Re: [PATCH v2] powerpc: fix alignment bug whithin the init sections
From: Christophe Leroy <hidden>
Date: 2021-01-11 07:07:02
Also in:
lkml
Le 02/01/2021 à 21:11, Ariel Marcovitch a écrit :
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 <redacted>Reviewed-by: Christophe Leroy <redacted>
quoted hunk ↗ jump to hunk
--- 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