1] fix p_align on PT_LOAD segment in DSO isn't honored

[Rongwei Wang]

Sorry, I took a mistake, sent this patch twice.

The patch twice sent were completely same. Just read one patch
is OK.

Sorry for this mistake again.

On 12/9/21 1:57 PM, Rongwei Wang via Libc-alpha wrote:
> Hi
> 
> This patch mainly to fix a reported bug:
> 
> "p_align on PT_LOAD segment in DSO isn't honored"
> https://sourceware.org/bugzilla/show_bug.cgi?id=28676
> 
> A testcase had been builded by H.J.Lu:
> https://sourceware.org/bugzilla/attachment.cgi?id=13838
> 
> And in Patch 1/1, I also show a simple testcase which
> modified from H.J.Lu.
> 
> And a similar bug in ELF binary was also reported:
> https://bugzilla.kernel.org/show_bug.cgi?id=215275
> 
> A related fix patch could been found:
> https://lore.kernel.org/linux-mm/20211009092658.59665-4-rongwei.wang@linux.alibaba.com/
> Originally, we send this patch for introducing .text
> hugepages, was not aware of it's bug. And now, I am
> not sure whether kernel maintainer will regards it as
> a bug. But it deserved try again.
> 
> Thanks.
> 
> Changelog:
> 
> RFC/v1 -> v2
> 
> - Patch "elf: align the mapping address of LOAD segments with p_align"
> fix coding format and add testcase in commit.
> 
> RFC link:
> https://patchwork.sourceware.org/project/glibc/patch/20211204045848.71105-2-rongwei.wang@linux.alibaba.com/
> 
> Rongwei Wang (1):
>    elf: align the mapping address of LOAD segments with p_align
> 
>   elf/dl-load.c         |  1 +
>   elf/dl-map-segments.h | 63 +++++++++++++++++++++++++++++++++++++++----
>   include/link.h        |  3 +++
>   3 files changed, 62 insertions(+), 5 deletions(-)
> 

Re: [PATCH v2 1/1] elf: align the mapping address of LOAD segments with p_align

[H.J. Lu]

On Wed, Dec 8, 2021 at 9:57 PM Rongwei Wang
<rongwei.wang@linux.alibaba.com> wrote:
>
> Now, ld.so always map the LOAD segments and aligned by base
> page size (e.g. 4k in x86 or 4k, 16k and 64k in arm64). This
> is a bug, and had been reported:
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=28676
>
> This patch mainly to fix it. In this patch, ld.so can align
> the mapping address of the first LOAD segment with p_align
> when p_align is greater than the current base page size.
>
> A testcase:
> main.c:
>
> extern void dso_test(void);
> int main(void)
> {
>     dso_test();
>     getchar();
>
>     return 0;
> }
>
> load.c, used to generate libload.so:
>
> int foo  __attribute__((aligned(0x200000))) = 1;
> void dso_test(void)
> {
>     printf("dso test\n");
>     printf("foo: %p\n", &foo);
> }
>
> The steps:
> $ gcc -O2 -fPIC -c -o load.o load.c
> $ gcc -shared -Wl,-z,max-page-size=0x200000 -o libload.so load.o
> $ gcc -no-pie -Wl,-z,max-page-size=0x200000 -O2 -o dso main.c libload.so -Wl,-R,.
>
> Before fixing:
> $ ./dso
> dso test
> foo: 0xffff88ae2000
>
> After fixed:
> $ ./dso
> dso test
> foo: 0xffff9e000000
>
> And this fix can help code segments use huge pages become
> simple and available.

Please include a testcase, like

https://gitlab.com/x86-glibc/glibc/-/commits/users/hjl/pr28676/master

> Signed-off-by: Xu Yu <xuyu@linux.alibaba.com>
> Signed-off-by: Rongwei Wang <rongwei.wang@linux.alibaba.com>
> ---
>  elf/dl-load.c         |  1 +
>  elf/dl-map-segments.h | 63 +++++++++++++++++++++++++++++++++++++++----
>  include/link.h        |  3 +++
>  3 files changed, 62 insertions(+), 5 deletions(-)
>
> diff --git a/elf/dl-load.c b/elf/dl-load.c
> index e39980fb19..136cfe2fa8 100644
> --- a/elf/dl-load.c
> +++ b/elf/dl-load.c
> @@ -1154,6 +1154,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
>           c->dataend = ph->p_vaddr + ph->p_filesz;
>           c->allocend = ph->p_vaddr + ph->p_memsz;
>           c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
> +          l->l_load_align = ph->p_align;

Can you add an alignment field to

/* This structure describes one PT_LOAD command.
   Its details have been expanded out and converted.  */
struct loadcmd
{
  ElfW(Addr) mapstart, mapend, dataend, allocend;
  ElfW(Off) mapoff;
  int prot;                             /* PROT_* bits.  */
};

instead?

