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Message-Id: <20141024.125346.511017911263580664.davem@davemloft.net>
Date: Fri, 24 Oct 2014 12:53:46 -0400 (EDT)
From: David Miller <davem@...emloft.net>
To: sam@...nborg.org
Cc: mroos@...ux.ee, linux-kernel@...r.kernel.org,
sparclinux@...r.kernel.org
Subject: Re: unaligned accesses in SLAB etc.
From: Sam Ravnborg <sam@...nborg.org>
Date: Fri, 24 Oct 2014 06:54:55 +0200
> A minor detail.
>
>> [PATCH] sparc64: Fix register corruption in top-most kernel stack frame during boot.
>>
>> - call start_kernel
>> + call start_early_boot
>
> Maybe add a comment about stack use - as per your nice patch description.
Added.
>> +void __init start_early_boot(void)
>
> This will likely result in sparse complaining about:
> fuction not declared - should it be static?
>
> A prototype in include/asm/setup.h would be nice.
Done.
This is the final patch I'll be using and submitting to -stable as well.
====================
[PATCH] sparc64: Fix register corruption in top-most kernel stack frame during boot.
Meelis Roos reported that kernels built with gcc-4.9 do not boot, we
eventually narrowed this down to only impacting machines using
UltraSPARC-III and derivitive cpus.
The crash happens right when the first user process is spawned:
[ 54.451346] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004
[ 54.451346]
[ 54.571516] CPU: 1 PID: 1 Comm: init Not tainted 3.16.0-rc2-00211-gd7933ab #96
[ 54.666431] Call Trace:
[ 54.698453] [0000000000762f8c] panic+0xb0/0x224
[ 54.759071] [000000000045cf68] do_exit+0x948/0x960
[ 54.823123] [000000000042cbc0] fault_in_user_windows+0xe0/0x100
[ 54.902036] [0000000000404ad0] __handle_user_windows+0x0/0x10
[ 54.978662] Press Stop-A (L1-A) to return to the boot prom
[ 55.050713] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004
Further investigation showed that compiling only per_cpu_patch() with
an older compiler fixes the boot.
Detailed analysis showed that the function is not being miscompiled by
gcc-4.9, but it is using a different register allocation ordering.
With the gcc-4.9 compiled function, something during the code patching
causes some of the %i* input registers to get corrupted. Perhaps
we have a TLB miss path into the firmware that is deep enough to
cause a register window spill and subsequent restore when we get
back from the TLB miss trap.
Let's plug this up by doing two things:
1) Stop using the firmware stack for client interface calls into
the firmware. Just use the kernel's stack.
2) As soon as we can, call into a new function "start_early_boot()"
to put a one-register-window buffer between the firmware's
deepest stack frame and the top-most initial kernel one.
Reported-by: Meelis Roos <mroos@...ux.ee>
Tested-by: Meelis Roos <mroos@...ux.ee>
Signed-off-by: David S. Miller <davem@...emloft.net>
---
arch/sparc/include/asm/oplib_64.h | 3 ++-
arch/sparc/include/asm/setup.h | 2 ++
arch/sparc/kernel/entry.h | 3 ---
arch/sparc/kernel/head_64.S | 40 ++++-----------------------------------
arch/sparc/kernel/hvtramp.S | 1 -
arch/sparc/kernel/setup_64.c | 28 +++++++++++++++++++--------
arch/sparc/kernel/trampoline_64.S | 12 +++++++-----
arch/sparc/prom/cif.S | 5 ++---
arch/sparc/prom/init_64.c | 6 +++---
arch/sparc/prom/p1275.c | 2 --
10 files changed, 40 insertions(+), 62 deletions(-)
diff --git a/arch/sparc/include/asm/oplib_64.h b/arch/sparc/include/asm/oplib_64.h
index f346824..2e3a4ad 100644
--- a/arch/sparc/include/asm/oplib_64.h
+++ b/arch/sparc/include/asm/oplib_64.h
@@ -62,7 +62,8 @@ struct linux_mem_p1275 {
/* You must call prom_init() before using any of the library services,
* preferably as early as possible. Pass it the romvec pointer.
