From: Stas Sergeev <stsp2@yandex.ru>
To: libc-alpha@sourceware.org
Cc: Stas Sergeev <stsp2@yandex.ru>
Subject: [PATCH 03/14] rework maphole
Date: Thu, 18 May 2023 13:28:43 +0500 [thread overview]
Message-ID: <20230518082854.3903342-4-stsp2@yandex.ru> (raw)
In-Reply-To: <20230518082854.3903342-1-stsp2@yandex.ru>
Remove "has_holes" argument that was used to mprotect the entire
initial mapping as PROT_NONE. Instead apply PROT_NONE at each
individual hole.
This is needed to make it possible to split the protection stage
from mmap stage.
The test-suite was run on x86_64/64 and showed no regressions.
Signed-off-by: Stas Sergeev <stsp2@yandex.ru>
---
elf/dl-load.c | 8 +++----
elf/dl-load.h | 3 +--
elf/dl-map-segments.h | 52 ++++++++++++++++++++++++++-----------------
3 files changed, 36 insertions(+), 27 deletions(-)
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 39c63ff1b3..4007a4aae3 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1089,7 +1089,6 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
/* Scan the program header table, collecting its load commands. */
struct loadcmd loadcmds[l->l_phnum];
size_t nloadcmds = 0;
- bool has_holes = false;
bool empty_dynamic = false;
ElfW(Addr) p_align_max = 0;
@@ -1141,6 +1140,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
if (powerof2 (ph->p_align) && ph->p_align > p_align_max)
p_align_max = ph->p_align;
c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
+ c->maphole = 0;
DIAG_PUSH_NEEDS_COMMENT;
@@ -1153,8 +1153,8 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
#endif
/* Determine whether there is a gap between the last segment
and this one. */
- if (nloadcmds > 1 && c[-1].mapend != c->mapstart)
- has_holes = true;
+ if (nloadcmds > 1 && c[-1].mapend < c->mapstart)
+ c[-1].maphole = c->mapstart - c[-1].mapend;
DIAG_POP_NEEDS_COMMENT;
/* Optimize a common case. */
@@ -1256,7 +1256,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
l_map_start, l_map_end, l_addr, l_contiguous, l_text_end, l_phdr
*/
errstring = _dl_map_segments (l, fd, header, type, loadcmds, nloadcmds,
- maplength, has_holes, loader);
+ maplength, loader);
if (__glibc_unlikely (errstring != NULL))
{
/* Mappings can be in an inconsistent state: avoid unmap. */
diff --git a/elf/dl-load.h b/elf/dl-load.h
index ecf6910c68..029181e8c8 100644
--- a/elf/dl-load.h
+++ b/elf/dl-load.h
@@ -75,7 +75,7 @@ ELF_PREFERRED_ADDRESS_DATA;
Its details have been expanded out and converted. */
struct loadcmd
{
- ElfW(Addr) mapstart, mapend, dataend, allocend, mapalign;
+ ElfW(Addr) mapstart, mapend, dataend, allocend, mapalign, maphole;
ElfW(Off) mapoff;
int prot; /* PROT_* bits. */
};
@@ -118,7 +118,6 @@ static const char *_dl_map_segments (struct link_map *l, int fd,
const struct loadcmd loadcmds[],
size_t nloadcmds,
const size_t maplength,
- bool has_holes,
struct link_map *loader);
/* All the error message strings _dl_map_segments might return are
diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
index 6a6127f773..080199b76e 100644
--- a/elf/dl-map-segments.h
+++ b/elf/dl-map-segments.h
@@ -77,7 +77,7 @@ static __always_inline const char *
_dl_map_segments (struct link_map *l, int fd,
const ElfW(Ehdr) *header, int type,
const struct loadcmd loadcmds[], size_t nloadcmds,
- const size_t maplength, bool has_holes,
+ const size_t maplength,
struct link_map *loader)
{
const struct loadcmd *c = loadcmds;
@@ -106,25 +106,6 @@ _dl_map_segments (struct link_map *l, int fd,
l->l_map_end = l->l_map_start + maplength;
l->l_addr = l->l_map_start - c->mapstart;
-
- if (has_holes)
- {
- /* Change protection on the excess portion to disallow all access;
- the portions we do not remap later will be inaccessible as if
- unallocated. Then jump into the normal segment-mapping loop to
- handle the portion of the segment past the end of the file
- mapping. */
- if (__glibc_unlikely (loadcmds[nloadcmds - 1].mapstart <
- c->mapend))
- return N_("ELF load command address/offset not page-aligned");
- if (__glibc_unlikely
- (__mprotect ((caddr_t) (l->l_addr + c->mapend),
- loadcmds[nloadcmds - 1].mapstart - c->mapend,
- PROT_NONE) < 0))
- return DL_MAP_SEGMENTS_ERROR_MPROTECT;
- }
-
- l->l_contiguous = 1;
}
else
{
@@ -136,11 +117,14 @@ _dl_map_segments (struct link_map *l, int fd,
if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED))
return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
l->l_map_end = l->l_map_start + maplength;
- l->l_contiguous = !has_holes;
}
+ /* Reset to 0 later if hole found. */
+ l->l_contiguous = 1;
while (c < &loadcmds[nloadcmds])
{
+ ElfW(Addr) hole_start, hole_size;
+
if (c->mapend > c->mapstart
/* Map the segment contents from the file. */
&& (__mmap ((void *) (l->l_addr + c->mapstart),
@@ -157,11 +141,15 @@ _dl_map_segments (struct link_map *l, int fd,
/* Extra zero pages should appear at the end of this segment,
after the data mapped from the file. */
ElfW(Addr) zero, zeroend, zeropage;
+ ElfW(Off) hole_off;
zero = l->l_addr + c->dataend;
zeroend = l->l_addr + c->allocend;
zeropage = ((zero + GLRO(dl_pagesize) - 1)
& ~(GLRO(dl_pagesize) - 1));
+ hole_start = ALIGN_UP (c->allocend, GLRO(dl_pagesize));
+ hole_off = hole_start - c->mapend;
+ hole_size = c->maphole - hole_off;
if (zeroend < zeropage)
/* All the extra data is in the last page of the segment.
@@ -194,6 +182,28 @@ _dl_map_segments (struct link_map *l, int fd,
return DL_MAP_SEGMENTS_ERROR_MPROTECT;
}
}
+ else
+ {
+ hole_start = c->mapend;
+ hole_size = c->maphole;
+ }
+
+ if (__glibc_unlikely (c->maphole))
+ {
+ if (__glibc_likely (type == ET_DYN))
+ {
+ if (hole_size)
+ {
+ if (__mprotect ((caddr_t) (l->l_addr + hole_start),
+ hole_size, PROT_NONE) < 0)
+ return DL_MAP_SEGMENTS_ERROR_MPROTECT;
+ }
+ }
+ else if (l->l_contiguous)
+ {
+ l->l_contiguous = 0;
+ }
+ }
++c;
}
--
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 ` [PATCH 01/14] elf: switch _dl_map_segment() to anonymous mapping Stas Sergeev
2023-05-18 8:28 ` [PATCH 02/14] use initial mmap also for ET_EXEC Stas Sergeev
2023-05-18 8:28 ` Stas Sergeev [this message]
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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