>
>           /* Determine whether there is a gap between the last segment
>              and this one.  */
> diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
> index ac9f09ab4c..fad98eb984 100644
> --- a/elf/dl-map-segments.h
> +++ b/elf/dl-map-segments.h
> @@ -18,6 +18,48 @@
>
>  #include <dl-load.h>
>
> +static __always_inline void *
> +_dl_map_segments_align (const struct loadcmd *c,
> +                        ElfW(Addr) mappref, int fd, size_t alignment,
> +                        const size_t maplength)
> +{
> +  unsigned long map_start, map_start_align, map_end;

Use ElfW(Addr) instead of long.

> +  unsigned long maplen = (maplength >= alignment) ?
> +                         (maplength + alignment) : (2 * alignment);
> +
> +  /* Allocate enough space to ensure that address aligned by
> +     p_align is included. */
> +  map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplen,
> +                                   PROT_NONE,
> +                                   MAP_ANONYMOUS | MAP_PRIVATE,
> +                                   -1, 0);
> +  if (__glibc_unlikely ((void *) map_start == MAP_FAILED))
> +    {
> +      /* If mapping a aligned address failed, then ... */

an aligned

> +      map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
> +                                       c->prot,
> +                                       MAP_COPY|MAP_FILE,
> +                                       fd, c->mapoff);
> +
> +      return (void *) map_start;
> +    }
> +  map_start_align = ALIGN_UP(map_start, alignment);
> +  map_end = map_start_align + maplength;
> +
> +  /* Remember which part of the address space this object uses.  */
> +  map_start_align = (ElfW(Addr)) __mmap ((void *) map_start_align, maplength,
> +                                         c->prot,
> +                                         MAP_COPY|MAP_FILE|MAP_FIXED,
> +                                         fd, c->mapoff);
> +  if (__glibc_unlikely ((void *) map_start_align == MAP_FAILED))
> +    return MAP_FAILED;
> +  if (map_start_align > map_start)
> +    __munmap((void *)map_start, map_start_align - map_start);
> +  __munmap((void *)map_end, map_start + maplen - map_end);
> +
> +  return (void *) map_start_align;
> +}
> +
>  /* This implementation assumes (as does the corresponding implementation
>     of _dl_unmap_segments, in dl-unmap-segments.h) that shared objects
>     are always laid out with all segments contiguous (or with gaps
> @@ -52,11 +94,22 @@ _dl_map_segments (struct link_map *l, int fd,
>                                    c->mapstart & GLRO(dl_use_load_bias))
>             - MAP_BASE_ADDR (l));
>
> -      /* Remember which part of the address space this object uses.  */
> -      l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
> -                                            c->prot,
> -                                            MAP_COPY|MAP_FILE,
> -                                            fd, c->mapoff);
> +      /* During mapping, align the mapping address of the LOAD segments
> +         according to own p_align. This helps OS map its code segment to
> +         huge pages. */
> +      if (l->l_load_align > GLRO(dl_pagesize))
> +        {
> +          l->l_map_start = (ElfW(Addr)) _dl_map_segments_align (c, mappref,
> +                                       fd, l->l_load_align, maplength);
> +        }
> +      else
> +        {
> +          /* Remember which part of the address space this object uses.  */
> +          l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
> +                                                c->prot,
> +                                                MAP_COPY|MAP_FILE,
> +                                                fd, c->mapoff);
> +        }

Don't use {} for a single statement.

>        if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED))
>          return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
>
> diff --git a/include/link.h b/include/link.h
> index aea268439c..fc6ce29fab 100644
> --- a/include/link.h
> +++ b/include/link.h
> @@ -298,6 +298,9 @@ struct link_map
>
>      /* Thread-local storage related info.  */
>
> +    /* Alignment requirement of the LOAD block.  */
> +    size_t l_load_align;
> +
>      /* Start of the initialization image.  */
>      void *l_tls_initimage;
>      /* Size of the initialization image.  */
> --
> 2.27.0
>


-- 
H.J.

[PATCH v3] elf: Properly align PT_LOAD segments [BZ #28676]

[H.J. Lu]

