* [Bug 1885332] Re: Error in user-mode calculation of ELF aux vector's AT_PHDR
2020-06-26 20:17 [Bug 1885332] [NEW] Error in user-mode calculation of ELF aux vector's AT_PHDR Langston
@ 2020-06-26 23:05 ` Langston
2020-06-29 17:09 ` Langston
` (10 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: Langston @ 2020-06-26 23:05 UTC (permalink / raw)
To: qemu-devel
I just confirmed that this is still a problem on git tag v5.0.0, where I
applied the following:
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 619c054cc4..093656d059 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -2016,6 +2016,7 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
/* There must be exactly DLINFO_ITEMS entries here, or the assert
* on info->auxv_len will trigger.
*/
+ printf("PHDR: %x\n", (abi_ulong)(info->load_addr + exec->e_phoff));
NEW_AUX_ENT(AT_PHDR, (abi_ulong)(info->load_addr + exec->e_phoff));
NEW_AUX_ENT(AT_PHENT, (abi_ulong)(sizeof (struct elf_phdr)));
NEW_AUX_ENT(AT_PHNUM, (abi_ulong)(exec->e_phnum));
and saw:
PHDR: ae000
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https://bugs.launchpad.net/bugs/1885332
Title:
Error in user-mode calculation of ELF aux vector's AT_PHDR
Status in QEMU:
New
Bug description:
I have an (admittedly strange) statically-linked ELF binary for Linux that runs just fine on top of the Linux kernel in QEMU full-system emulation, but crashes before main in user-mode emulation. Specifically, it crashes when initializing thread-local storage in glibc's _dl_aux_init, because it reads out a strange value from the AT_PHDR entry of the ELF aux vector.
The binary has these program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x065874 0x00075874 0x00075874 0x00570 0x00570 R 0x4
PHDR 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x000000 0x00010000 0x00010000 0x65de8 0x65de8 R E 0x10000
LOAD 0x066b7c 0x00086b7c 0x00086b7c 0x02384 0x02384 RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x066b7c 0x00086b7c 0x00086b7c 0x00010 0x00030 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x8
GNU_RELRO 0x066b7c 0x00086b7c 0x00086b7c 0x00484 0x00484 R 0x1
LOAD 0x07e000 0x00089000 0x00089000 0x03f44 0x03f44 R E 0x1000
LOAD 0x098000 0x00030000 0x00030000 0x01000 0x01000 RW 0x1000
If I build the Linux kernel with the following patch to the very end
of create_elf_tables in fs/binfmt_elf.c
/* Put the elf_info on the stack in the right place. */
elf_addr_t *my_auxv = (elf_addr_t *) mm->saved_auxv;
int i;
for (i = 0; i < 15; i++) {
printk("0x%x = 0x%x", my_auxv[2*i], my_auxv[(2*i)+ 1]);
}
if (copy_to_user(sp, mm->saved_auxv, ei_index * sizeof(elf_addr_t)))
return -EFAULT;
return 0;
and run it like this:
qemu-system-arm \
-M versatilepb \
-nographic \
-dtb ./dts/versatile-pb.dtb \
-kernel zImage \
-M versatilepb \
-m 128M \
-append "earlyprintk=vga,keep" \
-initrd initramfs
after I've built the kernel initramfs like this (where "init" is the
binary in question):
make ARCH=arm versatile_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all -j10
cp "$1" arch/arm/boot/init
cd arch/arm/boot
echo init | cpio -o --format=newc > initramfs
then I get the following output. This is the kernel's view of the aux
vector for this binary:
0x10 = 0x1d7
0x6 = 0x1000
0x11 = 0x64
0x3 = 0x900000
0x4 = 0x20
0x5 = 0xb
0x7 = 0x0
0x8 = 0x0
0x9 = 0x101b8
0xb = 0x0
0xc = 0x0
0xd = 0x0
0xe = 0x0
0x17 = 0x0
0x19 = 0xbec62fb5
However, if I run "qemu-arm -g 12345 binary" and use GDB to peek at
the aux vector at the beginning of __libc_start_init (for example,
using this Python GDB API script: https://gist.github.com/langston-
barrett/5573d64ae0c9953e2fa0fe26847a5e1e), then I see the following
values:
AT_PHDR = 0xae000
AT_PHENT = 0x20
AT_PHNUM = 0xb
AT_PAGESZ = 0x1000
AT_BASE = 0x0
AT_FLAGS = 0x0
AT_ENTRY = 0x10230
AT_UID = 0x3e9
AT_EUID = 0x3e9
AT_GID = 0x3e9
AT_EGID = 0x3e9
AT_HWCAP = 0x1fb8d7
AT_CLKTCK = 0x64
AT_RANDOM = -0x103c0
AT_HWCAP2 = 0x1f
AT_NULL = 0x0
The crucial difference is in AT_PHDR (0x3), which is indeed the
virtual address of the PHDR segment when the kernel calculates it, but
is not when QEMU calculates it.
qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1885332/+subscriptions
^ permalink raw reply [flat|nested] 13+ messages in thread
* [Bug 1885332] Re: Error in user-mode calculation of ELF aux vector's AT_PHDR
2020-06-26 20:17 [Bug 1885332] [NEW] Error in user-mode calculation of ELF aux vector's AT_PHDR Langston
2020-06-26 23:05 ` [Bug 1885332] " Langston
@ 2020-06-29 17:09 ` Langston
2020-07-10 18:09 ` Dmitry
` (9 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: Langston @ 2020-06-29 17:09 UTC (permalink / raw)
To: qemu-devel
Taking a peek at how Linux and QEMU calculate AT_PHDR for static
binaries reveals the following. Both involve the program headers' offset
(e_phoff) added to a value I'll call load_addr (as in the kernel).
In the kernel, load_addr is
elf_ppnt->p_vaddr - elf_ppnt->p_offset
where elf_ppnt is the program header entry of the first segment with
type LOAD:
https://github.com/torvalds/linux/blob/242b23319809e05170b3cc0d44d3b4bd202bb073/fs/binfmt_elf.c#L1120
In QEMU, load_addr is set to an earlier value loaddr, which is set to
min_i(phdr[i].p_vaddr - phdr[i].p_offset)
where min_i is the minimum over indices "i" of LOAD segments.
https://github.com/qemu/qemu/blob/9e7f1469b9994d910fc1b185c657778bde51639c
/linux-user/elfload.c#L2407. If you perform this calculation by hand for
the program headers posted at the beginning of this thread, you'll get
ae000, as expected.
The problem here is that QEMU takes a minimum where Linux just takes the
first value. Presumably, changing QEMU's behavior to match that of the
kernel wouldn't break anything that wouldn't be broken if it really ran
on Linux. Unfortunately, Linux's ELF loader is much more picky than the
ELF standard, but that's a whole other story...
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1885332
Title:
Error in user-mode calculation of ELF aux vector's AT_PHDR
Status in QEMU:
New
Bug description:
I have an (admittedly strange) statically-linked ELF binary for Linux that runs just fine on top of the Linux kernel in QEMU full-system emulation, but crashes before main in user-mode emulation. Specifically, it crashes when initializing thread-local storage in glibc's _dl_aux_init, because it reads out a strange value from the AT_PHDR entry of the ELF aux vector.
