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[174.21.72.5]) by smtp.gmail.com with ESMTPSA id gb10-20020a056a00628a00b006e6ae26625asm1581948pfb.68.2024.04.11.13.31.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Apr 2024 13:31:58 -0700 (PDT) Message-ID: <40d41dde-6fb6-4667-9761-e15c52f9d5b1@linaro.org> Date: Thu, 11 Apr 2024 13:31:56 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 04/13] hw/mips/malta: Add re-usable rng_seed_hex_new() method From: Richard Henderson To: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org Cc: qemu-arm@nongnu.org, qemu-block@nongnu.org, qemu-ppc@nongnu.org, Aurelien Jarno , Jiaxun Yang References: <20240411101550.99392-1-philmd@linaro.org> <20240411101550.99392-5-philmd@linaro.org> <89453f6f-1ffe-4141-a8aa-fde7319f3e17@linaro.org> Content-Language: en-US In-Reply-To: <89453f6f-1ffe-4141-a8aa-fde7319f3e17@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::42a; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x42a.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 4/11/24 13:07, Richard Henderson wrote: > On 4/11/24 03:15, Philippe Mathieu-Daudé wrote: >> Extract common code from reinitialize_rng_seed() and >> load_kernel() to rng_seed_hex_new(). >> >> Signed-off-by: Philippe Mathieu-Daudé >> --- >>   hw/mips/malta.c | 20 ++++++++++++-------- >>   1 file changed, 12 insertions(+), 8 deletions(-) >> >> diff --git a/hw/mips/malta.c b/hw/mips/malta.c >> index af74008c82..9fc6a7d313 100644 >> --- a/hw/mips/malta.c >> +++ b/hw/mips/malta.c >> @@ -850,15 +850,24 @@ static void G_GNUC_PRINTF(3, 4) prom_set(uint32_t *prom_buf, int >> index, >>       va_end(ap); >>   } >> -static void reinitialize_rng_seed(void *opaque) >> +static char *rng_seed_hex_new(void) >>   { >> -    char *rng_seed_hex = opaque; >>       uint8_t rng_seed[32]; >> +    char rng_seed_hex[sizeof(rng_seed) * 2 + 1]; >>       qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed)); >>       for (size_t i = 0; i < sizeof(rng_seed); ++i) { >>           sprintf(rng_seed_hex + i * 2, "%02x", rng_seed[i]); >>       } >> + >> +    return g_strdup(rng_seed_hex); >> +} >> + >> +static void reinitialize_rng_seed(void *opaque) >> +{ >> +    g_autofree char *rng_seed_hex = rng_seed_hex_new(); >> + >> +    strcpy(opaque, rng_seed_hex); >>   } > > Though it isn't deprecated, strcpy isn't really any safer than sprintf. > We don't need to be copying text around quite as much as this. > > How about: > > #define RNG_SEED_SIZE 32 > > static void rng_seed_hex_new(char buf[2 * RNG_SEED_SIZE + 1]) > { >     static const char hex = "0123456789abcdef"; >     uint8_t rng_seed[RNG_SEED_SIZE]; > >     qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed)); >     for (int i = 0; i < RNG_SEED_SIZE; ++i) { >         buf[i * 2 + 0] = hex[rng_seed[i] / 16]; >         buf[i * 2 + 1] = hex[rng_seed[i] % 16]; Hmm. Maybe a static inline char hexdump_nibble(unsigned val) { return (val < 10 ? '0' : 'a') + val; } static inline void hexdump_byte(char *out, uint8_t byte) { out[0] = hexdump_nibble(byte >> 4); out[1] = hexdump_nibble(byte & 15); } in "qemu/cutils.h", for use elsewhere including util/hexdump.c. r~