MIPS: Fix CONFIG_CMDLINE handling

Commit 8ce355cf2e38 ("MIPS: Setup boot_command_line before
plat_mem_setup") fixed a problem for systems which have
CONFIG_CMDLINE_BOOL=y & use a DT with a chosen node that has either no
bootargs property or an empty one. In this configuration
early_init_dt_scan_chosen() copies CONFIG_CMDLINE into
boot_command_line, but the MIPS code doesn't know this so it appends
CONFIG_CMDLINE (via builtin_cmdline) to boot_command_line again. The
result is that boot_command_line contains the arguments from
CONFIG_CMDLINE twice.

That commit took the approach of simply setting up boot_command_line
from the MIPS code before early_init_dt_scan_chosen() runs, causing it
not to copy CONFIG_CMDLINE to boot_command_line if a chosen node with no
bootargs property is found.

Unfortunately this is problematic for systems which do have a non-empty
bootargs property & CONFIG_CMDLINE_BOOL=y. There
early_init_dt_scan_chosen() will overwrite boot_command_line with the
arguments from DT, which means we lose those from CONFIG_CMDLINE
entirely. This breaks CONFIG_MIPS_CMDLINE_DTB_EXTEND. If we have
CONFIG_MIPS_CMDLINE_FROM_BOOTLOADER or
CONFIG_MIPS_CMDLINE_BUILTIN_EXTEND selected and the DT has a bootargs
property which we should ignore, it will instead be honoured breaking
those configurations too.

Fix this by reverting commit 8ce355cf2e38 ("MIPS: Setup
boot_command_line before plat_mem_setup") to restore the former
behaviour, and fixing the CONFIG_CMDLINE duplication issue by
initializing boot_command_line to a non-empty string that
early_init_dt_scan_chosen() will not overwrite with CONFIG_CMDLINE.

This is a little ugly, but cleanup in this area is on its way. In the
meantime this is at least easy to backport & contains the ugliness
within arch/mips/.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Fixes: 8ce355cf2e38 ("MIPS: Setup boot_command_line before plat_mem_setup")
References: https://patchwork.linux-mips.org/patch/18804/
Patchwork: https://patchwork.linux-mips.org/patch/20813/
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Jaedon Shin <jaedon.shin@gmail.com>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org # v4.16+

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index c71d1eb7da5944b182c287aae347488a7594529b..8aaaa42f91ed6626809366e4ca7e533dbeb43bfc 100644 (file)
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -846,6 +846,34 @@ static void __init arch_mem_init(char **cmdline_p)
        struct memblock_region *reg;
        extern void plat_mem_setup(void);
 
+       /*
+        * Initialize boot_command_line to an innocuous but non-empty string in
+        * order to prevent early_init_dt_scan_chosen() from copying
+        * CONFIG_CMDLINE into it without our knowledge. We handle
+        * CONFIG_CMDLINE ourselves below & don't want to duplicate its
+        * content because repeating arguments can be problematic.
+        */
+       strlcpy(boot_command_line, " ", COMMAND_LINE_SIZE);
+
+       /* call board setup routine */
+       plat_mem_setup();
+
+       /*
+        * Make sure all kernel memory is in the maps.  The "UP" and
+        * "DOWN" are opposite for initdata since if it crosses over
+        * into another memory section you don't want that to be
+        * freed when the initdata is freed.
+        */
+       arch_mem_addpart(PFN_DOWN(__pa_symbol(&_text)) << PAGE_SHIFT,
+                        PFN_UP(__pa_symbol(&_edata)) << PAGE_SHIFT,
+                        BOOT_MEM_RAM);
+       arch_mem_addpart(PFN_UP(__pa_symbol(&__init_begin)) << PAGE_SHIFT,
+                        PFN_DOWN(__pa_symbol(&__init_end)) << PAGE_SHIFT,
+                        BOOT_MEM_INIT_RAM);
+
+       pr_info("Determined physical RAM map:\n");
+       print_memory_map();
+
 #if defined(CONFIG_CMDLINE_BOOL) && defined(CONFIG_CMDLINE_OVERRIDE)
        strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
 #else
@@ -873,26 +901,6 @@ static void __init arch_mem_init(char **cmdline_p)
        }
 #endif
 #endif
-
-       /* call board setup routine */
-       plat_mem_setup();
-
-       /*
-        * Make sure all kernel memory is in the maps.  The "UP" and
-        * "DOWN" are opposite for initdata since if it crosses over
-        * into another memory section you don't want that to be
-        * freed when the initdata is freed.
-        */
-       arch_mem_addpart(PFN_DOWN(__pa_symbol(&_text)) << PAGE_SHIFT,
-                        PFN_UP(__pa_symbol(&_edata)) << PAGE_SHIFT,
-                        BOOT_MEM_RAM);
-       arch_mem_addpart(PFN_UP(__pa_symbol(&__init_begin)) << PAGE_SHIFT,
-                        PFN_DOWN(__pa_symbol(&__init_end)) << PAGE_SHIFT,
-                        BOOT_MEM_INIT_RAM);
-
-       pr_info("Determined physical RAM map:\n");
-       print_memory_map();
-
        strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
 
        *cmdline_p = command_line;