The binary has these program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x065874 0x00075874 0x00075874 0x00570 0x00570 R 0x4
PHDR 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x000000 0x00010000 0x00010000 0x65de8 0x65de8 R E 0x10000
LOAD 0x066b7c 0x00086b7c 0x00086b7c 0x02384 0x02384 RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x066b7c 0x00086b7c 0x00086b7c 0x00010 0x00030 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x8
GNU_RELRO 0x066b7c 0x00086b7c 0x00086b7c 0x00484 0x00484 R 0x1
LOAD 0x07e000 0x00089000 0x00089000 0x03f44 0x03f44 R E 0x1000
LOAD 0x098000 0x00030000 0x00030000 0x01000 0x01000 RW 0x1000
If I build the Linux kernel with the following patch to the very end
of create_elf_tables in fs/binfmt_elf.c
/* Put the elf_info on the stack in the right place. */
elf_addr_t *my_auxv = (elf_addr_t *) mm->saved_auxv;
int i;
for (i = 0; i < 15; i++) {
printk("0x%x = 0x%x", my_auxv[2*i], my_auxv[(2*i)+ 1]);
}
if (copy_to_user(sp, mm->saved_auxv, ei_index * sizeof(elf_addr_t)))
return -EFAULT;
return 0;
and run it like this:
qemu-system-arm \
-M versatilepb \
-nographic \
-dtb ./dts/versatile-pb.dtb \
-kernel zImage \
-M versatilepb \
-m 128M \
-append "earlyprintk=vga,keep" \
-initrd initramfs
after I've built the kernel initramfs like this (where "init" is the
binary in question):
make ARCH=arm versatile_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all -j10
cp "$1" arch/arm/boot/init
cd arch/arm/boot
echo init | cpio -o --format=newc > initramfs
then I get the following output. This is the kernel's view of the aux
vector for this binary:
0x10 = 0x1d7
0x6 = 0x1000
0x11 = 0x64
0x3 = 0x900000
0x4 = 0x20
0x5 = 0xb
0x7 = 0x0
0x8 = 0x0
0x9 = 0x101b8
0xb = 0x0
0xc = 0x0
0xd = 0x0
0xe = 0x0
0x17 = 0x0
0x19 = 0xbec62fb5
However, if I run "qemu-arm -g 12345 binary" and use GDB to peek at
the aux vector at the beginning of __libc_start_init (for example,
using this Python GDB API script: https://gist.github.com/langston-
barrett/5573d64ae0c9953e2fa0fe26847a5e1e), then I see the following
values:
AT_PHDR = 0xae000
AT_PHENT = 0x20
AT_PHNUM = 0xb
AT_PAGESZ = 0x1000
AT_BASE = 0x0
AT_FLAGS = 0x0
AT_ENTRY = 0x10230
AT_UID = 0x3e9
AT_EUID = 0x3e9
AT_GID = 0x3e9
AT_EGID = 0x3e9
AT_HWCAP = 0x1fb8d7
AT_CLKTCK = 0x64
AT_RANDOM = -0x103c0
AT_HWCAP2 = 0x1f
AT_NULL = 0x0
The crucial difference is in AT_PHDR (0x3), which is indeed the
virtual address of the PHDR segment when the kernel calculates it, but
is not when QEMU calculates it.
qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1885332/+subscriptions
^ permalink raw reply [flat|nested] 13+ messages in thread
* [Bug 1885332] Re: Error in user-mode calculation of ELF aux vector's AT_PHDR
2020-06-26 20:17 [Bug 1885332] [NEW] Error in user-mode calculation of ELF aux vector's AT_PHDR Langston
2020-06-26 23:05 ` [Bug 1885332] " Langston
2020-06-29 17:09 ` Langston
@ 2020-07-10 18:09 ` Dmitry
2020-07-10 18:14 ` Dmitry
` (8 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: Dmitry @ 2020-07-10 18:09 UTC (permalink / raw)
To: qemu-devel
@langston0 Thanks for detailed explanation, got the same problem for
qemu-s390.
The way to reproduce (linux kernel >= 4.8, for example: Ubuntu 18.04):
# Register qemu binfmt_misc handlers
$ docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
$ cat Dockerfile.s390x
FROM s390x/ubuntu
RUN apt-get update && \
apt-get install -y \
gcc make libpcre3-dev libreadline-dev
RUN cd /home && git clone https://github.com/nginx/njs
RUN cd /home/njs && ./configure --cc-opt='-O0 -static -lm -lrt -pthread
-Wl,--whole-archive -lpthread -ltinfo -Wl,--no-whole-archive' && make
njs
$ docker build -t njs/390x -f Dockerfile.s390x .
# check the binary (WORKS!)
# inside docker s390 binaries are executed using qemu-s390-static from the host
$ docker run -t njs/390x /home/njs/build/njs -c 'console.log("hello")'
hello
# copy binary to host
$ docker run -v `pwd`:/m -ti njs/390x cp /home/njs/build/njs /m/njs-s390
# deregister binfmt handler
$ sudo bash -c "echo -1 > /proc/sys/fs/binfmt_misc/qemu-s390x"
# run qemu gdb
$ qemu-s390x -g 12345 ./njs-s390
# in a separate terminal
$ gdb-multiarch ./njs-s390 -ex 'target remote localhost:12345'
0x0000000001000520 in _start ()
(gdb) si
0x0000000001000524 in _start ()
(gdb) si
0x000000000100052a in _start ()
(gdb) c
Continuing.
Program received signal SIGILL, Illegal instruction.
0x00000000011a418c in _dl_aux_init ()
(gdb) bt
#0 0x00000000011a418c in _dl_aux_init ()
#1 0x00000000011663f0 in __libc_start_main ()
#2 0x0000000001000564 in _start ()
qemu-s390x --version
qemu-s390x version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.28)
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1885332
Title:
Error in user-mode calculation of ELF aux vector's AT_PHDR
Status in QEMU:
New
Bug description:
I have an (admittedly strange) statically-linked ELF binary for Linux that runs just fine on top of the Linux kernel in QEMU full-system emulation, but crashes before main in user-mode emulation. Specifically, it crashes when initializing thread-local storage in glibc's _dl_aux_init, because it reads out a strange value from the AT_PHDR entry of the ELF aux vector.
The binary has these program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x065874 0x00075874 0x00075874 0x00570 0x00570 R 0x4
PHDR 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x000000 0x00010000 0x00010000 0x65de8 0x65de8 R E 0x10000
LOAD 0x066b7c 0x00086b7c 0x00086b7c 0x02384 0x02384 RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x066b7c 0x00086b7c 0x00086b7c 0x00010 0x00030 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x8
GNU_RELRO 0x066b7c 0x00086b7c 0x00086b7c 0x00484 0x00484 R 0x1
LOAD 0x07e000 0x00089000 0x00089000 0x03f44 0x03f44 R E 0x1000
LOAD 0x098000 0x00030000 0x00030000 0x01000 0x01000 RW 0x1000
If I build the Linux kernel with the following patch to the very end
of create_elf_tables in fs/binfmt_elf.c
/* Put the elf_info on the stack in the right place. */
elf_addr_t *my_auxv = (elf_addr_t *) mm->saved_auxv;
int i;
for (i = 0; i < 15; i++) {
printk("0x%x = 0x%x", my_auxv[2*i], my_auxv[(2*i)+ 1]);
}
if (copy_to_user(sp, mm->saved_auxv, ei_index * sizeof(elf_addr_t)))
return -EFAULT;
return 0;
and run it like this:
qemu-system-arm \
-M versatilepb \
-nographic \
-dtb ./dts/versatile-pb.dtb \
-kernel zImage \
-M versatilepb \
-m 128M \
-append "earlyprintk=vga,keep" \
-initrd initramfs
after I've built the kernel initramfs like this (where "init" is the
binary in question):
make ARCH=arm versatile_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all -j10
cp "$1" arch/arm/boot/init
cd arch/arm/boot
echo init | cpio -o --format=newc > initramfs
then I get the following output. This is the kernel's view of the aux
vector for this binary:
0x10 = 0x1d7
0x6 = 0x1000
0x11 = 0x64
0x3 = 0x900000
0x4 = 0x20
0x5 = 0xb
0x7 = 0x0
0x8 = 0x0
0x9 = 0x101b8
0xb = 0x0
0xc = 0x0
0xd = 0x0
0xe = 0x0
0x17 = 0x0
0x19 = 0xbec62fb5
However, if I run "qemu-arm -g 12345 binary" and use GDB to peek at
the aux vector at the beginning of __libc_start_init (for example,
using this Python GDB API script: https://gist.github.com/langston-
barrett/5573d64ae0c9953e2fa0fe26847a5e1e), then I see the following
values:
AT_PHDR = 0xae000
AT_PHENT = 0x20
AT_PHNUM = 0xb
AT_PAGESZ = 0x1000
AT_BASE = 0x0
AT_FLAGS = 0x0
AT_ENTRY = 0x10230
AT_UID = 0x3e9
AT_EUID = 0x3e9
AT_GID = 0x3e9
AT_EGID = 0x3e9
AT_HWCAP = 0x1fb8d7
AT_CLKTCK = 0x64
AT_RANDOM = -0x103c0
AT_HWCAP2 = 0x1f
AT_NULL = 0x0
The crucial difference is in AT_PHDR (0x3), which is indeed the
virtual address of the PHDR segment when the kernel calculates it, but
is not when QEMU calculates it.
qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1885332/+subscriptions
^ permalink raw reply [flat|nested] 13+ messages in thread
* [Bug 1885332] Re: Error in user-mode calculation of ELF aux vector's AT_PHDR
2020-06-26 20:17 [Bug 1885332] [NEW] Error in user-mode calculation of ELF aux vector's AT_PHDR Langston
` (2 preceding siblings ...)
2020-07-10 18:09 ` Dmitry
@ 2020-07-10 18:14 ` Dmitry
2020-07-10 18:18 ` Dmitry
` (7 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: Dmitry @ 2020-07-10 18:14 UTC (permalink / raw)
To: qemu-devel
BTW, before "sudo bash -c "echo -1 > /proc/sys/fs/binfmt_misc/qemu-
s390x"
njs-s390 also works on the host:
$ ./njs-s390 -c 'console.log("hello")'
hello
$ file njs-s390
njs-s390: ELF 64-bit MSB executable, IBM S/390, version 1 (GNU/Linux), statically linked, BuildID[sha1]=e37618578fb0a8c60f426826167a800e4f314ef3, for GNU/Linux 3.2.0, with debug_info, not stripped
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1885332
Title:
Error in user-mode calculation of ELF aux vector's AT_PHDR
Status in QEMU:
New
Bug description:
I have an (admittedly strange) statically-linked ELF binary for Linux that runs just fine on top of the Linux kernel in QEMU full-system emulation, but crashes before main in user-mode emulation. Specifically, it crashes when initializing thread-local storage in glibc's _dl_aux_init, because it reads out a strange value from the AT_PHDR entry of the ELF aux vector.
The binary has these program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x065874 0x00075874 0x00075874 0x00570 0x00570 R 0x4
PHDR 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x000000 0x00010000 0x00010000 0x65de8 0x65de8 R E 0x10000
LOAD 0x066b7c 0x00086b7c 0x00086b7c 0x02384 0x02384 RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x066b7c 0x00086b7c 0x00086b7c 0x00010 0x00030 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x8
GNU_RELRO 0x066b7c 0x00086b7c 0x00086b7c 0x00484 0x00484 R 0x1
LOAD 0x07e000 0x00089000 0x00089000 0x03f44 0x03f44 R E 0x1000
LOAD 0x098000 0x00030000 0x00030000 0x01000 0x01000 RW 0x1000
If I build the Linux kernel with the following patch to the very end
of create_elf_tables in fs/binfmt_elf.c
/* Put the elf_info on the stack in the right place. */
elf_addr_t *my_auxv = (elf_addr_t *) mm->saved_auxv;
int i;
for (i = 0; i < 15; i++) {
printk("0x%x = 0x%x", my_auxv[2*i], my_auxv[(2*i)+ 1]);
}
if (copy_to_user(sp, mm->saved_auxv, ei_index * sizeof(elf_addr_t)))
return -EFAULT;
return 0;
and run it like this:
qemu-system-arm \
-M versatilepb \
-nographic \
-dtb ./dts/versatile-pb.dtb \
-kernel zImage \
-M versatilepb \
-m 128M \
-append "earlyprintk=vga,keep" \
-initrd initramfs
after I've built the kernel initramfs like this (where "init" is the
binary in question):
make ARCH=arm versatile_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all -j10
cp "$1" arch/arm/boot/init
cd arch/arm/boot
echo init | cpio -o --format=newc > initramfs
then I get the following output. This is the kernel's view of the aux
vector for this binary:
0x10 = 0x1d7
0x6 = 0x1000
0x11 = 0x64
0x3 = 0x900000
0x4 = 0x20
0x5 = 0xb
0x7 = 0x0
0x8 = 0x0
0x9 = 0x101b8
0xb = 0x0
0xc = 0x0
0xd = 0x0
0xe = 0x0
0x17 = 0x0
0x19 = 0xbec62fb5
However, if I run "qemu-arm -g 12345 binary" and use GDB to peek at
the aux vector at the beginning of __libc_start_init (for example,
using this Python GDB API script: https://gist.github.com/langston-
barrett/5573d64ae0c9953e2fa0fe26847a5e1e), then I see the following
values:
AT_PHDR = 0xae000
AT_PHENT = 0x20
AT_PHNUM = 0xb
AT_PAGESZ = 0x1000
AT_BASE = 0x0
AT_FLAGS = 0x0
AT_ENTRY = 0x10230
AT_UID = 0x3e9
AT_EUID = 0x3e9
AT_GID = 0x3e9
AT_EGID = 0x3e9
AT_HWCAP = 0x1fb8d7
AT_CLKTCK = 0x64
AT_RANDOM = -0x103c0
AT_HWCAP2 = 0x1f
AT_NULL = 0x0
The crucial difference is in AT_PHDR (0x3), which is indeed the
virtual address of the PHDR segment when the kernel calculates it, but
is not when QEMU calculates it.
qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1885332/+subscriptions
^ permalink raw reply [flat|nested] 13+ messages in thread
* [Bug 1885332] Re: Error in user-mode calculation of ELF aux vector's AT_PHDR
2020-06-26 20:17 [Bug 1885332] [NEW] Error in user-mode calculation of ELF aux vector's AT_PHDR Langston
` (3 preceding siblings ...)
2020-07-10 18:14 ` Dmitry
@ 2020-07-10 18:18 ` Dmitry
2020-07-10 18:28 ` Langston
` (6 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: Dmitry @ 2020-07-10 18:18 UTC (permalink / raw)
To: qemu-devel
> runs just fine on top of the Linux kernel in QEMU full-system
emulation, but crashes before main in user-mode emulation
So it seems system vs user-mode is not the issue here, probably it is
related to gdb mode in user-mode qemu.
--
You received this bug notification because you are a member of qemu-
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https://bugs.launchpad.net/bugs/1885332
Title:
Error in user-mode calculation of ELF aux vector's AT_PHDR
Status in QEMU:
New
Bug description:
I have an (admittedly strange) statically-linked ELF binary for Linux that runs just fine on top of the Linux kernel in QEMU full-system emulation, but crashes before main in user-mode emulation. Specifically, it crashes when initializing thread-local storage in glibc's _dl_aux_init, because it reads out a strange value from the AT_PHDR entry of the ELF aux vector.