On Thu, Dec 09, 2021 at 07:14:10AM -0800, H.J. Lu wrote:
> On Wed, Dec 8, 2021 at 9:57 PM Rongwei Wang
> <rongwei.wang@linux.alibaba.com> wrote:
> >
> > Now, ld.so always map the LOAD segments and aligned by base
> > page size (e.g. 4k in x86 or 4k, 16k and 64k in arm64). This
> > is a bug, and had been reported:
> >
> > https://sourceware.org/bugzilla/show_bug.cgi?id=28676
> >
> > This patch mainly to fix it. In this patch, ld.so can align
> > the mapping address of the first LOAD segment with p_align
> > when p_align is greater than the current base page size.
> >
> > A testcase:
> > main.c:
> >
> > extern void dso_test(void);
> > int main(void)
> > {
> >     dso_test();
> >     getchar();
> >
> >     return 0;
> > }
> >
> > load.c, used to generate libload.so:
> >
> > int foo  __attribute__((aligned(0x200000))) = 1;
> > void dso_test(void)
> > {
> >     printf("dso test\n");
> >     printf("foo: %p\n", &foo);
> > }
> >
> > The steps:
> > $ gcc -O2 -fPIC -c -o load.o load.c
> > $ gcc -shared -Wl,-z,max-page-size=0x200000 -o libload.so load.o
> > $ gcc -no-pie -Wl,-z,max-page-size=0x200000 -O2 -o dso main.c libload.so -Wl,-R,.
> >
> > Before fixing:
> > $ ./dso
> > dso test
> > foo: 0xffff88ae2000
> >
> > After fixed:
> > $ ./dso
> > dso test
> > foo: 0xffff9e000000
> >
> > And this fix can help code segments use huge pages become
> > simple and available.
> 
> Please include a testcase, like
> 
> https://gitlab.com/x86-glibc/glibc/-/commits/users/hjl/pr28676/master
> 
> > Signed-off-by: Xu Yu <xuyu@linux.alibaba.com>
> > Signed-off-by: Rongwei Wang <rongwei.wang@linux.alibaba.com>
> > ---
> >  elf/dl-load.c         |  1 +
> >  elf/dl-map-segments.h | 63 +++++++++++++++++++++++++++++++++++++++----
> >  include/link.h        |  3 +++
> >  3 files changed, 62 insertions(+), 5 deletions(-)
> >
> > diff --git a/elf/dl-load.c b/elf/dl-load.c
> > index e39980fb19..136cfe2fa8 100644
> > --- a/elf/dl-load.c
> > +++ b/elf/dl-load.c
> > @@ -1154,6 +1154,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
> >           c->dataend = ph->p_vaddr + ph->p_filesz;
> >           c->allocend = ph->p_vaddr + ph->p_memsz;
> >           c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
> > +          l->l_load_align = ph->p_align;
> 
> Can you add an alignment field to
> 
> /* This structure describes one PT_LOAD command.
>    Its details have been expanded out and converted.  */
> struct loadcmd
> {
>   ElfW(Addr) mapstart, mapend, dataend, allocend;
>   ElfW(Off) mapoff;
>   int prot;                             /* PROT_* bits.  */
> };
> 
> instead?
> 

Hi,

I updated your patch.  Please take a look.


H.J.
--
When PT_LOAD segment alignment > the page size, allocate enough space
to ensure that the segment can be properly aligned.

This fixes [BZ #28676].
---
 elf/dl-load.c         |  1 +
 elf/dl-load.h         |  2 +-
 elf/dl-map-segments.h | 51 +++++++++++++++++++++++++++++++++++++++----
 3 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/elf/dl-load.c b/elf/dl-load.c
index bf8957e73c..9a23590bf4 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1150,6 +1150,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
 	  c->mapend = ALIGN_UP (ph->p_vaddr + ph->p_filesz, GLRO(dl_pagesize));
 	  c->dataend = ph->p_vaddr + ph->p_filesz;
 	  c->allocend = ph->p_vaddr + ph->p_memsz;
+	  c->mapalign = ph->p_align;
 	  c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
 
 	  /* Determine whether there is a gap between the last segment
diff --git a/elf/dl-load.h b/elf/dl-load.h
index e329d49a81..c121e3456c 100644
--- a/elf/dl-load.h
+++ b/elf/dl-load.h
@@ -74,7 +74,7 @@ ELF_PREFERRED_ADDRESS_DATA;
    Its details have been expanded out and converted.  */
 struct loadcmd
 {
-  ElfW(Addr) mapstart, mapend, dataend, allocend;
+  ElfW(Addr) mapstart, mapend, dataend, allocend, mapalign;
   ElfW(Off) mapoff;
   int prot;                             /* PROT_* bits.  */
 };
diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
index f9fb110ee3..f147ec232f 100644
--- a/elf/dl-map-segments.h
+++ b/elf/dl-map-segments.h
@@ -18,6 +18,52 @@
 
 #include <dl-load.h>
 
+/* Map a segment and align it properly.  */
+
+static __always_inline ElfW(Addr)
+_dl_map_segment (const struct loadcmd *c, ElfW(Addr) mappref,
+		 const size_t maplength, int fd)
+{
+  if (c->mapalign > GLRO(dl_pagesize))
+    {
+      /* If the segment alignment > the page size, allocate enough space
+         to ensure that the segment can be properly aligned.  */
+      ElfW(Addr) maplen = (maplength >= c->mapalign
+			   ? (maplength + c->mapalign)
+			   : (2 * c->mapalign));
+      ElfW(Addr) map_start
+	= (ElfW(Addr)) __mmap ((void *) mappref, maplen,
+			       PROT_NONE, MAP_ANONYMOUS|MAP_PRIVATE,
+			       -1, 0);
+      if (__glibc_unlikely ((void *) map_start == MAP_FAILED))
+	return map_start;
+
+      ElfW(Addr) map_start_aligned = ALIGN_UP (map_start, c->mapalign);
+      ElfW(Addr) map_end = map_start_aligned + maplength;
+      map_start_aligned
+	= (ElfW(Addr)) __mmap ((void *) map_start_aligned,
+			       maplength, c->prot,
+			       MAP_COPY|MAP_FILE|MAP_FIXED,
+			       fd, c->mapoff);
+      if (__glibc_likely ((void *) map_start_aligned != MAP_FAILED))
+	{
+	  /* Unmap the unused regions.  */
+	  ElfW(Addr) delta = map_start_aligned - map_start;
+	  if (delta)
+	    __munmap ((void *) map_start, delta);
+	  delta = map_start + maplen - map_end;
+	  if (delta)
+	    __munmap ((void *) map_end, delta);
+	}
+
+      return map_start_aligned;
+    }
+
+  return (ElfW(Addr)) __mmap ((void *) mappref, maplength,
+			      c->prot, MAP_COPY|MAP_FILE,
+			      fd, c->mapoff);
+}
+
 /* This implementation assumes (as does the corresponding implementation
    of _dl_unmap_segments, in dl-unmap-segments.h) that shared objects
    are always laid out with all segments contiguous (or with gaps
@@ -53,10 +99,7 @@ _dl_map_segments (struct link_map *l, int fd,
            - MAP_BASE_ADDR (l));
 
