CONFIG_CMDLINE_BOOL and CONFIG_CMDLINE_OVERRIDE was ignored during
options lookup in compressed kernel, including earlyprintk option,
so it was impossible to get earlyprintk messages from that stage
of boot process via command line provided at compile time.
Being able to enable earlyprintk via compile-time option might
be desirable for booting on systems with broken UEFI command line
arguments via EFISTUB.

v2 changes:

As Borislav Petkov stated, we can do the work just once and then
return correct command line pointer. Doing it this way require
us to perform string manipulations, so the first patch adds missing
strlcat() to compressed kernel, since this function simplifies
the code a lot.

If we need to concatenate strings, static buffer of fixed length
is used. The maximum command line length is set to the same value
as the one in the kernel setup code.

v3 changes:

v2 had a bug: cmd_line_ptr was set to a pointer to a buffer inside
a kernel before kernel relocation, that makes this pointer invalid.
It was fixed by replacing the pointer by a boolean variable.

Baskov Evgeniy (2):
         x86: Add strlcat() to compressed kernel
         x86: Parse CONFIG_CMDLINE in compressed kernel

 arch/x86/boot/compressed/cmdline.c | 24 +++++++++++++++++++++++-
 arch/x86/boot/compressed/string.c  | 15 +++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

CONFIG_CMDLINE_BOOL and CONFIG_CMDLINE_OVERRIDE were ignored during
options lookup in compressed kernel, including earlyprintk option,
so it was impossible to get earlyprintk messages from that stage
of boot process via command line provided at compile time.
Being able to enable earlyprintk via compile-time option might
be desirable for booting on systems with broken UEFI command line
arguments via EFISTUB.

Changes in v2:

* Compute resulting cmdline string once if needed and then reuse it.
  Store concatenation result in a static buffer.
* Add strlcat() to compressed kernel to simplify the code.

Changes in v3:

v2 had a bug: cmd_line_ptr was set to a pointer to a buffer inside
a kernel before kernel relocation, that makes this pointer invalid.

* Replace the pointer by a boolean variable to avoid storing a pointer,
  since it becomes invalid during kernel relocation.

Changes in v4:

* Use better wording for commit messages.
* Add buffer overflow check to strlcat().
* Factor out common logic of cmdline resolving into helper function.

Evgeniy Baskov (5):
  x86/boot: Add strlcat() to compressed kernel
  x86: Add resolve_cmdline() helper
  x86/setup: Use resolve_cmdline() in setup.c
  x86/boot: Use resolve_cmdline() in compressed kernel
  x86/boot: Remove no longer needed includes

 arch/x86/boot/compressed/cmdline.c          | 24 +++++++++++--
 arch/x86/boot/compressed/ident_map_64.c     |  4 ---
 arch/x86/boot/compressed/kaslr.c            |  4 ---
 arch/x86/boot/compressed/misc.h             |  1 +
 arch/x86/boot/compressed/string.c           | 19 +++++++++++
 arch/x86/include/asm/shared/setup-cmdline.h | 38 +++++++++++++++++++++
 arch/x86/kernel/setup.c                     | 22 +++---------
 arch/x86/purgatory/purgatory.c              |  1 +
 8 files changed, 85 insertions(+), 28 deletions(-)
 create mode 100644 arch/x86/include/asm/shared/setup-cmdline.h

-- 
2.36.1

strlcat() simplifies the code of command line
concatenation and reduces the probability of mistakes.

Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>

diff --git a/arch/x86/boot/compressed/string.c b/arch/x86/boot/compressed/string.c
index 81fc1eaa3229..6d74d31bf3d9 100644
--- a/arch/x86/boot/compressed/string.c
+++ b/arch/x86/boot/compressed/string.c
@@ -40,6 +40,25 @@ static void *____memcpy(void *dest, const void *src, size_t n)
 }
 #endif
 