*/
-void prom_init(void *cif_handler, void *cif_stack);
+void prom_init(void *cif_handler);
+void prom_init_report(void);
/* Boot argument acquisition, returns the boot command line string. */
char *prom_getbootargs(void);
diff --git a/arch/sparc/include/asm/setup.h b/arch/sparc/include/asm/setup.h
index f5fffd8..29d64b1 100644
--- a/arch/sparc/include/asm/setup.h
+++ b/arch/sparc/include/asm/setup.h
@@ -48,6 +48,8 @@ unsigned long safe_compute_effective_address(struct pt_regs *, unsigned int);
#endif
#ifdef CONFIG_SPARC64
+void __init start_early_boot(void);
+
/* unaligned_64.c */
int handle_ldf_stq(u32 insn, struct pt_regs *regs);
void handle_ld_nf(u32 insn, struct pt_regs *regs);
diff --git a/arch/sparc/kernel/entry.h b/arch/sparc/kernel/entry.h
index ebaba61..88d322b 100644
--- a/arch/sparc/kernel/entry.h
+++ b/arch/sparc/kernel/entry.h
@@ -65,13 +65,10 @@ struct pause_patch_entry {
extern struct pause_patch_entry __pause_3insn_patch,
__pause_3insn_patch_end;
-void __init per_cpu_patch(void);
void sun4v_patch_1insn_range(struct sun4v_1insn_patch_entry *,
struct sun4v_1insn_patch_entry *);
void sun4v_patch_2insn_range(struct sun4v_2insn_patch_entry *,
struct sun4v_2insn_patch_entry *);
-void __init sun4v_patch(void);
-void __init boot_cpu_id_too_large(int cpu);
extern unsigned int dcache_parity_tl1_occurred;
extern unsigned int icache_parity_tl1_occurred;
diff --git a/arch/sparc/kernel/head_64.S b/arch/sparc/kernel/head_64.S
index 4fdeb80..3d61fca 100644
--- a/arch/sparc/kernel/head_64.S
+++ b/arch/sparc/kernel/head_64.S
@@ -672,14 +672,12 @@ tlb_fixup_done:
sethi %hi(init_thread_union), %g6
or %g6, %lo(init_thread_union), %g6
ldx [%g6 + TI_TASK], %g4
- mov %sp, %l6
wr %g0, ASI_P, %asi
mov 1, %g1
sllx %g1, THREAD_SHIFT, %g1
sub %g1, (STACKFRAME_SZ + STACK_BIAS), %g1
add %g6, %g1, %sp
- mov 0, %fp
/* Set per-cpu pointer initially to zero, this makes
* the boot-cpu use the in-kernel-image per-cpu areas
@@ -706,44 +704,14 @@ tlb_fixup_done:
nop
#endif
- mov %l6, %o1 ! OpenPROM stack
call prom_init
mov %l7, %o0 ! OpenPROM cif handler
- /* Initialize current_thread_info()->cpu as early as possible.
- * In order to do that accurately we have to patch up the get_cpuid()
- * assembler sequences. And that, in turn, requires that we know
- * if we are on a Starfire box or not. While we're here, patch up
- * the sun4v sequences as well.
+ /* To create a one-register-window buffer between the kernel's
+ * initial stack and the last stack frame we use from the firmware,
+ * do the rest of the boot from a C helper function.
*/
- call check_if_starfire
- nop
- call per_cpu_patch
- nop
- call sun4v_patch
- nop
-
-#ifdef CONFIG_SMP
- call hard_smp_processor_id
- nop
- cmp %o0, NR_CPUS
- blu,pt %xcc, 1f
- nop
- call boot_cpu_id_too_large
- nop
- /* Not reached... */
-
-1:
-#else
- mov 0, %o0
-#endif
- sth %o0, [%g6 + TI_CPU]
-
- call prom_init_report
- nop
-
- /* Off we go.... */
- call start_kernel
+ call start_early_boot
nop
/* Not reached... */
diff --git a/arch/sparc/kernel/hvtramp.S b/arch/sparc/kernel/hvtramp.S
index b7ddcdd..cdbfec2 100644
--- a/arch/sparc/kernel/hvtramp.S
+++ b/arch/sparc/kernel/hvtramp.S
@@ -109,7 +109,6 @@ hv_cpu_startup:
sllx %g5, THREAD_SHIFT, %g5
sub %g5, (STACKFRAME_SZ + STACK_BIAS), %g5
add %g6, %g5, %sp
- mov 0, %fp
call init_irqwork_curcpu
nop
diff --git a/arch/sparc/kernel/setup_64.c b/arch/sparc/kernel/setup_64.c
index e629b83..c38d19f 100644
--- a/arch/sparc/kernel/setup_64.c
+++ b/arch/sparc/kernel/setup_64.c
@@ -30,6 +30,7 @@
#include <linux/cpu.h>
#include <linux/initrd.h>
#include <linux/module.h>
+#include <linux/start_kernel.h>
#include <asm/io.h>
#include <asm/processor.h>
