From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751396AbdBAT21 (ORCPT ); Wed, 1 Feb 2017 14:28:27 -0500 Received: from mail-it0-f49.google.com ([209.85.214.49]:36344 "EHLO mail-it0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750926AbdBAT20 (ORCPT ); Wed, 1 Feb 2017 14:28:26 -0500 MIME-Version: 1.0 In-Reply-To: <20170201190341.GA1060@gmail.com> References: <1485971102-23330-1-git-send-email-ard.biesheuvel@linaro.org> <1485971102-23330-2-git-send-email-ard.biesheuvel@linaro.org> <20170201190341.GA1060@gmail.com> From: Ard Biesheuvel Date: Wed, 1 Feb 2017 19:28:24 +0000 Message-ID: Subject: Re: [PATCH] efi: fdt: avoid FDT manipulation after ExitBootServices() To: Ingo Molnar Cc: Leif Lindholm , Mark Rutland , Thomas Gleixner , "H . Peter Anvin" , "linux-arm-kernel@lists.infradead.org" , Riku Voipio , Matt Fleming , "linux-kernel@vger.kernel.org" , "linux-efi@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1 February 2017 at 19:03, Ingo Molnar wrote: > > * Ard Biesheuvel wrote: > >> Some AArch64 UEFI implementations disable the MMU in ExitBootServices(), >> after which unaligned accesses to RAM are no longer supported. >> >> Commit abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the >> kernel") fixed an issue in the memory map handling of the stub FDT code, >> but inadvertently created an issue with such firmwares, by moving some >> of the FDT manipulation to after the invocation of ExitBootServices(). >> Given that the stub's libfdt implementation uses the ordinary, accelerated >> string functions, which rely on hardware handling of unaligned accesses, >> manipulating the FDT with the MMU off may result in alignment faults. >> >> So fix the situation by moving the update_fdt_memmap() call into the >> callback function invoked by efi_exit_boot_services() right before it >> calls the ExitBootServices() UEFI service (which is arguably a better >> place for it anyway) >> >> Note that disabling the MMU in ExitBootServices() is not compliant with >> the UEFI spec, and carries great risk due to the fact that switching from >> cached to uncached memory accesses halfway through compiler generated code >> (i.e., involving a stack) can never be done in a way that is architecturally >> safe. >> >> Cc: >> Fixes: abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the kernel") >> Tested-by: Riku Voipio >> Signed-off-by: Ard Biesheuvel >> --- >> drivers/firmware/efi/libstub/fdt.c | 14 +++----------- >> 1 file changed, 3 insertions(+), 11 deletions(-) >> >> diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c >> index 921dfa047202..260c4b4b492e 100644 >> --- a/drivers/firmware/efi/libstub/fdt.c >> +++ b/drivers/firmware/efi/libstub/fdt.c >> @@ -187,6 +187,7 @@ static efi_status_t update_fdt_memmap(void *fdt, struct efi_boot_memmap *map) >> struct exit_boot_struct { >> efi_memory_desc_t *runtime_map; >> int *runtime_entry_count; >> + void *new_fdt_addr; >> }; >> >> static efi_status_t exit_boot_func(efi_system_table_t *sys_table_arg, >> @@ -202,7 +203,7 @@ static efi_status_t exit_boot_func(efi_system_table_t *sys_table_arg, >> efi_get_virtmap(*map->map, *map->map_size, *map->desc_size, >> p->runtime_map, p->runtime_entry_count); >> >> - return EFI_SUCCESS; >> + return update_fdt_memmap(p->new_fdt_addr, map); >> } >> >> /* >> @@ -300,22 +301,13 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table, >> >> priv.runtime_map = runtime_map; >> priv.runtime_entry_count = &runtime_entry_count; >> + priv.new_fdt_addr = (void *)*new_fdt_addr; > > Nit: could the type cast by dropped? > new_fdt_addr is a pointer to unsigned long, so we can't drop the cast here without introducing it somewhere else. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ard Biesheuvel Subject: Re: [PATCH] efi: fdt: avoid FDT manipulation after ExitBootServices() Date: Wed, 1 Feb 2017 19:28:24 +0000 Message-ID: References: <1485971102-23330-1-git-send-email-ard.biesheuvel@linaro.org> <1485971102-23330-2-git-send-email-ard.biesheuvel@linaro.org> <20170201190341.GA1060@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <20170201190341.GA1060-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ingo Molnar Cc: Leif Lindholm , Mark Rutland , Thomas Gleixner , "H . Peter Anvin" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , Riku Voipio , Matt Fleming , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-efi@vger.kernel.org On 1 February 2017 at 19:03, Ingo Molnar wrote: > > * Ard Biesheuvel wrote: > >> Some AArch64 UEFI implementations disable the MMU in ExitBootServices(), >> after which unaligned accesses to RAM are no longer supported. >> >> Commit abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the >> kernel") fixed an issue in the memory map handling of the stub FDT code, >> but inadvertently created an issue with such firmwares, by moving some >> of the FDT manipulation to after the invocation of ExitBootServices(). >> Given that the stub's libfdt implementation uses the ordinary, accelerated >> string functions, which rely on hardware handling of unaligned accesses, >> manipulating the FDT with the MMU off may result in alignment faults. >> >> So fix the situation by