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authorH. Peter Anvin <hpa@zytor.com>2008-02-08 07:21:26 -0500
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-08 12:22:39 -0500
commitbdc807871d58285737d50dc6163d0feb72cb0dc2 (patch)
tree1a6d35f3537ed1a7460811549efd045ae97a0e6e /include
parent7ef3d2fd17c377ef64a2aa19677d17576606c3b4 (diff)
avoid overflows in kernel/time.c
When the conversion factor between jiffies and milli- or microseconds is not a single multiply or divide, as for the case of HZ == 300, we currently do a multiply followed by a divide. The intervening result, however, is subject to overflows, especially since the fraction is not simplified (for HZ == 300, we multiply by 300 and divide by 1000). This is exposed to the user when passing a large timeout to poll(), for example. This patch replaces the multiply-divide with a reciprocal multiplication on 32-bit platforms. When the input is an unsigned long, there is no portable way to do this on 64-bit platforms there is no portable way to do this since it requires a 128-bit intermediate result (which gcc does support on 64-bit platforms but may generate libgcc calls, e.g. on 64-bit s390), but since the output is a 32-bit integer in the cases affected, just simplify the multiply-divide (*3/10 instead of *300/1000). The reciprocal multiply used can have off-by-one errors in the upper half of the valid output range. This could be avoided at the expense of having to deal with a potential 65-bit intermediate result. Since the intent is to avoid overflow problems and most of the other time conversions are only semiexact, the off-by-one errors were considered an acceptable tradeoff. At Ralf Baechle's suggestion, this version uses a Perl script to compute the necessary constants. We already have dependencies on Perl for kernel compiles. This does, however, require the Perl module Math::BigInt, which is included in the standard Perl distribution starting with version 5.8.0. In order to support older versions of Perl, include a table of canned constants in the script itself, and structure the script so that Math::BigInt isn't required if pulling values from said table. Running the script requires that the HZ value is available from the Makefile. Thus, this patch also adds the Kconfig variable CONFIG_HZ to the architectures which didn't already have it (alpha, cris, frv, h8300, m32r, m68k, m68knommu, sparc, v850, and xtensa.) It does *not* touch the sh or sh64 architectures, since Paul Mundt has dealt with those separately in the sh tree. Signed-off-by: H. Peter Anvin <hpa@zytor.com> Cc: Ralf Baechle <ralf@linux-mips.org>, Cc: Sam Ravnborg <sam@ravnborg.org>, Cc: Paul Mundt <lethal@linux-sh.org>, Cc: Richard Henderson <rth@twiddle.net>, Cc: Michael Starvik <starvik@axis.com>, Cc: David Howells <dhowells@redhat.com>, Cc: Yoshinori Sato <ysato@users.sourceforge.jp>, Cc: Hirokazu Takata <takata@linux-m32r.org>, Cc: Geert Uytterhoeven <geert@linux-m68k.org>, Cc: Roman Zippel <zippel@linux-m68k.org>, Cc: William L. Irwin <sparclinux@vger.kernel.org>, Cc: Chris Zankel <chris@zankel.net>, Cc: H. Peter Anvin <hpa@zytor.com>, Cc: Jan Engelhardt <jengelh@computergmbh.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/asm-alpha/param.h10