The binary has these program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x065874 0x00075874 0x00075874 0x00570 0x00570 R 0x4
PHDR 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x000000 0x00010000 0x00010000 0x65de8 0x65de8 R E 0x10000
LOAD 0x066b7c 0x00086b7c 0x00086b7c 0x02384 0x02384 RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x066b7c 0x00086b7c 0x00086b7c 0x00010 0x00030 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x8
GNU_RELRO 0x066b7c 0x00086b7c 0x00086b7c 0x00484 0x00484 R 0x1
LOAD 0x07e000 0x00089000 0x00089000 0x03f44 0x03f44 R E 0x1000
LOAD 0x098000 0x00030000 0x00030000 0x01000 0x01000 RW 0x1000
If I build the Linux kernel with the following patch to the very end
of create_elf_tables in fs/binfmt_elf.c
/* Put the elf_info on the stack in the right place. */
elf_addr_t *my_auxv = (elf_addr_t *) mm->saved_auxv;
int i;
for (i = 0; i < 15; i++) {
printk("0x%x = 0x%x", my_auxv[2*i], my_auxv[(2*i)+ 1]);
}
if (copy_to_user(sp, mm->saved_auxv, ei_index * sizeof(elf_addr_t)))
return -EFAULT;
return 0;
and run it like this:
qemu-system-arm \
-M versatilepb \
-nographic \
-dtb ./dts/versatile-pb.dtb \
-kernel zImage \
-M versatilepb \
-m 128M \
-append "earlyprintk=vga,keep" \
-initrd initramfs
after I've built the kernel initramfs like this (where "init" is the
binary in question):
make ARCH=arm versatile_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all -j10
cp "$1" arch/arm/boot/init
cd arch/arm/boot
echo init | cpio -o --format=newc > initramfs
then I get the following output. This is the kernel's view of the aux
vector for this binary:
0x10 = 0x1d7
0x6 = 0x1000
0x11 = 0x64
0x3 = 0x900000
0x4 = 0x20
0x5 = 0xb
0x7 = 0x0
0x8 = 0x0
0x9 = 0x101b8
0xb = 0x0
0xc = 0x0
0xd = 0x0
0xe = 0x0
0x17 = 0x0
0x19 = 0xbec62fb5
However, if I run "qemu-arm -g 12345 binary" and use GDB to peek at
the aux vector at the beginning of __libc_start_init (for example,
using this Python GDB API script: https://gist.github.com/langston-
barrett/5573d64ae0c9953e2fa0fe26847a5e1e), then I see the following
values:
AT_PHDR = 0xae000
AT_PHENT = 0x20
AT_PHNUM = 0xb
AT_PAGESZ = 0x1000
AT_BASE = 0x0
AT_FLAGS = 0x0
AT_ENTRY = 0x10230
AT_UID = 0x3e9
AT_EUID = 0x3e9
AT_GID = 0x3e9
AT_EGID = 0x3e9
AT_HWCAP = 0x1fb8d7
AT_CLKTCK = 0x64
AT_RANDOM = -0x103c0
AT_HWCAP2 = 0x1f
AT_NULL = 0x0
The crucial difference is in AT_PHDR (0x3), which is indeed the
virtual address of the PHDR segment when the kernel calculates it, but
is not when QEMU calculates it.
qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1885332/+subscriptions
^ permalink raw reply [flat|nested] 13+ messages in thread
* [Bug 1885332] Re: Error in user-mode calculation of ELF aux vector's AT_PHDR
2020-06-26 20:17 [Bug 1885332] [NEW] Error in user-mode calculation of ELF aux vector's AT_PHDR Langston
` (4 preceding siblings ...)
2020-07-10 18:18 ` Dmitry
@ 2020-07-10 18:28 ` Langston
2020-07-10 19:12 ` Dmitry
` (5 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: Langston @ 2020-07-10 18:28 UTC (permalink / raw)
To: qemu-devel
@Dimitry To confirm that this is really the same issue (and not an
unrelated crash in the same function), could you post:
1. the ELF headers ("readelf -h"),
2. the program headers ("readelf -l"), and
3. the output (the AUX VECTOR section) from this GDB script (suitably modified for your program), when connecting to QEMU's GDB server? https://gist.github.com/langston-barrett/5573d64ae0c9953e2fa0fe26847a5e1e
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1885332
Title:
Error in user-mode calculation of ELF aux vector's AT_PHDR
Status in QEMU:
New
Bug description:
I have an (admittedly strange) statically-linked ELF binary for Linux that runs just fine on top of the Linux kernel in QEMU full-system emulation, but crashes before main in user-mode emulation. Specifically, it crashes when initializing thread-local storage in glibc's _dl_aux_init, because it reads out a strange value from the AT_PHDR entry of the ELF aux vector.
The binary has these program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x065874 0x00075874 0x00075874 0x00570 0x00570 R 0x4
PHDR 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x000000 0x00010000 0x00010000 0x65de8 0x65de8 R E 0x10000
LOAD 0x066b7c 0x00086b7c 0x00086b7c 0x02384 0x02384 RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x066b7c 0x00086b7c 0x00086b7c 0x00010 0x00030 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x8
GNU_RELRO 0x066b7c 0x00086b7c 0x00086b7c 0x00484 0x00484 R 0x1
LOAD 0x07e000 0x00089000 0x00089000 0x03f44 0x03f44 R E 0x1000
LOAD 0x098000 0x00030000 0x00030000 0x01000 0x01000 RW 0x1000
If I build the Linux kernel with the following patch to the very end
of create_elf_tables in fs/binfmt_elf.c
/* Put the elf_info on the stack in the right place. */
elf_addr_t *my_auxv = (elf_addr_t *) mm->saved_auxv;
int i;
for (i = 0; i < 15; i++) {
printk("0x%x = 0x%x", my_auxv[2*i], my_auxv[(2*i)+ 1]);
}
if (copy_to_user(sp, mm->saved_auxv, ei_index * sizeof(elf_addr_t)))
return -EFAULT;
return 0;
and run it like this:
qemu-system-arm \
-M versatilepb \
-nographic \
-dtb ./dts/versatile-pb.dtb \
-kernel zImage \
-M versatilepb \
-m 128M \
-append "earlyprintk=vga,keep" \
-initrd initramfs
after I've built the kernel initramfs like this (where "init" is the
binary in question):
make ARCH=arm versatile_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all -j10
cp "$1" arch/arm/boot/init
cd arch/arm/boot
echo init | cpio -o --format=newc > initramfs
then I get the following output. This is the kernel's view of the aux
vector for this binary:
0x10 = 0x1d7
0x6 = 0x1000
0x11 = 0x64
0x3 = 0x900000
0x4 = 0x20
0x5 = 0xb
0x7 = 0x0
0x8 = 0x0
0x9 = 0x101b8
0xb = 0x0
0xc = 0x0
0xd = 0x0
0xe = 0x0
0x17 = 0x0
0x19 = 0xbec62fb5
However, if I run "qemu-arm -g 12345 binary" and use GDB to peek at
the aux vector at the beginning of __libc_start_init (for example,
using this Python GDB API script: https://gist.github.com/langston-
barrett/5573d64ae0c9953e2fa0fe26847a5e1e), then I see the following
values:
AT_PHDR = 0xae000
AT_PHENT = 0x20
AT_PHNUM = 0xb
AT_PAGESZ = 0x1000
AT_BASE = 0x0
AT_FLAGS = 0x0
AT_ENTRY = 0x10230
AT_UID = 0x3e9
AT_EUID = 0x3e9
AT_GID = 0x3e9
AT_EGID = 0x3e9
AT_HWCAP = 0x1fb8d7
AT_CLKTCK = 0x64
AT_RANDOM = -0x103c0
AT_HWCAP2 = 0x1f
AT_NULL = 0x0
The crucial difference is in AT_PHDR (0x3), which is indeed the
virtual address of the PHDR segment when the kernel calculates it, but
is not when QEMU calculates it.
qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1885332/+subscriptions
^ permalink raw reply [flat|nested] 13+ messages in thread
* [Bug 1885332] Re: Error in user-mode calculation of ELF aux vector's AT_PHDR
2020-06-26 20:17 [Bug 1885332] [NEW] Error in user-mode calculation of ELF aux vector's AT_PHDR Langston
` (5 preceding siblings ...)
2020-07-10 18:28 ` Langston
@ 2020-07-10 19:12 ` Dmitry
2020-07-11 12:00 ` Dmitry
` (4 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: Dmitry @ 2020-07-10 19:12 UTC (permalink / raw)
To: qemu-devel
@Langston will do tomorrow. s390x ABI requires heavy changes to the
python script.
