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Content-Language: en-US From: Bagas Sanjaya To: hapter@420blaze.it, mingo@redhat.com Cc: tglx@linutronix.de, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, Andi Kleen , Andrew Morton , Linux Kernel Mailing List , Linux Memory Management List References: In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 95F0020003 X-Stat-Signature: kennwnycd9u8ykrjson1sdpu6r6ywqor X-HE-Tag: 1707706118-777413 X-HE-Meta: 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 gDGeTZrI 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000009, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/12/24 09:43, Bagas Sanjaya wrote: > On Sun, Feb 11, 2024 at 08:52:45AM +0000, hapter@420blaze.it wrote: >> I've found that passing in MAP_32BIT for mmap() will always return an >> address above 0x40000000. The problem seems to lie in > From one gigabyte up? >> arch/x86/kernek/sys_x86_64.c, where the following comment is the only thing >> close to a hint(Line 100): >> >> /* This is usually used needed to map code in small >> model, so it needs to be in the first 31bit. Limit >> it to that. This means we need to move the >> unmapped base down for this case. This can give >> conflicts with the heap, but we assume that glibc >> malloc knows how to fall back to mmap. Give it 1GB >> of playground for now. -AK */ >> >> Unfortunately this does not supply a rationale for starting from 0x40000000, >> which seems very arbitrary, and the git commit has been there since the >> beginning of time (i.e. as far the the git history goes), so the git blame >> has not helped much to clarify it. I was also not able to find who "AK" was. > > That was from commit 717db2f9f36805 ("[PATCH] x86-64 updates for 2.5.54") > in tglx/history.git repo [1], authored by Andi Kleen. Cc'ing him. > [1]: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/arch/x86_64/kernel/sys_x86_64.c?id=717db2f9f36805d85c695771ea7d712812896aa7 -- An old man doll... just what I always wanted! - Clara