lkml.org 
[lkml]   [2022]   [Jun]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] x86/mm: Fix RESERVE_BRK() for older binutils
Date
With binutils 2.26, RESERVE_BRK() causes a build failure:

/tmp/ccnGOKZ5.s: Assembler messages:
/tmp/ccnGOKZ5.s:98: Error: missing ')'
/tmp/ccnGOKZ5.s:98: Error: missing ')'
/tmp/ccnGOKZ5.s:98: Error: missing ')'
/tmp/ccnGOKZ5.s:98: Error: junk at end of line, first unrecognized
character is `U'

The problem is this line:

RESERVE_BRK(early_pgt_alloc, INIT_PGT_BUF_SIZE)

Specifically, the INIT_PGT_BUF_SIZE macro which (via PAGE_SIZE's use
_AC()) has a "1UL", which makes older versions of the assembler unhappy.
Unfortunately the _AC() macro doesn't work for inline asm.

Fix it (and further simplify RESERVE_BRK) by taking a completely
different approach. Instead of specifying the "nobits" at compile-time,
do so at link-time. Then the variable can just be allocated in C.

Note this changes the name of the variable from .brk.##name to
__brk_##name. The variable names aren't actually used anywhere, so it's
harmless.

Reported-by: Joe Damato <jdamato@fastly.com>
Fixes: a1e2c031ec39 ("x86/mm: Simplify RESERVE_BRK()")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
arch/x86/include/asm/setup.h | 35 +++++++++++++++++------------------
arch/x86/kernel/vmlinux.lds.S | 2 +-
2 files changed, 18 insertions(+), 19 deletions(-)

diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index 7590ac2570b9..ef9bb6caad8c 100644
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -108,19 +108,11 @@ 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.
- *
- * 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.
+ * Reserve space in the .brk section. The size is in bytes.
*/
-#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")
+#define RESERVE_BRK(name, size) \
+ __section(".brk_reservation") __aligned(1) __used \
+ static char __brk_##name[size]

extern void probe_roms(void);
#ifdef __i386__
@@ -133,12 +125,19 @@ asmlinkage void __init x86_64_start_reservations(char *real_mode_data);

#endif /* __i386__ */
#endif /* _SETUP */
-#else
-#define RESERVE_BRK(name,sz) \
- .pushsection .brk_reservation,"aw",@nobits; \
-.brk.name: \
-1: .skip sz; \
- .size .brk.name,.-1b; \
+
+#else /* __ASSEMBLY */
+
+.macro __RESERVE_BRK name, size
+ .pushsection .brk_reservation, "aw"
+SYM_DATA_START(__brk_\name)
+ .skip \size
+SYM_DATA_END(__brk_\name)
.popsection
+.endm
+
+#define RESERVE_BRK(name, size) __RESERVE_BRK name, size
+
#endif /* __ASSEMBLY__ */
+
#endif /* _ASM_X86_SETUP_H */
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index f5f6dc2e8007..9b63f8a00b4f 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -385,7 +385,7 @@ SECTIONS
__end_of_kernel_reserve = .;

. = ALIGN(PAGE_SIZE);
- .brk : AT(ADDR(.brk) - LOAD_OFFSET) {
+ .brk (NOLOAD) : AT(ADDR(.brk) - LOAD_OFFSET) {
__brk_base = .;
. += 64 * 1024; /* 64k alignment slop space */
*(.brk_reservation) /* areas brk users have reserved */
--
2.34.3
\
 
 \ /
  Last update: 2022-06-08 17:45    [W:0.074 / U:0.824 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site