From: Stas Sergeev <stsp2@yandex.ru>
To: libc-alpha@sourceware.org
Cc: Stas Sergeev <stsp2@yandex.ru>
Subject: [PATCH 01/14] elf: switch _dl_map_segment() to anonymous mapping
Date: Thu, 18 May 2023 13:28:41 +0500 [thread overview]
Message-ID: <20230518082854.3903342-2-stsp2@yandex.ru> (raw)
In-Reply-To: <20230518082854.3903342-1-stsp2@yandex.ru>
_dl_map_segment() was mapping entire file image and then was skipping
the load of the first segment. Switch _dl_map_segment() to anonymous
mapping and do not skip the map of the first segment.
Use PROT_READ|PROT_WRITE as a protection. _dl_map_segments() later
sets the proper protection for both file-mapped and anonymous parts.
The test-suite was run on x86_64/64 and showed no regressions.
Signed-off-by: Stas Sergeev <stsp2@yandex.ru>
---
elf/dl-map-segments.h | 69 ++++++++++++++++++++++---------------------
1 file changed, 35 insertions(+), 34 deletions(-)
diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
index 504cfc0a41..ed7675cabf 100644
--- a/elf/dl-map-segments.h
+++ b/elf/dl-map-segments.h
@@ -22,18 +22,22 @@
/* 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)
+_dl_map_segment (ElfW(Addr) mappref, size_t maplength, size_t mapalign)
{
- if (__glibc_likely (c->mapalign <= GLRO(dl_pagesize)))
- return (ElfW(Addr)) __mmap ((void *) mappref, maplength, c->prot,
- MAP_COPY|MAP_FILE, fd, c->mapoff);
+ int err;
+ /* MAP_COPY is a special flag combination for solibs. */
+ unsigned int map_flags = MAP_ANONYMOUS | MAP_COPY;
+ unsigned int prot = PROT_READ | PROT_WRITE;
+
+ if (__glibc_likely (mapalign <= GLRO(dl_pagesize)))
+ return (ElfW(Addr)) __mmap ((void *) mappref, maplength, prot,
+ map_flags, -1, 0);
/* 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) maplen = (maplength >= mapalign
+ ? (maplength + mapalign)
+ : (2 * mapalign));
ElfW(Addr) map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplen,
PROT_NONE,
MAP_ANONYMOUS|MAP_PRIVATE,
@@ -41,26 +45,24 @@ _dl_map_segment (const struct loadcmd *c, ElfW(Addr) mappref,
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
+ ElfW(Addr) map_start_aligned = ALIGN_UP (map_start, mapalign);
+ err = __mprotect ((void *) map_start_aligned, maplength, prot);
+ if (__glibc_unlikely (err))
{
- /* 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;
- map_end = ALIGN_UP (map_end, GLRO(dl_pagesize));
- delta = map_start + maplen - map_end;
- if (delta)
- __munmap ((void *) map_end, delta);
+ __munmap ((void *) map_start, maplen);
+ return (ElfW(Addr)) MAP_FAILED;
}
+ /* 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;
+ map_end = ALIGN_UP (map_end, GLRO(dl_pagesize));
+ delta = map_start + maplen - map_end;
+ if (delta)
+ __munmap ((void *) map_end, delta);
+
return map_start_aligned;
}
@@ -98,7 +100,7 @@ _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 = _dl_map_segment (c, mappref, maplength, fd);
+ l->l_map_start = _dl_map_segment (mappref, maplength, c->mapalign);
if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED))
return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
@@ -123,14 +125,14 @@ _dl_map_segments (struct link_map *l, int fd,
}
l->l_contiguous = 1;
-
- goto postmap;
}
-
- /* Remember which part of the address space this object uses. */
- l->l_map_start = c->mapstart + l->l_addr;
- l->l_map_end = l->l_map_start + maplength;
- l->l_contiguous = !has_holes;
+ else
+ {
+ /* Remember which part of the address space this object uses. */
+ l->l_map_start = c->mapstart + l->l_addr;
+ l->l_map_end = l->l_map_start + maplength;
+ l->l_contiguous = !has_holes;
+ }
while (c < &loadcmds[nloadcmds])
{
@@ -143,7 +145,6 @@ _dl_map_segments (struct link_map *l, int fd,
== MAP_FAILED))
return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
- postmap:
_dl_postprocess_loadcmd (l, header, c);
if (c->allocend > c->dataend)
--
2.39.2
next prev parent reply other threads:[~2023-05-18 8:29 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-18 8:28 [PATCH 00/14] implement RTLD_NORELOCATE api [BZ #30007] Stas Sergeev
2023-05-18 8:28 ` Stas Sergeev [this message]
2023-05-18 8:28 ` [PATCH 02/14] use initial mmap also for ET_EXEC Stas Sergeev
2023-05-18 8:28 ` [PATCH 03/14] rework maphole Stas Sergeev
2023-05-18 8:28 ` [PATCH 04/14] split do_reloc_1() from dl_open_worker_begin() Stas Sergeev
2023-05-18 8:28 ` [PATCH 05/14] split do_reloc_2() out of do_open_worker() Stas Sergeev
2023-05-18 8:28 ` [PATCH 06/14] move relocation into _dl_object_reloc() func Stas Sergeev
2023-05-18 8:28 ` [PATCH 07/14] split out _dl_finalize_segments() Stas Sergeev
2023-05-18 8:28 ` [PATCH 08/14] finalize elf segments on a relocation step Stas Sergeev
2023-05-18 8:28 ` [PATCH 09/14] implement RTLD_NORELOCATE dlopen() flag Stas Sergeev
2023-05-18 8:28 ` [PATCH 10/14] add test-case for RTLD_NORELOCATE Stas Sergeev
2023-05-18 8:28 ` [PATCH 11/14] implement dlrelocate() function Stas Sergeev
2023-05-18 8:28 ` [PATCH 12/14] implement RTLD_DI_MAPINFO dlinfo() request Stas Sergeev
2023-05-18 8:28 ` [PATCH 13/14] implement dlset_object_base() function Stas Sergeev
2023-05-18 8:28 ` [PATCH 14/14] implement RTLD_DI_DEPLIST dlinfo() request Stas Sergeev
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