       /* Remember which part of the address space this object uses.  */
-      l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
-                                            c->prot,
-                                            MAP_COPY|MAP_FILE,
-                                            fd, c->mapoff);
+      l->l_map_start = _dl_map_segment (c, mappref, maplength, fd);
       if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED))
         return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
 
-- 
2.33.1

[PATCH v4] elf: Properly align PT_LOAD segments [BZ #28676]

[H.J. Lu]

On Thu, Dec 09, 2021 at 10:04:32AM -0800, H.J. Lu wrote:
> On Thu, Dec 09, 2021 at 07:14:10AM -0800, H.J. Lu wrote:
> 
> Hi,
> 
> I updated your patch.  Please take a look.
> 
> 
> H.J.
> --
> When PT_LOAD segment alignment > the page size, allocate enough space
> to ensure that the segment can be properly aligned.
> 
> This fixes [BZ #28676].


H.J.
---
Changes in v4:

1. Call unmap when the second mmap fails.

When PT_LOAD segment alignment > the page size, allocate enough space
to ensure that the segment can be properly aligned.

This fixes [BZ #28676].
---
 elf/dl-load.c         |  1 +
 elf/dl-load.h         |  2 +-
 elf/dl-map-segments.h | 49 +++++++++++++++++++++++++++++++++++++++----
 3 files changed, 47 insertions(+), 5 deletions(-)

diff --git a/elf/dl-load.c b/elf/dl-load.c
index bf8957e73c..9a23590bf4 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1150,6 +1150,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
 	  c->mapend = ALIGN_UP (ph->p_vaddr + ph->p_filesz, GLRO(dl_pagesize));
 	  c->dataend = ph->p_vaddr + ph->p_filesz;
 	  c->allocend = ph->p_vaddr + ph->p_memsz;
+	  c->mapalign = ph->p_align;
 	  c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
 
 	  /* Determine whether there is a gap between the last segment
diff --git a/elf/dl-load.h b/elf/dl-load.h
index e329d49a81..c121e3456c 100644
--- a/elf/dl-load.h
+++ b/elf/dl-load.h
@@ -74,7 +74,7 @@ ELF_PREFERRED_ADDRESS_DATA;
    Its details have been expanded out and converted.  */
 struct loadcmd
 {
-  ElfW(Addr) mapstart, mapend, dataend, allocend;
+  ElfW(Addr) mapstart, mapend, dataend, allocend, mapalign;
   ElfW(Off) mapoff;
   int prot;                             /* PROT_* bits.  */
 };
diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
index f9fb110ee3..f710cf2e48 100644
--- a/elf/dl-map-segments.h
+++ b/elf/dl-map-segments.h
@@ -18,6 +18,50 @@
 
 #include <dl-load.h>
 
+/* Map a segment and align it properly.  */
+
+static __always_inline ElfW(Addr)
+_dl_map_segment (const struct loadcmd *c, ElfW(Addr) mappref,
+		 const size_t maplength, int fd)
+{
+  if (__glibc_likely (c->mapalign <= GLRO(dl_pagesize)))
+    return (ElfW(Addr)) __mmap ((void *) mappref, maplength, c->prot,
+				MAP_COPY|MAP_FILE, fd, c->mapoff);
+
+  /* If the segment alignment > the page size, allocate enough space to
+     ensure that the segment can be properly aligned.  */
+  ElfW(Addr) maplen = (maplength >= c->mapalign
+		       ? (maplength + c->mapalign)
+		       : (2 * c->mapalign));
+  ElfW(Addr) map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplen,
+					      PROT_NONE,
+					      MAP_ANONYMOUS|MAP_PRIVATE,
+					      -1, 0);
+  if (__glibc_unlikely ((void *) map_start == MAP_FAILED))
+    return map_start;
+
+  ElfW(Addr) map_start_aligned = ALIGN_UP (map_start, c->mapalign);
+  map_start_aligned = (ElfW(Addr)) __mmap ((void *) map_start_aligned,
+					   maplength, c->prot,
+					   MAP_COPY|MAP_FILE|MAP_FIXED,
+					   fd, c->mapoff);
+  if (__glibc_unlikely ((void *) map_start == MAP_FAILED))
+    __munmap ((void *) map_start, maplen);
+  else
+    {
+      /* Unmap the unused regions.  */
+      ElfW(Addr) delta = map_start_aligned - map_start;
+      if (delta)
+	__munmap ((void *) map_start, delta);
+      ElfW(Addr) map_end = map_start_aligned + maplength;
+      delta = map_start + maplen - map_end;
+      if (delta)
+	__munmap ((void *) map_end, delta);
+    }
+
+  return map_start_aligned;
+}
+
 /* This implementation assumes (as does the corresponding implementation
    of _dl_unmap_segments, in dl-unmap-segments.h) that shared objects
    are always laid out with all segments contiguous (or with gaps
@@ -53,10 +97,7 @@ _dl_map_segments (struct link_map *l, int fd,
            - MAP_BASE_ADDR (l));
 
