This is a bug that can cause early crashes in configurations 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 is mapped 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, I made these sections page aligned.
Fixes: 060ef9d89d18 ("powerpc32: PAGE_EXEC required for inittext")
Signed-off-by: Ariel Marcovitch <ariel.marcovi...@gmail.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 326e113d2e45..e3a7c90c03f4 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -179,6 +179,11 @@ SECTIONS
#endif
} :text
+ /* .init.text is made RO and .exit.text is not, so we must
+ * ensure these sections reside in separate physical pages.
+ */
+ . = ALIGN(PAGE_SIZE);
+
/* .exit.text is discarded at runtime, not link time,
* to deal with references from __bug_table
*/
@@ -186,6 +191,8 @@ SECTIONS
EXIT_TEXT
}
+ . = ALIGN(PAGE_SIZE);
+
.init.data : AT(ADDR(.init.data) - LOAD_OFFSET) {
INIT_DATA
}
base-commit: 1398820fee515873379809a6415930ad0764b2f6
--
2.17.1