-rw-r--r--include/asm-cris/param.h2
-rw-r--r--include/asm-frv/param.h2
-rw-r--r--include/asm-h8300/param.h2
-rw-r--r--include/asm-m32r/param.h2
-rw-r--r--include/asm-m68k/param.h2
-rw-r--r--include/asm-m68knommu/param.h8
-rw-r--r--include/asm-sparc/param.h2
-rw-r--r--include/asm-v850/anna.h6
-rw-r--r--include/asm-v850/as85ep1.h6
-rw-r--r--include/asm-v850/fpga85e2c.h6
-rw-r--r--include/asm-v850/param.h3
-rw-r--r--include/asm-v850/rte_cb.h6
-rw-r--r--include/asm-v850/sim.h5
-rw-r--r--include/asm-v850/sim85e2.h6
-rw-r--r--include/asm-xtensa/param.h2
16 files changed, 10 insertions, 60 deletions
diff --git a/include/asm-alpha/param.h b/include/asm-alpha/param.h
index 214e7996346f..0982f1d39499 100644
--- a/include/asm-alpha/param.h
+++ b/include/asm-alpha/param.h
@@ -5,15 +5,7 @@
5 hardware ignores reprogramming. We also need userland buy-in to the 5 hardware ignores reprogramming. We also need userland buy-in to the
6 change in HZ, since this is visible in the wait4 resources etc. */ 6 change in HZ, since this is visible in the wait4 resources etc. */
7 7
8 8#define HZ CONFIG_HZ
9#ifndef HZ
10# ifndef CONFIG_ALPHA_RAWHIDE
11# define HZ 1024
12# else
13# define HZ 1200
14# endif
15#endif
16
17#define USER_HZ HZ 9#define USER_HZ HZ
18 10
19#define EXEC_PAGESIZE 8192 11#define EXEC_PAGESIZE 8192
diff --git a/include/asm-cris/param.h b/include/asm-cris/param.h
index b24972639832..0e47994e40be 100644
--- a/include/asm-cris/param.h
+++ b/include/asm-cris/param.h
@@ -3,7 +3,7 @@
3 3
4/* Currently we assume that HZ=100 is good for CRIS. */ 4/* Currently we assume that HZ=100 is good for CRIS. */
5#ifdef __KERNEL__ 5#ifdef __KERNEL__
6# define HZ 100 /* Internal kernel timer frequency */ 6# define HZ CONFIG_HZ /* Internal kernel timer frequency */
7# define USER_HZ 100 /* .. some user interfaces are in "ticks" */ 7# define USER_HZ 100 /* .. some user interfaces are in "ticks" */
8# define CLOCKS_PER_SEC (USER_HZ) /* like times() */ 8# define CLOCKS_PER_SEC (USER_HZ) /* like times() */
9#endif 9#endif
diff --git a/include/asm-frv/param.h b/include/asm-frv/param.h
index 365653b1726c..6859dd503ed3 100644
--- a/include/asm-frv/param.h
+++ b/include/asm-frv/param.h
@@ -2,7 +2,7 @@
2#define _ASM_PARAM_H 2#define _ASM_PARAM_H
3 3
4#ifdef __KERNEL__ 4#ifdef __KERNEL__
5#define HZ 1000 /* Internal kernel timer frequency */ 5#define HZ CONFIG_HZ /* Internal kernel timer frequency */
6#define USER_HZ 100 /* .. some user interfaces are in "ticks" */ 6#define USER_HZ 100 /* .. some user interfaces are in "ticks" */
7#define CLOCKS_PER_SEC (USER_HZ) /* like times() */ 7#define CLOCKS_PER_SEC (USER_HZ) /* like times() */
8#endif 8#endif
diff --git a/include/asm-h8300/param.h b/include/asm-h8300/param.h
index c25806ed1fb3..04f64f100379 100644
--- a/include/asm-h8300/param.h
+++ b/include/asm-h8300/param.h
@@ -3,7 +3,7 @@
3 3
4 4
5#ifndef HZ 5#ifndef HZ
6#define HZ 100 6#define HZ CONFIG_HZ
7#endif 7#endif
8 8
9#ifdef __KERNEL__ 9#ifdef __KERNEL__
diff --git a/include/asm-m32r/param.h b/include/asm-m32r/param.h
index 3e14026e39cd..94c770196048 100644
--- a/include/asm-m32r/param.h
+++ b/include/asm-m32r/param.h
@@ -2,7 +2,7 @@
