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Date: Sat, 2 Jan 2021 22:11:56 +0200 From: Ariel Marcovitch <arielmarcovitch@...il.com> To: mpe@...erman.id.au Cc: benh@...nel.crashing.org, paulus@...ba.org, christophe.leroy@...roup.eu, keescook@...omium.org, dja@...ens.net, npiggin@...il.com, naveen.n.rao@...ux.vnet.ibm.com, maskray@...gle.com, ariel.marcovitch@...il.com, oss@...error.net, linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org Subject: [PATCH v2] powerpc: fix alignment bug whithin the init sections This is a bug that causes early crashes in builds with a .exit.text section smaller than a page and a .init.text section that ends in the beginning of a physical page (this is kinda random, which might explain why this wasn't really encountered before). The init sections are ordered like this: .init.text .exit.text .init.data Currently, these sections aren't page aligned. Because the init code might become read-only at runtime and because the .init.text section can potentially reside on the same physical page as .init.data, the beginning of .init.data might be mapped read-only along with .init.text. Then when the kernel tries to modify a variable in .init.data (like kthreadd_done, used in kernel_init()) the kernel panics. To avoid this, make _einittext page aligned and also align .exit.text to make sure .init.data is always seperated from the text segments. Fixes: 060ef9d89d18 ("powerpc32: PAGE_EXEC required for inittext") Signed-off-by: Ariel Marcovitch <ariel.marcovitch@...il.com> --- arch/powerpc/kernel/vmlinux.lds.S | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S index 6db90cdf11da..b6c765d8e7ee 100644 --- a/arch/powerpc/kernel/vmlinux.lds.S +++ b/arch/powerpc/kernel/vmlinux.lds.S @@ -187,6 +187,11 @@ SECTIONS .init.text : AT(ADDR(.init.text) - LOAD_OFFSET) { _sinittext = .; INIT_TEXT + + /* .init.text might be RO so we must + * ensure this section ends in a page boundary. + */ + . = ALIGN(PAGE_SIZE); _einittext = .; #ifdef CONFIG_PPC64 *(.tramp.ftrace.init); @@ -200,6 +205,8 @@ SECTIONS EXIT_TEXT } + . = ALIGN(PAGE_SIZE); + .init.data : AT(ADDR(.init.data) - LOAD_OFFSET) { INIT_DATA } base-commit: 2c85ebc57b3e1817b6ce1a6b703928e113a90442 -- 2.17.1
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