cregit-Linux how code gets into the kernel

Release 4.11 arch/arm/include/asm/div64.h

#ifndef __ASM_ARM_DIV64

#define __ASM_ARM_DIV64

#include <linux/types.h>
#include <asm/compiler.h>

/*
 * The semantics of __div64_32() are:
 *
 * uint32_t __div64_32(uint64_t *n, uint32_t base)
 * {
 *      uint32_t remainder = *n % base;
 *      *n = *n / base;
 *      return remainder;
 * }
 *
 * In other words, a 64-bit dividend with a 32-bit divisor producing
 * a 64-bit result and a 32-bit remainder.  To accomplish this optimally
 * we override the generic version in lib/div64.c to call our __do_div64
 * assembly implementation with completely non standard calling convention
 * for arguments and results (beware).
 */

#ifdef __ARMEB__

#define __xh "r0"

#define __xl "r1"
#else

#define __xl "r0"

#define __xh "r1"
#endif


static inline uint32_t __div64_32(uint64_t *n, uint32_t base) { register unsigned int __base asm("r4") = base; register unsigned long long __n asm("r0") = *n; register unsigned long long __res asm("r2"); register unsigned int __rem asm(__xh); asm( __asmeq("%0", __xh) __asmeq("%1", "r2") __asmeq("%2", "r0") __asmeq("%3", "r4") "bl __do_div64" : "=r" (__rem), "=r" (__res) : "r" (__n), "r" (__base) : "ip", "lr", "cc"); *n = __res; return __rem; }

Contributors

PersonTokensPropCommitsCommitProp
Nico Pitre66100.00%2100.00%
Total66100.00%2100.00%

#define __div64_32 __div64_32 #if !defined(CONFIG_AEABI) /* * In OABI configurations, some uses of the do_div function * cause gcc to run out of registers. To work around that, * we can force the use of the out-of-line version for * configurations that build a OABI kernel. */ #define do_div(n, base) __div64_32(&(n), base) #else /* * gcc versions earlier than 4.0 are simply too problematic for the * __div64_const32() code in asm-generic/div64.h. First there is * gcc PR 15089 that tend to trig on more complex constructs, spurious * .global __udivsi3 are inserted even if none of those symbols are * referenced in the generated code, and those gcc versions are not able * to do constant propagation on long long values anyway. */ #define __div64_const32_is_OK (__GNUC__ >= 4)
static inline uint64_t __arch_xprod_64(uint64_t m, uint64_t n, bool bias) { unsigned long long res; register unsigned int tmp asm("ip") = 0; if (!bias) { asm ( "umull %Q0, %R0, %Q1, %Q2\n\t" "mov %Q0, #0" : "=&r" (res) : "r" (m), "r" (n) : "cc"); } else if (!(m & ((1ULL << 63) | (1ULL << 31)))) { res = m; asm ( "umlal %Q0, %R0, %Q1, %Q2\n\t" "mov %Q0, #0" : "+&r" (res) : "r" (m), "r" (n) : "cc"); } else { asm ( "umull %Q0, %R0, %Q2, %Q3\n\t" "cmn %Q0, %Q2\n\t" "adcs %R0, %R0, %R2\n\t" "adc %Q0, %1, #0" : "=&r" (res), "+&r" (tmp) : "r" (m), "r" (n) : "cc"); } if (!(m & ((1ULL << 63) | (1ULL << 31)))) { asm ( "umlal %R0, %Q0, %R1, %Q2\n\t" "umlal %R0, %Q0, %Q1, %R2\n\t" "mov %R0, #0\n\t" "umlal %Q0, %R0, %R1, %R2" : "+&r" (res) : "r" (m), "r" (n) : "cc"); } else { asm ( "umlal %R0, %Q0, %R2, %Q3\n\t" "umlal %R0, %1, %Q2, %R3\n\t" "mov %R0, #0\n\t" "adds %Q0, %1, %Q0\n\t" "adc %R0, %R0, #0\n\t" "umlal %Q0, %R0, %R2, %R3" : "+&r" (res), "+&r" (tmp) : "r" (m), "r" (n) : "cc"); } return res; }

Contributors

PersonTokensPropCommitsCommitProp
Nico Pitre10096.15%266.67%
Linus Torvalds (pre-git)43.85%133.33%
Total104100.00%3100.00%

#define __arch_xprod_64 __arch_xprod_64 #include <asm-generic/div64.h> #endif #endif

Overall Contributors

PersonTokensPropCommitsCommitProp
Nico Pitre22290.61%555.56%
Linus Torvalds (pre-git)145.71%111.11%
Arnd Bergmann52.04%111.11%
Stephen Hemminger20.82%111.11%
David Howells20.82%111.11%
Total245100.00%9100.00%
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