Re: [PATCH 2/8] CMDLINE: drivers: of: ifdef out cmdline section

On Wed, Apr 07, 2021 at 05:59:15PM -0500, Rob Herring wrote:

On Tue, Mar 30, 2021 at 04:17:53PM -0700, Daniel Walker wrote:

quoted

On Tue, Mar 30, 2021 at 02:49:13PM -0500, Rob Herring wrote:

quoted

On Tue, Mar 30, 2021 at 12:57 PM Daniel Walker [off-list ref] wrote:

quoted

It looks like there's some seepage of cmdline stuff into
the generic device tree code. This conflicts with the
generic cmdline implementation so I remove it in the case
when that's enabled.

Cc: xe-linux-external@cisco.com
Signed-off-by: Ruslan Ruslichenko <redacted>
Signed-off-by: Daniel Walker <redacted>
---
 drivers/of/fdt.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index dcc1dd96911a..d8805cd9717a 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c

@@ -25,6 +25,7 @@
 #include <linux/serial_core.h>
 #include <linux/sysfs.h>
 #include <linux/random.h>
+#include <linux/cmdline.h>

 #include <asm/setup.h>  /* for COMMAND_LINE_SIZE */
 #include <asm/page.h>

@@ -1050,6 +1051,18 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,

        /* Retrieve command line */
        p = of_get_flat_dt_prop(node, "bootargs", &l);
+
+#if defined(CONFIG_GENERIC_CMDLINE) && defined(CONFIG_GENERIC_CMDLINE_OF)

Moving in the wrong direction... This code already has too many
#ifdef's. I like Christophe's version as it gets rid of all the code
here.

 
It's temporary .. Notice CONFIG_GENERIC_CMDLINE_OF is only used on PowerPC. I
experienced doubling on arm64 when this was used (i.e. the append and prepend
was added twice).

I don't think there are any other users which can't be moved outside the device
tree code, but powerpc uses this function three times during boot up plus the
prom_init user. It's possible to use the generic command line in all four places,
but it become space inefficient.

What's the 3rd use? I count kaslr code and in 
early_init_dt_scan_chosen_ppc. Do we need to build the command line for 
kaslr seed? Getting any build time value from the kernel is pointless.

I think I may have been mistaken. I added a dump_stack() , but there may have
been other stack traces during bootup on prior -rcX's I was testing.

I re-ran the test and I only see one user on powerpc and powerpc64,

powerpc64,

[    T0] Call Trace:
[    T0] [c000000001517d00] [c00000000077e910] dump_stack+0xc4/0x114 (unreliable)
[    T0] [c000000001517d50] [c000000001186fb4] early_init_dt_scan_chosen+0x238/0x324
[    T0] [c000000001517de0] [c000000001138b00] early_init_dt_scan_chosen_ppc+0x20/0x194
[    T0] [c000000001517e10] [c000000001186ae0] of_scan_flat_dt+0xc8/0x130
[    T0] [c000000001517e70] [c000000001139404] early_init_devtree+0xa4/0x48c
[    T0] [c000000001517f10] [c00000000113ac90] early_setup+0xc8/0x254
[    T0] [c000000001517f90] [000000000000c754] 0xc754

powerpc32,

Call Trace:
[c06bbee0] [c067e334] early_init_dt_scan_chosen+0xf8/0x1dc (unreliable)
[c06bbf10] [c0666ec4] early_init_dt_scan_chosen_ppc+0x18/0x6c
[c06bbf30] [c067e048] of_scan_flat_dt+0x98/0xf4
[c06bbf70] [c0667234] early_init_devtree+0x48/0x2d0
[c06bbfb0] [c06679cc] machine_init+0x98/0xcc
[c06bbff0] [c0000398] set_ivor+0x114/0x154

I think it would be possible to just move the generic handling entire into
architecture code.

Daniel