@@ -162,7 +163,7 @@ char reboot_command[COMMAND_LINE_SIZE];
static struct pt_regs fake_swapper_regs = { { 0, }, 0, 0, 0, 0 };
-void __init per_cpu_patch(void)
+static void __init per_cpu_patch(void)
{
struct cpuid_patch_entry *p;
unsigned long ver;
@@ -254,7 +255,7 @@ void sun4v_patch_2insn_range(struct sun4v_2insn_patch_entry *start,
}
}
-void __init sun4v_patch(void)
+static void __init sun4v_patch(void)
{
extern void sun4v_hvapi_init(void);
@@ -323,14 +324,25 @@ static void __init pause_patch(void)
}
}
-#ifdef CONFIG_SMP
-void __init boot_cpu_id_too_large(int cpu)
+void __init start_early_boot(void)
{
- prom_printf("Serious problem, boot cpu id (%d) >= NR_CPUS (%d)\n",
- cpu, NR_CPUS);
- prom_halt();
+ int cpu;
+
+ check_if_starfire();
+ per_cpu_patch();
+ sun4v_patch();
+
+ cpu = hard_smp_processor_id();
+ if (cpu >= NR_CPUS) {
+ prom_printf("Serious problem, boot cpu id (%d) >= NR_CPUS (%d)\n",
+ cpu, NR_CPUS);
+ prom_halt();
+ }
+ current_thread_info()->cpu = cpu;
+
+ prom_init_report();
+ start_kernel();
}
-#endif
/* On Ultra, we support all of the v8 capabilities. */
unsigned long sparc64_elf_hwcap = (HWCAP_SPARC_FLUSH | HWCAP_SPARC_STBAR |
diff --git a/arch/sparc/kernel/trampoline_64.S b/arch/sparc/kernel/trampoline_64.S
index 737f8cb..88ede1d 100644
--- a/arch/sparc/kernel/trampoline_64.S
+++ b/arch/sparc/kernel/trampoline_64.S
@@ -109,10 +109,13 @@ startup_continue:
brnz,pn %g1, 1b
nop
- sethi %hi(p1275buf), %g2
- or %g2, %lo(p1275buf), %g2
- ldx [%g2 + 0x10], %l2
- add %l2, -(192 + 128), %sp
+ /* Get onto temporary stack which will be in the locked
+ * kernel image.
+ */
+ sethi %hi(tramp_stack), %g1
+ or %g1, %lo(tramp_stack), %g1
+ add %g1, TRAMP_STACK_SIZE, %g1
+ sub %g1, STACKFRAME_SZ + STACK_BIAS + 256, %sp
flushw
/* Setup the loop variables:
@@ -394,7 +397,6 @@ after_lock_tlb:
sllx %g5, THREAD_SHIFT, %g5
sub %g5, (STACKFRAME_SZ + STACK_BIAS), %g5
add %g6, %g5, %sp
- mov 0, %fp
rdpr %pstate, %o1
or %o1, PSTATE_IE, %o1
diff --git a/arch/sparc/prom/cif.S b/arch/sparc/prom/cif.S
index 9c86b4b..8050f38 100644
--- a/arch/sparc/prom/cif.S
+++ b/arch/sparc/prom/cif.S
@@ -11,11 +11,10 @@
.text
.globl prom_cif_direct
prom_cif_direct:
+ save %sp, -192, %sp
sethi %hi(p1275buf), %o1
or %o1, %lo(p1275buf), %o1
- ldx [%o1 + 0x0010], %o2 ! prom_cif_stack
- save %o2, -192, %sp
- ldx [%i1 + 0x0008], %l2 ! prom_cif_handler
+ ldx [%o1 + 0x0008], %l2 ! prom_cif_handler
mov %g4, %l0
mov %g5, %l1
mov %g6, %l3
diff --git a/arch/sparc/prom/init_64.c b/arch/sparc/prom/init_64.c
index d95db75..110b0d7 100644
--- a/arch/sparc/prom/init_64.c
+++ b/arch/sparc/prom/init_64.c
@@ -26,13 +26,13 @@ phandle prom_chosen_node;
* It gets passed the pointer to the PROM vector.
*/
-extern void prom_cif_init(void *, void *);
+extern void prom_cif_init(void *);
-void __init prom_init(void *cif_handler, void *cif_stack)
+void __init prom_init(void *cif_handler)
{
phandle node;
- prom_cif_init(cif_handler, cif_stack);
+ prom_cif_init(cif_handler);
prom_chosen_node = prom_finddevice(prom_chosen_path);
if (!prom_chosen_node || (s32)prom_chosen_node == -1)
diff --git a/arch/sparc/prom/p1275.c b/arch/sparc/prom/p1275.c
index b2340f0..545d8bb 100644
--- a/arch/sparc/prom/p1275.c
+++ b/arch/sparc/prom/p1275.c
@@ -20,7 +20,6 @@
struct {
long prom_callback; /* 0x00 */
void (*prom_cif_handler)(long *); /* 0x08 */
- unsigned long prom_cif_stack; /* 0x10 */
} p1275buf;
extern void prom_world(int);
@@ -52,5 +51,4 @@ void p1275_cmd_direct(unsigned long *args)
void prom_cif_init(void *cif_handler, void *cif_stack)
{
p1275buf.prom_cif_handler = (void (*)(long *))cif_handler;
- p1275buf.prom_cif_stack = (unsigned long)cif_stack;
}
--
1.8.1.2
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