* [PATCH] linux-user: fix issues with mmap on 4K guest on 16K host and library load
@ 2026-08-05 16:40 Andreas Kemnade
2026-08-07 21:26 ` Helge Deller
0 siblings, 1 reply; 4+ messages in thread
From: Andreas Kemnade @ 2026-08-05 16:40 UTC (permalink / raw)
To: qemu-devel; +Cc: sre, Andreas Kemnade
Strace in qemu:
198005 openat(AT_FDCWD,"/lib/arm-linux-gnueabihf/libselinux.so.1",O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
198005 read(3,0x40802570,512) = 512
198005 statx(3,"",AT_EMPTY_PATH|AT_NO_AUTOMOUNT|AT_STATX_SYNC_AS_STAT,STATX_BASIC_STATS,0x408022a8) = 0
198005 mmap2(NULL,269428,PROT_NONE,MAP_PRIVATE|MAP_ANONYMOUS|MAP_DENYWRITE,-1,0) = 0x40868000
198005 mmap2(0x40870000,203892,PROT_EXEC|PROT_READ,MAP_PRIVATE|MAP_DENYWRITE|MAP_FIXED,3,0) = 0x40870000
198005 munmap(0x40868000,32768) = 0
198005 munmap(0x408a2000,31860) = 0
198005 mprotect(0x40890000,61440,PROT_NONE) = 0
198005 mmap2(0x4089f000,8192,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_DENYWRITE|MAP_FIXED,3,0x1f) = -1 errno=14 (Bad address)
strace outside qemu:
[pid 195331] readlinkat(AT_FDCWD, "/usr/lib", 0x7fffd1a7fd00, 1023) = -1 EINVAL (Invalid argument)
[pid 195331] readlinkat(AT_FDCWD, "/usr/lib/arm-linux-gnueabihf", 0x7fffd1a7fd00, 1023) = -1 EINVAL (Invalid argument)
[pid 195331] readlinkat(AT_FDCWD, "/usr/lib/arm-linux-gnueabihf/libselinux.so.1", 0x7fffd1a7fd00, 1023) = -1 EINVAL (Invalid argument)
[pid 195331] faccessat(AT_FDCWD, "/usr/gnemul/qemu-arm/lib/arm-linux-gnueabihf/libselinux.so.1", F_OK) = -1 ENOENT (No such file or directory)
[pid 195331] openat(AT_FDCWD, "/lib/arm-linux-gnueabihf/libselinux.so.1", O_RDONLY|O_CLOEXEC) = 3
[pid 195331] read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\0\0\0\0004\0\0\0"..., 512) = 512
[pid 195331] statx(3, "", AT_STATX_SYNC_AS_STAT|AT_NO_AUTOMOUNT|AT_EMPTY_PATH, STATX_BASIC_STATS, {stx_mask=STATX_ALL|STATX_MNT_ID|STATX_SUBVOL, stx_attributes=0, stx_mode=S_IFREG|0644, stx_size=132612, ...}) = 0
[pid 195331] mmap(0x408a8000, 16384, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_DENYWRITE, -1, 0) = 0x408a8000
[pid 195331] mprotect(0x408a8000, 16384, PROT_WRITE) = 0
[pid 195331] mprotect(0x408a8000, 16384, PROT_NONE) = 0
[pid 195331] mmap(0x40868000, 262144, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_DENYWRITE, -1, 0) = 0x40868000
[pid 195331] mprotect(0x408a0000, 16384, PROT_WRITE) = 0
[pid 195331] pread64(3, "", 8192, 196608) = 0
[pid 195331] mprotect(0x408a0000, 16384, PROT_READ) = 0
[pid 195331] mmap(0x40870000, 196608, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0) = 0x40870000
[pid 195331] mmap(0x40868000, 32768, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x40868000
[pid 195331] mmap(0x408a4000, 32768, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x408a4000
[pid 195331] mprotect(0x4089c000, 16384, PROT_READ) = 0
[pid 195331] mprotect(0x40890000, 49152, PROT_NONE) = 0
[pid 195331] mprotect(0x4089c000, 16384, PROT_WRITE) = 0
[pid 195331] pread64(3, 0x4089f000, 4096, 126976) = -1 EFAULT (Bad address)
That makes simple commands like ls --version to fail.