+size_t strlcat(char *dest, const char *src, size_t count)
+{
+	size_t dsize = strlen(dest);
+	size_t len = strlen(src);
+	size_t res = dsize + len;
+
+	/* This would be a bug */
+	if (dsize >= count)
+		error("strlcat(): destination too big\n");
+
+	dest += dsize;
+	count -= dsize;
+	if (len >= count)
+		len = count-1;
+	memcpy(dest, src, len);
+	dest[len] = 0;
+	return res;
+}
+
 void *memset(void *s, int c, size_t n)
 {
 	int i;
diff --git a/arch/x86/purgatory/purgatory.c b/arch/x86/purgatory/purgatory.c
index 7558139920f8..65f0cedb65ae 100644
--- a/arch/x86/purgatory/purgatory.c
+++ b/arch/x86/purgatory/purgatory.c
@@ -57,3 +57,4 @@ void purgatory(void)
  * arch/x86/boot/compressed/string.c
  */
 void warn(const char *msg) {}
+void error(char *m) {}
-- 
2.36.1

Command line needs to be combined in both compressed and uncompressed
kernel from built-in and boot command line strings, which requires
non-trivial logic depending on CONFIG_CMDLINE_BOOL and
CONFIG_CMDLINE_OVERRIDE.

Add a helper function to avoid code duplication.

Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>

 create mode 100644 arch/x86/include/asm/shared/setup-cmdline.h

diff --git a/arch/x86/include/asm/shared/setup-cmdline.h b/arch/x86/include/asm/shared/setup-cmdline.h
new file mode 100644
index 000000000000..9822e5af4925
--- /dev/null
+++ b/arch/x86/include/asm/shared/setup-cmdline.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _ASM_X86_SETUP_CMDLINE_H
+#define _ASM_X86_SETUP_CMDLINE_H
+
+#define _SETUP
+#include <asm/setup.h> /* For COMMAND_LINE_SIZE */
+#undef _SETUP
+
+#include <linux/string.h>
+
+#ifdef CONFIG_CMDLINE_BOOL
+#define COMMAND_LINE_INIT CONFIG_CMDLINE
+#else
+#define COMMAND_LINE_INIT ""
+#endif
+
+/*
+ * command_line and boot_command_line are expected to be at most
+ * COMMAND_LINE_SIZE length. command_line needs to be initialized
+ * with COMMAND_LINE_INIT.
+ */
+
+static inline void resolve_cmdline(char *command_line,
+				   const char *boot_command_line)
+{
+#ifdef CONFIG_CMDLINE_BOOL
+	if (!IS_ENABLED(CONFIG_CMDLINE_OVERRIDE)) {
+		/* Append boot loader cmdline to builtin */
+		strlcat(command_line, " ", COMMAND_LINE_SIZE);
+		strlcat(command_line, boot_command_line, COMMAND_LINE_SIZE);
+	}
+#else
+	strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
+#endif
+}
+
+#endif /* _ASM_X86_SETUP_CMDLINE_H */
-- 
2.36.1

On Wed, May 25, 2022 at 01:10:10PM +0300, Evgeniy Baskov wrote:
> Command line needs to be combined in both compressed and uncompressed
> kernel from built-in and boot command line strings, which requires
> non-trivial logic depending on CONFIG_CMDLINE_BOOL and
> CONFIG_CMDLINE_OVERRIDE.
> 
> Add a helper function to avoid code duplication.
> 
> Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>
> 

You have some weird configuration to your git send-email which doesn't
add the "---" to split the patch commit message from the diffstat.

>  create mode 100644 arch/x86/include/asm/shared/setup-cmdline.h
> 
> diff --git a/arch/x86/include/asm/shared/setup-cmdline.h b/arch/x86/include/asm/shared/setup-cmdline.h

Just cmdline.h I'd say.

> new file mode 100644
> index 000000000000..9822e5af4925
> --- /dev/null
> +++ b/arch/x86/include/asm/shared/setup-cmdline.h
> @@ -0,0 +1,38 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef _ASM_X86_SETUP_CMDLINE_H
> +#define _ASM_X86_SETUP_CMDLINE_H
> +
> +#define _SETUP
> +#include <asm/setup.h> /* For COMMAND_LINE_SIZE */
> +#undef _SETUP
> +
> +#include <linux/string.h>
> +
> +#ifdef CONFIG_CMDLINE_BOOL
> +#define COMMAND_LINE_INIT CONFIG_CMDLINE
> +#else
> +#define COMMAND_LINE_INIT ""
> +#endif
> +
> +/*
> + * command_line and boot_command_line are expected to be at most
> + * COMMAND_LINE_SIZE length. command_line needs to be initialized
> + * with COMMAND_LINE_INIT.
> + */
> +


^ Superfluous newline.

