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readme: more info on kernel panics, oops an backtraces.

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myinsmod: use either finit or init
This commit is contained in:
Ciro Santilli
2018-04-14 19:11:13 +01:00
parent 7b0bd10c0b
commit a08a87dc0f
8 changed files with 398 additions and 51 deletions
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6
kernel_module/README.adoc
View File

@@ -4,7 +4,11 @@
. Debugging
.. link:hello.c[]
.. link:hello2.c[]
. Panic and friends
.. link:panic.c[]
.. link:oops.c[]
.. link:warn_on.c[]
.. link:warn_on.c[]
. Module utils
.. link:params.c[]
.. link:vermagic.c[]
@@ -40,6 +44,8 @@
.. link:kstrto.c[]
. Misc
.. link:ring0.c[]
. ARM
.. link:pmccntr.c[]
. Hardware device drivers
.. link:pci_min.c[]
.. link:pci.c[]

19
kernel_module/dump_stack.c Normal file
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@@ -0,0 +1,19 @@
#include <linux/module.h>
#include <linux/kernel.h>
static int myinit(void)
{
pr_info("dump_stack myinit\n");
dump_stack();
pr_info("dump_stack after\n");
return 0;
}
static void myexit(void)
{
pr_info("panic myexit\n");
}
module_init(myinit)
module_exit(myexit)
MODULE_LICENSE("GPL");

19
kernel_module/oops.c Normal file
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@@ -0,0 +1,19 @@
#include <linux/module.h>
#include <linux/kernel.h>
static int myinit(void)
{
pr_info("oops myinit\n");
*(int *)0 = 0;
pr_info("oops after\n");
return 0;
}
static void myexit(void)
{
pr_info("oops myexit\n");
}
module_init(myinit)
module_exit(myexit)
MODULE_LICENSE("GPL");

17
kernel_module/panic.c
View File

@@ -1,28 +1,17 @@
/*
It will happen eventually, so you might as well learn do deal with it.
TODO: how to scroll up to see full trace? Shift + Page Up does not work as it normally does:
https://superuser.com/questions/848412/scrolling-up-the-failed-screen-with-kernel-panic
The alternative is to get the serial data out streamed to console or to a file:
- https://superuser.com/questions/269228/write-qemu-booting-virtual-machine-output-to-a-file
- http://www.reactos.org/wiki/QEMU#Redirect_to_a_file
*/
#include <linux/module.h>
#include <linux/kernel.h>
static int myinit(void)
{
pr_info("panic init\n");
pr_info("panic myinit\n");
panic("hello panic");
pr_info("panic after\n");
return 0;
}
static void myexit(void)
{
pr_info("panic cleanup\n");
pr_info("panic myexit\n");
}
module_init(myinit)

48
kernel_module/ring0.h
View File

@@ -24,33 +24,35 @@ typedef struct {
void ring0_get_control_regs(Ring0Regs *ring0_regs)
{
#ifdef __x86_64__
#if defined(__x86_64__)
__asm__ __volatile__ (
"mov %%cr0, %%rax\n\t"
"mov %%eax, %0\n\t"
"mov %%cr2, %%rax\n\t"
"mov %%eax, %1\n\t"
"mov %%cr3, %%rax\n\t"
"mov %%eax, %2\n\t"
: "=m" (ring0_regs->cr0),
"=m" (ring0_regs->cr2),
"=m" (ring0_regs->cr3)
: /* no input */
: "%rax"
"mov %%cr0, %%rax;"
"mov %%eax, %0;"
"mov %%cr2, %%rax;"
"mov %%eax, %1;"
"mov %%cr3, %%rax;"
"mov %%eax, %2;"
: "=m" (ring0_regs->cr0),
"=m" (ring0_regs->cr2),
"=m" (ring0_regs->cr3)
:
: "%rax"
);
#elif defined(__i386__)
__asm__ __volatile__ (
"mov %%cr0, %%eax\n\t"
"mov %%eax, %0\n\t"
"mov %%cr2, %%eax\n\t"
"mov %%eax, %1\n\t"
"mov %%cr3, %%eax\n\t"
"mov %%eax, %2\n\t"
: "=m" (ring0_regs->cr0),
"=m" (ring0_regs->cr2),
"=m" (ring0_regs->cr3)
: /* no input */
: "%eax"
"mov %%cr0, %%eax;"
"mov %%eax, %0;"
"mov %%cr2, %%eax;"
"mov %%eax, %1;"
"mov %%cr3, %%eax;"
"mov %%eax, %2;"
: "=m" (ring0_regs->cr0),
"=m" (ring0_regs->cr2),
"=m" (ring0_regs->cr3)
:
: "%eax"
);
#endif
}
#endif

45
kernel_module/user/myinsmod.c
View File

@@ -7,17 +7,19 @@
#include <unistd.h>
#include <stdlib.h>
#define init_module(mod, len, opts) syscall(__NR_init_module, mod, len, opts)
#define init_module(module_image, len, param_values) syscall(__NR_init_module, module_image, len, param_values)
#define finit_module(fd, param_values, flags) syscall(__NR_finit_module, fd, param_values, flags)
int main(int argc, char **argv) {
const char *params;
int fd;
int fd, use_finit;
size_t image_size;
struct stat st;
void *image;
/* CLI handling. */
if (argc < 2) {
puts("Usage ./prog mymodule.ko [args]");
puts("Usage ./prog mymodule.ko [args="" [use_finit=0]");
return EXIT_FAILURE;
}
if (argc < 3) {
@@ -25,16 +27,33 @@ int main(int argc, char **argv) {
} else {
params = argv[2];
}
fd = open(argv[1], O_RDONLY);
fstat(fd, &st);
image_size = st.st_size;
image = malloc(image_size);
read(fd, image, image_size);
close(fd);
if (init_module(image, image_size, params) != 0) {
perror("init_module");
return EXIT_FAILURE;
if (argc < 4) {
use_finit = 0;
} else {
use_finit = (argv[3][0] != '0');
}
/* Action. */
fd = open(argv[1], O_RDONLY);
if (use_finit) {
puts("finit");
if (finit_module(fd, params, 0) != 0) {
perror("finit_module");
return EXIT_FAILURE;
}
close(fd);
} else {
puts("init");
fstat(fd, &st);
image_size = st.st_size;
image = malloc(image_size);
read(fd, image, image_size);
close(fd);
if (init_module(image, image_size, params) != 0) {
perror("init_module");
return EXIT_FAILURE;
}
free(image);
}
free(image);
return EXIT_SUCCESS;
}

23
kernel_module/warn_on.c Normal file
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@@ -0,0 +1,23 @@
/*
Prints a backtrace.
*/
#include <linux/module.h>
#include <linux/kernel.h>
static int myinit(void)
{
pr_info("warn_on init\n");
WARN_ON("warn_on do it");
pr_info("warn_on after\n");
return 0;
}
static void myexit(void)
{
pr_info("warn_on cleanup\n");
}
module_init(myinit)
module_exit(myexit)
MODULE_LICENSE("GPL");