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1885332
Title:
Error in user-mode calculation of ELF aux vector's AT_PHDR
Status in QEMU:
New
Bug description:
I have an (admittedly strange) statically-linked ELF binary for Linux that runs just fine on top of the Linux kernel in QEMU full-system emulation, but crashes before main in user-mode emulation. Specifically, it crashes when initializing thread-local storage in glibc's _dl_aux_init, because it reads out a strange value from the AT_PHDR entry of the ELF aux vector.
The binary has these program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x065874 0x00075874 0x00075874 0x00570 0x00570 R 0x4
PHDR 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x000000 0x00010000 0x00010000 0x65de8 0x65de8 R E 0x10000
LOAD 0x066b7c 0x00086b7c 0x00086b7c 0x02384 0x02384 RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x066b7c 0x00086b7c 0x00086b7c 0x00010 0x00030 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x8
GNU_RELRO 0x066b7c 0x00086b7c 0x00086b7c 0x00484 0x00484 R 0x1
LOAD 0x07e000 0x00089000 0x00089000 0x03f44 0x03f44 R E 0x1000
LOAD 0x098000 0x00030000 0x00030000 0x01000 0x01000 RW 0x1000
If I build the Linux kernel with the following patch to the very end
of create_elf_tables in fs/binfmt_elf.c
/* Put the elf_info on the stack in the right place. */
elf_addr_t *my_auxv = (elf_addr_t *) mm->saved_auxv;
int i;
for (i = 0; i < 15; i++) {
printk("0x%x = 0x%x", my_auxv[2*i], my_auxv[(2*i)+ 1]);
}
if (copy_to_user(sp, mm->saved_auxv, ei_index * sizeof(elf_addr_t)))
return -EFAULT;
return 0;
and run it like this:
qemu-system-arm \
-M versatilepb \
-nographic \
-dtb ./dts/versatile-pb.dtb \
-kernel zImage \
-M versatilepb \
-m 128M \
-append "earlyprintk=vga,keep" \
-initrd initramfs
after I've built the kernel initramfs like this (where "init" is the
binary in question):
make ARCH=arm versatile_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all -j10
cp "$1" arch/arm/boot/init
cd arch/arm/boot
echo init | cpio -o --format=newc > initramfs
then I get the following output. This is the kernel's view of the aux
vector for this binary:
0x10 = 0x1d7
0x6 = 0x1000
0x11 = 0x64
0x3 = 0x900000
0x4 = 0x20
0x5 = 0xb
0x7 = 0x0
0x8 = 0x0
0x9 = 0x101b8
0xb = 0x0
0xc = 0x0
0xd = 0x0
0xe = 0x0
0x17 = 0x0
0x19 = 0xbec62fb5
However, if I run "qemu-arm -g 12345 binary" and use GDB to peek at
the aux vector at the beginning of __libc_start_init (for example,
using this Python GDB API script: https://gist.github.com/langston-
barrett/5573d64ae0c9953e2fa0fe26847a5e1e), then I see the following
values:
AT_PHDR = 0xae000
AT_PHENT = 0x20
AT_PHNUM = 0xb
AT_PAGESZ = 0x1000
AT_BASE = 0x0
AT_FLAGS = 0x0
AT_ENTRY = 0x10230
AT_UID = 0x3e9
AT_EUID = 0x3e9
AT_GID = 0x3e9
AT_EGID = 0x3e9
AT_HWCAP = 0x1fb8d7
AT_CLKTCK = 0x64
AT_RANDOM = -0x103c0
AT_HWCAP2 = 0x1f
AT_NULL = 0x0
The crucial difference is in AT_PHDR (0x3), which is indeed the
virtual address of the PHDR segment when the kernel calculates it, but
is not when QEMU calculates it.
qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1885332/+subscriptions
^ permalink raw reply [flat|nested] 13+ messages in thread
* [Bug 1885332] Re: Error in user-mode calculation of ELF aux vector's AT_PHDR
2020-06-26 20:17 [Bug 1885332] [NEW] Error in user-mode calculation of ELF aux vector's AT_PHDR Langston
` (6 preceding siblings ...)
2020-07-10 19:12 ` Dmitry
@ 2020-07-11 12:00 ` Dmitry
2020-07-13 13:02 ` Dmitry
` (3 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: Dmitry @ 2020-07-11 12:00 UTC (permalink / raw)
To: qemu-devel
When I switch to armv7 the issue goes away
$ cat Dockerfile.armv7
FROM arm32v7/ubuntu
RUN apt-get update && \
apt-get install -y \
gcc make libpcre3-dev libreadline-dev git
RUN cd /home && git clone https://github.com/nginx/njs
RUN cd /home/njs && ./configure --cc-opt='-O0 -static -lm -lrt -pthread
-Wl,--whole-archive -lpthread -ltinfo -Wl,--no-whole-archive' && make
njs
$ docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
$ docker build -t njs/armv7 -f Dockerfile.armv7 .
$ docker run -v `pwd`:/m -ti njs/armv7 cp /home/njs/build/njs /m/njs-armv7
$ readelf -l ./njs-armv7
Elf file type is EXEC (Executable file)
Entry point 0x12fb9
There are 7 program headers, starting at offset 52
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x1be338 0x001ce338 0x001ce338 0x009b8 0x009b8 R 0x4
LOAD 0x000000 0x00010000 0x00010000 0x1becf4 0x1becf4 R E 0x10000
LOAD 0x1bedfc 0x001dedfc 0x001dedfc 0x17674 0x1c2cc RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x1bedfc 0x001dedfc 0x001dedfc 0x00038 0x00060 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x10
GNU_RELRO 0x1bedfc 0x001dedfc 0x001dedfc 0x0e204 0x0e204 R 0x1
Section to Segment mapping:
Segment Sections...
00 .ARM.exidx
01 .note.ABI-tag .note.gnu.build-id .rel.dyn .init .iplt .text __libc_freeres_fn __libc_thread_freeres_fn .fini .rodata .stapsdt.base __libc_subfreeres __libc_IO_vtables __libc_atexit __libc_thread_subfreeres .ARM.extab .ARM.exidx .eh_frame
02 .tdata .init_array .fini_array .data.rel.ro .got .data .bss __libc_freeres_ptrs
03 .note.ABI-tag .note.gnu.build-id
04 .tdata .tbss
05
06 .tdata .init_array .fini_array .data.rel.ro
$ readelf -h ./njs-armv7
ELF Header:
Magic: 7f 45 4c 46 01 01 01 03 00 00 00 00 00 00 00 00
Class: ELF32
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - GNU
ABI Version: 0
Type: EXEC (Executable file)
Machine: ARM
Version: 0x1
Entry point address: 0x12fb9
Start of program headers: 52 (bytes into file)
Start of section headers: 5696248 (bytes into file)
Flags: 0x5000400, Version5 EABI, hard-float ABI
Size of this header: 52 (bytes)
Size of program headers: 32 (bytes)
Number of program headers: 7
Size of section headers: 40 (bytes)
Number of section headers: 42
Section header string table index: 41
$ qemu-arm -g 12345 ./njs-armv7 -c 'console.log("HH")'
$ gdb-multiarch ./njs-armv7 -ex 'source showstack.py'
ARGUMENTS
---------
argc = 3
arg 0 = ./njs-armv7
arg 1 = -c
arg 2 = console.log("HH")
...
