On Wed, Mar 14, 2018 at 09:31:05AM -0700, Palmer Dabbelt wrote:
> Systems that boot without a chosen node in the device tree should still
> respect the command lines that are built into the kernel. This patch
> avoids bailing out of the command line argument parsing code when there
> is no chosen node in the device tree. This is necessary to boot
> straight to a root file system (ie, without an initramfs)
>
> The intent here is that the only functional change is to copy
> CONFIG_CMDLINE into data if both of them are valid (ie, CONFIG_CMDLINE
> is defined and data is non-null) on systems where there is no chosen
> device tree node. I don't actually know what the return values do so I
> just preserved them.
>
> Thanks to Trung and Moritz for finding the bug during our ELC hackathon
> (and providing the first fix), and Michal for suggesting this fix (which
> is cleaner than what I was doing). I've given this very minimal
> testing: it fixes the RISC-V bug (in conjunction with a patch to move
> from COMMANDLINE_OVERRIDE to COMMANDLINE_FORCE), still works on systems
> with and without the chosen node, and builds on ARM64.
>
> CC: Michael J Clark <mjc@xxxxxxxxxx>
> CC: Trung Tran <trung.tran@xxxxxxxxx>
> CC: Moritz Fischer <mdf@xxxxxxxxxx>
> Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxx>
> ---
> drivers/of/fdt.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 84aa9d676375..60241b1cb024 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1084,9 +1084,12 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
>
> pr_debug("search \"chosen\", depth: %d, uname: %s\n", depth, uname);
>
> - if (depth != 1 || !data ||
> + if (!data)
> + goto no_data;
Just "return 0" here.
> +
> + if (depth != 1 ||
> (strcmp(uname, "chosen") != 0 && strcmp(uname, "chosen@0") != 0))
> - return 0;
> + goto no_chosen;
>
> early_init_dt_check_for_initrd(node);
>
> @@ -1117,6 +1120,13 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
>
> /* break now */
> return 1;
> +
> +no_chosen:
> +#ifdef CONFIG_CMDLINE
> + strlcpy(data, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
Best case, this is going to needlessly copy the string on every single
node that is not /chosen.
Worst case, I think this changes behavior. For example, first you copy
CONFIG_CMDLINE into data, then on a later iteration, you strlcat
CONFIG_CMDLINE into data if CONFIG_CMDLINE_EXTEND is enable. There could
also be some unintended behavior if data has a string to start with.
I'd really like to see this function re-written to just find the /chosen
node and then handle each property one by one. The iterating approach is
silly. I assume it predates libfdt and we didn't have nice functions to
find nodes by path (or any other way).
I'm working on a patch to re-structure this function. Will send it out
in the next day.
> +#endif
> +no_data:
> + return 0;
> }
>
> #ifdef CONFIG_HAVE_MEMBLOCK
> --
> 2.16.1
>
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