Tested was arm32 on a arm64 only host.
Fix that issue by truncating file mapping and replacing out-of-file
mappings by anonymous mappings.
Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
---
linux-user/mmap.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 423c77856a..4fce6fae3c 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -796,6 +796,32 @@ static abi_long mmap_h_gt_g(abi_ulong start, abi_ulong len,
bool misaligned_offset = false;
size_t host_len;
+ if (!(flags & MAP_ANONYMOUS)) {
+ struct stat sb;
+
+ if (fstat(fd, &sb) == -1) {
+ return -1;
+ }
+ if (offset >= sb.st_size) {
+ /*
+ * The entire map is beyond the end of the file.
+ * Transform it to an anonymous mapping.
+ */
+ flags |= MAP_ANONYMOUS;
+ fd = -1;
+ offset = 0;
+ } else if (offset + len > sb.st_size) {
+ /*
+ * A portion of the map is beyond the end of the file.
+ * Truncate the file portion of the allocation.
+ */
+ len = sb.st_size - offset;
+ len = len + host_page_size - 1;
+ len /= host_page_size;
+ len *= host_page_size;
+ }
+ }
+
if (start || (flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
want_p = g2h_untagged(start);
}
--
2.47.3
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] linux-user: fix issues with mmap on 4K guest on 16K host and library load
2026-08-05 16:40 [PATCH] linux-user: fix issues with mmap on 4K guest on 16K host and library load Andreas Kemnade
@ 2026-08-07 21:26 ` Helge Deller
2026-08-08 1:59 ` Richard Henderson
2026-08-08 13:40 ` Andreas Kemnade
0 siblings, 2 replies; 4+ messages in thread
From: Helge Deller @ 2026-08-07 21:26 UTC (permalink / raw)
To: Andreas Kemnade, qemu-devel; +Cc: sre
On 8/5/26 18:40, Andreas Kemnade wrote:
> Strace in qemu:
> 198005 openat(AT_FDCWD,"/lib/arm-linux-gnueabihf/libselinux.so.1",O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
> 198005 read(3,0x40802570,512) = 512
> 198005 statx(3,"",AT_EMPTY_PATH|AT_NO_AUTOMOUNT|AT_STATX_SYNC_AS_STAT,STATX_BASIC_STATS,0x408022a8) = 0
> 198005 mmap2(NULL,269428,PROT_NONE,MAP_PRIVATE|MAP_ANONYMOUS|MAP_DENYWRITE,-1,0) = 0x40868000
> 198005 mmap2(0x40870000,203892,PROT_EXEC|PROT_READ,MAP_PRIVATE|MAP_DENYWRITE|MAP_FIXED,3,0) = 0x40870000
> 198005 munmap(0x40868000,32768) = 0
> 198005 munmap(0x408a2000,31860) = 0
> 198005 mprotect(0x40890000,61440,PROT_NONE) = 0
> 198005 mmap2(0x4089f000,8192,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_DENYWRITE|MAP_FIXED,3,0x1f) = -1 errno=14 (Bad address)
>
> strace outside qemu:
> [pid 195331] readlinkat(AT_FDCWD, "/usr/lib", 0x7fffd1a7fd00, 1023) = -1 EINVAL (Invalid argument)
> [pid 195331] readlinkat(AT_FDCWD, "/usr/lib/arm-linux-gnueabihf", 0x7fffd1a7fd00, 1023) = -1 EINVAL (Invalid argument)
> [pid 195331] readlinkat(AT_FDCWD, "/usr/lib/arm-linux-gnueabihf/libselinux.so.1", 0x7fffd1a7fd00, 1023) = -1 EINVAL (Invalid argument)
> [pid 195331] faccessat(AT_FDCWD, "/usr/gnemul/qemu-arm/lib/arm-linux-gnueabihf/libselinux.so.1", F_OK) = -1 ENOENT (No such file or directory)
