From: "H.J. Lu" <hjl.tools@gmail.com>
To: Rongwei Wang <rongwei.wang@linux.alibaba.com>,
GNU C Library <libc-alpha@sourceware.org>,
Florian Weimer <fweimer@redhat.com>,
xuyu@linux.alibaba.com, gavin.dg@linux.alibaba.com
Subject: [PATCH v4] elf: Properly align PT_LOAD segments [BZ #28676]
Date: Thu, 9 Dec 2021 11:29:17 -0800 [thread overview]
Message-ID: <YbJZDQzd0fcU0oxF@gmail.com> (raw)
In-Reply-To: <YbJFMFz5Ni7tzDMm@gmail.com>
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
next prev parent reply other threads:[~2021-12-09 19:29 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-09 5:57 [PATCH v2 0/1] fix p_align on PT_LOAD segment in DSO isn't honored Rongwei Wang
2021-12-09 5:57 ` [PATCH v2 1/1] elf: align the mapping address of LOAD segments with p_align Rongwei Wang
2021-12-09 15:14 ` H.J. Lu
2021-12-09 18:04 ` [PATCH v3] elf: Properly align PT_LOAD segments [BZ #28676] H.J. Lu
2021-12-09 19:29 ` H.J. Lu [this message]
2021-12-10 1:58 ` [PATCH v4] " Rongwei Wang
2021-12-10 2:24 ` H.J. Lu
2021-12-10 2:34 ` Rongwei Wang
2021-12-09 6:36 ` [PATCH v2 0/1] fix p_align on PT_LOAD segment in DSO isn't honored Rongwei Wang
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