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Message-ID: <45b5a4d3-b79f-aa66-67e9-2a57bbfb938e@quicinc.com>
Date: Mon, 12 Feb 2024 19:04:03 +0530
From: Mukesh Ojha <quic_mojha@...cinc.com>
To: Kees Cook <keescook@...omium.org>, Tony Luck <tony.luck@...el.com>,
"Guilherme G. Piccoli" <gpiccoli@...lia.com>
CC: <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-arm-msm@...r.kernel.org>, <linux-hardening@...r.kernel.org>,
<linux-remoteproc@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-mediatek@...ts.infradead.org>,
<linux-samsung-soc@...r.kernel.org>, <kernel@...cinc.com>,
<corbet@....net>, <andersson@...nel.org>, <konrad.dybcio@...aro.org>,
<robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
<conor+dt@...nel.org>, <mathieu.poirier@...aro.org>, <vigneshr@...com>,
<nm@...com>, <matthias.bgg@...il.com>, <kgene@...nel.org>,
<alim.akhtar@...sung.com>, <bmasney@...hat.com>
Subject: Re: [PATCH v8 08/10] pstore/ram: Add dynamic ramoops region support
through commandline
Hi @Kees/@...y/@...lherme,
Wanted to get your early feedback, especially on 8th and 9th patch.
please suggest.
-Mukesh
On 1/31/2024 4:38 PM, Mukesh Ojha wrote:
> The reserved memory region for ramoops is assumed to be at a fixed
> and known location when read from the devicetree. This may not be
> required for something like Qualcomm's minidump which is interested
> in knowing addresses of ramoops region but it does not put hard
> requirement of address being fixed as most of its SoC does not
> support warm reset and does not use pstorefs at all instead it has
> firmware way of collecting ramoops region if it gets to know the
> address and register it with apss minidump table which is sitting
> in shared memory region in DDR and firmware will have access to
> these table during reset and collects it on crash of SoC.
>
> So, add the support of reserving ramoops region to be dynamically
> allocated early during boot if it is request through command line
> via 'dyn_ramoops_size=<size>' and fill up reserved resource structure
> and export the structure, so that it can be read by ramoops driver.
>
> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
> ---
> Documentation/admin-guide/ramoops.rst | 23 +++++++++-
> fs/pstore/Kconfig | 15 ++++++
> fs/pstore/ram.c | 66 +++++++++++++++++++++++++--
> include/linux/pstore_ram.h | 5 ++
> init/main.c | 3 ++
> 5 files changed, 108 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/admin-guide/ramoops.rst b/Documentation/admin-guide/ramoops.rst
> index e9f85142182d..6de61002f9e9 100644
> --- a/Documentation/admin-guide/ramoops.rst
> +++ b/Documentation/admin-guide/ramoops.rst
> @@ -33,6 +33,13 @@ memory are implementation defined, and won't work on many ARMs such as omaps.
> Setting ``mem_type=2`` attempts to treat the memory region as normal memory,
> which enables full cache on it. This can improve the performance.
>
> +Ramoops supports its memory to be allocated dynamically during early boot
> +for plaforms that do not have support for warm boot i.e., no assurance
> +that Ram content will be preserved across boot and for these platforms
> +giving static Ramoops memory is not necessary as it has separate backend
> +mechanism to retrieve ramoops content on system failure. More about
> +how to enable Dynamic ramoops in ``Setting the parameters`` A.b section.
> +
> The memory area is divided into ``record_size`` chunks (also rounded down to
> power of two) and each kmesg dump writes a ``record_size`` chunk of
> information.
> @@ -59,7 +66,7 @@ Setting the parameters
>
> Setting the ramoops parameters can be done in several different manners:
>
> - A. Use the module parameters (which have the names of the variables described
> + A.a Use the module parameters (which have the names of the variables described
> as before). For quick debugging, you can also reserve parts of memory during
> boot and then use the reserved memory for ramoops. For example, assuming a
> machine with > 128 MB of memory, the following kernel command line will tell
> @@ -68,6 +75,20 @@ Setting the ramoops parameters can be done in several different manners:
>
> mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1
>
> + A.b Ramoops memory can be also be dynamically reserved by Kernel and in such
> + scenario ``mem_address`` i.e., Ramoops base address can be anywhere in the RAM
> + instead of being fixed and predefined. A separate command line option
> + ``dyn_ramoops_size=<size>`` and kernel config CONFIG_PSTORE_DYNAMIC_RAMOOPS
> + are provided to facilitate Dynamic Ramoops memory reservation during early boot.
> + The command line option and the config should only be used in the presence of
> + separate backend which knows how to recover Dynamic Ramoops region otherwise
> + regular ramoops functionality will be impacted.
> + ``mem_size`` should not be used if Dynamic Ramoops support is requested and if
> + both are given ``mem_size`` value is overwritten with ``dyn_ramoops_size`` value
> + i.e., Dynamic Ramoops takes precedence::
> +
> + dyn_ramoops_size=2M ramoops.console_size=2097152
> +
> B. Use Device Tree bindings, as described in
> ``Documentation/devicetree/bindings/reserved-memory/ramoops.yaml``.
