[PATCH] firmware: coreboot: Register bus in module init

[PATCH] firmware: coreboot: Register bus in module init

[Brian Norris]

The coreboot_table driver registers a coreboot bus while probing a
"coreboot_table" device representing the coreboot table memory region.
Probing this device (i.e., registering the bus) is a dependency for the
module_init() functions of any driver for this bus (e.g.,
memconsole-coreboot.c / memconsole_driver_init()).

With synchronous probe, this dependency works OK, as the link order in
the Makefile ensures coreboot_table_driver_init() (and thus,
coreboot_table_probe()) completes before a coreboot device driver tries
to add itself to the bus.

With asynchronous probe, however, coreboot_table_probe() may race with
memconsole_driver_init(), and so we're liable to hit one of these two:

1. coreboot_driver_register() eventually hits "[...] the bus was not
   initialized.", and the memconsole driver fails to register; or
2. coreboot_driver_register() gets past #1, but still races with
   bus_register() and hits some other undefined/crashing behavior (e.g.,
   in driver_find() [1])

We can resolve this by registering the bus in our initcall, and only
deferring "device" work (scanning the coreboot memory region and
creating sub-devices) to probe().

[1] Example failure, using 'driver_async_probe=*' kernel command line:

[    0.114217] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010
...
[    0.114307] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.1.0-rc1 #63
[    0.114316] Hardware name: Google Scarlet (DT)
...
[    0.114488] Call trace:
[    0.114494]  _raw_spin_lock+0x34/0x60
[    0.114502]  kset_find_obj+0x28/0x84
[    0.114511]  driver_find+0x30/0x50
[    0.114520]  driver_register+0x64/0x10c
[    0.114528]  coreboot_driver_register+0x30/0x3c
[    0.114540]  memconsole_driver_init+0x24/0x30
[    0.114550]  do_one_initcall+0x154/0x2e0
[    0.114560]  do_initcall_level+0x134/0x160
[    0.114571]  do_initcalls+0x60/0xa0
[    0.114579]  do_basic_setup+0x28/0x34
[    0.114588]  kernel_init_freeable+0xf8/0x150
[    0.114596]  kernel_init+0x2c/0x12c
[    0.114607]  ret_from_fork+0x10/0x20
[    0.114624] Code: 5280002b 1100054a b900092a f9800011 (885ffc01)
[    0.114631] ---[ end trace 0000000000000000 ]---

Fixes: b81e3140e412 ("firmware: coreboot: Make bus registration symmetric")
Cc: <stable@vger.kernel.org>
Signed-off-by: Brian Norris <briannorris@chromium.org>
---
Currently, get_maintainers.pl tells me Greg should pick this up. But I
CC the chrome-platform list too, since it seems reasonable for Google
folks (probably ChromeOS folks are most active here?) to maintain
Google/Chrome drivers.

Let me know if y'all would like this official, and I'll push out a
MAINTAINERS patch.

 drivers/firmware/google/coreboot_table.c | 37 +++++++++++++++++++-----
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/drivers/firmware/google/coreboot_table.c b/drivers/firmware/google/coreboot_table.c
index c52bcaa9def6..9ca21feb9d45 100644
--- a/drivers/firmware/google/coreboot_table.c
+++ b/drivers/firmware/google/coreboot_table.c
@@ -149,12 +149,8 @@ static int coreboot_table_probe(struct platform_device *pdev)
 	if (!ptr)
 		return -ENOMEM;
 
-	ret = bus_register(&coreboot_bus_type);
-	if (!ret) {
-		ret = coreboot_table_populate(dev, ptr);
-		if (ret)
-			bus_unregister(&coreboot_bus_type);
-	}
+	ret = coreboot_table_populate(dev, ptr);
+
 	memunmap(ptr);
 
 	return ret;
@@ -169,7 +165,6 @@ static int __cb_dev_unregister(struct device *dev, void *dummy)
 static int coreboot_table_remove(struct platform_device *pdev)
 {
 	bus_for_each_dev(&coreboot_bus_type, NULL, NULL, __cb_dev_unregister);
-	bus_unregister(&coreboot_bus_type);
 	return 0;
 }
 
@@ -199,6 +194,32 @@ static struct platform_driver coreboot_table_driver = {
 		.of_match_table = of_match_ptr(coreboot_of_match),
 	},
 };
-module_platform_driver(coreboot_table_driver);
+
+static int __init coreboot_table_driver_init(void)
+{
+	int ret;
+
+	ret = bus_register(&coreboot_bus_type);
+	if (ret)
+		return ret;
+
+	ret = platform_driver_register(&coreboot_table_driver);
+	if (ret) {
+		bus_unregister(&coreboot_bus_type);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void __exit coreboot_table_driver_exit(void)
+{
+	platform_driver_unregister(&coreboot_table_driver);
+	bus_unregister(&coreboot_bus_type);
+}
+
+module_init(coreboot_table_driver_init);
+module_exit(coreboot_table_driver_exit);
+
 MODULE_AUTHOR("Google, Inc.");
 MODULE_LICENSE("GPL");
-- 
2.38.0.413.g74048e4d9e-goog

