Re: [PATCH 2/3] arm64: module: Use module_init_layout_section() to spot init sections

From: Catalin Marinas <catalin.marinas@arm.com>
To: James Morse <james.morse@arm.com>
Cc: linux-modules@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Luis Chamberlain <mcgrof@kernel.org>,
	Will Deacon <will@kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	Russell King <rmk+kernel@armlinux.org.uk>,
	Jessica Yu <jeyu@kernel.org>,
	Adam Johnston <adam.johnston@arm.com>
Subject: Re: [PATCH 2/3] arm64: module: Use module_init_layout_section() to spot init sections
Date: Wed, 2 Aug 2023 18:00:40 +0100	[thread overview]
Message-ID: <ZMqLuE9jSPi+RbGd@arm.com> (raw)
In-Reply-To: <20230801145409.8935-3-james.morse@arm.com>

On Tue, Aug 01, 2023 at 02:54:08PM +0000, James Morse wrote:
> Today module_frob_arch_sections() spots init sections from their
> 'init' prefix, and uses this to keep the init PLTs separate from the rest.
> 
> module_emit_plt_entry() uses within_module_init() to determine if a
> location is in the init text or not, but this depends on whether
> core code thought this was an init section.
> 
> Naturally the logic is different.
> 
> module_init_layout_section() groups the init and exit text together if
> module unloading is disabled, as the exit code will never run. The result
> is kernels with this configuration can't load all their modules because
> there are not enough PLTs for the combined init+exit section.
> 
> This results in the following:
> | WARNING: CPU: 2 PID: 51 at arch/arm64/kernel/module-plts.c:99 module_emit_plt_entry+0x184/0x1cc
> | Modules linked in: crct10dif_common
> | CPU: 2 PID: 51 Comm: modprobe Not tainted 6.5.0-rc4-yocto-standard-dirty #15208
> | Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
> | pstate: 20400005 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> | pc : module_emit_plt_entry+0x184/0x1cc
> | lr : module_emit_plt_entry+0x94/0x1cc
> | sp : ffffffc0803bba60
> [...]
> | Call trace:
> |  module_emit_plt_entry+0x184/0x1cc
> |  apply_relocate_add+0x2bc/0x8e4
> |  load_module+0xe34/0x1bd4
> |  init_module_from_file+0x84/0xc0
> |  __arm64_sys_finit_module+0x1b8/0x27c
> |  invoke_syscall.constprop.0+0x5c/0x104
> |  do_el0_svc+0x58/0x160
> |  el0_svc+0x38/0x110
> |  el0t_64_sync_handler+0xc0/0xc4
> |  el0t_64_sync+0x190/0x194
> 
> A previous patch exposed module_init_layout_section(), use that so the
> logic is the same.
> 
> Reported-by: Adam Johnston <adam.johnston@arm.com>
> Tested-by: Adam Johnston <adam.johnston@arm.com>
> Fixes: 055f23b74b20 ("module: check for exit sections in layout_sections() instead of module_init_section()")
> Cc: <stable@vger.kernel.org> # 5.15.x: 60a0aab7463ee69 arm64: module-plts: inline linux/moduleloader.h
> Cc: <stable@vger.kernel.org> # 5.15.x
> Signed-off-by: James Morse <james.morse@arm.com>

Acked-by: Catalin Marinas <catalin.marinas@arm.com>