AUX VECTOR
----------
AT_PHDR = 10034
AT_PHENT = 20
AT_PHNUM = 7
AT_PAGESZ = 1000
AT_BASE = 0
AT_FLAGS = 0
AT_ENTRY = 12fb9
AT_UID = 3e9
AT_EUID = 3e9
AT_GID = 3e9
AT_EGID = 3e9
AT_HWCAP = 1fb8d7
AT_CLKTCK = 64
AT_RANDOM = -104a0
AT_HWCAP2 = 1f
AT_NULL = 0
$ qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.28)
Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1885332
Title:
Error in user-mode calculation of ELF aux vector's AT_PHDR
Status in QEMU:
New
Bug description:
I have an (admittedly strange) statically-linked ELF binary for Linux that runs just fine on top of the Linux kernel in QEMU full-system emulation, but crashes before main in user-mode emulation. Specifically, it crashes when initializing thread-local storage in glibc's _dl_aux_init, because it reads out a strange value from the AT_PHDR entry of the ELF aux vector.
The binary has these program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x065874 0x00075874 0x00075874 0x00570 0x00570 R 0x4
PHDR 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x000000 0x00010000 0x00010000 0x65de8 0x65de8 R E 0x10000
LOAD 0x066b7c 0x00086b7c 0x00086b7c 0x02384 0x02384 RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x066b7c 0x00086b7c 0x00086b7c 0x00010 0x00030 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x8
GNU_RELRO 0x066b7c 0x00086b7c 0x00086b7c 0x00484 0x00484 R 0x1
LOAD 0x07e000 0x00089000 0x00089000 0x03f44 0x03f44 R E 0x1000
LOAD 0x098000 0x00030000 0x00030000 0x01000 0x01000 RW 0x1000
If I build the Linux kernel with the following patch to the very end
of create_elf_tables in fs/binfmt_elf.c
/* Put the elf_info on the stack in the right place. */
elf_addr_t *my_auxv = (elf_addr_t *) mm->saved_auxv;
int i;
for (i = 0; i < 15; i++) {
printk("0x%x = 0x%x", my_auxv[2*i], my_auxv[(2*i)+ 1]);
}
if (copy_to_user(sp, mm->saved_auxv, ei_index * sizeof(elf_addr_t)))
return -EFAULT;
return 0;
and run it like this:
qemu-system-arm \
-M versatilepb \
-nographic \
-dtb ./dts/versatile-pb.dtb \
-kernel zImage \
-M versatilepb \
-m 128M \
-append "earlyprintk=vga,keep" \
-initrd initramfs
after I've built the kernel initramfs like this (where "init" is the
binary in question):
make ARCH=arm versatile_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all -j10
cp "$1" arch/arm/boot/init
cd arch/arm/boot
echo init | cpio -o --format=newc > initramfs
then I get the following output. This is the kernel's view of the aux
vector for this binary:
0x10 = 0x1d7
0x6 = 0x1000
0x11 = 0x64
0x3 = 0x900000
0x4 = 0x20
0x5 = 0xb
0x7 = 0x0
0x8 = 0x0
0x9 = 0x101b8
0xb = 0x0
0xc = 0x0
0xd = 0x0
0xe = 0x0
0x17 = 0x0
0x19 = 0xbec62fb5
However, if I run "qemu-arm -g 12345 binary" and use GDB to peek at
the aux vector at the beginning of __libc_start_init (for example,
using this Python GDB API script: https://gist.github.com/langston-
barrett/5573d64ae0c9953e2fa0fe26847a5e1e), then I see the following
values:
AT_PHDR = 0xae000
AT_PHENT = 0x20
AT_PHNUM = 0xb
AT_PAGESZ = 0x1000
AT_BASE = 0x0
AT_FLAGS = 0x0
AT_ENTRY = 0x10230
AT_UID = 0x3e9
AT_EUID = 0x3e9
AT_GID = 0x3e9
AT_EGID = 0x3e9
AT_HWCAP = 0x1fb8d7
AT_CLKTCK = 0x64
AT_RANDOM = -0x103c0
AT_HWCAP2 = 0x1f
AT_NULL = 0x0
The crucial difference is in AT_PHDR (0x3), which is indeed the
virtual address of the PHDR segment when the kernel calculates it, but
is not when QEMU calculates it.
qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1885332/+subscriptions
^ permalink raw reply [flat|nested] 13+ messages in thread
* [Bug 1885332] Re: Error in user-mode calculation of ELF aux vector's AT_PHDR
2020-06-26 20:17 [Bug 1885332] [NEW] Error in user-mode calculation of ELF aux vector's AT_PHDR Langston
` (7 preceding siblings ...)
2020-07-11 12:00 ` Dmitry
@ 2020-07-13 13:02 ` Dmitry
2021-05-07 3:03 ` Thomas Huth
` (2 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: Dmitry @ 2020-07-13 13:02 UTC (permalink / raw)
To: qemu-devel
Built the latest QEMU, the issue goes away
$ bin/debug/native/s390x-linux-user/qemu-s390x --version
qemu-s390x version 5.0.50 (v5.0.0-2358-g6c87d9f311-dirty)
Copyright (c) 2003-2020 Fabrice Bellard and the QEMU Project developers
$ bin/debug/native/s390x-linux-user/qemu-s390x ../njs/njs-s390 -c 'console.log("HI")'
HI
So my issue seems unrelated, sorry for bothering.
--
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https://bugs.launchpad.net/bugs/1885332
Title:
Error in user-mode calculation of ELF aux vector's AT_PHDR
Status in QEMU:
New
Bug description:
I have an (admittedly strange) statically-linked ELF binary for Linux that runs just fine on top of the Linux kernel in QEMU full-system emulation, but crashes before main in user-mode emulation. Specifically, it crashes when initializing thread-local storage in glibc's _dl_aux_init, because it reads out a strange value from the AT_PHDR entry of the ELF aux vector.
The binary has these program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x065874 0x00075874 0x00075874 0x00570 0x00570 R 0x4
PHDR 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x000000 0x00010000 0x00010000 0x65de8 0x65de8 R E 0x10000
LOAD 0x066b7c 0x00086b7c 0x00086b7c 0x02384 0x02384 RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x066b7c 0x00086b7c 0x00086b7c 0x00010 0x00030 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x8
GNU_RELRO 0x066b7c 0x00086b7c 0x00086b7c 0x00484 0x00484 R 0x1
LOAD 0x07e000 0x00089000 0x00089000 0x03f44 0x03f44 R E 0x1000
LOAD 0x098000 0x00030000 0x00030000 0x01000 0x01000 RW 0x1000
If I build the Linux kernel with the following patch to the very end
of create_elf_tables in fs/binfmt_elf.c
/* Put the elf_info on the stack in the right place. */
elf_addr_t *my_auxv = (elf_addr_t *) mm->saved_auxv;
int i;
for (i = 0; i < 15; i++) {
printk("0x%x = 0x%x", my_auxv[2*i], my_auxv[(2*i)+ 1]);
}
if (copy_to_user(sp, mm->saved_auxv, ei_index * sizeof(elf_addr_t)))
return -EFAULT;
return 0;
and run it like this:
qemu-system-arm \
-M versatilepb \
-nographic \
-dtb ./dts/versatile-pb.dtb \
-kernel zImage \
-M versatilepb \
-m 128M \
-append "earlyprintk=vga,keep" \
-initrd initramfs
after I've built the kernel initramfs like this (where "init" is the
binary in question):
make ARCH=arm versatile_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all -j10
cp "$1" arch/arm/boot/init
cd arch/arm/boot
echo init | cpio -o --format=newc > initramfs
then I get the following output. This is the kernel's view of the aux
vector for this binary:
0x10 = 0x1d7
0x6 = 0x1000
0x11 = 0x64
0x3 = 0x900000
0x4 = 0x20
0x5 = 0xb
0x7 = 0x0
0x8 = 0x0
0x9 = 0x101b8
0xb = 0x0
0xc = 0x0
0xd = 0x0
0xe = 0x0
0x17 = 0x0
0x19 = 0xbec62fb5
However, if I run "qemu-arm -g 12345 binary" and use GDB to peek at
the aux vector at the beginning of __libc_start_init (for example,
using this Python GDB API script: https://gist.github.com/langston-
barrett/5573d64ae0c9953e2fa0fe26847a5e1e), then I see the following
values:
AT_PHDR = 0xae000
AT_PHENT = 0x20
AT_PHNUM = 0xb
AT_PAGESZ = 0x1000
AT_BASE = 0x0
AT_FLAGS = 0x0
AT_ENTRY = 0x10230
AT_UID = 0x3e9
AT_EUID = 0x3e9
AT_GID = 0x3e9
AT_EGID = 0x3e9
AT_HWCAP = 0x1fb8d7
AT_CLKTCK = 0x64
AT_RANDOM = -0x103c0
AT_HWCAP2 = 0x1f
AT_NULL = 0x0
The crucial difference is in AT_PHDR (0x3), which is indeed the
virtual address of the PHDR segment when the kernel calculates it, but
is not when QEMU calculates it.
qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1885332/+subscriptions
^ permalink raw reply [flat|nested] 13+ messages in thread
* [Bug 1885332] Re: Error in user-mode calculation of ELF aux vector's AT_PHDR
2020-06-26 20:17 [Bug 1885332] [NEW] Error in user-mode calculation of ELF aux vector's AT_PHDR Langston
` (8 preceding siblings ...)
