Ladybird/ladybird
1
0
Fork 0
mirror of https://github.com/LadybirdBrowser/ladybird.git synced 2025-06-10 18:10:56 +09:00
Code Activity

Kernel+LibC: Publish a "kernel info page" and use it for gettimeofday()

Browse source 
This patch adds a single "kernel info page" that is mappable read-only
by any process and contains the current time of day.

This is then used to implement a version of gettimeofday() that doesn't
have to make a syscall.

To protect against race condition issues, the info page also has a
serial number which is incremented whenever the kernel updates the
contents of the page. Make sure to verify that the serial number is the
same before and after reading the information you want from the page.
This commit is contained in:
Andreas Kling 2019-12-15 21:29:26 +01:00
parent 931e4b7f5e
commit 77cf607cda
Notes: sideshowbarker 2024-07-19 10:50:40 +09:00
6 changed files with 62 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

16
Libraries/LibC/time.cpp
View file

@ -1,10 +1,11 @@
#include <Kernel/KernelInfoPage.h>
#include <Kernel/Syscall.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <sys/time.h>
#include <sys/times.h>
#include <time.h>
#include <string.h>
extern "C" {
@ -21,8 +22,17 @@ time_t time(time_t* tloc)
int gettimeofday(struct timeval* __restrict__ tv, void* __restrict__)
{
int rc = syscall(SC_gettimeofday, tv);
__RETURN_WITH_ERRNO(rc, rc, -1);
static volatile KernelInfoPage* kernel_info;
if (!kernel_info)
kernel_info = (volatile KernelInfoPage*)syscall(SC_get_kernel_info_page);
for (;;) {
auto serial = kernel_info->serial;
*tv = const_cast<struct timeval&>(kernel_info->now);
if (serial == kernel_info->serial)
break;
}
return 0;
}
char* ctime(const time_t*)