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[PATCH 3.2 06/60] m68k: Define asmlinkage_protect

From Ben Hutchings <ben@decadent.org.uk>
Newsgroups linux.kernel
Subject [PATCH 3.2 06/60] m68k: Define asmlinkage_protect
Date 2015-11-15 03:20 +0100
Message-ID <quV59-3JS-51@gated-at.bofh.it> (permalink)
References <quUVr-3GF-3@gated-at.bofh.it>
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3.2.73-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Andreas Schwab <schwab@linux-m68k.org>

commit 8474ba74193d302e8340dddd1e16c85cc4b98caf upstream.

Make sure the compiler does not modify arguments of syscall functions.
This can happen if the compiler generates a tailcall to another
function.  For example, without asmlinkage_protect sys_openat is compiled
into this function:

sys_openat:
	clr.l %d0
	move.w 18(%sp),%d0
	move.l %d0,16(%sp)
	jbra do_sys_open

Note how the fourth argument is modified in place, modifying the register
%d4 that gets restored from this stack slot when the function returns to
user-space.  The caller may expect the register to be unmodified across
system calls.

Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 arch/m68k/include/asm/linkage.h | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

--- a/arch/m68k/include/asm/linkage.h
+++ b/arch/m68k/include/asm/linkage.h
@@ -4,4 +4,34 @@
 #define __ALIGN .align 4
 #define __ALIGN_STR ".align 4"
 
+/*
+ * Make sure the compiler doesn't do anything stupid with the
+ * arguments on the stack - they are owned by the *caller*, not
+ * the callee. This just fools gcc into not spilling into them,
+ * and keeps it from doing tailcall recursion and/or using the
+ * stack slots for temporaries, since they are live and "used"
+ * all the way to the end of the function.
+ */
+#define asmlinkage_protect(n, ret, args...) \
+	__asmlinkage_protect##n(ret, ##args)
+#define __asmlinkage_protect_n(ret, args...) \
+	__asm__ __volatile__ ("" : "=r" (ret) : "0" (ret), ##args)
+#define __asmlinkage_protect0(ret) \
+	__asmlinkage_protect_n(ret)
+#define __asmlinkage_protect1(ret, arg1) \
+	__asmlinkage_protect_n(ret, "m" (arg1))
+#define __asmlinkage_protect2(ret, arg1, arg2) \
+	__asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2))
+#define __asmlinkage_protect3(ret, arg1, arg2, arg3) \
+	__asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3))
+#define __asmlinkage_protect4(ret, arg1, arg2, arg3, arg4) \
+	__asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3), \
+			      "m" (arg4))
+#define __asmlinkage_protect5(ret, arg1, arg2, arg3, arg4, arg5) \
+	__asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3), \
+			      "m" (arg4), "m" (arg5))
+#define __asmlinkage_protect6(ret, arg1, arg2, arg3, arg4, arg5, arg6) \
+	__asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3), \
+			      "m" (arg4), "m" (arg5), "m" (arg6))
+
 #endif

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[PATCH 3.2 00/60] 3.2.73-rc1 review Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:10 +0100
  [PATCH 3.2 43/60] dm btree remove: fix a bug when rebalancing  nodes after removal Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:10 +0100
  [PATCH 3.2 27/60] 3w-9xxx: don't unmap bounce buffered commands Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:10 +0100
  [PATCH 3.2 12/60] genirq: Fix race in register_irq_proc() Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:10 +0100
  [PATCH 3.2 31/60] iommu/vt-d: fix range computation when making  room for large pages Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:10 +0100
  [PATCH 3.2 28/60] xen-blkfront: check for null drvdata in  blkback_changed (XenbusStateClosing) Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:10 +0100
  [PATCH 3.2 32/60] xhci: don't finish a TD if we get a short  transfer event mid TD Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:10 +0100
  [PATCH 3.2 46/60] md/raid1: don't clear bitmap bit when  bad-block-list write fails. Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:10 +0100
  [PATCH 3.2 24/60] iwlwifi: dvm: fix D3 firmware PN programming Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:10 +0100
  [PATCH 3.2 04/60] regmap: debugfs: Don't bother actually printing  when calculating max length Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:10 +0100
  [PATCH 3.2 55/60] asix: Don't reset PHY on if_up for ASIX 88772 Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 08/60] UBI: Validate data_size Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 53/60] skbuff: Fix skb checksum partial check. Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 38/60] IB/cm: Fix rb-tree duplicate free and  use-after-free Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 20/60] usb: Add device quirk for Logitech PTZ cameras Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 33/60] xhci: handle no ping response error properly Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 19/60] USB: Add reset-resume quirk for two Plantronics  usb headphones. Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 44/60] dm btree: fix leak of bufio-backed block in  btree_split_beneath error path Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 40/60] powerpc/rtas: Validate rtas.entry before  calling enter_rtas() Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 34/60] xhci: Switch Intel Lynx Point LP ports to EHCI  on shutdown. Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 07/60] x86/xen: Do not clip xen_e820_map to  xen_e820_map_entries when sanitizing map Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 03/60] regmap: debugfs: Ensure we don't underflow when  printing access masks Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 51/60] net: add length argument to  skb_copy_and_csum_datagram_iovec Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 05/60] ath9k: declare required extra tx headroom Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 39/60] drm/nouveau/gem: return only valid domain when  there's only one Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 06/60] m68k: Define asmlinkage_protect Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 26/60] sched/core: Fix TASK_DEAD race in  finish_task_switch() Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 45/60] md/raid1: ensure device failure recorded before  write request returns. Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 15/60] md/raid0: update queue parameter in a safer  location. Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 59/60] KEYS: Fix race between key destruction and  finding a keyring by name Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 23/60] ppp: don't override sk->sk_state in  pppoe_flush_dev() Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 49/60] mvsas: Fix NULL pointer dereference in  mvs_slot_task_free Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 58/60] KVM: x86: work around infinite loop in  microcode when #AC is delivered Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:20 +0100
  [PATCH 3.2 42/60] ppp: fix pppoe_dev deletion condition in  pppoe_release() Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:30 +0100
  [PATCH 3.2 10/60] MIPS: dma-default: Fix 32-bit fall back to GFP_DMA Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:30 +0100
  [PATCH 3.2 50/60] sched: declare pid_alive as inline Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:30 +0100
  [PATCH 3.2 17/60] clocksource: Fix abs() usage w/ 64bit values Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:30 +0100
  [PATCH 3.2 36/60] crypto: api - Only abort operations on fatal signal Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:30 +0100
  [PATCH 3.2 16/60] md/raid0: apply base queue limits *before*  disk_stack_limits Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:30 +0100
  [PATCH 3.2 47/60] md/raid10: ensure device failure recorded  before write request returns. Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:30 +0100
  [PATCH 3.2 57/60] Failing to send a CLOSE if file is opened  WRONLY and server reboots on a 4.x mount Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:30 +0100
  [PATCH 3.2 14/60] [SMB3] Do not fall back to SMBWriteX in  set_file_size error cases Ben Hutchings <ben@decadent.org.uk> - 2015-11-15 03:30 +0100
  Re: [PATCH 3.2 00/60] 3.2.73-rc1 review Guenter Roeck <linux@roeck-us.net> - 2015-11-15 14:50 +0100
    Re: [PATCH 3.2 00/60] 3.2.73-rc1 review Ben Hutchings <ben@decadent.org.uk> - 2015-11-16 12:20 +0100

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