Re: [PATCH] firmware: coreboot: Register bus in module init

[Guenter Roeck]

On 10/19/22 18:10, Brian Norris wrote:
> The coreboot_table driver registers a coreboot bus while probing a
> "coreboot_table" device representing the coreboot table memory region.
> Probing this device (i.e., registering the bus) is a dependency for the
> module_init() functions of any driver for this bus (e.g.,
> memconsole-coreboot.c / memconsole_driver_init()).
> 
> With synchronous probe, this dependency works OK, as the link order in
> the Makefile ensures coreboot_table_driver_init() (and thus,
> coreboot_table_probe()) completes before a coreboot device driver tries
> to add itself to the bus.
> 
> With asynchronous probe, however, coreboot_table_probe() may race with
> memconsole_driver_init(), and so we're liable to hit one of these two:
> 
> 1. coreboot_driver_register() eventually hits "[...] the bus was not
>     initialized.", and the memconsole driver fails to register; or
> 2. coreboot_driver_register() gets past #1, but still races with
>     bus_register() and hits some other undefined/crashing behavior (e.g.,
>     in driver_find() [1])
> 
> We can resolve this by registering the bus in our initcall, and only
> deferring "device" work (scanning the coreboot memory region and
> creating sub-devices) to probe().
> 
> [1] Example failure, using 'driver_async_probe=*' kernel command line:
> 
> [    0.114217] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010
> ...
> [    0.114307] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.1.0-rc1 #63
> [    0.114316] Hardware name: Google Scarlet (DT)
> ...
> [    0.114488] Call trace:
> [    0.114494]  _raw_spin_lock+0x34/0x60
> [    0.114502]  kset_find_obj+0x28/0x84
> [    0.114511]  driver_find+0x30/0x50
> [    0.114520]  driver_register+0x64/0x10c
> [    0.114528]  coreboot_driver_register+0x30/0x3c
> [    0.114540]  memconsole_driver_init+0x24/0x30
> [    0.114550]  do_one_initcall+0x154/0x2e0
> [    0.114560]  do_initcall_level+0x134/0x160
> [    0.114571]  do_initcalls+0x60/0xa0
> [    0.114579]  do_basic_setup+0x28/0x34
> [    0.114588]  kernel_init_freeable+0xf8/0x150
> [    0.114596]  kernel_init+0x2c/0x12c
> [    0.114607]  ret_from_fork+0x10/0x20
> [    0.114624] Code: 5280002b 1100054a b900092a f9800011 (885ffc01)
> [    0.114631] ---[ end trace 0000000000000000 ]---
> 
> Fixes: b81e3140e412 ("firmware: coreboot: Make bus registration symmetric")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Brian Norris <briannorris@chromium.org>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
> Currently, get_maintainers.pl tells me Greg should pick this up. But I
> CC the chrome-platform list too, since it seems reasonable for Google
> folks (probably ChromeOS folks are most active here?) to maintain
> Google/Chrome drivers.
> 
> Let me know if y'all would like this official, and I'll push out a
> MAINTAINERS patch.
> 

I think that would be a good idea.

Guenter

>   drivers/firmware/google/coreboot_table.c | 37 +++++++++++++++++++-----
>   1 file changed, 29 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/firmware/google/coreboot_table.c b/drivers/firmware/google/coreboot_table.c
> index c52bcaa9def6..9ca21feb9d45 100644
> --- a/drivers/firmware/google/coreboot_table.c
> +++ b/drivers/firmware/google/coreboot_table.c
> @@ -149,12 +149,8 @@ static int coreboot_table_probe(struct platform_device *pdev)
>   	if (!ptr)
>   		return -ENOMEM;
>   
> -	ret = bus_register(&coreboot_bus_type);
> -	if (!ret) {
> -		ret = coreboot_table_populate(dev, ptr);
> -		if (ret)
> -			bus_unregister(&coreboot_bus_type);
> -	}
> +	ret = coreboot_table_populate(dev, ptr);
> +
>   	memunmap(ptr);
>   
>   	return ret;
> @@ -169,7 +165,6 @@ static int __cb_dev_unregister(struct device *dev, void *dummy)
>   static int coreboot_table_remove(struct platform_device *pdev)
>   {
>   	bus_for_each_dev(&coreboot_bus_type, NULL, NULL, __cb_dev_unregister);
> -	bus_unregister(&coreboot_bus_type);
>   	return 0;
>   }
>   
> @@ -199,6 +194,32 @@ static struct platform_driver coreboot_table_driver = {
>   		.of_match_table = of_match_ptr(coreboot_of_match),
>   	},
>   };
> -module_platform_driver(coreboot_table_driver);
> +
> +static int __init coreboot_table_driver_init(void)
> +{
> +	int ret;
> +
> +	ret = bus_register(&coreboot_bus_type);
> +	if (ret)
> +		return ret;
> +
> +	ret = platform_driver_register(&coreboot_table_driver);
> +	if (ret) {
> +		bus_unregister(&coreboot_bus_type);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static void __exit coreboot_table_driver_exit(void)
> +{
> +	platform_driver_unregister(&coreboot_table_driver);
> +	bus_unregister(&coreboot_bus_type);
> +}
> +
> +module_init(coreboot_table_driver_init);
> +module_exit(coreboot_table_driver_exit);
> +
>   MODULE_AUTHOR("Google, Inc.");
>   MODULE_LICENSE("GPL");

