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09 Apr 2020 17:34:01 +0200 Subject: Re: linux-user: keep the name-ending parenthesis in /proc/self/stat To: =?UTF-8?Q?Alex_Benn=c3=a9e?= References: <87wo6oadcc.fsf@linaro.org> From: Brice Goglin Autocrypt: addr=Brice.Goglin@inria.fr; prefer-encrypt=mutual; keydata= mQINBFNg91oBEADMfOyfz9iilNPe1Yy3pheXLf5O/Vpr+gFJoXcjA80bMeSWBf4on8Mt5Fg/ jpVuNBhii0Zyq4Lip1I2ve+WQjfL3ixYQqvNRLgfw/FL0gNHSOe9dVFo0ol0lT+vu3AXOVmh AM4IrsOp2Tmt+w89Oyvu+xwHW54CJX3kXp4c7COz79A6OhbMEPQUreerTavSvYpH5pLY55WX qOSdjmlXD45yobQbMg9rFBy1BECrj4DJSpym/zJMFVnyC5yAq2RdPFRyvYfS0c491adD/iw9 eFZY1XWj+WqLSW8zEejdl78npWOucfin7eAKvov5Bqa1MLGS/2ojVMHXJN0qpStpKcueV5Px igX8i4O4pPT10xCXZ7R6KIGUe1FE0N7MLErLvBF6AjMyiFHix9rBG0pWADgCQUUFjc8YBKng nwIKl39uSpk5W5rXbZ9nF3Gp/uigTBNVvaLO4PIDw9J3svHQwCB31COsUWS1QhoLMIQPdUkk GarScanm8i37Ut9G+nB4nLeDRYpPIVBFXFD/DROIEfLqOXNbGwOjDd5RWuzA0TNzJSeOkH/0 qYr3gywjiE81zALO3UeDj8TaPAv3Dmu7SoI86Bl7qm6UOnSL7KQxZWuMTlU3BF3d+0Ly0qxv k1XRPrL58IyoHIgAVom0uUnLkRKHczdhGDpNzsQDJaO71EPp8QARAQABtCRCcmljZSBHb2ds aW4gPEJyaWNlLkdvZ2xpbkBpbnJpYS5mcj6JAjgEEwECACIFAlNg+aMCGwMGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAAAoJEESRkPMjWr076RoQAJhJ1q5+wlHIf+YvM0N1V1hQyf+aL35+ BPqxlyw4H65eMWIN/63yWhcxrLwNCdgY1WDWGoiW8KVCCHwJAmrXukFvXjsvShLQJavWRgKH eea12T9XtLc6qY/DEi2/rZvjOCKsMjnc1CYW71jbofaQP6lJsmC+RPWrnL/kjZyVrVrg7/Jo GemLmi/Ny7nLAOt6uL0MC/Mwld14Yud57Qz6VTDGSOvpNacbkJtcCwL3KZDBfSDnZtSbeclY srXoMnFXEJJjKJ6kcJrZDYPrNPkgFpSId/WKJ5pZBoRsKH/w2OdxwtXKCYHksMCiI4+4fVFD WlmVNYzW8ZKXjAstLh+xGABkLVXs+0WjvC67iTZBXTmbYJ5eodv8U0dCIR/dxjK9wxVKbIr2 D+UVbGlfqUuh1zzL68YsOg3L0Xc6TQglKVl6RxX87fCU8ycIs9pMbXeRDoJohflo8NUDpljm zqGlZxBjvb40p37ReJ+VfjWqAvVh+6JLaMpeva/2K1Nvr9O/DOkSRNetrd86PslrIwz8yP4l FaeG0dUwdRdnToNz6E8lbTVOwximW+nwEqOZUs1pQNKDejruN7Xnorr7wVBfp6zZmFCcmlw9 8pSMV3p85wg6nqJnBkQNTzlljycBvZLVvqc6hPOSXpXf5tjkuUVWgtbCc8TDEQFx8Phkgda6 K1LNuQINBFNg91oBEADp3vwjw8tQBnNfYJNJMs6AXC8PXB5uApT1pJ0fioaXvifPNL6gzsGt AF53aLeqB7UXuByHr8Bmsz7BvwA06XfXXdyLQP+8Oz3ZnUpw5inDIzLpRbUuAjI+IjUtguIK AkU1rZNdCXMOqEwCaomRitwaiX9H7yiDTKCUaqx8yAuAQWactWDdyFii2FA7IwVlD/GBqMWV weZsMfeWgPumKB3jyElm1RpkzULrtKbu7MToMH2fmWqBtTkRptABkY7VEd8qENKJBZKJGisk Fk6ylp8VzZdwbAtEDDTGK00Vg4PZGiIGbQo8mBqbc63DY+MdyUEksTTu2gTcqZMm/unQUJA8 xB4JrTAyljo/peIt6lsQa4+/eVolfKL1t1C3DY8f4wMoqnZORagnWA2oHsLsYKvcnqzA0QtY IIb1S1YatV+MNMFf3HuN7xr/jWlfdt59quXiOHU3qxIzXJo/OfC3mwNW4zQWJkG233UOf6YE rmrSaTIBTIWF8CxGY9iXPaJGNYSUa6R/VJS09EWeZgRz9Gk3h5AyDrdo5RFN9HNwOj41o0cj eLDF69092Lg5p5isuOqsrlPi5imHKcDtrXS7LacUI6H0c8onWoH9LuW99WznEtFgPJg++TAv f9M2x57Gzl+/nYTB5/Kpl1qdPPC91zUipiKbnF5f8bQpol0WC+ovmQARAQABiQIfBBgBAgAJ BQJTYPdaAhsMAAoJEESRkPMjWr074+0P/iEcN27dx3oBTzoeGEBhZUVQRZ7w4A61H/vW8oO8 IPkZv9kFr5pCfIonmHEbBlg6yfjeHXwF5SF2ywWRKkRsFHpaFWywxqk9HWXu8cGR1pFsrwC3 EdossuVbEFNmhjHvcAo11nJ7JFzPTEnlPjE6OY9tEDwl+kp1WvyXqNk9bosaX8ivikhmhB47 7BA3Kv8uUE7UL6p7CBdqumaOFISi1we5PYE4P/6YcyhQ9Z2wH6ad2PpwAFNBwxSu+xCrVmaD skAwknf6UVPN3bt67sFAaVgotepx6SPhBuH4OSOxVHMDDLMu7W7pJjnSKzMcAyXmdjON05Sz SaILwfceByvHAnvcFh2pXK9U4E/SyWZDJEcGRRt79akzZxls52stJK/2Tsr0vKtZVAwogiaK uSp+m6BRQcVVhTo/Kq3E0tSnsTHFeIO6QFHKJCJv4FRE3Dmtz15lueihUBowsq9Hk+u3UiLo SmrMAZ6KgA4SQxB2p8/M53kNJl92HHc9nc//aCQDi1R71NyhtSx+6PyivoBkuaKYs+S4pHmt sFE+5+pkUNROtm4ExLen4N4OL6Kq85mWGf2f6hd+OWtn8we1mADjDtdnDHuv+3E3cacFJPP/ wFV94ZhqvW4QcyBWcRNFA5roa7vcnu/MsCcBoheR0UdYsOnJoEpSZswvC/BGqJTkA2sf Message-ID: <149b6a99-fa9e-7ba2-6325-3ad1ff151f6c@inria.fr> Date: Thu, 9 Apr 2020 17:34:01 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <87wo6oadcc.fsf@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 192.134.164.83 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Le 09/04/2020 à 17:27, Alex Bennée a écrit : > Brice Goglin writes: > >> When the program name is very long, qemu-user may truncate it in >> /proc/self/stat. However the truncation must keep the ending ") " >> to conform to the proc manpage which says: >> (2) comm %s >> The filename of the executable, in parentheses. This >> is visible whether or not the executable is swapped >> out. >> >> To reproduce: >> $ ln -s /bin/cat >> $ qemu-x86_64 ./ /proc/self/stat >> >> Before the patch, you get: >> 1134631 (0 0 0 0 0 0 0 0 ... >> After the patch: >> 1134631 () 0 0 0 0 0 0 0 0 ... >> >> This fixes an issue with hwloc failing to parse /proc/self/stat >> when Ludovic Courtes was testing it in Guix over qemu-aarch64. >> >> Signed-off-by: Philippe_Mathieu-Daudé >> Signed-off-by: Brice Goglin >> >> diff --git a/linux-user/syscall.c b/linux-user/syscall.c >> --- a/linux-user/syscall.c >> +++ b/linux-user/syscall.c >> @@ -7305,7 +7305,11 @@ static int open_self_stat(void *cpu_env, int fd) >> snprintf(buf, sizeof(buf), "%"PRId64 " ", val); >> } else if (i == 1) { >> /* app name */ >> - snprintf(buf, sizeof(buf), "(%s) ", ts->bprm->argv[0]); >> + char *ptr = buf; >> + >> + *ptr++ = '('; >> + ptr = stpncpy(ptr, ts->bprm->argv[0], sizeof(buf) - 3); >> + strcpy(ptr, ") "); > why not just use a format string: > > snprintf(buf, sizeof(buf), "(%.125s) ", ts->bprm->argv[0]); > Go ahead and apply what you want (maybe 124 instead of 125 because of the ending \0). My commit message above explains how to test things very quickly. I don't use qemu-user or Guix myself, and I can't spend time debugging/testing this further. Thank you Brice