       /* Remember which part of the address space this object uses.  */
-      l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
-                                            c->prot,
-                                            MAP_COPY|MAP_FILE,
-                                            fd, c->mapoff);
+      l->l_map_start = _dl_map_segment (c, mappref, maplength, fd);
       if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED))
         return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
 
-- 
2.33.1

Re: [PATCH v4] elf: Properly align PT_LOAD segments [BZ #28676]

[Rongwei Wang]

Hi, lhj

Thanks for your help! It's much better than my version.
And I find a small bug. you can check it again if available.

On 12/10/21 3:29 AM, H.J. Lu wrote:
> On Thu, Dec 09, 2021 at 10:04:32AM -0800, H.J. Lu wrote:
>> On Thu, Dec 09, 2021 at 07:14:10AM -0800, H.J. Lu wrote:
>>
>> Hi,
>>
>> I updated your patch.  Please take a look.
>>
>>
>> H.J.
>> --
>> When PT_LOAD segment alignment > the page size, allocate enough space
>> to ensure that the segment can be properly aligned.
>>
>> This fixes [BZ #28676].
> 
> 
> H.J.
> ---
> Changes in v4:
> 
> 1. Call unmap when the second mmap fails.
> 
> When PT_LOAD segment alignment > the page size, allocate enough space
> to ensure that the segment can be properly aligned.
> 
> This fixes [BZ #28676].
> ---
>   elf/dl-load.c         |  1 +
>   elf/dl-load.h         |  2 +-
>   elf/dl-map-segments.h | 49 +++++++++++++++++++++++++++++++++++++++----
>   3 files changed, 47 insertions(+), 5 deletions(-)
> 
> diff --git a/elf/dl-load.c b/elf/dl-load.c
> index bf8957e73c..9a23590bf4 100644
> --- a/elf/dl-load.c
> +++ b/elf/dl-load.c
> @@ -1150,6 +1150,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
>   	  c->mapend = ALIGN_UP (ph->p_vaddr + ph->p_filesz, GLRO(dl_pagesize));
>   	  c->dataend = ph->p_vaddr + ph->p_filesz;
>   	  c->allocend = ph->p_vaddr + ph->p_memsz;
> +	  c->mapalign = ph->p_align;
>   	  c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
>   
>   	  /* Determine whether there is a gap between the last segment
> diff --git a/elf/dl-load.h b/elf/dl-load.h
> index e329d49a81..c121e3456c 100644
> --- a/elf/dl-load.h
> +++ b/elf/dl-load.h
> @@ -74,7 +74,7 @@ ELF_PREFERRED_ADDRESS_DATA;
>      Its details have been expanded out and converted.  */
>   struct loadcmd
>   {
> -  ElfW(Addr) mapstart, mapend, dataend, allocend;
> +  ElfW(Addr) mapstart, mapend, dataend, allocend, mapalign;
>     ElfW(Off) mapoff;
>     int prot;                             /* PROT_* bits.  */
>   };
> diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
> index f9fb110ee3..f710cf2e48 100644
> --- a/elf/dl-map-segments.h
> +++ b/elf/dl-map-segments.h
> @@ -18,6 +18,50 @@
>   
>   #include <dl-load.h>
>   
> +/* Map a segment and align it properly.  */
> +
> +static __always_inline ElfW(Addr)
> +_dl_map_segment (const struct loadcmd *c, ElfW(Addr) mappref,
> +		 const size_t maplength, int fd)
> +{
> +  if (__glibc_likely (c->mapalign <= GLRO(dl_pagesize)))
> +    return (ElfW(Addr)) __mmap ((void *) mappref, maplength, c->prot,
> +				MAP_COPY|MAP_FILE, fd, c->mapoff);
> +
> +  /* If the segment alignment > the page size, allocate enough space to
> +     ensure that the segment can be properly aligned.  */
> +  ElfW(Addr) maplen = (maplength >= c->mapalign
> +		       ? (maplength + c->mapalign)
> +		       : (2 * c->mapalign));
> +  ElfW(Addr) map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplen,
> +					      PROT_NONE,
> +					      MAP_ANONYMOUS|MAP_PRIVATE,
> +					      -1, 0);
> +  if (__glibc_unlikely ((void *) map_start == MAP_FAILED))
> +    return map_start;
> +
> +  ElfW(Addr) map_start_aligned = ALIGN_UP (map_start, c->mapalign);
> +  map_start_aligned = (ElfW(Addr)) __mmap ((void *) map_start_aligned,
> +					   maplength, c->prot,
> +					   MAP_COPY|MAP_FILE|MAP_FIXED,
> +					   fd, c->mapoff);
> +  if (__glibc_unlikely ((void *) map_start == MAP_FAILED))
Is map_start_aligned here?