> +static inline void resolve_cmdline(char *command_line,
> +				   const char *boot_command_line)

cmdline_prepare() I'd say.

> +{
> +#ifdef CONFIG_CMDLINE_BOOL
> +	if (!IS_ENABLED(CONFIG_CMDLINE_OVERRIDE)) {
> +		/* Append boot loader cmdline to builtin */
> +		strlcat(command_line, " ", COMMAND_LINE_SIZE);
> +		strlcat(command_line, boot_command_line, COMMAND_LINE_SIZE);
> +	}
> +#else
> +	strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);

So that has been switched to strscpy() in the meantime:

8a33d96bd178 ("x86/setup: Use strscpy() to replace deprecated strlcpy()")

Please redo your set ontop of latest tip/master.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

On 2022-08-26 14:35, Borislav Petkov wrote:
> On Wed, May 25, 2022 at 01:10:10PM +0300, Evgeniy Baskov wrote:
>> Command line needs to be combined in both compressed and uncompressed
>> kernel from built-in and boot command line strings, which requires
>> non-trivial logic depending on CONFIG_CMDLINE_BOOL and
>> CONFIG_CMDLINE_OVERRIDE.
>> 
>> Add a helper function to avoid code duplication.
>> 
>> Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>
>> 
> 
> You have some weird configuration to your git send-email which doesn't
> add the "---" to split the patch commit message from the diffstat.

Thanks, apparently "--summary" removes that.

...
> 
> So that has been switched to strscpy() in the meantime:
> 
> 8a33d96bd178 ("x86/setup: Use strscpy() to replace deprecated 
> strlcpy()")

I did already replace strlcpy() in v5, but since there are new changes
needed, I will send v6 with those changes applied soon.
So, please, ignore v5 then.

> 
> Please redo your set ontop of latest tip/master.

Will do.

Thanks,
Evgeniy Baskov

Use a common helper function for command line resolving in
arch/x86/kernel/setup.c for code unification.

Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 249981bf3d8a..880465e26da2 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -47,6 +47,7 @@
 #include <asm/pci-direct.h>
 #include <asm/prom.h>
 #include <asm/proto.h>
+#include <asm/shared/setup-cmdline.h>
 #include <asm/thermal.h>
 #include <asm/unwind.h>
 #include <asm/vsyscall.h>
@@ -164,10 +165,7 @@ unsigned long saved_video_mode;
 #define RAMDISK_PROMPT_FLAG		0x8000
 #define RAMDISK_LOAD_FLAG		0x4000
 
-static char __initdata command_line[COMMAND_LINE_SIZE];
-#ifdef CONFIG_CMDLINE_BOOL
-static char __initdata builtin_cmdline[COMMAND_LINE_SIZE] = CONFIG_CMDLINE;
-#endif
+static char command_line[COMMAND_LINE_SIZE] __initdata = COMMAND_LINE_INIT;
 
 #if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
 struct edd edd;
@@ -901,20 +899,8 @@ void __init setup_arch(char **cmdline_p)
 	bss_resource.start = __pa_symbol(__bss_start);
 	bss_resource.end = __pa_symbol(__bss_stop)-1;
 
-#ifdef CONFIG_CMDLINE_BOOL
-#ifdef CONFIG_CMDLINE_OVERRIDE
-	strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
-#else
-	if (builtin_cmdline[0]) {
-		/* append boot loader cmdline to builtin */
-		strlcat(builtin_cmdline, " ", COMMAND_LINE_SIZE);
-		strlcat(builtin_cmdline, boot_command_line, COMMAND_LINE_SIZE);
-		strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
-	}
-#endif
-#endif
-
-	strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
+	resolve_cmdline(command_line, boot_command_line);
+	strlcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
 	*cmdline_p = command_line;
 
 	/*
-- 
2.36.1

CONFIG_CMDLINE_BOOL and CONFIG_CMDLINE_OVERRIDE were ignored during
options lookup in compressed kernel, including earlyprintk option,
so it was impossible to get earlyprintk messages from that stage
of boot process via command line provided at compile time.
Being able to enable earlyprintk via compile-time option might
be desirable for booting on systems with broken UEFI command line
arguments via EFISTUB.

