Messages in this thread Patch in this message | | | Date | Thu, 5 Mar 2020 10:39:39 -0800 | Subject | [PATCH] um: Fix overlapping ELF segments when statically linked | From | David Gow <> |
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When statically linked, the .text section in UML kernels is not page aligned, causing it to share a page with the executable headers. As .text and the executable headers have different permissions, this causes the kernel to wish to map the same page twice (once as headers with r-- permissions, once as .text with r-x permissions), causing a segfault, and a nasty message printed to the host kernel's dmesg:
"Uhuuh, elf segment at 0000000060000000 requested but the memory is mapped already"
By aligning the .text to a page boundary (as in the dynamically linked version in dyn.lds.S), there is no such overlap, and the kernel runs correctly.
Signed-off-by: David Gow <davidgow@google.com> --- I'm not 100% sure what triggered this -- possibly a change to the host kernel on my machine -- as I'm able to reproduce the issue as far back as in 4.4, but it seems to be reproducible easily on my machine with defconfig + CONFIG_STATIC_LINK=y.
arch/um/kernel/uml.lds.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/um/kernel/uml.lds.S b/arch/um/kernel/uml.lds.S index 9f21443be2c9..3b6dab3d4501 100644 --- a/arch/um/kernel/uml.lds.S +++ b/arch/um/kernel/uml.lds.S @@ -19,10 +19,10 @@ SECTIONS __binary_start = START; . = START + SIZEOF_HEADERS; + . = ALIGN(PAGE_SIZE); _text = .; INIT_TEXT_SECTION(0) - . = ALIGN(PAGE_SIZE); .text : { -- 2.25.0.265.gbab2e86ba0-goog
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