> [pid 195331] openat(AT_FDCWD, "/lib/arm-linux-gnueabihf/libselinux.so.1", O_RDONLY|O_CLOEXEC) = 3
> [pid 195331] read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\0\0\0\0004\0\0\0"..., 512) = 512
> [pid 195331] statx(3, "", AT_STATX_SYNC_AS_STAT|AT_NO_AUTOMOUNT|AT_EMPTY_PATH, STATX_BASIC_STATS, {stx_mask=STATX_ALL|STATX_MNT_ID|STATX_SUBVOL, stx_attributes=0, stx_mode=S_IFREG|0644, stx_size=132612, ...}) = 0
> [pid 195331] mmap(0x408a8000, 16384, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_DENYWRITE, -1, 0) = 0x408a8000
> [pid 195331] mprotect(0x408a8000, 16384, PROT_WRITE) = 0
> [pid 195331] mprotect(0x408a8000, 16384, PROT_NONE) = 0
> [pid 195331] mmap(0x40868000, 262144, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_DENYWRITE, -1, 0) = 0x40868000
> [pid 195331] mprotect(0x408a0000, 16384, PROT_WRITE) = 0
> [pid 195331] pread64(3, "", 8192, 196608) = 0
> [pid 195331] mprotect(0x408a0000, 16384, PROT_READ) = 0
> [pid 195331] mmap(0x40870000, 196608, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0) = 0x40870000
> [pid 195331] mmap(0x40868000, 32768, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x40868000
> [pid 195331] mmap(0x408a4000, 32768, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x408a4000
> [pid 195331] mprotect(0x4089c000, 16384, PROT_READ) = 0
> [pid 195331] mprotect(0x40890000, 49152, PROT_NONE) = 0
> [pid 195331] mprotect(0x4089c000, 16384, PROT_WRITE) = 0
> [pid 195331] pread64(3, 0x4089f000, 4096, 126976) = -1 EFAULT (Bad address)
>
> That makes simple commands like ls --version to fail.
> Tested was arm32 on a arm64 only host.
>
> Fix that issue by truncating file mapping and replacing out-of-file
> mappings by anonymous mappings.
Could you please explain "the issue" and not just referring to the strace?
It's not that easy to see the problem.
Thanks!
Helge
Btw: you patch might fix this problem, but you may run into other problems too,
see e.g.: https://gitlab.com/qemu-project/qemu/-/work_items/3410
> Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
> ---
> linux-user/mmap.c | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/linux-user/mmap.c b/linux-user/mmap.c
> index 423c77856a..4fce6fae3c 100644
> --- a/linux-user/mmap.c
> +++ b/linux-user/mmap.c
> @@ -796,6 +796,32 @@ static abi_long mmap_h_gt_g(abi_ulong start, abi_ulong len,
> bool misaligned_offset = false;
> size_t host_len;
>
> + if (!(flags & MAP_ANONYMOUS)) {
> + struct stat sb;
> +
> + if (fstat(fd, &sb) == -1) {
> + return -1;
> + }
> + if (offset >= sb.st_size) {
> + /*
> + * The entire map is beyond the end of the file.
> + * Transform it to an anonymous mapping.
> + */
> + flags |= MAP_ANONYMOUS;
> + fd = -1;
> + offset = 0;
> + } else if (offset + len > sb.st_size) {
> + /*
> + * A portion of the map is beyond the end of the file.
> + * Truncate the file portion of the allocation.
