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Code Issues Releases Wiki Activity

fix order of calling set_bios_mode()

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Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
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Alexander Kuleshov 2018-06-14 23:47:54 +06:00
parent 5880a60e6e
commit b4f824db27
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1 changed files with 18 additions and 18 deletions
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36
Booting/linux-bootstrap-2.md
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@ -358,6 +358,24 @@ if (cpu_level < req_level) {
The `check_cpu` function checks the CPU's flags, the presence of [long mode](http://en.wikipedia.org/wiki/Long_mode) in the case of x86_64(64-bit) CPU, checks the processor's vendor and makes preparations for certain vendors like turning off SSE+SSE2 for AMD if they are missing, etc. The `check_cpu` function checks the CPU's flags, the presence of [long mode](http://en.wikipedia.org/wiki/Long_mode) in the case of x86_64(64-bit) CPU, checks the processor's vendor and makes preparations for certain vendors like turning off SSE+SSE2 for AMD if they are missing, etc.
at the next step, we may see a call to the `set_bios_mode` function after setup code found that a CPU is suitable. As we may see, this function is implemented only for the `x86_64` mode:
```C
static void set_bios_mode(void)
{
#ifdef CONFIG_X86_64
struct biosregs ireg;
initregs(&ireg);
ireg.ax = 0xec00;
ireg.bx = 2;
intcall(0x15, &ireg, NULL);
#endif
}
```
The `set_bios_mode` function executes the `0x15` BIOS interrupt to tell the BIOS that [long mode](https://en.wikipedia.org/wiki/Long_mode) (if `bx == 2`) will be used.
Memory detection Memory detection
-------------------------------------------------------------------------------- --------------------------------------------------------------------------------
@ -404,24 +422,6 @@ You can see the result of this in the `dmesg` output, something like:
[ 0.000000] BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved [ 0.000000] BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
``` ```
Next, we may see a call to the `set_bios_mode` function. As we may see, this function is implemented only for the `x86_64` mode:
```C
static void set_bios_mode(void)
{
#ifdef CONFIG_X86_64
struct biosregs ireg;
initregs(&ireg);
ireg.ax = 0xec00;
ireg.bx = 2;
intcall(0x15, &ireg, NULL);
#endif
}
```
The `set_bios_mode` function executes the `0x15` BIOS interrupt to tell the BIOS that [long mode](https://en.wikipedia.org/wiki/Long_mode) (if `bx == 2`) will be used.
Keyboard initialization Keyboard initialization
-------------------------------------------------------------------------------- --------------------------------------------------------------------------------