> +    __munmap ((void *) map_start, maplen);
> +  else
> +    {
> +      /* Unmap the unused regions.  */
> +      ElfW(Addr) delta = map_start_aligned - map_start;
> +      if (delta)
> +	__munmap ((void *) map_start, delta);
> +      ElfW(Addr) map_end = map_start_aligned + maplength;
> +      delta = map_start + maplen - map_end;
> +      if (delta)
> +	__munmap ((void *) map_end, delta);
> +    }
> +
> +  return map_start_aligned;
> +}
> +
>   /* This implementation assumes (as does the corresponding implementation
>      of _dl_unmap_segments, in dl-unmap-segments.h) that shared objects
>      are always laid out with all segments contiguous (or with gaps
> @@ -53,10 +97,7 @@ _dl_map_segments (struct link_map *l, int fd,
>              - MAP_BASE_ADDR (l));
>   
>         /* Remember which part of the address space this object uses.  */
> -      l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
> -                                            c->prot,
> -                                            MAP_COPY|MAP_FILE,
> -                                            fd, c->mapoff);
> +      l->l_map_start = _dl_map_segment (c, mappref, maplength, fd);
>         if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED))
>           return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
>   
> 
All is OK for me.

And I am not sure whether I need to add a testcase in one new patch, 
because I saw you had submitted the testcase: 
https://gitlab.com/x86-glibc/glibc/-/commit/ba63c1cb2ea1b0ae421f66756771ff4c89d4a470

I will test it again, and send out PATCH v5.

Thanks.

Re: [PATCH v4] elf: Properly align PT_LOAD segments [BZ #28676]

[H.J. Lu]