> + */
> + len = sb.st_size - offset;
> + len = len + host_page_size - 1;
> + len /= host_page_size;
> + len *= host_page_size;
> + }
> + }
> +
> if (start || (flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
> want_p = g2h_untagged(start);
> }
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] linux-user: fix issues with mmap on 4K guest on 16K host and library load
2026-08-07 21:26 ` Helge Deller
@ 2026-08-08 1:59 ` Richard Henderson
2026-08-08 13:40 ` Andreas Kemnade
1 sibling, 0 replies; 4+ messages in thread
From: Richard Henderson @ 2026-08-08 1:59 UTC (permalink / raw)
To: qemu-devel
On 8/7/26 14:26, Helge Deller wrote:
> On 8/5/26 18:40, Andreas Kemnade wrote:
>> Strace in qemu:
>> 198005 openat(AT_FDCWD,"/lib/arm-linux-gnueabihf/libselinux.so.1",O_RDONLY|O_LARGEFILE|
>> O_CLOEXEC) = 3
>> 198005 read(3,0x40802570,512) = 512
>> 198005 statx(3,"",AT_EMPTY_PATH|AT_NO_AUTOMOUNT|
>> AT_STATX_SYNC_AS_STAT,STATX_BASIC_STATS,0x408022a8) = 0
>> 198005 mmap2(NULL,269428,PROT_NONE,MAP_PRIVATE|MAP_ANONYMOUS|MAP_DENYWRITE,-1,0) =
>> 0x40868000
>> 198005 mmap2(0x40870000,203892,PROT_EXEC|PROT_READ,MAP_PRIVATE|MAP_DENYWRITE|
>> MAP_FIXED,3,0) = 0x40870000
>> 198005 munmap(0x40868000,32768) = 0
>> 198005 munmap(0x408a2000,31860) = 0
>> 198005 mprotect(0x40890000,61440,PROT_NONE) = 0
>> 198005 mmap2(0x4089f000,8192,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_DENYWRITE|
>> MAP_FIXED,3,0x1f) = -1 errno=14 (Bad address)
>>
>> strace outside qemu:
>> [pid 195331] readlinkat(AT_FDCWD, "/usr/lib", 0x7fffd1a7fd00, 1023) = -1 EINVAL (Invalid
>> argument)
>> [pid 195331] readlinkat(AT_FDCWD, "/usr/lib/arm-linux-gnueabihf", 0x7fffd1a7fd00, 1023)
>> = -1 EINVAL (Invalid argument)
>> [pid 195331] readlinkat(AT_FDCWD, "/usr/lib/arm-linux-gnueabihf/libselinux.so.1",
>> 0x7fffd1a7fd00, 1023) = -1 EINVAL (Invalid argument)
>> [pid 195331] faccessat(AT_FDCWD, "/usr/gnemul/qemu-arm/lib/arm-linux-gnueabihf/
>> libselinux.so.1", F_OK) = -1 ENOENT (No such file or directory)
>> [pid 195331] openat(AT_FDCWD, "/lib/arm-linux-gnueabihf/libselinux.so.1", O_RDONLY|
>> O_CLOEXEC) = 3
>> [pid 195331] read(3,
>> "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\0\0\0\0004\0\0\0"..., 512) = 512
>> [pid 195331] statx(3, "", AT_STATX_SYNC_AS_STAT|AT_NO_AUTOMOUNT|AT_EMPTY_PATH,
>> STATX_BASIC_STATS, {stx_mask=STATX_ALL|STATX_MNT_ID|STATX_SUBVOL, stx_attributes=0,
>> stx_mode=S_IFREG|0644, stx_size=132612, ...}) = 0
>> [pid 195331] mmap(0x408a8000, 16384, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|
>> MAP_DENYWRITE, -1, 0) = 0x408a8000
>> [pid 195331] mprotect(0x408a8000, 16384, PROT_WRITE) = 0
>> [pid 195331] mprotect(0x408a8000, 16384, PROT_NONE) = 0
>> [pid 195331] mmap(0x40868000, 262144, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|
>> MAP_DENYWRITE, -1, 0) = 0x40868000
>> [pid 195331] mprotect(0x408a0000, 16384, PROT_WRITE) = 0
>> [pid 195331] pread64(3, "", 8192, 196608) = 0
>> [pid 195331] mprotect(0x408a0000, 16384, PROT_READ) = 0
>> [pid 195331] mmap(0x40870000, 196608, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3,
>> 0) = 0x40870000
>> [pid 195331] mmap(0x40868000, 32768, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|
>> MAP_NORESERVE, -1, 0) = 0x40868000
>> [pid 195331] mmap(0x408a4000, 32768, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|
>> MAP_NORESERVE, -1, 0) = 0x408a4000
>> [pid 195331] mprotect(0x4089c000, 16384, PROT_READ) = 0
>> [pid 195331] mprotect(0x40890000, 49152, PROT_NONE) = 0
>> [pid 195331] mprotect(0x4089c000, 16384, PROT_WRITE) = 0
>> [pid 195331] pread64(3, 0x4089f000, 4096, 126976) = -1 EFAULT (Bad address)
>>
>> That makes simple commands like ls --version to fail.
