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6feeee8efc
The following sequence triggers a kernel stack overflow on s390x:
mount -t tracefs tracefs /sys/kernel/tracing
cd /sys/kernel/tracing
echo function_graph > current_tracer
[crash]
This is because preempt_count_{add,sub} are in the list of traced
functions, which can be demonstrated by:
echo preempt_count_add >set_ftrace_filter
echo function_graph > current_tracer
[crash]
The stack overflow happens because get_tod_clock_monotonic() gets called
by ftrace but itself calls preempt_{disable,enable}(), which leads to a
endless recursion. Fix this by using preempt_{disable,enable}_notrace().
Fixes: 011620688a ("s390/time: ensure get_clock_monotonic() returns monotonic values")
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
256 lines
6.1 KiB
C
256 lines
6.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* S390 version
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* Copyright IBM Corp. 1999
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*
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* Derived from "include/asm-i386/timex.h"
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* Copyright (C) 1992, Linus Torvalds
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*/
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#ifndef _ASM_S390_TIMEX_H
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#define _ASM_S390_TIMEX_H
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#include <linux/preempt.h>
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#include <linux/time64.h>
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#include <asm/lowcore.h>
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/* The value of the TOD clock for 1.1.1970. */
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#define TOD_UNIX_EPOCH 0x7d91048bca000000ULL
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extern u64 clock_comparator_max;
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/* Inline functions for clock register access. */
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static inline int set_tod_clock(__u64 time)
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{
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int cc;
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asm volatile(
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" sck %1\n"
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" ipm %0\n"
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" srl %0,28\n"
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: "=d" (cc) : "Q" (time) : "cc");
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return cc;
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}
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static inline int store_tod_clock(__u64 *time)
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{
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int cc;
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asm volatile(
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" stck %1\n"
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" ipm %0\n"
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" srl %0,28\n"
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: "=d" (cc), "=Q" (*time) : : "cc");
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return cc;
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}
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static inline void set_clock_comparator(__u64 time)
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{
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asm volatile("sckc %0" : : "Q" (time));
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}
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static inline void store_clock_comparator(__u64 *time)
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{
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asm volatile("stckc %0" : "=Q" (*time));
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}
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void clock_comparator_work(void);
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void __init time_early_init(void);
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extern unsigned char ptff_function_mask[16];
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/* Function codes for the ptff instruction. */
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#define PTFF_QAF 0x00 /* query available functions */
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#define PTFF_QTO 0x01 /* query tod offset */
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#define PTFF_QSI 0x02 /* query steering information */
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#define PTFF_QUI 0x04 /* query UTC information */
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#define PTFF_ATO 0x40 /* adjust tod offset */
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#define PTFF_STO 0x41 /* set tod offset */
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#define PTFF_SFS 0x42 /* set fine steering rate */
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#define PTFF_SGS 0x43 /* set gross steering rate */
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/* Query TOD offset result */
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struct ptff_qto {
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unsigned long long physical_clock;
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unsigned long long tod_offset;
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unsigned long long logical_tod_offset;
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unsigned long long tod_epoch_difference;
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} __packed;
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static inline int ptff_query(unsigned int nr)
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{
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unsigned char *ptr;
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ptr = ptff_function_mask + (nr >> 3);
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return (*ptr & (0x80 >> (nr & 7))) != 0;
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}
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/* Query UTC information result */
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struct ptff_qui {
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unsigned int tm : 2;
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unsigned int ts : 2;
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unsigned int : 28;
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unsigned int pad_0x04;
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unsigned long leap_event;
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short old_leap;
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short new_leap;
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unsigned int pad_0x14;
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unsigned long prt[5];
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unsigned long cst[3];
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unsigned int skew;
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unsigned int pad_0x5c[41];
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} __packed;
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/*
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* ptff - Perform timing facility function
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* @ptff_block: Pointer to ptff parameter block
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* @len: Length of parameter block
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* @func: Function code
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* Returns: Condition code (0 on success)
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*/
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#define ptff(ptff_block, len, func) \
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({ \
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struct addrtype { char _[len]; }; \
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register unsigned int reg0 asm("0") = func; \
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register unsigned long reg1 asm("1") = (unsigned long) (ptff_block);\
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int rc; \
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\
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asm volatile( \
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" .word 0x0104\n" \
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" ipm %0\n" \
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" srl %0,28\n" \
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: "=d" (rc), "+m" (*(struct addrtype *) reg1) \
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: "d" (reg0), "d" (reg1) : "cc"); \
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rc; \