2020-07-13 13:02 ` Dmitry
@ 2021-05-07 3:03 ` Thomas Huth
2021-05-07 18:06 ` Langston
2021-05-12 11:02 ` Thomas Huth
11 siblings, 0 replies; 13+ messages in thread
From: Thomas Huth @ 2021-05-07 3:03 UTC (permalink / raw)
To: qemu-devel
The QEMU project is currently moving its bug tracking to another system.
For this we need to know which bugs are still valid and which could be
closed already. Thus we are setting the bug state to "Incomplete" now.
If the bug has already been fixed in the latest upstream version of QEMU,
then please close this ticket as "Fix released".
If it is not fixed yet and you think that this bug report here is still
valid, then you have two options:
1) If you already have an account on gitlab.com, please open a new ticket
for this problem in our new tracker here:
https://gitlab.com/qemu-project/qemu/-/issues
and then close this ticket here on Launchpad (or let it expire auto-
matically after 60 days). Please mention the URL of this bug ticket on
Launchpad in the new ticket on GitLab.
2) If you don't have an account on gitlab.com and don't intend to get
one, but still would like to keep this ticket opened, then please switch
the state back to "New" within the next 60 days (otherwise it will get
closed as "Expired"). We will then eventually migrate the ticket auto-
matically to the new system (but you won't be the reporter of the bug
in the new system and thus won't get notified on changes anymore).
Thank you and sorry for the inconvenience.
** Changed in: qemu
Status: New => Incomplete
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1885332
Title:
Error in user-mode calculation of ELF aux vector's AT_PHDR
Status in QEMU:
Incomplete
Bug description:
I have an (admittedly strange) statically-linked ELF binary for Linux that runs just fine on top of the Linux kernel in QEMU full-system emulation, but crashes before main in user-mode emulation. Specifically, it crashes when initializing thread-local storage in glibc's _dl_aux_init, because it reads out a strange value from the AT_PHDR entry of the ELF aux vector.
The binary has these program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x065874 0x00075874 0x00075874 0x00570 0x00570 R 0x4
PHDR 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x000000 0x00010000 0x00010000 0x65de8 0x65de8 R E 0x10000
LOAD 0x066b7c 0x00086b7c 0x00086b7c 0x02384 0x02384 RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x066b7c 0x00086b7c 0x00086b7c 0x00010 0x00030 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x8
GNU_RELRO 0x066b7c 0x00086b7c 0x00086b7c 0x00484 0x00484 R 0x1
LOAD 0x07e000 0x00089000 0x00089000 0x03f44 0x03f44 R E 0x1000
LOAD 0x098000 0x00030000 0x00030000 0x01000 0x01000 RW 0x1000
If I build the Linux kernel with the following patch to the very end
of create_elf_tables in fs/binfmt_elf.c
/* Put the elf_info on the stack in the right place. */
elf_addr_t *my_auxv = (elf_addr_t *) mm->saved_auxv;
int i;
for (i = 0; i < 15; i++) {
printk("0x%x = 0x%x", my_auxv[2*i], my_auxv[(2*i)+ 1]);
}
if (copy_to_user(sp, mm->saved_auxv, ei_index * sizeof(elf_addr_t)))
return -EFAULT;
return 0;
and run it like this:
qemu-system-arm \
-M versatilepb \
-nographic \
-dtb ./dts/versatile-pb.dtb \
-kernel zImage \
-M versatilepb \
-m 128M \
-append "earlyprintk=vga,keep" \
-initrd initramfs
after I've built the kernel initramfs like this (where "init" is the
binary in question):
make ARCH=arm versatile_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all -j10
cp "$1" arch/arm/boot/init
cd arch/arm/boot
echo init | cpio -o --format=newc > initramfs
then I get the following output. This is the kernel's view of the aux
vector for this binary:
0x10 = 0x1d7
0x6 = 0x1000
0x11 = 0x64
0x3 = 0x900000
0x4 = 0x20
0x5 = 0xb
0x7 = 0x0
0x8 = 0x0
0x9 = 0x101b8
0xb = 0x0
0xc = 0x0
0xd = 0x0
0xe = 0x0
0x17 = 0x0
0x19 = 0xbec62fb5
However, if I run "qemu-arm -g 12345 binary" and use GDB to peek at
the aux vector at the beginning of __libc_start_init (for example,
using this Python GDB API script: https://gist.github.com/langston-
barrett/5573d64ae0c9953e2fa0fe26847a5e1e), then I see the following
values:
AT_PHDR = 0xae000
AT_PHENT = 0x20
AT_PHNUM = 0xb
AT_PAGESZ = 0x1000
AT_BASE = 0x0
AT_FLAGS = 0x0
AT_ENTRY = 0x10230
AT_UID = 0x3e9
AT_EUID = 0x3e9
AT_GID = 0x3e9
AT_EGID = 0x3e9
AT_HWCAP = 0x1fb8d7
AT_CLKTCK = 0x64
AT_RANDOM = -0x103c0
AT_HWCAP2 = 0x1f
AT_NULL = 0x0
The crucial difference is in AT_PHDR (0x3), which is indeed the
virtual address of the PHDR segment when the kernel calculates it, but
is not when QEMU calculates it.
qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1885332/+subscriptions
^ permalink raw reply [flat|nested] 13+ messages in thread
* [Bug 1885332] Re: Error in user-mode calculation of ELF aux vector's AT_PHDR
2020-06-26 20:17 [Bug 1885332] [NEW] Error in user-mode calculation of ELF aux vector's AT_PHDR Langston
` (9 preceding siblings ...)
2021-05-07 3:03 ` Thomas Huth
@ 2021-05-07 18:06 ` Langston
2021-05-12 11:02 ` Thomas Huth
11 siblings, 0 replies; 13+ messages in thread
From: Langston @ 2021-05-07 18:06 UTC (permalink / raw)
To: qemu-devel
** Changed in: qemu
Status: Incomplete => New
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1885332
Title:
Error in user-mode calculation of ELF aux vector's AT_PHDR
Status in QEMU:
New
Bug description:
I have an (admittedly strange) statically-linked ELF binary for Linux that runs just fine on top of the Linux kernel in QEMU full-system emulation, but crashes before main in user-mode emulation. Specifically, it crashes when initializing thread-local storage in glibc's _dl_aux_init, because it reads out a strange value from the AT_PHDR entry of the ELF aux vector.