Re: [PATCH] firmware: coreboot: Register bus in module init

[Stephen Boyd]

Quoting Brian Norris (2022-10-19 18:10:53)
[...]
> [    0.114560]  do_initcall_level+0x134/0x160
> [    0.114571]  do_initcalls+0x60/0xa0
> [    0.114579]  do_basic_setup+0x28/0x34
> [    0.114588]  kernel_init_freeable+0xf8/0x150
> [    0.114596]  kernel_init+0x2c/0x12c
> [    0.114607]  ret_from_fork+0x10/0x20
> [    0.114624] Code: 5280002b 1100054a b900092a f9800011 (885ffc01)
> [    0.114631] ---[ end trace 0000000000000000 ]---
>
> Fixes: b81e3140e412 ("firmware: coreboot: Make bus registration symmetric")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Brian Norris <briannorris@chromium.org>
> ---

Reviewed-by: Stephen Boyd <swboyd@chromium.org>

> diff --git a/drivers/firmware/google/coreboot_table.c b/drivers/firmware/google/coreboot_table.c
> index c52bcaa9def6..9ca21feb9d45 100644
> --- a/drivers/firmware/google/coreboot_table.c
> +++ b/drivers/firmware/google/coreboot_table.c
> @@ -199,6 +194,32 @@ static struct platform_driver coreboot_table_driver = {
>                 .of_match_table = of_match_ptr(coreboot_of_match),
>         },
>  };
> -module_platform_driver(coreboot_table_driver);
> +
> +static int __init coreboot_table_driver_init(void)
> +{
> +       int ret;
> +
> +       ret = bus_register(&coreboot_bus_type);
> +       if (ret)
> +               return ret;
> +
> +       ret = platform_driver_register(&coreboot_table_driver);
> +       if (ret) {
> +               bus_unregister(&coreboot_bus_type);
> +               return ret;
> +       }
> +
> +       return 0;

This could be 'return ret' and two lines could be saved, but that is
super nitpick so whatever.

Re: [PATCH] firmware: coreboot: Register bus in module init

[Brian Norris]

On Wed, Oct 19, 2022 at 06:20:08PM -0700, Guenter Roeck wrote:
> On 10/19/22 18:10, Brian Norris wrote:
> > Currently, get_maintainers.pl tells me Greg should pick this up. But I
> > CC the chrome-platform list too, since it seems reasonable for Google
> > folks (probably ChromeOS folks are most active here?) to maintain
> > Google/Chrome drivers.
> > 
> > Let me know if y'all would like this official, and I'll push out a
> > MAINTAINERS patch.
> > 
> 
> I think that would be a good idea.

Done:

[PATCH] MAINTAINERS: Add drivers/firmware/google/ entry
https://lore.kernel.org/lkml/20221021172624.1.I119456791d197eb7d159f09e7479d8759008a954@changeid/

Brian

Re: [PATCH] firmware: coreboot: Register bus in module init

[patchwork-bot+chrome-platform]

Hello:

This patch was applied to chrome-platform/linux.git (for-kernelci)
by Greg Kroah-Hartman <gregkh@linuxfoundation.org>:

On Wed, 19 Oct 2022 18:10:53 -0700 you wrote:
> The coreboot_table driver registers a coreboot bus while probing a
> "coreboot_table" device representing the coreboot table memory region.
> Probing this device (i.e., registering the bus) is a dependency for the
> module_init() functions of any driver for this bus (e.g.,
> memconsole-coreboot.c / memconsole_driver_init()).
> 
> With synchronous probe, this dependency works OK, as the link order in
> the Makefile ensures coreboot_table_driver_init() (and thus,
> coreboot_table_probe()) completes before a coreboot device driver tries
> to add itself to the bus.
> 
> [...]

Here is the summary with links:
  - firmware: coreboot: Register bus in module init
    https://git.kernel.org/chrome-platform/c/65946690ed8d

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH] firmware: coreboot: Register bus in module init

[patchwork-bot+chrome-platform]

Hello:

This patch was applied to chrome-platform/linux.git (for-next)
by Greg Kroah-Hartman <gregkh@linuxfoundation.org>:

On Wed, 19 Oct 2022 18:10:53 -0700 you wrote:
> The coreboot_table driver registers a coreboot bus while probing a
> "coreboot_table" device representing the coreboot table memory region.
> Probing this device (i.e., registering the bus) is a dependency for the
> module_init() functions of any driver for this bus (e.g.,
> memconsole-coreboot.c / memconsole_driver_init()).
> 
> With synchronous probe, this dependency works OK, as the link order in
> the Makefile ensures coreboot_table_driver_init() (and thus,
> coreboot_table_probe()) completes before a coreboot device driver tries
> to add itself to the bus.
> 
> [...]

Here is the summary with links:
  - firmware: coreboot: Register bus in module init
    https://git.kernel.org/chrome-platform/c/65946690ed8d

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html