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Tue, 31 Oct 2023 05:09:09 -0700 (PDT) X-Google-Smtp-Source: AGHT+IH4NyRx/ZQUpCLnU7TzKh0C9+tR4/ZkgeEh5ewi2aTeOrEAcWeOS1jH0TJk7+Lcz3ofKtGdxA== X-Received: by 2002:a2e:9dd9:0:b0:2c5:2475:f848 with SMTP id x25-20020a2e9dd9000000b002c52475f848mr10086866ljj.15.1698754148709; Tue, 31 Oct 2023 05:09:08 -0700 (PDT) Received: from [10.0.29.1] ([159.148.28.2]) by smtp.gmail.com with ESMTPSA id t5-20020a2e5345000000b002c013211ec7sm180400ljd.100.2023.10.31.05.09.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 31 Oct 2023 05:09:08 -0700 (PDT) Message-ID: Date: Tue, 31 Oct 2023 14:09:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC v2 1/2] riscv: allow resume after exception Content-Language: en-US, de-DE To: Xiang W Cc: Rick Chen , Leo , Sughosh Ganu , Anup Patel , Kautuk Consul , Chanho Park , u-boot@lists.denx.de References: <20231029084533.44607-1-heinrich.schuchardt@canonical.com> <20231029084533.44607-2-heinrich.schuchardt@canonical.com> From: Heinrich Schuchardt In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: u-boot@lists.denx.de X-Mailman-Version: 2.1.39 Precedence: list List-Id: U-Boot discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: u-boot-bounces@lists.denx.de Sender: "U-Boot" X-Virus-Scanned: clamav-milter 0.103.8 at phobos.denx.de X-Virus-Status: Clean On 10/31/23 09:53, Xiang W wrote: > setjmp can be called in set_resume. Unfortunately this is not possible. A longjmp buffer only stores register values and not the stack content. Let's assume that setjmp() is moved into set_resume(): Let a function call set_resume(). The caller's address will be on the stack. Once the set_resume returns and the caller invokes another function the original stack content will be overwritten. When an exception occurs the longjmp will reenter set_resume() with the original stack pointer value pointing to a stack that does not match the original call to set_resume and set_resume will return to a random address. Best regards Heinrich > > Regards, > Xiang W > > Heinrich Schuchardt 于2023年10月29日周日 16:56写道： >> >> If CSRs like seed are readable by S-mode, may not be determinable by >> S-mode. For safe driver probing allow to resume via a longjmp after an >> exception. >> >> Signed-off-by: Heinrich Schuchardt >> --- >> v2: >> new patch >> --- >> arch/riscv/lib/interrupts.c | 13 +++++++++++++ >> include/interrupt.h | 22 ++++++++++++++++++++++ >> 2 files changed, 35 insertions(+) >> create mode 100644 include/interrupt.h >> >> diff --git a/arch/riscv/lib/interrupts.c b/arch/riscv/lib/interrupts.c >> index 02dbcfd423..a26ccc721f 100644 >> --- a/arch/riscv/lib/interrupts.c >> +++ b/arch/riscv/lib/interrupts.c >> @@ -12,6 +12,7 @@ >> #include >> #include >> #include >> +#include >> #include >> #include >> #include >> @@ -21,6 +22,13 @@ >> >> DECLARE_GLOBAL_DATA_PTR; >> >> +static struct resume_data *resume; >> + >> +void set_resume(struct resume_data *data) >> +{ >> + resume = data; >> +} >> + >> static void show_efi_loaded_images(uintptr_t epc) >> { >> efi_print_image_infos((void *)epc); >> @@ -105,6 +113,11 @@ static void _exit_trap(ulong code, ulong epc, ulong tval, struct pt_regs *regs) >> "Store/AMO page fault", >> }; >> >> + if (resume) { >> + resume->code = code; >> + longjmp(resume->jump, 1); >> + } >> + >> if (code < ARRAY_SIZE(exception_code)) >> printf("Unhandled exception: %s\n", exception_code[code]); >> else >> diff --git a/include/interrupt.h b/include/interrupt.h >> new file mode 100644 >> index 0000000000..1baa60bcf2 >> --- /dev/null >> +++ b/include/interrupt.h >> @@ -0,0 +1,22 @@ >> +/* SPDX-License-Identifier: GPL-2.0-or-later */ >> + >> +#include >> + >> +/** >> + * struct resume_data - data for resume after interrupt >> + */ >> +struct resume_data { >> + /** @jump: longjmp buffer */ >> + jmp_buf jump; >> + /** @code: exception code */ >> + ulong code; >> +}; >> + >> +/** >> + * set_resume() - set longjmp buffer for resuming after interrupt >> + * >> + * When resuming the exception code will be returned in @data->code. >> + * >> + * @data: pointer to structure with longjmp address >> + */ >> +void set_resume(struct resume_data *data); >> -- >> 2.40.1 >>