> For example::
> diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig
> index 3acc38600cd1..b8bdbd2f0e73 100644
> --- a/fs/pstore/Kconfig
> +++ b/fs/pstore/Kconfig
> @@ -81,6 +81,21 @@ config PSTORE_RAM
>
> For more information, see Documentation/admin-guide/ramoops.rst.
>
> +config PSTORE_DYNAMIC_RAMOOPS
> + bool "Reserve ramoops region dynamically"
> + select PSTORE_RAM
> + help
> + This enables the dynamic reservation of ramoops region for a special case
> + where there is no need to access the logs from pstorefs on next boot;
> + instead there is separate backend mechanism like minidump present which has
> + awareness about the dynamic ramoops region and can recover the logs. This is
> + enabled via command line parameter dyn_ramoops_size=<size> and should not be
> + used in absence of separate backend which knows how to recover this dynamic
> + region.
> +
> + Note whenever this config is selected ramoops driver will be built statically
> + into kernel.
> +
> config PSTORE_ZONE
> tristate
> depends on PSTORE
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index 88b34fdbf759..1faf0835700b 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -20,6 +20,7 @@
> #include <linux/compiler.h>
> #include <linux/of.h>
> #include <linux/of_address.h>
> +#include <linux/memblock.h>
> #include <linux/mm.h>
>
> #include "internal.h"
> @@ -103,6 +104,59 @@ struct ramoops_context {
> };
>
> static struct platform_device *dummy;
> +static struct resource dyn_ramoops_res = {
> + .name = "ramoops",
> + .start = 0,
> + .end = 0,
> + .flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
> + .desc = IORES_DESC_NONE,
> +};
> +static int dyn_ramoops_size;
> +
> +#ifdef CONFIG_PSTORE_DYNAMIC_RAMOOPS
> +static int __init parse_dyn_ramoops_size(char *p)
> +{
> + char *tmp;
> +
> + dyn_ramoops_size = memparse(p, &tmp);
> + if (p == tmp) {
> + pr_err("ramoops: memory size expected\n");
> + dyn_ramoops_size = 0;
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +early_param("dyn_ramoops_size", parse_dyn_ramoops_size);
> +
> +/*
> + * setup_dynamic_ramoops() - Reserve memory for dynamic ramoops
> + *
> + * Enables dynamic reserve memory support for ramoops through
> + * command line.
> + */
> +void __init setup_dynamic_ramoops(void)
> +{
> + unsigned long long ramoops_base;
> + unsigned long long ramoops_size;
> +
> + if (!dyn_ramoops_size)
> + return;
> +
> + ramoops_base = memblock_phys_alloc_range(dyn_ramoops_size, SMP_CACHE_BYTES,
> + 0, MEMBLOCK_ALLOC_NOLEAKTRACE);
> + if (!ramoops_base) {
> + pr_err("cannot allocate ramoops dynamic memory (size:0x%llx).\n",
> + ramoops_size);
> + dyn_ramoops_size = 0;
> + return;
> + }
> +
> + dyn_ramoops_res.start = ramoops_base;
> + dyn_ramoops_res.end = ramoops_base + dyn_ramoops_size - 1;
> + insert_resource(&iomem_resource, &dyn_ramoops_res);
> +}
> +#endif
>
> static int ramoops_pstore_open(struct pstore_info *psi)
> {
> @@ -915,13 +969,19 @@ static void __init ramoops_register_dummy(void)
>
> /*
> * Prepare a dummy platform data structure to carry the module
> - * parameters. If mem_size isn't set, then there are no module
> - * parameters, and we can skip this.
> + * parameters.
> + *
> + * dyn_ramoops_size takes precedence over mem_size if it is
> + * enabled and valid.
> */
> - if (!mem_size)
> + if (!dyn_ramoops_size && !mem_size)
> return;
>
> pr_info("using module parameters\n");
> + if (dyn_ramoops_size) {
> + mem_size = dyn_ramoops_size;
> + mem_address = dyn_ramoops_res.start;
> + }
>
> memset(&pdata, 0, sizeof(pdata));
> pdata.mem_size = mem_size;
> diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h
> index 9d65ff94e216..1efff7a38333 100644
> --- a/include/linux/pstore_ram.h
> +++ b/include/linux/pstore_ram.h
> @@ -39,4 +39,9 @@ struct ramoops_platform_data {
> struct persistent_ram_ecc_info ecc_info;
> };
>
> +#ifdef CONFIG_PSTORE_DYNAMIC_RAMOOPS
> +void __init setup_dynamic_ramoops(void);
> +#else
> +static inline void __init setup_dynamic_ramoops(void) {}
> +#endif
> #endif
> diff --git a/init/main.c b/init/main.c
> index ef3ce41b8fc5..3d74241bcb2b 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -99,6 +99,8 @@
> #include <linux/init_syscalls.h>
> #include <linux/stackdepot.h>
> #include <linux/randomize_kstack.h>
> +#include <linux/moduleloader.h>
> +#include <linux/pstore_ram.h>
> #include <net/net_namespace.h>
>
> #include <asm/io.h>
> @@ -890,6 +892,7 @@ void start_kernel(void)
> pr_notice("%s", linux_banner);
> early_security_init();
> setup_arch(&command_line);
> + setup_dynamic_ramoops();
> setup_boot_config();
> setup_command_line(command_line);
> setup_nr_cpu_ids();
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