This is a note to let you know that I've just added the patch titled
x86/mm: Simplify RESERVE_BRK()
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-mm-simplify-reserve_brk.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a210bdbea666487df5665a541554374bdfa9833a Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Date: Fri, 6 May 2022 14:14:32 +0200
Subject: x86/mm: Simplify RESERVE_BRK()
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
commit a1e2c031ec3949b8c039b739c0b5bf9c30007b00 upstream.
RESERVE_BRK() reserves data in the .brk_reservation section. The data
is initialized to zero, like BSS, so the macro specifies 'nobits' to
prevent the data from taking up space in the vmlinux binary. The only
way to get the compiler to do that (without putting the variable in .bss
proper) is to use inline asm.
The macro also has a hack which encloses the inline asm in a discarded
function, which allows the size to be passed (global inline asm doesn't
allow inputs).
Remove the need for the discarded function hack by just stringifying the
size rather than supplying it as an input to the inline asm.
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lore.kernel.org/r/20220506121631.133110232@xxxxxxxxxxxxx
[nathan: Fix conflict due to lack of 2b6ff7dea670 and 33def8498fdd]
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/setup.h | 30 +++++++++++-------------------
1 file changed, 11 insertions(+), 19 deletions(-)
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -91,27 +91,19 @@ extern unsigned long _brk_end;
void *extend_brk(size_t size, size_t align);
/*
- * Reserve space in the brk section. The name must be unique within
- * the file, and somewhat descriptive. The size is in bytes. Must be
- * used at file scope.
+ * Reserve space in the brk section. The name must be unique within the file,
+ * and somewhat descriptive. The size is in bytes.
*
- * (This uses a temp function to wrap the asm so we can pass it the
- * size parameter; otherwise we wouldn't be able to. We can't use a
- * "section" attribute on a normal variable because it always ends up
- * being @progbits, which ends up allocating space in the vmlinux
- * executable.)
+ * The allocation is done using inline asm (rather than using a section
+ * attribute on a normal variable) in order to allow the use of @nobits, so
+ * that it doesn't take up any space in the vmlinux file.
*/
-#define RESERVE_BRK(name,sz) \
- static void __section(.discard.text) __used notrace \
- __brk_reservation_fn_##name##__(void) { \
- asm volatile ( \
- ".pushsection .brk_reservation,\"aw\",@nobits;" \
- ".brk." #name ":" \
- " 1:.skip %c0;" \
- " .size .brk." #name ", . - 1b;" \
- " .popsection" \
- : : "i" (sz)); \
- }
+#define RESERVE_BRK(name, size) \
+ asm(".pushsection .brk_reservation,\"aw\",@nobits\n\t" \
+ ".brk." #name ":\n\t" \
+ ".skip " __stringify(size) "\n\t" \
+ ".size .brk." #name ", " __stringify(size) "\n\t" \
+ ".popsection\n\t")
/* Helper for reserving space for arrays of things */
#define RESERVE_BRK_ARRAY(type, name, entries) \
Patches currently in stable-queue which might be from jpoimboe@xxxxxxxxxx are
queue-4.19/x86-mm-simplify-reserve_brk.patch
