Re: [PATCH] arm64: fix KASAN_INLINE

[Mark Rutland <mark.rutland@arm.com>]

On Wed, Jul 13, 2022 at 03:09:49PM +0100, Mark Rutland wrote:
> Since commit:
> 
>   a004393f45d9a55e ("arm64: idreg-override: use early FDT mapping in ID map")
> 
> Kernels built with KASAN_INLINE=y die early in boot before producing any
> console output. This is because the accesses made to the FDT (e.g. in
> generic string processing functions) are instrumented with KASAN, and
> with KASAN_INLINE=y any access to an address in TTBR0 results in a bogus
> shadow VA, resulting in a data abort.
> 
> This patch fixes this by reverting commits:
> 
>   7559d9f97581654f ("arm64: setup: drop early FDT pointer helpers")
>   bd0c3fa21878b6d0 ("arm64: idreg-override: use early FDT mapping in ID map")
> 
> ... and using the TTBR1 fixmap mapping of the FDT.
> 
> Note that due to a later commit:
> 
>   b65e411d6cc2f12a ("arm64: Save state of HCR_EL2.E2H before switch to EL1")
> 
> ... which altered the prototype of init_feature_override() (and
> invocation from head.S), commit bd0c3fa21878b6d0 does not revert
> cleanly, and I've fixed that up manually.
> 

Whoops; this was meant to have:

  Signed-off-by: Mark Rutland <mark.rutland@arm.com>

... but I somehow messed that up.

Will, are you happy to fold that in?

Mark.

> Fixes: a004393f45d9a55e ("arm64: idreg-override: use early FDT mapping in ID map")
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Will Deacon <will@kernel.org>
> ---
>  arch/arm64/include/asm/setup.h     |  3 +++
>  arch/arm64/kernel/head.S           |  5 +++--
>  arch/arm64/kernel/idreg-override.c | 17 +++++++++++------
>  arch/arm64/kernel/setup.c          | 15 +++++++++++++++
>  4 files changed, 32 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/setup.h b/arch/arm64/include/asm/setup.h
> index 5f147a418281..6437df661700 100644
> --- a/arch/arm64/include/asm/setup.h
> +++ b/arch/arm64/include/asm/setup.h
> @@ -5,6 +5,9 @@
>  
>  #include <uapi/asm/setup.h>
>  
> +void *get_early_fdt_ptr(void);
> +void early_fdt_map(u64 dt_phys);
> +
>  /*
>   * These two variables are used in the head.S file.
>   */
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 29d641290293..cefe6a73ee54 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -456,8 +456,9 @@ SYM_FUNC_START_LOCAL(__primary_switched)
>  #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
>  	bl	kasan_early_init
>  #endif
> -	mov	x0, x22				// pass FDT address in x0
> -	mov	x1, x20				// pass the full boot status
> +	mov	x0, x21				// pass FDT address in x0
> +	bl	early_fdt_map			// Try mapping the FDT early
> +	mov	x0, x20				// pass the full boot status
>  	bl	init_feature_override		// Parse cpu feature overrides
>  	mov	x0, x20
>  	bl	finalise_el2			// Prefer VHE if possible
> diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
> index 42883657f711..1b0542c69738 100644
> --- a/arch/arm64/kernel/idreg-override.c
> +++ b/arch/arm64/kernel/idreg-override.c
> @@ -262,11 +262,16 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
>  	} while (1);
>  }
>  
> -static __init const u8 *get_bootargs_cmdline(const void *fdt)
> +static __init const u8 *get_bootargs_cmdline(void)
>  {
>  	const u8 *prop;
> +	void *fdt;
>  	int node;
>  
> +	fdt = get_early_fdt_ptr();
> +	if (!fdt)
> +		return NULL;
> +
>  	node = fdt_path_offset(fdt, "/chosen");
>  	if (node < 0)
>  		return NULL;
> @@ -278,9 +283,9 @@ static __init const u8 *get_bootargs_cmdline(const void *fdt)
>  	return strlen(prop) ? prop : NULL;
>  }
>  
> -static __init void parse_cmdline(const void *fdt)
> +static __init void parse_cmdline(void)
>  {
> -	const u8 *prop = get_bootargs_cmdline(fdt);
> +	const u8 *prop = get_bootargs_cmdline();
>  
>  	if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
>  		__parse_cmdline(CONFIG_CMDLINE, true);
> @@ -290,9 +295,9 @@ static __init void parse_cmdline(const void *fdt)
>  }
>  
>  /* Keep checkers quiet */
> -void init_feature_override(const void *fdt, u64 boot_status);
> +void init_feature_override(u64 boot_status);
>  
> -asmlinkage void __init init_feature_override(const void *fdt, u64 boot_status)
> +asmlinkage void __init init_feature_override(u64 boot_status)
>  {
>  	int i;
>  
> @@ -305,7 +310,7 @@ asmlinkage void __init init_feature_override(const void *fdt, u64 boot_status)
>  
>  	__boot_status = boot_status;
>  
> -	parse_cmdline(fdt);
> +	parse_cmdline();
>  
>  	for (i = 0; i < ARRAY_SIZE(regs); i++) {
>  		if (regs[i]->override)
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index d0e6c7a291da..fea3223704b6 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -163,6 +163,21 @@ static void __init smp_build_mpidr_hash(void)
>  		pr_warn("Large number of MPIDR hash buckets detected\n");
>  }
>  
> +static void *early_fdt_ptr __initdata;
> +
> +void __init *get_early_fdt_ptr(void)
> +{
> +	return early_fdt_ptr;
> +}
> +
> +asmlinkage void __init early_fdt_map(u64 dt_phys)
> +{
> +	int fdt_size;
> +
> +	early_fixmap_init();
> +	early_fdt_ptr = fixmap_remap_fdt(dt_phys, &fdt_size, PAGE_KERNEL);
> +}
> +
>  static void __init setup_machine_fdt(phys_addr_t dt_phys)
>  {
>  	int size;
> -- 
> 2.30.2
> 

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