moving the update_fdt_memmap() call into the >> callback function invoked by efi_exit_boot_services() right before it >> calls the ExitBootServices() UEFI service (which is arguably a better >> place for it anyway) >> >> Note that disabling the MMU in ExitBootServices() is not compliant with >> the UEFI spec, and carries great risk due to the fact that switching from >> cached to uncached memory accesses halfway through compiler generated code >> (i.e., involving a stack) can never be done in a way that is architecturally >> safe. >> >> Cc: >> Fixes: abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the kernel") >> Tested-by: Riku Voipio >> Signed-off-by: Ard Biesheuvel >> --- >> drivers/firmware/efi/libstub/fdt.c | 14 +++----------- >> 1 file changed, 3 insertions(+), 11 deletions(-) >> >> diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c >> index 921dfa047202..260c4b4b492e 100644 >> --- a/drivers/firmware/efi/libstub/fdt.c >> +++ b/drivers/firmware/efi/libstub/fdt.c >> @@ -187,6 +187,7 @@ static efi_status_t update_fdt_memmap(void *fdt, struct efi_boot_memmap *map) >> struct exit_boot_struct { >> efi_memory_desc_t *runtime_map; >> int *runtime_entry_count; >> + void *new_fdt_addr; >> }; >> >> static efi_status_t exit_boot_func(efi_system_table_t *sys_table_arg, >> @@ -202,7 +203,7 @@ static efi_status_t exit_boot_func(efi_system_table_t *sys_table_arg, >> efi_get_virtmap(*map->map, *map->map_size, *map->desc_size, >> p->runtime_map, p->runtime_entry_count); >> >> - return EFI_SUCCESS; >> + return update_fdt_memmap(p->new_fdt_addr, map); >> } >> >> /* >> @@ -300,22 +301,13 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table, >> >> priv.runtime_map = runtime_map; >> priv.runtime_entry_count = &runtime_entry_count; >> + priv.new_fdt_addr = (void *)*new_fdt_addr; > > Nit: could the type cast by dropped? > new_fdt_addr is a pointer to unsigned long, so we can't drop the cast here without introducing it somewhere else. From mboxrd@z Thu Jan 1 00:00:00 1970 From: ard.biesheuvel@linaro.org (Ard Biesheuvel) Date: Wed, 1 Feb 2017 19:28:24 +0000 Subject: [PATCH] efi: fdt: avoid FDT manipulation after ExitBootServices() In-Reply-To: <20170201190341.GA1060@gmail.com> References: <1485971102-23330-1-git-send-email-ard.biesheuvel@linaro.org> <1485971102-23330-2-git-send-email-ard.biesheuvel@linaro.org> <20170201190341.GA1060@gmail.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 1 February 2017 at 19:03, Ingo Molnar wrote: > > * Ard Biesheuvel wrote: > >> Some AArch64 UEFI implementations disable the MMU in ExitBootServices(), >> after which unaligned accesses to RAM are no longer supported. >> >> Commit abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the >> kernel") fixed an issue in the memory map handling of the stub FDT code, >> but inadvertently created an issue with such firmwares, by moving some >> of the FDT manipulation to after the invocation of ExitBootServices(). >> Given that the stub's libfdt implementation uses the ordinary, accelerated >> string functions, which rely on hardware handling of unaligned accesses, >> manipulating the FDT with the MMU off may result in alignment faults. >> >> So fix the situation by moving the update_fdt_memmap() call into the >> callback function invoked by efi_exit_boot_services() right before it >> calls the ExitBootServices() UEFI service (which is arguably a better >> place for it anyway) >> >> Note that disabling the MMU in ExitBootServices() is not compliant with >> the UEFI spec, and carries great risk due to the fact that switching from >> cached to uncached memory accesses halfway through compiler generated code >> (i.e., involving a stack) can never be done in a way that is architecturally >> safe. >> >> Cc: >> Fixes: abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the kernel") >> Tested-by: Riku Voipio >> Signed-off-by: Ard Biesheuvel >> --- >> drivers/firmware/efi/libstub/fdt.c | 14 +++----------- >> 1 file changed, 3 insertions(+), 11 deletions(-) >> >> diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c >> index 921dfa047202..260c4b4b492e 100644 >> --- a/drivers/firmware/efi/libstub/fdt.c >> +++ b/drivers/firmware/efi/libstub/fdt.c >> @@ -187,6 +187,7 @@ static efi_status_t update_fdt_memmap(void *fdt, struct efi_boot_memmap *map) >> struct exit_boot_struct { >> efi_memory_desc_t *runtime_map; >> int *runtime_entry_count; >> + void *new_fdt_addr; >> }; >> >> static efi_status_t exit_boot_func(efi_system_table_t *sys_table_arg, >> @@ -202,7 +203,7 @@ static efi_status_t exit_boot_func(efi_system_table_t *sys_table_arg, >> efi_get_virtmap(*map->map, *map->map_size, *map->desc_size, >> p->runtime_map, p->runtime_entry_count); >> >> - return EFI_SUCCESS; >> + return update_fdt_memmap(p->new_fdt_addr, map); >> } >> >> /* >> @@ -300,22 +301,13 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table, >> >> priv.runtime_map = runtime_map; >> priv.runtime_entry_count = &runtime_entry_count; >> + priv.new_fdt_addr = (void *)*new_fdt_addr; > > Nit: could the type cast by dropped? > new_fdt_addr is a pointer to unsigned long, so we can't drop the cast here without introducing it somewhere else.