From 6569580de7ae367def89b7671029cb97c1965574 Mon Sep 17 00:00:00 2001 From: Vivek Goyal Date: Thu, 7 Dec 2006 02:14:03 +0100 Subject: [PATCH] i386: Distinguish absolute symbols Ld knows about 2 kinds of symbols, absolute and section relative. Section relative symbols symbols change value when a section is moved and absolute symbols do not. Currently in the linker script we have several labels marking the beginning and ending of sections that are outside of sections, making them absolute symbols. Having a mixture of absolute and section relative symbols refereing to the same data is currently harmless but it is confusing. This must be done carefully as newer revs of ld do not place symbols that appear in sections without data and instead ld makes those symbols global :( My ultimate goal is to build a relocatable kernel. The safest and least intrusive technique is to generate relocation entries so the kernel can be relocated at load time. The only penalty would be an increase in the size of the kernel binary. The problem is that if absolute and relocatable symbols are not properly specified absolute symbols will be relocated or section relative symbols won't be, which is fatal. The practical motivation is that when generating kernels that will run from a reserved area for analyzing what caused a kernel panic, it is simpler if you don't need to hard code the physical memory location they will run at, especially for the distributions. [AK: and merged:] o Also put a message so that in future people can be aware of it and avoid introducing absolute symbols. Signed-off-by: Eric W. Biederman Signed-off-by: Vivek Goyal Signed-off-by: Andi Kleen --- include/asm-generic/vmlinux.lds.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'include/asm-generic') diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index e60d6f21fa6..9f4747780da 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -11,8 +11,8 @@ #define RODATA \ . = ALIGN(4096); \ - __start_rodata = .; \ .rodata : AT(ADDR(.rodata) - LOAD_OFFSET) { \ + VMLINUX_SYMBOL(__start_rodata) = .; \ *(.rodata) *(.rodata.*) \ *(__vermagic) /* Kernel version magic */ \ } \ @@ -119,17 +119,17 @@ *(__ksymtab_strings) \ } \ \ + /* Unwind data binary search table */ \ + EH_FRAME_HDR \ + \ /* Built-in module parameters. */ \ __param : AT(ADDR(__param) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___param) = .; \ *(__param) \ VMLINUX_SYMBOL(__stop___param) = .; \ + VMLINUX_SYMBOL(__end_rodata) = .; \ } \ \ - /* Unwind data binary search table */ \ - EH_FRAME_HDR \ - \ - __end_rodata = .; \ . = ALIGN(4096); #define SECURITY_INIT \ -- cgit v1.2.3 From b65780e123ba9b762276482bbfb52836e4d41fd9 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Thu, 7 Dec 2006 02:14:19 +0100 Subject: [PATCH] unwinder: move .eh_frame to RODATA The .eh_frame section contents is never written to, so it can as well benefit from CONFIG_DEBUG_RODATA. Diff-ed against firstfloor tree. Signed-off-by: Jan Beulich Signed-off-by: Andi Kleen --- include/asm-generic/vmlinux.lds.h | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) (limited to 'include/asm-generic') diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 9f4747780da..4d4c62d1105 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -119,8 +119,7 @@ *(__ksymtab_strings) \ } \ \ - /* Unwind data binary search table */ \ - EH_FRAME_HDR \ + EH_FRAME \ \ /* Built-in module parameters. */ \ __param : AT(ADDR(__param) - LOAD_OFFSET) { \ @@ -162,15 +161,23 @@ VMLINUX_SYMBOL(__kprobes_text_end) = .; #ifdef CONFIG_STACK_UNWIND - /* Unwind data binary search table */ -#define EH_FRAME_HDR \ +#define EH_FRAME \ + /* Unwind data binary search table */ \ + . = ALIGN(8); \ .eh_frame_hdr : AT(ADDR(.eh_frame_hdr) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start_unwind_hdr) = .; \ *(.eh_frame_hdr) \ VMLINUX_SYMBOL(__end_unwind_hdr) = .; \ + } \ + /* Unwind data */ \ + . = ALIGN(8); \ + .eh_frame : AT(ADDR(.eh_frame) - LOAD_OFFSET) { \ + VMLINUX_SYMBOL(__start_unwind) = .; \ + *(.eh_frame) \ + VMLINUX_SYMBOL(__end_unwind) = .; \ } #else -#define EH_FRAME_HDR +#define EH_FRAME #endif /* DWARF debug sections. -- cgit v1.2.3