On Thu, Dec 9, 2021 at 5:58 PM Rongwei Wang
<rongwei.wang@linux.alibaba.com> wrote:
>
>
> Hi, lhj
>
> Thanks for your help! It's much better than my version.
> And I find a small bug. you can check it again if available.
>
> On 12/10/21 3:29 AM, H.J. Lu wrote:
> > On Thu, Dec 09, 2021 at 10:04:32AM -0800, H.J. Lu wrote:
> >> On Thu, Dec 09, 2021 at 07:14:10AM -0800, H.J. Lu wrote:
> >>
> >> Hi,
> >>
> >> I updated your patch.  Please take a look.
> >>
> >>
> >> H.J.
> >> --
> >> When PT_LOAD segment alignment > the page size, allocate enough space
> >> to ensure that the segment can be properly aligned.
> >>
> >> This fixes [BZ #28676].
> >
> >
> > H.J.
> > ---
> > Changes in v4:
> >
> > 1. Call unmap when the second mmap fails.
> >
> > When PT_LOAD segment alignment > the page size, allocate enough space
> > to ensure that the segment can be properly aligned.
> >
> > This fixes [BZ #28676].
> > ---
> >   elf/dl-load.c         |  1 +
> >   elf/dl-load.h         |  2 +-
> >   elf/dl-map-segments.h | 49 +++++++++++++++++++++++++++++++++++++++----
> >   3 files changed, 47 insertions(+), 5 deletions(-)
> >
> > diff --git a/elf/dl-load.c b/elf/dl-load.c
> > index bf8957e73c..9a23590bf4 100644
> > --- a/elf/dl-load.c
> > +++ b/elf/dl-load.c
> > @@ -1150,6 +1150,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
> >         c->mapend = ALIGN_UP (ph->p_vaddr + ph->p_filesz, GLRO(dl_pagesize));
> >         c->dataend = ph->p_vaddr + ph->p_filesz;
> >         c->allocend = ph->p_vaddr + ph->p_memsz;
> > +       c->mapalign = ph->p_align;
> >         c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
> >
> >         /* Determine whether there is a gap between the last segment
> > diff --git a/elf/dl-load.h b/elf/dl-load.h
> > index e329d49a81..c121e3456c 100644
> > --- a/elf/dl-load.h
> > +++ b/elf/dl-load.h
> > @@ -74,7 +74,7 @@ ELF_PREFERRED_ADDRESS_DATA;
> >      Its details have been expanded out and converted.  */
> >   struct loadcmd
> >   {
> > -  ElfW(Addr) mapstart, mapend, dataend, allocend;
> > +  ElfW(Addr) mapstart, mapend, dataend, allocend, mapalign;
> >     ElfW(Off) mapoff;
> >     int prot;                             /* PROT_* bits.  */
> >   };
> > diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
> > index f9fb110ee3..f710cf2e48 100644
> > --- a/elf/dl-map-segments.h
> > +++ b/elf/dl-map-segments.h
> > @@ -18,6 +18,50 @@
> >
> >   #include <dl-load.h>
> >
> > +/* Map a segment and align it properly.  */
> > +
> > +static __always_inline ElfW(Addr)
> > +_dl_map_segment (const struct loadcmd *c, ElfW(Addr) mappref,
> > +              const size_t maplength, int fd)
> > +{
> > +  if (__glibc_likely (c->mapalign <= GLRO(dl_pagesize)))
> > +    return (ElfW(Addr)) __mmap ((void *) mappref, maplength, c->prot,
> > +                             MAP_COPY|MAP_FILE, fd, c->mapoff);
> > +
> > +  /* If the segment alignment > the page size, allocate enough space to
> > +     ensure that the segment can be properly aligned.  */
> > +  ElfW(Addr) maplen = (maplength >= c->mapalign
> > +                    ? (maplength + c->mapalign)
> > +                    : (2 * c->mapalign));
> > +  ElfW(Addr) map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplen,
> > +                                           PROT_NONE,
> > +                                           MAP_ANONYMOUS|MAP_PRIVATE,
> > +                                           -1, 0);
> > +  if (__glibc_unlikely ((void *) map_start == MAP_FAILED))
> > +    return map_start;
> > +
> > +  ElfW(Addr) map_start_aligned = ALIGN_UP (map_start, c->mapalign);
> > +  map_start_aligned = (ElfW(Addr)) __mmap ((void *) map_start_aligned,
> > +                                        maplength, c->prot,
> > +                                        MAP_COPY|MAP_FILE|MAP_FIXED,
> > +                                        fd, c->mapoff);
> > +  if (__glibc_unlikely ((void *) map_start == MAP_FAILED))
> Is map_start_aligned here?
>
> > +    __munmap ((void *) map_start, maplen);
> > +  else
> > +    {
> > +      /* Unmap the unused regions.  */
> > +      ElfW(Addr) delta = map_start_aligned - map_start;
> > +      if (delta)
> > +     __munmap ((void *) map_start, delta);
> > +      ElfW(Addr) map_end = map_start_aligned + maplength;
> > +      delta = map_start + maplen - map_end;
> > +      if (delta)
> > +     __munmap ((void *) map_end, delta);
> > +    }
> > +
> > +  return map_start_aligned;
> > +}
> > +
> >   /* This implementation assumes (as does the corresponding implementation
> >      of _dl_unmap_segments, in dl-unmap-segments.h) that shared objects
> >      are always laid out with all segments contiguous (or with gaps
> > @@ -53,10 +97,7 @@ _dl_map_segments (struct link_map *l, int fd,
> >              - MAP_BASE_ADDR (l));
> >
> >         /* Remember which part of the address space this object uses.  */
> > -      l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
> > -                                            c->prot,
> > -                                            MAP_COPY|MAP_FILE,
> > -                                            fd, c->mapoff);
> > +      l->l_map_start = _dl_map_segment (c, mappref, maplength, fd);
> >         if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED))
> >           return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
> >
> >
> All is OK for me.
>
> And I am not sure whether I need to add a testcase in one new patch,
> because I saw you had submitted the testcase:
> https://gitlab.com/x86-glibc/glibc/-/commit/ba63c1cb2ea1b0ae421f66756771ff4c89d4a470

No, I didn't submit it.

> I will test it again, and send out PATCH v5.

Please include my testcase in your v5 patch.

Thanks.


--
H.J.

Re: [PATCH v4] elf: Properly align PT_LOAD segments [BZ #28676]

[Rongwei Wang]