2#define _ASM_M32R_PARAM_H 2#define _ASM_M32R_PARAM_H
3 3
4#ifdef __KERNEL__ 4#ifdef __KERNEL__
5# define HZ 100 /* Internal kernel timer frequency */ 5# define HZ CONFIG_HZ /* Internal kernel timer frequency */
6# define USER_HZ 100 /* .. some user interfaces are in "ticks" */ 6# define USER_HZ 100 /* .. some user interfaces are in "ticks" */
7# define CLOCKS_PER_SEC (USER_HZ) /* like times() */ 7# define CLOCKS_PER_SEC (USER_HZ) /* like times() */
8#endif 8#endif
diff --git a/include/asm-m68k/param.h b/include/asm-m68k/param.h
index 60f409d81658..536a27888358 100644
--- a/include/asm-m68k/param.h
+++ b/include/asm-m68k/param.h
@@ -2,7 +2,7 @@
2#define _M68K_PARAM_H 2#define _M68K_PARAM_H
3 3
4#ifdef __KERNEL__ 4#ifdef __KERNEL__
5# define HZ 100 /* Internal kernel timer frequency */ 5# define HZ CONFIG_HZ /* Internal kernel timer frequency */
6# define USER_HZ 100 /* .. some user interfaces are in "ticks" */ 6# define USER_HZ 100 /* .. some user interfaces are in "ticks" */
7# define CLOCKS_PER_SEC (USER_HZ) /* like times() */ 7# define CLOCKS_PER_SEC (USER_HZ) /* like times() */
8#endif 8#endif
diff --git a/include/asm-m68knommu/param.h b/include/asm-m68knommu/param.h
index 4c9904d6512e..96c451018324 100644
--- a/include/asm-m68knommu/param.h
+++ b/include/asm-m68knommu/param.h
@@ -1,13 +1,7 @@
1#ifndef _M68KNOMMU_PARAM_H 1#ifndef _M68KNOMMU_PARAM_H
2#define _M68KNOMMU_PARAM_H 2#define _M68KNOMMU_PARAM_H
3 3
4 4#define HZ CONFIG_HZ
5#if defined(CONFIG_CLEOPATRA)
6#define HZ 1000
7#endif
8#ifndef HZ
9#define HZ 100
10#endif
11 5
12#ifdef __KERNEL__ 6#ifdef __KERNEL__
13#define USER_HZ HZ 7#define USER_HZ HZ
diff --git a/include/asm-sparc/param.h b/include/asm-sparc/param.h
index beaf02d364f2..86ba59af9d2c 100644
--- a/include/asm-sparc/param.h
+++ b/include/asm-sparc/param.h
@@ -3,7 +3,7 @@
3#define _ASMSPARC_PARAM_H 3#define _ASMSPARC_PARAM_H
4 4
5#ifdef __KERNEL__ 5#ifdef __KERNEL__
6# define HZ 100 /* Internal kernel timer frequency */ 6# define HZ CONFIG_HZ /* Internal kernel timer frequency */
7# define USER_HZ 100 /* .. some user interfaces are in "ticks" */ 7# define USER_HZ 100 /* .. some user interfaces are in "ticks" */
8# define CLOCKS_PER_SEC (USER_HZ) 8# define CLOCKS_PER_SEC (USER_HZ)
9#endif 9#endif
diff --git a/include/asm-v850/anna.h b/include/asm-v850/anna.h
index 3be77d5ecfce..cd5eaee103b0 100644
--- a/include/asm-v850/anna.h
+++ b/include/asm-v850/anna.h
@@ -134,10 +134,4 @@ extern void anna_uart_pre_configure (unsigned chan,
134#define V850E_TIMER_D_TMCD_CS_MIN 1 /* min 2^1 divider */ 134#define V850E_TIMER_D_TMCD_CS_MIN 1 /* min 2^1 divider */
135 135
136 136
137/* For <asm/param.h> */
138#ifndef HZ
139#define HZ 100
140#endif
141
142
143#endif /* __V850_ANNA_H__ */ 137#endif /* __V850_ANNA_H__ */
diff --git a/include/asm-v850/as85ep1.h b/include/asm-v850/as85ep1.h
index 659bc910ffd7..5a5ca9073d09 100644
--- a/include/asm-v850/as85ep1.h
+++ b/include/asm-v850/as85ep1.h
@@ -149,10 +149,4 @@ extern void as85ep1_uart_pre_configure (unsigned chan,
149#define V850E_TIMER_D_TMCD_CS_MIN 2 /* min 2^2 divider */ 149#define V850E_TIMER_D_TMCD_CS_MIN 2 /* min 2^2 divider */
150 150
151 151
152/* For <asm/param.h> */
153#ifndef HZ
154#define HZ 100
