Hi Al,
On 13.10.2012 02:53, Al Viro wrote:
> The last bits of infrastructure for kernel_thread() et.al., with alpha/arm/x86
> use of those. Plus sanitizing the asm glue and do_notify_resume() on alpha,
> fixing the "disabled irq while running task_work stuff" breakage there.
>
> At that point the rest of kernel_thread/kernel_execve/sys_execve work can
> be done independently for different architectures. The only pending bits
> that do depend on having all architectures converted are restrictred to
> fs/* and kernel/* - that'll obviously have to wait for the next cycle.
> I thought we'd have to wait for all of them done before we start eliminating
> the longjump-style insanity in kernel_execve(), but it turned out there's
> a very simple way to do that without flagday-style changes.
>
> Please, pull from
> git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal for-linus
>
> Shortlog:
> Al Viro (12):
[...]
> arm: switch to saner kernel_execve() semantics
[...]
> Diffstat:
[...]
> arch/arm/include/asm/unistd.h | 1 -
> arch/arm/kernel/entry-common.S | 29 +--------
> arch/arm/kernel/process.c | 5 +-
I rebased my ARM development branch and figured that your patch 9fff2fa
("arm: switch to saner kernel_execve() semantics") breaks the boot on my
board right after init is invoked via NFS:
[ 4.682072] VFS: Mounted root (nfs filesystem) on device 0:12.
[ 4.690744] devtmpfs: mounted
[ 4.694395] Freeing init memory: 172K
[ 5.291417] Internal error: Oops - undefined instruction: 0 [#1] SMP
THUMB2
[ 5.298734] Modules linked in:
[ 5.301952] CPU: 0 Not tainted (3.6.0-11053-g56c8535 #128)
[ 5.308071] PC is at cpsw_probe+0x422/0x9ac
[ 5.312459] LR is at trace_hardirqs_on_caller+0x8f/0xfc
[ 5.317934] pc : [<c03493de>] lr : [<c005e81f>] psr: 60000113
[ 5.317934] sp : cf055fb0 ip : 00000000 fp : 00000000
[ 5.329944] r10: 00000000 r9 : 00000000 r8 : 00000000
[ 5.335413] r7 : 00000000 r6 : 00000000 r5 : c034458d r4 : 00000000
[ 5.342244] r3 : cf057a40 r2 : 00000000 r1 : 00000001 r0 : 00000000
[ 5.349078] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM
Segment user
[ 5.356546] Control: 50c5387d Table: 8f434019 DAC: 00000015
[ 5.362562] Process init (pid: 1, stack limit = 0xcf054240)
[ 5.368395] Stack: (0xcf055fb0 to 0xcf056000)
[ 5.372961] 5fa0: 00000001
00000000 00000000 00000000
[ 5.381525] 5fc0: cf055fb0 c000d1a8 00000000 00000000 00000000
00000000 00000000 00000000
[ 5.390091] 5fe0: 00000000 bee83f10 00000000 b6fdedd0 00000010
00000000 aaaabfaf a8babbaa
[ 5.398664] Code: 2206a010 718ef508 0184f8da f8b1f65d (3070f8d8)
[ 5.405049] ---[ end trace f92e44d0ab15d037 ]---
[ 5.410424] Kernel panic - not syncing: Attempted to kill init!
exitcode=0x0000000b
Looking at the patch, I see it does two things:
a) kill the special treatment formerly done by ret_from_kernel_thread
b) switch over to generic execve for ARM
I know too little about the internals here, but reverting the latter
part fixes the boot for me. Find attached the patch I used locally for
that, on top of Linus' current merge tree (4d7127d).
FWIW, the config I'm using is here: http://pastebin.com/JPwAYmrD
I can test patches if you have any for me.
Thanks,
Daniel
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 261fdd0..1bc092e 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -12,7 +12,6 @@ config ARM
select GENERIC_IRQ_PROBE
select GENERIC_IRQ_SHOW
select GENERIC_KERNEL_THREAD
- select GENERIC_KERNEL_EXECVE
select GENERIC_PCI_IOMAP
select GENERIC_SMP_IDLE_THREAD
select GENERIC_STRNCPY_FROM_USER
diff --git a/arch/arm/include/asm/unistd.h b/arch/arm/include/asm/unistd.h
index 8f60b6e..202bc3a 100644
--- a/arch/arm/include/asm/unistd.h
+++ b/arch/arm/include/asm/unistd.h
@@ -42,6 +42,7 @@
#define __ARCH_WANT_SYS_SOCKETCALL
#endif
#define __ARCH_WANT_SYS_EXECVE
+#define __ARCH_WANT_KERNEL_EXECVE
/*
* "Conditional" syscalls
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 417bac1..c05bd28 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -94,6 +94,18 @@ ENTRY(ret_from_fork)
b ret_slow_syscall
ENDPROC(ret_from_fork)
+/*
+ * turn a kernel thread into userland process
+ * use: ret_from_kernel_execve(struct pt_regs *normal)
+ */
+ENTRY(ret_from_kernel_execve)
+ mov why, #0 @ not a syscall
+ str why, [r0, #S_R0] @ ... and we want 0 in ->ARM_r0 as well
+ get_thread_info tsk @ thread structure
+ mov sp, r0 @ stack pointer just under pt_regs
+ b ret_slow_syscall
+ENDPROC(ret_from_kernel_execve)
+
.equ NR_syscalls,0
#define CALL(x) .equ NR_syscalls,NR_syscalls+1
#include "calls.S"
