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From: Eva Kotova <nyandarknessgirl@gmail.com>
To: coelacanthus@outlook.com
Cc: c141028@gmail.com, dramforever@live.com,
	linux-riscv@lists.infradead.org, palmer@dabbelt.com,
	xc-tan@outlook.com
Subject: Re: [PATCH] riscv: mmap with PROT_WRITE but no PROT_READ is invalid
Date: Thu, 6 Oct 2022 22:17:25 +0300	[thread overview]
Message-ID: <a69ee775-e565-3d72-eb5f-8378616694d3@gmail.com> (raw)
In-Reply-To: <PH7PR14MB559464DBDD310E755F5B21E8CEDC9@PH7PR14MB5594.namprd14.prod.outlook.com>

On Tue, 31 May 2022 00:56:52 PDT (-0700), coelacanthus@outlook.com wrote:
 > As mentioned in Table 4.5 in RISC-V spec Volume 2 Section 4.3, write
 > but not read is "Reserved for future use.". For now, they are not valid.
 > In the current code, -wx is marked as invalid, but -w- is not marked
 > as invalid.

This patch breaks OpenJDK/Java on RISC-V, as it tries to create a w-only 
protective page:

#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (mmap) failed to map 4096 bytes for failed to 
allocate memory for PaX check.
# An error report file with more information is saved as:
# /root/hs_err_pid107.log

I bisected to this commit since on Linux 5.19+ java no longer works.
Perhaps some fallback should be implemented, to prevent userspace 
breakage. It is currently documented, that at least on i386 PROT_WRITE 
mappings imply PROT_READ (See man mmap(2) NOTES), this would be a good 
place to start.

Best regards,
Eva

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  parent reply	other threads:[~2022-10-06 19:19 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-31  7:56 [PATCH] riscv: mmap with PROT_WRITE but no PROT_READ is invalid Celeste Liu
2022-07-21 23:19 ` Palmer Dabbelt
2022-10-06 19:17 ` Eva Kotova [this message]
2022-10-06 19:29   ` Conor Dooley
2022-10-11 11:23   ` Heinrich Schuchardt
2022-10-11 11:31     ` Coelacanthus
2022-10-06 19:20 ` Eva Kotova
2022-10-06 19:26   ` Conor Dooley
2022-10-06 19:55     ` Eva Kotova
2022-10-06 20:03       ` Conor Dooley

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