From: Rongwei Wang <rongwei.wang@linux.alibaba.com>
To: libc-alpha@sourceware.org, hjl.tools@gmail.com,
fweimer@redhat.com, adhemerval.zanella@linaro.org
Cc: xuyu@linux.alibaba.com, gavin.dg@linux.alibaba.com
Subject: [PATCH v6 1/2] elf: Properly align PT_LOAD segments [BZ #28676]
Date: Mon, 13 Dec 2021 10:51:02 +0800 [thread overview]
Message-ID: <20211213025103.48472-2-rongwei.wang@linux.alibaba.com> (raw)
In-Reply-To: <20211213025103.48472-1-rongwei.wang@linux.alibaba.com>
When PT_LOAD segment alignment > the page size, allocate
enough space to ensure that the segment can be properly
aligned.
And this change helps code segments use huge pages become
simple and available.
This fixes [BZ #28676].
Signed-off-by: Xu Yu <xuyu@linux.alibaba.com>
Signed-off-by: Rongwei Wang <rongwei.wang@linux.alibaba.com>
---
elf/dl-load.c | 2 ++
elf/dl-load.h | 3 ++-
elf/dl-map-segments.h | 50 +++++++++++++++++++++++++++++++++++++++----
3 files changed, 50 insertions(+), 5 deletions(-)
diff --git a/elf/dl-load.c b/elf/dl-load.c
index bf8957e73c..721593135e 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1,5 +1,6 @@
/* Map in a shared object's segments from the file.
Copyright (C) 1995-2021 Free Software Foundation, Inc.
+ Copyright The GNU Toolchain Authors.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -1150,6 +1151,7 @@ _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..e6dabcb336 100644
--- a/elf/dl-load.h
+++ b/elf/dl-load.h
@@ -1,5 +1,6 @@
/* Map in a shared object's segments from the file.
Copyright (C) 1995-2021 Free Software Foundation, Inc.
+ Copyright The GNU Toolchain Authors.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -74,7 +75,7 @@ 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..70a4c40695 100644
--- a/elf/dl-map-segments.h
+++ b/elf/dl-map-segments.h
@@ -1,5 +1,6 @@
/* Map in a shared object's segments. Generic version.
Copyright (C) 1995-2021 Free Software Foundation, Inc.
+ Copyright The GNU Toolchain Authors.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -18,6 +19,50 @@
#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_aligned == 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 +98,7 @@ _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;
--
2.27.0
next prev parent reply other threads:[~2021-12-13 2:51 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-04 4:58 [PATCH RFC 0/1] make ld.so map .text LOAD ssegments and aligned by p_align Rongwei Wang
2021-12-04 4:58 ` [PATCH RFC 1/1] elf: align the mapping address of LOAD segments with p_align Rongwei Wang
2021-12-04 18:10 ` Florian Weimer
2021-12-06 2:47 ` Rongwei Wang
2021-12-06 14:48 ` H.J. Lu
2021-12-08 2:14 ` Rongwei Wang
2021-12-08 2:33 ` H.J. Lu
2021-12-08 3:04 ` Rongwei Wang
2021-12-08 23:52 ` H.J. Lu
2021-12-09 1:43 ` Rongwei Wang
2021-12-10 12:39 ` [PATCH v5 0/2] fix p_align on PT_LOAD segment in DSO isn't honored Rongwei Wang
2021-12-10 12:39 ` [PATCH v5 1/2] elf: Properly align PT_LOAD segments Rongwei Wang
2021-12-10 15:43 ` H.J. Lu
2021-12-10 15:45 ` Florian Weimer
2021-12-10 18:54 ` H.J. Lu
2021-12-10 18:57 ` H.J. Lu
2021-12-10 12:39 ` [PATCH v5 2/2] Add a testcase to check alignment of PT_LOAD segment Rongwei Wang
2021-12-10 13:48 ` Adhemerval Zanella
2021-12-10 15:41 ` H.J. Lu
2021-12-10 18:56 ` H.J. Lu
2021-12-10 20:05 ` Adhemerval Zanella
2021-12-10 20:24 ` H.J. Lu
2021-12-10 21:34 ` Adhemerval Zanella
2021-12-10 13:13 ` [PATCH v5 0/2] fix p_align on PT_LOAD segment in DSO isn't honored H.J. Lu
2021-12-10 13:58 ` Rongwei Wang
2021-12-13 2:51 ` [PATCH v6 " Rongwei Wang
2021-12-13 2:51 ` Rongwei Wang [this message]
2021-12-13 11:05 ` [PATCH v6 1/2] elf: Properly align PT_LOAD segments [BZ #28676] Szabolcs Nagy
2021-12-13 11:17 ` Florian Weimer
2021-12-13 11:35 ` Szabolcs Nagy
2021-12-13 11:59 ` Florian Weimer
2021-12-13 13:20 ` H.J. Lu
2021-12-13 13:26 ` Florian Weimer
2021-12-13 13:34 ` H.J. Lu
2021-12-13 11:46 ` Andreas Schwab
2021-12-13 11:52 ` Szabolcs Nagy
2021-12-13 14:51 ` Rongwei Wang
2021-12-13 17:37 ` Szabolcs Nagy
2021-12-13 17:50 ` Florian Weimer
2021-12-13 2:51 ` [PATCH v6 2/2] Add a testcase to check alignment of PT_LOAD segment Rongwei Wang
2021-12-14 2:03 ` [PATCH v6 0/2] fix p_align on PT_LOAD segment in DSO isn't honored Fangrui Song
2021-12-14 3:56 ` H.J. Lu
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