155#endif
156
157
158#endif /* __V850_AS85EP1_H__ */ 152#endif /* __V850_AS85EP1_H__ */
diff --git a/include/asm-v850/fpga85e2c.h b/include/asm-v850/fpga85e2c.h
index d32f04504b13..23aae666c718 100644
--- a/include/asm-v850/fpga85e2c.h
+++ b/include/asm-v850/fpga85e2c.h
@@ -79,10 +79,4 @@ extern char _r0_ram;
79#endif 79#endif
80 80
81 81
82/* For <asm/param.h> */
83#ifndef HZ
84#define HZ 122 /* actually, 8.192ms ticks =~ 122.07 */
85#endif
86
87
88#endif /* __V850_FPGA85E2C_H__ */ 82#endif /* __V850_FPGA85E2C_H__ */
diff --git a/include/asm-v850/param.h b/include/asm-v850/param.h
index 3c65bd573782..281832690290 100644
--- a/include/asm-v850/param.h
+++ b/include/asm-v850/param.h
@@ -23,8 +23,7 @@
23#define MAXHOSTNAMELEN 64 /* max length of hostname */ 23#define MAXHOSTNAMELEN 64 /* max length of hostname */
24 24
25#ifdef __KERNEL__ 25#ifdef __KERNEL__
26#include <asm/machdep.h> /* For HZ */ 26# define HZ CONFIG_HZ
27
28# define USER_HZ 100 27# define USER_HZ 100
29# define CLOCKS_PER_SEC USER_HZ 28# define CLOCKS_PER_SEC USER_HZ
30#endif 29#endif
diff --git a/include/asm-v850/rte_cb.h b/include/asm-v850/rte_cb.h
index e85d261b79bf..db9879f00aa7 100644
--- a/include/asm-v850/rte_cb.h
+++ b/include/asm-v850/rte_cb.h
@@ -69,12 +69,6 @@
69#endif /* CONFIG_RTE_MB_A_PCI */ 69#endif /* CONFIG_RTE_MB_A_PCI */
70 70
71 71
72/* For <asm/param.h> */
73#ifndef HZ
74#define HZ 100
75#endif
76
77
78#ifndef __ASSEMBLY__ 72#ifndef __ASSEMBLY__
79extern void rte_cb_early_init (void); 73extern void rte_cb_early_init (void);
80extern void rte_cb_init_irqs (void); 74extern void rte_cb_init_irqs (void);
diff --git a/include/asm-v850/sim.h b/include/asm-v850/sim.h
index 10236abbe9be..026932d476cd 100644
--- a/include/asm-v850/sim.h
+++ b/include/asm-v850/sim.h
@@ -40,11 +40,6 @@
40#define R0_RAM_ADDR 0xFFFFF000 40#define R0_RAM_ADDR 0xFFFFF000
41 41
42 42
43/* For <asm/param.h> */
44#ifndef HZ
45#define HZ 24 /* Minimum supported frequency. */
46#endif
47
48/* For <asm/irq.h> */ 43/* For <asm/irq.h> */
49#define NUM_CPU_IRQS 6 44#define NUM_CPU_IRQS 6
50 45
diff --git a/include/asm-v850/sim85e2.h b/include/asm-v850/sim85e2.h
index 17dd4fa318e6..8b4d6974066c 100644
--- a/include/asm-v850/sim85e2.h
+++ b/include/asm-v850/sim85e2.h
@@ -66,10 +66,4 @@
66#define R0_RAM_ADDR 0xFFFFE000 66#define R0_RAM_ADDR 0xFFFFE000
67 67
68 68
69/* For <asm/param.h> */
70#ifndef HZ
71#define HZ 24 /* Minimum supported frequency. */
72#endif
73
74
75#endif /* __V850_SIM85E2_H__ */ 69#endif /* __V850_SIM85E2_H__ */
diff --git a/include/asm-xtensa/param.h b/include/asm-xtensa/param.h
index ce3a336cad07..82ad34d92d35 100644
--- a/include/asm-xtensa/param.h
+++ b/include/asm-xtensa/param.h
@@ -12,7 +12,7 @@
12#define _XTENSA_PARAM_H 12#define _XTENSA_PARAM_H
13 13
14#ifdef __KERNEL__ 14#ifdef __KERNEL__
15# define HZ 100 /* internal timer frequency */ 15# define HZ CONFIG_HZ /* internal timer frequency */
16# define USER_HZ 100 /* for user interfaces in "ticks" */ 16# define USER_HZ 100 /* for user interfaces in "ticks" */
17# define CLOCKS_PER_SEC (USER_HZ) /* frequnzy at which times() counts */ 17# define CLOCKS_PER_SEC (USER_HZ) /* frequnzy at which times() counts */
18#endif 18#endif