>> Tested was arm32 on a arm64 only host.
>>
>> Fix that issue by truncating file mapping and replacing out-of-file
>> mappings by anonymous mappings.
>
> Could you please explain "the issue" and not just referring to the strace?
> It's not that easy to see the problem.
>
> Thanks!
> Helge
>
> Btw: you patch might fix this problem, but you may run into other problems too,
> see e.g.: https://gitlab.com/qemu-project/qemu/-/work_items/3410
>
>
>> Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
>> ---
>> linux-user/mmap.c | 26 ++++++++++++++++++++++++++
>> 1 file changed, 26 insertions(+)
>>
>> diff --git a/linux-user/mmap.c b/linux-user/mmap.c
>> index 423c77856a..4fce6fae3c 100644
>> --- a/linux-user/mmap.c
>> +++ b/linux-user/mmap.c
>> @@ -796,6 +796,32 @@ static abi_long mmap_h_gt_g(abi_ulong start, abi_ulong len,
>> bool misaligned_offset = false;
>> size_t host_len;
>> + if (!(flags & MAP_ANONYMOUS)) {
>> + struct stat sb;
>> +
>> + if (fstat(fd, &sb) == -1) {
>> + return -1;
>> + }
>> + if (offset >= sb.st_size) {
>> + /*
>> + * The entire map is beyond the end of the file.
>> + * Transform it to an anonymous mapping.
>> + */
>> + flags |= MAP_ANONYMOUS;
>> + fd = -1;
>> + offset = 0;
This is incorrect. Even natively, accessing past the end of the file should SIGBUS.
For host page size > guest page size, as we are here, you should never encounter that
particular emulation problem.
I've no idea what you're trying to solve.
r~
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] linux-user: fix issues with mmap on 4K guest on 16K host and library load
2026-08-07 21:26 ` Helge Deller
2026-08-08 1:59 ` Richard Henderson
@ 2026-08-08 13:40 ` Andreas Kemnade
1 sibling, 0 replies; 4+ messages in thread
From: Andreas Kemnade @ 2026-08-08 13:40 UTC (permalink / raw)
To: Helge Deller; +Cc: qemu-devel, sre
On Fri, 7 Aug 2026 23:26:07 +0200
Helge Deller <deller@gmx.de> wrote:
> On 8/5/26 18:40, Andreas Kemnade wrote:
> > Strace in qemu:
> > 198005 openat(AT_FDCWD,"/lib/arm-linux-gnueabihf/libselinux.so.1",O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
> > 198005 read(3,0x40802570,512) = 512
> > 198005 statx(3,"",AT_EMPTY_PATH|AT_NO_AUTOMOUNT|AT_STATX_SYNC_AS_STAT,STATX_BASIC_STATS,0x408022a8) = 0
> > 198005 mmap2(NULL,269428,PROT_NONE,MAP_PRIVATE|MAP_ANONYMOUS|MAP_DENYWRITE,-1,0) = 0x40868000
> > 198005 mmap2(0x40870000,203892,PROT_EXEC|PROT_READ,MAP_PRIVATE|MAP_DENYWRITE|MAP_FIXED,3,0) = 0x40870000
Size of the file: 132612: allocated: 203892
End address: 0x408a1c74
> > 198005 munmap(0x40868000,32768) = 0
> > 198005 munmap(0x408a2000,31860) = 0
> > 198005 mprotect(0x40890000,61440,PROT_NONE) = 0
which just ends at 0x4089f000 (not 16K aligned)
> > 198005 mmap2(0x4089f000,8192,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_DENYWRITE|MAP_FIXED,3,0x1f) = -1 errno=14 (Bad address)
> >
mmap2 sitting in that area mapping a part of the same file.