On 12/10/21 10:24 AM, H.J. Lu wrote:
> On Thu, Dec 9, 2021 at 5:58 PM Rongwei Wang
> <rongwei.wang@linux.alibaba.com> wrote:
>>
>>
>> Hi, lhj
>>
>> Thanks for your help! It's much better than my version.
>> And I find a small bug. you can check it again if available.
>>
>> On 12/10/21 3:29 AM, H.J. Lu wrote:
>>> On Thu, Dec 09, 2021 at 10:04:32AM -0800, H.J. Lu wrote:
>>>> On Thu, Dec 09, 2021 at 07:14:10AM -0800, H.J. Lu wrote:
>>>>
>>>> Hi,
>>>>
>>>> I updated your patch.  Please take a look.
>>>>
>>>>
>>>> H.J.
>>>> --
>>>> When PT_LOAD segment alignment > the page size, allocate enough space
>>>> to ensure that the segment can be properly aligned.
>>>>
>>>> This fixes [BZ #28676].
>>>
>>>
>>> H.J.
>>> ---
>>> Changes in v4:
>>>
>>> 1. Call unmap when the second mmap fails.
>>>
>>> When PT_LOAD segment alignment > the page size, allocate enough space
>>> to ensure that the segment can be properly aligned.
>>>
>>> This fixes [BZ #28676].
>>> ---
>>>    elf/dl-load.c         |  1 +
>>>    elf/dl-load.h         |  2 +-
>>>    elf/dl-map-segments.h | 49 +++++++++++++++++++++++++++++++++++++++----
>>>    3 files changed, 47 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/elf/dl-load.c b/elf/dl-load.c
>>> index bf8957e73c..9a23590bf4 100644
>>> --- a/elf/dl-load.c
>>> +++ b/elf/dl-load.c
>>> @@ -1150,6 +1150,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
>>>          c->mapend = ALIGN_UP (ph->p_vaddr + ph->p_filesz, GLRO(dl_pagesize));
>>>          c->dataend = ph->p_vaddr + ph->p_filesz;
>>>          c->allocend = ph->p_vaddr + ph->p_memsz;
>>> +       c->mapalign = ph->p_align;
>>>          c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
>>>
>>>          /* Determine whether there is a gap between the last segment
>>> diff --git a/elf/dl-load.h b/elf/dl-load.h
>>> index e329d49a81..c121e3456c 100644
>>> --- a/elf/dl-load.h
>>> +++ b/elf/dl-load.h
>>> @@ -74,7 +74,7 @@ ELF_PREFERRED_ADDRESS_DATA;
>>>       Its details have been expanded out and converted.  */
>>>    struct loadcmd
>>>    {
>>> -  ElfW(Addr) mapstart, mapend, dataend, allocend;
>>> +  ElfW(Addr) mapstart, mapend, dataend, allocend, mapalign;
>>>      ElfW(Off) mapoff;
>>>      int prot;                             /* PROT_* bits.  */
>>>    };
>>> diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
>>> index f9fb110ee3..f710cf2e48 100644
>>> --- a/elf/dl-map-segments.h
>>> +++ b/elf/dl-map-segments.h
>>> @@ -18,6 +18,50 @@
>>>
>>>    #include <dl-load.h>
>>>
>>> +/* Map a segment and align it properly.  */
>>> +
>>> +static __always_inline ElfW(Addr)
>>> +_dl_map_segment (const struct loadcmd *c, ElfW(Addr) mappref,
>>> +              const size_t maplength, int fd)
>>> +{
>>> +  if (__glibc_likely (c->mapalign <= GLRO(dl_pagesize)))
>>> +    return (ElfW(Addr)) __mmap ((void *) mappref, maplength, c->prot,
>>> +                             MAP_COPY|MAP_FILE, fd, c->mapoff);
>>> +
>>> +  /* If the segment alignment > the page size, allocate enough space to
>>> +     ensure that the segment can be properly aligned.  */
>>> +  ElfW(Addr) maplen = (maplength >= c->mapalign
>>> +                    ? (maplength + c->mapalign)
>>> +                    : (2 * c->mapalign));
>>> +  ElfW(Addr) map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplen,
>>> +                                           PROT_NONE,
>>> +                                           MAP_ANONYMOUS|MAP_PRIVATE,
>>> +                                           -1, 0);
>>> +  if (__glibc_unlikely ((void *) map_start == MAP_FAILED))
>>> +    return map_start;
>>> +
>>> +  ElfW(Addr) map_start_aligned = ALIGN_UP (map_start, c->mapalign);
>>> +  map_start_aligned = (ElfW(Addr)) __mmap ((void *) map_start_aligned,
>>> +                                        maplength, c->prot,
>>> +                                        MAP_COPY|MAP_FILE|MAP_FIXED,
>>> +                                        fd, c->mapoff);
>>> +  if (__glibc_unlikely ((void *) map_start == MAP_FAILED))
>> Is map_start_aligned here?
>>
>>> +    __munmap ((void *) map_start, maplen);
>>> +  else
>>> +    {
>>> +      /* Unmap the unused regions.  */
>>> +      ElfW(Addr) delta = map_start_aligned - map_start;
>>> +      if (delta)
>>> +     __munmap ((void *) map_start, delta);
>>> +      ElfW(Addr) map_end = map_start_aligned + maplength;
>>> +      delta = map_start + maplen - map_end;
>>> +      if (delta)
>>> +     __munmap ((void *) map_end, delta);
>>> +    }
>>> +
>>> +  return map_start_aligned;
>>> +}
>>> +
>>>    /* This implementation assumes (as does the corresponding implementation
>>>       of _dl_unmap_segments, in dl-unmap-segments.h) that shared objects
>>>       are always laid out with all segments contiguous (or with gaps
>>> @@ -53,10 +97,7 @@ _dl_map_segments (struct link_map *l, int fd,
>>>               - MAP_BASE_ADDR (l));
>>>
>>>          /* Remember which part of the address space this object uses.  */
>>> -      l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
>>> -                                            c->prot,
>>> -                                            MAP_COPY|MAP_FILE,
>>> -                                            fd, c->mapoff);
>>> +      l->l_map_start = _dl_map_segment (c, mappref, maplength, fd);
>>>          if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED))
>>>            return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
>>>
>>>
>> All is OK for me.
>>
>> And I am not sure whether I need to add a testcase in one new patch,
>> because I saw you had submitted the testcase:
>> https://gitlab.com/x86-glibc/glibc/-/commit/ba63c1cb2ea1b0ae421f66756771ff4c89d4a470
> 
> No, I didn't submit it.
> 
>> I will test it again, and send out PATCH v5.
> 
> Please include my testcase in your v5 patch.
Ok

Thanks.

> 
> Thanks.
> 
> 
> --
> H.J.
>