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})
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static inline unsigned long long local_tick_disable(void)
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{
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unsigned long long old;
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old = S390_lowcore.clock_comparator;
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S390_lowcore.clock_comparator = clock_comparator_max;
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set_clock_comparator(S390_lowcore.clock_comparator);
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return old;
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}
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static inline void local_tick_enable(unsigned long long comp)
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{
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S390_lowcore.clock_comparator = comp;
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set_clock_comparator(S390_lowcore.clock_comparator);
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}
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#define CLOCK_TICK_RATE 1193180 /* Underlying HZ */
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#define STORE_CLOCK_EXT_SIZE 16 /* stcke writes 16 bytes */
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typedef unsigned long long cycles_t;
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static inline void get_tod_clock_ext(char *clk)
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{
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typedef struct { char _[STORE_CLOCK_EXT_SIZE]; } addrtype;
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asm volatile("stcke %0" : "=Q" (*(addrtype *) clk) : : "cc");
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}
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static inline unsigned long long get_tod_clock(void)
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{
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unsigned char clk[STORE_CLOCK_EXT_SIZE];
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get_tod_clock_ext(clk);
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return *((unsigned long long *)&clk[1]);
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}
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static inline unsigned long long get_tod_clock_fast(void)
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{
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#ifdef CONFIG_HAVE_MARCH_Z9_109_FEATURES
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unsigned long long clk;
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asm volatile("stckf %0" : "=Q" (clk) : : "cc");
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return clk;
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#else
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return get_tod_clock();
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#endif
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}
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static inline cycles_t get_cycles(void)
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{
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return (cycles_t) get_tod_clock() >> 2;
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}
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int get_phys_clock(unsigned long *clock);
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void init_cpu_timer(void);
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extern unsigned char tod_clock_base[16] __aligned(8);
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/**
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* get_clock_monotonic - returns current time in clock rate units
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*
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* The clock and tod_clock_base get changed via stop_machine.
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* Therefore preemption must be disabled, otherwise the returned
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* value is not guaranteed to be monotonic.
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*/
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static inline unsigned long long get_tod_clock_monotonic(void)
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{
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unsigned long long tod;
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preempt_disable_notrace();
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tod = get_tod_clock() - *(unsigned long long *) &tod_clock_base[1];
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preempt_enable_notrace();
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return tod;
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}
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/**
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* tod_to_ns - convert a TOD format value to nanoseconds
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* @todval: to be converted TOD format value
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* Returns: number of nanoseconds that correspond to the TOD format value
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*
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* Converting a 64 Bit TOD format value to nanoseconds means that the value
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* must be divided by 4.096. In order to achieve that we multiply with 125
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* and divide by 512:
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*
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* ns = (todval * 125) >> 9;
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*
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* In order to avoid an overflow with the multiplication we can rewrite this.
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* With a split todval == 2^9 * th + tl (th upper 55 bits, tl lower 9 bits)
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* we end up with
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*
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* ns = ((2^9 * th + tl) * 125 ) >> 9;
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* -> ns = (th * 125) + ((tl * 125) >> 9);
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*
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*/
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static inline unsigned long long tod_to_ns(unsigned long long todval)
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{
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return ((todval >> 9) * 125) + (((todval & 0x1ff) * 125) >> 9);
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}
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/**
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* tod_after - compare two 64 bit TOD values
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* @a: first 64 bit TOD timestamp
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* @b: second 64 bit TOD timestamp
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*
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* Returns: true if a is later than b
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*/
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static inline int tod_after(unsigned long long a, unsigned long long b)
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{
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if (MACHINE_HAS_SCC)
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return (long long) a > (long long) b;
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return a > b;
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}
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/**
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* tod_after_eq - compare two 64 bit TOD values
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* @a: first 64 bit TOD timestamp
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* @b: second 64 bit TOD timestamp
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*
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* Returns: true if a is later than b
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*/
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static inline int tod_after_eq(unsigned long long a, unsigned long long b)
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{
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if (MACHINE_HAS_SCC)
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return (long long) a >= (long long) b;
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return a >= b;
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}
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#endif
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