The early_printk function is usable only after the setup_early_printk will
be executed. We pass 'earlyprintk' through the kernel command line, so it
will be usable only after the 'parse_early_param' will be executed. This means
that we have usable earlyprintk only during early boot, kernel decompression
and after call of the 'parse_early_param'. This patchset makes earlyprintk
usable before the call of the 'parse_early_param'.
This patch makes setup_early_printk visible for head{32,64}.c. So the
'early_printk' function will be usabable after decompression of the
kernel and before parse_early_param will be called. It also must be
safe if CONFIG_CMDLINE_BOOL and CONFIG_CMDLINE_OVERRIDE are set, because
setup_cmdline function will be called before setup_early_printk.
Tested it with qemu, so early_printk() is usable and prints to serial
console right after setup_early_printk function called.
Signed-off-by: Alexander Kuleshov <kuleshovm...@gmail.com>
---
arch/x86/include/asm/serial.h | 3 +++
arch/x86/kernel/early_printk.c | 25 +++++++++++++++++++++++++
arch/x86/kernel/head32.c | 5 +++++
arch/x86/kernel/head64.c | 5 +++++
4 files changed, 38 insertions(+)
diff --git a/arch/x86/include/asm/serial.h b/arch/x86/include/asm/serial.h
index 8378b8c..198f041 100644
--- a/arch/x86/include/asm/serial.h
+++ b/arch/x86/include/asm/serial.h
@@ -26,4 +26,7 @@
{ .uart = 0, BASE_BAUD, 0x3E8, 4, STD_COMX_FLAGS }, /*
ttyS2 */ \
{ .uart = 0, BASE_BAUD, 0x2E8, 3, STD_COM4_FLAGS }, /*
ttyS3 */
+/* used by arch/x86/kernel/head{32,64}.c */
+int __init setup_early_serial_console(void);
+
#endif /* _ASM_X86_SERIAL_H */
diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index 89427d8..96425c3 100644
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -385,4 +385,29 @@ static int __init setup_early_printk(char *buf)
return 0;
}
+int __init setup_early_serial_console(void)
+{
+#ifdef CONFIG_EARLY_PRINTK
+ char *arg;
+
+ /*
+ * make sure that we have:
+ * "serial,0x3f8,115200"
+ * "serial,ttyS0,115200"
+ * "ttyS0,115200"
+ */
+ arg = strstr(boot_command_line, "earlyprintk=serial");
+ if (!arg)
+ arg = strstr(boot_command_line, "earlyprintk=ttyS");
+ if (!arg)
+ return -1;
+
+ arg = strstr(boot_command_line, "earlyprintk=");
+ /* += strlen("earlyprintk"); */
+ arg += 12;
+
+ return setup_early_printk(arg);
+#endif
+}
+
early_param("earlyprintk", setup_early_printk);
diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c
index 92e8b5f..d325d0c 100644
--- a/arch/x86/kernel/head32.c
+++ b/arch/x86/kernel/head32.c
@@ -32,6 +32,11 @@ static void __init i386_default_early_setup(void)
asmlinkage __visible void __init i386_start_kernel(void)
{
setup_builtin_cmdline();
+ setup_early_serial_console();
+
+ if (console_loglevel >= CONSOLE_LOGLEVEL_DEBUG)
+ early_printk("Kernel alive\n");
+
cr4_init_shadow();
sanitize_boot_params(&boot_params);
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 38da21c..06fcc1b 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -173,6 +173,11 @@ asmlinkage __visible void __init x86_64_start_kernel(char
* real_mode_data)
copy_bootdata(__va(real_mode_data));
setup_builtin_cmdline();
+ setup_early_serial_console();
+
+ if (console_loglevel >= CONSOLE_LOGLEVEL_DEBUG)
+ early_printk("Kernel alive\n");
+
/*
* Load microcode early on BSP.
*/
--
2.4.0
--
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