[v1] microblaze: fix signal-frame handling for NPTL

[PATCH 0/2] microblaze: fix signal-frame handling for NPTL

Posted by Ramin Moussavi 3 days, 15 hours ago

Two independent fixes to the microblaze signal-delivery path, both found
while bringing the uClibc-ng NPTL test suite up on microblazeel under
qemu-system (petalogix-s3adsp1800).

Patch 1 wires up sigaltstack(), which is currently routed to
sys_ni_syscall even though the signal code fully supports an alternate
stack - microblaze is the only architecture leaving it unimplemented.

Patch 2 reserves the ABI argument-home area at the top of the signal
frame.  The MicroBlaze calling convention lets a handler store its
incoming register arguments into [r1+4]..[r1+28]; since r1 points at
struct rt_sigframe on entry, those stores land in siginfo/ucontext and
corrupt the signal state.  An eight-word leading gap moves them into
scratch space.

Both were tested with the uClibc-ng NPTL tests; the affected tests
(tst-cancel20/21, tst-cancelx20/21, tst-signal6, tst-timer4/5,
tst-mqueue5) now pass.  checkpatch --strict is clean and both apply to
current linux-next.

Ramin Moussavi (2):
  microblaze: wire up sigaltstack
  microblaze: reserve the ABI argument-home area in the signal frame

 arch/microblaze/kernel/signal.c             | 7 +++++++
 arch/microblaze/kernel/syscalls/syscall.tbl | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

-- 
2.53.0

[PATCH v2 0/2] microblaze: fix signal-frame handling for NPTL

Posted by Ramin Moussavi 2 days, 23 hours ago

Two independent fixes to the microblaze signal-delivery path, both found
while bringing the uClibc-ng NPTL test suite up on microblazeel under
qemu-system (petalogix-s3adsp1800).

Patch 1 wires up sigaltstack(), which is currently routed to
sys_ni_syscall even though the signal code fully supports an alternate
stack - microblaze is the only architecture leaving it unimplemented.

Patch 2 reserves the ABI argument-home area at the top of the signal
frame.  The MicroBlaze calling convention reserves [r1+0] for the return
address and lets a handler store its incoming register arguments r5..r10
into [r1+4]..[r1+24]; since r1 points at struct rt_sigframe on entry,
those stores land in siginfo/ucontext and corrupt the signal state.  A
seven-word leading gap moves them into scratch space.

Both were tested with the uClibc-ng NPTL tests; the affected tests
(tst-cancel20/21, tst-cancelx20/21, tst-signal6, tst-timer4/5,
tst-mqueue5) pass.  checkpatch --strict is clean and both apply to
current linux-next.

Changes since v1 [1]:
 - Patch 2: shrink the gap from eight to seven words.  Michal pointed
   out that the home area is exactly seven words (r15 at r1+0, r5..r10
   at r1+4..r1+24); the eighth word was never written by the ABI.
   Retested on qemu - tst-timer4/5, tst-mqueue5, tst-signal6 still pass.
 - Patch 2: fix the offset range in the commit message and the in-code
   comment ([r1+4]..[r1+24], not [r1+28]).
 - Patch 1: unchanged.

[1] https://lore.kernel.org/all/cover.1780587199.git.lordrasmus@gmail.com/

Ramin Moussavi (2):
  microblaze: wire up sigaltstack
  microblaze: reserve the ABI argument-home area in the signal frame

 arch/microblaze/kernel/signal.c             | 8 ++++++++
 arch/microblaze/kernel/syscalls/syscall.tbl | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

-- 
2.53.0

Re: [PATCH v2 0/2] microblaze: fix signal-frame handling for NPTL

Posted by Michal Simek 2 days, 23 hours ago


On 6/5/26 10:20, Ramin Moussavi wrote:
> Two independent fixes to the microblaze signal-delivery path, both found
> while bringing the uClibc-ng NPTL test suite up on microblazeel under
> qemu-system (petalogix-s3adsp1800).
> 
> Patch 1 wires up sigaltstack(), which is currently routed to
> sys_ni_syscall even though the signal code fully supports an alternate
> stack - microblaze is the only architecture leaving it unimplemented.
> 
> Patch 2 reserves the ABI argument-home area at the top of the signal
> frame.  The MicroBlaze calling convention reserves [r1+0] for the return
> address and lets a handler store its incoming register arguments r5..r10
> into [r1+4]..[r1+24]; since r1 points at struct rt_sigframe on entry,
> those stores land in siginfo/ucontext and corrupt the signal state.  A
> seven-word leading gap moves them into scratch space.
> 
> Both were tested with the uClibc-ng NPTL tests; the affected tests
> (tst-cancel20/21, tst-cancelx20/21, tst-signal6, tst-timer4/5,
> tst-mqueue5) pass.  checkpatch --strict is clean and both apply to
> current linux-next.
> 
> Changes since v1 [1]:
>   - Patch 2: shrink the gap from eight to seven words.  Michal pointed
>     out that the home area is exactly seven words (r15 at r1+0, r5..r10
>     at r1+4..r1+24); the eighth word was never written by the ABI.
>     Retested on qemu - tst-timer4/5, tst-mqueue5, tst-signal6 still pass.
>   - Patch 2: fix the offset range in the commit message and the in-code
>     comment ([r1+4]..[r1+24], not [r1+28]).
>   - Patch 1: unchanged.
> 
> [1] https://lore.kernel.org/all/cover.1780587199.git.lordrasmus@gmail.com/
> 
> Ramin Moussavi (2):
>    microblaze: wire up sigaltstack
>    microblaze: reserve the ABI argument-home area in the signal frame
> 
>   arch/microblaze/kernel/signal.c             | 8 ++++++++
>   arch/microblaze/kernel/syscalls/syscall.tbl | 2 +-
>   2 files changed, 9 insertions(+), 1 deletion(-)
> 