> > strace outside qemu:
> > [pid 195331] readlinkat(AT_FDCWD, "/usr/lib", 0x7fffd1a7fd00, 1023) = -1 EINVAL (Invalid argument)
> > [pid 195331] readlinkat(AT_FDCWD, "/usr/lib/arm-linux-gnueabihf", 0x7fffd1a7fd00, 1023) = -1 EINVAL (Invalid argument)
> > [pid 195331] readlinkat(AT_FDCWD, "/usr/lib/arm-linux-gnueabihf/libselinux.so.1", 0x7fffd1a7fd00, 1023) = -1 EINVAL (Invalid argument)
> > [pid 195331] faccessat(AT_FDCWD, "/usr/gnemul/qemu-arm/lib/arm-linux-gnueabihf/libselinux.so.1", F_OK) = -1 ENOENT (No such file or directory)
> > [pid 195331] openat(AT_FDCWD, "/lib/arm-linux-gnueabihf/libselinux.so.1", O_RDONLY|O_CLOEXEC) = 3
> > [pid 195331] read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\0\0\0\0004\0\0\0"..., 512) = 512
> > [pid 195331] statx(3, "", AT_STATX_SYNC_AS_STAT|AT_NO_AUTOMOUNT|AT_EMPTY_PATH, STATX_BASIC_STATS, {stx_mask=STATX_ALL|STATX_MNT_ID|STATX_SUBVOL, stx_attributes=0, stx_mode=S_IFREG|0644, stx_size=132612, ...}) = 0
> > [pid 195331] mmap(0x408a8000, 16384, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_DENYWRITE, -1, 0) = 0x408a8000
> > [pid 195331] mprotect(0x408a8000, 16384, PROT_WRITE) = 0
> > [pid 195331] mprotect(0x408a8000, 16384, PROT_NONE) = 0
> > [pid 195331] mmap(0x40868000, 262144, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_DENYWRITE, -1, 0) = 0x40868000
> > [pid 195331] mprotect(0x408a0000, 16384, PROT_WRITE) = 0
> > [pid 195331] pread64(3, "", 8192, 196608) = 0
> > [pid 195331] mprotect(0x408a0000, 16384, PROT_READ) = 0
> > [pid 195331] mmap(0x40870000, 196608, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0) = 0x40870000
> > [pid 195331] mmap(0x40868000, 32768, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x40868000
> > [pid 195331] mmap(0x408a4000, 32768, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x408a4000
> > [pid 195331] mprotect(0x4089c000, 16384, PROT_READ) = 0
> > [pid 195331] mprotect(0x40890000, 49152, PROT_NONE) = 0
ends at 0x4089c000
> > [pid 195331] mprotect(0x4089c000, 16384, PROT_WRITE) = 0
> > [pid 195331] pread64(3, 0x4089f000, 4096, 126976) = -1 EFAULT (Bad address)
> >
reads from write-only area created by the mprotect before.
> > That makes simple commands like ls --version to fail.
> > Tested was arm32 on a arm64 only host.
> >
> > Fix that issue by truncating file mapping and replacing out-of-file
> > mappings by anonymous mappings.
>
> Could you please explain "the issue" and not just referring to the strace?
> It's not that easy to see the problem.
>
> Thanks!
> Helge
>
> Btw: you patch might fix this problem, but you may run into other problems too,
> see e.g.: https://gitlab.com/qemu-project/qemu/-/work_items/3410
>
That is correct, but at least increases the amount of platforms to be
debootstrappable. Or maybe some better chances for same bitbake run
to get through.
Regards,
Andreas
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2026-08-08 13:40 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2026-08-05 16:40 [PATCH] linux-user: fix issues with mmap on 4K guest on 16K host and library load Andreas Kemnade
2026-08-07 21:26 ` Helge Deller
2026-08-08 1:59 ` Richard Henderson
2026-08-08 13:40 ` Andreas Kemnade
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