Use a common helper function to handle CONFIG_CMDLINE_* in compressed
kernel.

Place command_line_init explicitly in '.data' section since it is
used before '.bss' section is zeroed and it is expected to be equal
to zero.

Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>

diff --git a/arch/x86/boot/compressed/cmdline.c b/arch/x86/boot/compressed/cmdline.c
index f1add5d85da9..77a758146531 100644
--- a/arch/x86/boot/compressed/cmdline.c
+++ b/arch/x86/boot/compressed/cmdline.c
@@ -12,6 +12,15 @@ static inline char rdfs8(addr_t addr)
 	return *((char *)(fs + addr));
 }
 #include "../cmdline.c"
+
+static char command_line[COMMAND_LINE_SIZE] __section(".data") = COMMAND_LINE_INIT;
+static bool command_line_init __section(".data");
+
+/*
+ * This always returns runtime command line and does not account for built-in
+ * command line, so this should not be used for cmdline parsing.
+ * Use get_cmdline() instead.
+ */
 unsigned long get_cmd_line_ptr(void)
 {
 	unsigned long cmd_line_ptr = boot_params->hdr.cmd_line_ptr;
@@ -20,11 +29,22 @@ unsigned long get_cmd_line_ptr(void)
 
 	return cmd_line_ptr;
 }
+
+static inline unsigned long get_cmdline(void)
+{
+	if (!command_line_init) {
+		resolve_cmdline(command_line, (char *)get_cmd_line_ptr());
+		command_line_init = 1;
+	}
+
+	return (unsigned long)command_line;
+}
+
 int cmdline_find_option(const char *option, char *buffer, int bufsize)
 {
-	return __cmdline_find_option(get_cmd_line_ptr(), option, buffer, bufsize);
+	return __cmdline_find_option(get_cmdline(), option, buffer, bufsize);
 }
 int cmdline_find_option_bool(const char *option)
 {
-	return __cmdline_find_option_bool(get_cmd_line_ptr(), option);
+	return __cmdline_find_option_bool(get_cmdline(), option);
 }
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 4910bf230d7b..e30159dc81b4 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -26,6 +26,7 @@
 #include <asm/boot.h>
 #include <asm/bootparam.h>
 #include <asm/desc_defs.h>
+#include <asm/shared/setup-cmdline.h>
 
 #include "tdx.h"
 
-- 
2.36.1

x86/incldue/asm/shared/setup-cmdline.h header already provides
COMMAND_LINE_SIZE definition.

Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>

diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
index 44c350d627c7..7dc0300529fa 100644
--- a/arch/x86/boot/compressed/ident_map_64.c
+++ b/arch/x86/boot/compressed/ident_map_64.c
@@ -33,10 +33,6 @@
 #define __PAGE_OFFSET __PAGE_OFFSET_BASE
 #include "../../mm/ident_map.c"
 
-#define _SETUP
-#include <asm/setup.h>	/* For COMMAND_LINE_SIZE */
-#undef _SETUP
-
 extern unsigned long get_cmd_line_ptr(void);
 
 /* Used by PAGE_KERN* macros: */
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 4a3f223973f4..39e455c105a7 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -31,10 +31,6 @@
 #include <linux/ctype.h>
 #include <generated/utsrelease.h>
 
-#define _SETUP
-#include <asm/setup.h>	/* For COMMAND_LINE_SIZE */
-#undef _SETUP
-
 extern unsigned long get_cmd_line_ptr(void);
 
 /* Simplified build-specific string for starting entropy. */
-- 
2.36.1