The binary has these program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x065874 0x00075874 0x00075874 0x00570 0x00570 R 0x4
PHDR 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x000000 0x00010000 0x00010000 0x65de8 0x65de8 R E 0x10000
LOAD 0x066b7c 0x00086b7c 0x00086b7c 0x02384 0x02384 RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x066b7c 0x00086b7c 0x00086b7c 0x00010 0x00030 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x8
GNU_RELRO 0x066b7c 0x00086b7c 0x00086b7c 0x00484 0x00484 R 0x1
LOAD 0x07e000 0x00089000 0x00089000 0x03f44 0x03f44 R E 0x1000
LOAD 0x098000 0x00030000 0x00030000 0x01000 0x01000 RW 0x1000
If I build the Linux kernel with the following patch to the very end
of create_elf_tables in fs/binfmt_elf.c
/* Put the elf_info on the stack in the right place. */
elf_addr_t *my_auxv = (elf_addr_t *) mm->saved_auxv;
int i;
for (i = 0; i < 15; i++) {
printk("0x%x = 0x%x", my_auxv[2*i], my_auxv[(2*i)+ 1]);
}
if (copy_to_user(sp, mm->saved_auxv, ei_index * sizeof(elf_addr_t)))
return -EFAULT;
return 0;
and run it like this:
qemu-system-arm \
-M versatilepb \
-nographic \
-dtb ./dts/versatile-pb.dtb \
-kernel zImage \
-M versatilepb \
-m 128M \
-append "earlyprintk=vga,keep" \
-initrd initramfs
after I've built the kernel initramfs like this (where "init" is the
binary in question):
make ARCH=arm versatile_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all -j10
cp "$1" arch/arm/boot/init
cd arch/arm/boot
echo init | cpio -o --format=newc > initramfs
then I get the following output. This is the kernel's view of the aux
vector for this binary:
0x10 = 0x1d7
0x6 = 0x1000
0x11 = 0x64
0x3 = 0x900000
0x4 = 0x20
0x5 = 0xb
0x7 = 0x0
0x8 = 0x0
0x9 = 0x101b8
0xb = 0x0
0xc = 0x0
0xd = 0x0
0xe = 0x0
0x17 = 0x0
0x19 = 0xbec62fb5
However, if I run "qemu-arm -g 12345 binary" and use GDB to peek at
the aux vector at the beginning of __libc_start_init (for example,
using this Python GDB API script: https://gist.github.com/langston-
barrett/5573d64ae0c9953e2fa0fe26847a5e1e), then I see the following
values:
AT_PHDR = 0xae000
AT_PHENT = 0x20
AT_PHNUM = 0xb
AT_PAGESZ = 0x1000
AT_BASE = 0x0
AT_FLAGS = 0x0
AT_ENTRY = 0x10230
AT_UID = 0x3e9
AT_EUID = 0x3e9
AT_GID = 0x3e9
AT_EGID = 0x3e9
AT_HWCAP = 0x1fb8d7
AT_CLKTCK = 0x64
AT_RANDOM = -0x103c0
AT_HWCAP2 = 0x1f
AT_NULL = 0x0
The crucial difference is in AT_PHDR (0x3), which is indeed the
virtual address of the PHDR segment when the kernel calculates it, but
is not when QEMU calculates it.
qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1885332/+subscriptions
^ permalink raw reply [flat|nested] 13+ messages in thread
* [Bug 1885332] Re: Error in user-mode calculation of ELF aux vector's AT_PHDR
2020-06-26 20:17 [Bug 1885332] [NEW] Error in user-mode calculation of ELF aux vector's AT_PHDR Langston
` (10 preceding siblings ...)
2021-05-07 18:06 ` Langston
@ 2021-05-12 11:02 ` Thomas Huth
11 siblings, 0 replies; 13+ messages in thread
From: Thomas Huth @ 2021-05-12 11:02 UTC (permalink / raw)
To: qemu-devel
This is an automated cleanup. This bug report has been moved to QEMU's
new bug tracker on gitlab.com and thus gets marked as 'expired' now.
Please continue with the discussion here:
https://gitlab.com/qemu-project/qemu/-/issues/275
** Changed in: qemu
Status: New => Expired
** Bug watch added: gitlab.com/qemu-project/qemu/-/issues #275
https://gitlab.com/qemu-project/qemu/-/issues/275
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1885332
Title:
Error in user-mode calculation of ELF aux vector's AT_PHDR
Status in QEMU:
Expired
Bug description:
I have an (admittedly strange) statically-linked ELF binary for Linux that runs just fine on top of the Linux kernel in QEMU full-system emulation, but crashes before main in user-mode emulation. Specifically, it crashes when initializing thread-local storage in glibc's _dl_aux_init, because it reads out a strange value from the AT_PHDR entry of the ELF aux vector.
The binary has these program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x065874 0x00075874 0x00075874 0x00570 0x00570 R 0x4
PHDR 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x0a3000 0x00900000 0x00900000 0x00160 0x00160 R 0x1000
LOAD 0x000000 0x00010000 0x00010000 0x65de8 0x65de8 R E 0x10000
LOAD 0x066b7c 0x00086b7c 0x00086b7c 0x02384 0x02384 RW 0x10000
NOTE 0x000114 0x00010114 0x00010114 0x00044 0x00044 R 0x4
TLS 0x066b7c 0x00086b7c 0x00086b7c 0x00010 0x00030 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x8
GNU_RELRO 0x066b7c 0x00086b7c 0x00086b7c 0x00484 0x00484 R 0x1
LOAD 0x07e000 0x00089000 0x00089000 0x03f44 0x03f44 R E 0x1000
LOAD 0x098000 0x00030000 0x00030000 0x01000 0x01000 RW 0x1000
If I build the Linux kernel with the following patch to the very end
of create_elf_tables in fs/binfmt_elf.c
/* Put the elf_info on the stack in the right place. */
elf_addr_t *my_auxv = (elf_addr_t *) mm->saved_auxv;
int i;
for (i = 0; i < 15; i++) {
printk("0x%x = 0x%x", my_auxv[2*i], my_auxv[(2*i)+ 1]);
}
if (copy_to_user(sp, mm->saved_auxv, ei_index * sizeof(elf_addr_t)))
return -EFAULT;
return 0;
and run it like this:
qemu-system-arm \
-M versatilepb \
-nographic \
-dtb ./dts/versatile-pb.dtb \
-kernel zImage \
-M versatilepb \
-m 128M \
-append "earlyprintk=vga,keep" \
-initrd initramfs
after I've built the kernel initramfs like this (where "init" is the
binary in question):
make ARCH=arm versatile_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all -j10
cp "$1" arch/arm/boot/init
cd arch/arm/boot
echo init | cpio -o --format=newc > initramfs
then I get the following output. This is the kernel's view of the aux
vector for this binary:
0x10 = 0x1d7
0x6 = 0x1000
0x11 = 0x64
0x3 = 0x900000
0x4 = 0x20
0x5 = 0xb
0x7 = 0x0
0x8 = 0x0
0x9 = 0x101b8
0xb = 0x0
0xc = 0x0
0xd = 0x0
0xe = 0x0
0x17 = 0x0
0x19 = 0xbec62fb5
However, if I run "qemu-arm -g 12345 binary" and use GDB to peek at
the aux vector at the beginning of __libc_start_init (for example,
using this Python GDB API script: https://gist.github.com/langston-
barrett/5573d64ae0c9953e2fa0fe26847a5e1e), then I see the following
values:
AT_PHDR = 0xae000
AT_PHENT = 0x20
AT_PHNUM = 0xb
AT_PAGESZ = 0x1000
AT_BASE = 0x0
AT_FLAGS = 0x0
AT_ENTRY = 0x10230
AT_UID = 0x3e9
AT_EUID = 0x3e9
AT_GID = 0x3e9
AT_EGID = 0x3e9
AT_HWCAP = 0x1fb8d7
AT_CLKTCK = 0x64
AT_RANDOM = -0x103c0
AT_HWCAP2 = 0x1f
AT_NULL = 0x0
The crucial difference is in AT_PHDR (0x3), which is indeed the
virtual address of the PHDR segment when the kernel calculates it, but
is not when QEMU calculates it.
qemu-arm --version
qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1885332/+subscriptions
^ permalink raw reply [flat|nested] 13+ messages in thread