2 issues here.

1. Do not send it as reply to v1 but separately.
2. Author of patch is not matching SOB in the email
You are sending it from
Ramin Moussavi <lordrasmus@gmail.com>
and SOB has
Ramin Moussavi <ramin.moussavi@yacoub.de>

Please fix it and send v3

Thanks,
Michal

-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Xilinx Microblaze
Maintainer of Linux kernel - Xilinx Zynq ARM and ZynqMP/Versal ARM64 SoCs
U-Boot custodian - Xilinx Microblaze/Zynq/ZynqMP/Versal/Versal NET SoCs
TF-A maintainer - Xilinx ZynqMP/Versal/Versal NET SoCs

[PATCH v2 1/2] microblaze: wire up sigaltstack

Posted by Ramin Moussavi 2 days, 23 hours ago

sigaltstack is wired to sys_ni_syscall - microblaze is the only
architecture without it - although the microblaze signal delivery code
fully supports the alternate signal stack: get_sigframe() picks the
stack via sigsp(), setup_rt_frame() saves it with __save_altstack() and
sys_rt_sigreturn() calls restore_altstack().

Wire it up to sys_sigaltstack.

Tested on qemu petalogix-s3adsp1800 (microblazeel, kernel 6.5.10 and
syscall table unchanged in current mainline) with the uClibc-ng test
suite: the five sigaltstack-dependent NPTL tests (tst-cancel20/21,
tst-cancelx20/21, tst-signal6) pass; before this change sigaltstack()
returned ENOSYS.

Signed-off-by: Ramin Moussavi <ramin.moussavi@yacoub.de>
---
 arch/microblaze/kernel/syscalls/syscall.tbl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index 223d26303..b4ce48e8a 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -193,7 +193,7 @@
 183	common	getcwd				sys_getcwd
 184	common	capget				sys_capget
 185	common	capset				sys_capset
-186	common	sigaltstack			sys_ni_syscall
+186	common	sigaltstack			sys_sigaltstack
 187	common	sendfile			sys_sendfile
 188	common	getpmsg				sys_ni_syscall
 189	common	putpmsg				sys_ni_syscall
-- 
2.53.0

[PATCH v2 2/2] microblaze: reserve the ABI argument-home area in the signal frame

Posted by Ramin Moussavi 2 days, 23 hours ago

The MicroBlaze procedure call standard reserves [r1+0] for the return
address and lets a callee store its incoming register arguments r5..r10
into the caller-provided home slots at [r1+4]..[r1+24].  When the kernel
enters a signal handler it sets r1 to point at struct rt_sigframe, whose
leading members are the siginfo and ucontext prepared for the handler.
A handler that homes its arguments - which an unoptimised (-O0) build
always does - therefore overwrites the start of siginfo/ucontext,
corrupting the signal state that the handler and sys_rt_sigreturn()
depend on.

Reserve the home area by making a seven-word gap the first member of
struct rt_sigframe, so the handler's argument stores land in scratch
space instead of clobbering siginfo.

Tested on qemu-system-microblazeel (petalogix-s3adsp1800) with the
uClibc-ng NPTL test suite: tst-timer4, tst-timer5, tst-mqueue5 and
tst-signal6 pass; before this change they failed because the handler
clobbered the signal frame.

Signed-off-by: Ramin Moussavi <ramin.moussavi@yacoub.de>
---
 arch/microblaze/kernel/signal.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/microblaze/kernel/signal.c b/arch/microblaze/kernel/signal.c
index c78a0ff48..9cca06d60 100644
--- a/arch/microblaze/kernel/signal.c
+++ b/arch/microblaze/kernel/signal.c
@@ -49,6 +49,14 @@ struct sigframe {
 };
 
 struct rt_sigframe {
+	/*
+	 * Home area for the handler's register arguments: the MicroBlaze
+	 * ABI reserves [r1+0] for the return address and lets the callee
+	 * store r5..r10 at [r1+4]..[r1+24], and r1 points at this frame
+	 * when the handler is entered.  Without the gap those stores
+	 * corrupt info/uc.
+	 */
+	unsigned long abi_gap[7];
 	struct siginfo info;
 	struct ucontext uc;
 	unsigned long tramp[2];	/* signal trampoline */
-- 
2.53.0