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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2] make use of .startof.() and .sizeof.() assembler expressions
Section start symbols frequently obscure the actual symbol name living
at the start of the section. Eliminate them where they can be replaced
by linker resolved .startof.* symbols. (Section end symbols may have
the same undesirable effect, but they're less easy to eliminate, as
they'd need to be represented by the sum of .startof.<section> and
.sizeof.<section>).
Along those lines use .sizeof.* where section sizes get calculated
from the difference of section and and section start symbols.
Note that this would be nice for the build-id section too, but:
- The generated (by ld) section names differ between ELF and COFF/PE
(ELF: .note.gnu.build-id; COFF/PE[2.26+]: .buildid), yet we compile
version.c just once (and hence can use only either of the necessary
.startof./.sizeof. forms).
- The ELF section name needs to be quoted in the .startof./.sizeof.
expressions, yet that quoting is supported only by gas 2.26+.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v2: Also replace __base_relocs_{start,end}. Comment out linker script
assertion on .bss start alignment.
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -184,10 +184,10 @@ hyp: PRINT("- Xen starting in Hyp mod
bne skip_bss
PRINT("- Zero BSS -\r\n")
- ldr r0, =__bss_start /* Load start & end of bss */
- ldr r1, =__bss_end
+ ldr r0, =.startof.(.bss) /* Load start & size of bss */
+ ldr r1, =.sizeof.(.bss)
add r0, r0, r10 /* Apply physical offset */
- add r1, r1, r10
+ add r1, r1, r0 /* Calculate end of bss */
mov r2, #0
1: str r2, [r0], #4
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -318,10 +318,10 @@ el2: PRINT("- Xen starting at EL2 -\r
cbnz x22, skip_bss
PRINT("- Zero BSS -\r\n")
- ldr x0, =__bss_start /* Load start & end of bss */
- ldr x1, =__bss_end
+ ldr x0, =.startof.(.bss) /* Load start & size of bss */
+ ldr x1, =.sizeof.(.bss)
add x0, x0, x20 /* Apply physical offset */
- add x1, x1, x20
+ add x1, x1, x0 /* Calculate end of .bss */
1: str xzr, [x0], #8
cmp x0, x1
--- a/xen/arch/arm/device.c
+++ b/xen/arch/arm/device.c
@@ -21,8 +21,8 @@
#include <xen/errno.h>
#include <xen/lib.h>
-extern const struct device_desc _sdevice[], _edevice[];
-extern const struct acpi_device_desc _asdevice[], _aedevice[];
+extern const struct device_desc _sdevice[] asm(".startof.(.dev.info)");
+extern const struct device_desc _edevice[];
int __init device_init(struct dt_device_node *dev, enum device_class class,
const void *data)
@@ -51,6 +51,11 @@ int __init device_init(struct dt_device_
return -EBADF;
}
+#ifdef CONFIG_ACPI
+
+extern const struct acpi_device_desc _asdevice[] asm(".startof.(.adev.info)");
+extern const struct acpi_device_desc _aedevice[];
+
int __init acpi_device_init(enum device_class class, const void *data, int
class_type)
{
const struct acpi_device_desc *desc;
@@ -68,6 +73,8 @@ int __init acpi_device_init(enum device_
return -EBADF;
}
+#endif
+
enum device_class device_get_class(const struct dt_device_node *dev)
{
const struct device_desc *desc;
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2058,7 +2058,7 @@ static void __init find_gnttab_region(st
* enough space for a large grant table
*/
kinfo->gnttab_start = __pa(_stext);
- kinfo->gnttab_size = (_etext - _stext) & PAGE_MASK;
+ kinfo->gnttab_size = _sizeof_text & PAGE_MASK;
/* Make sure the grant table will fit in the region */
if ( (kinfo->gnttab_size >> PAGE_SHIFT) < max_grant_frames )
--- a/xen/arch/arm/platform.c
+++ b/xen/arch/arm/platform.c
@@ -22,7 +22,8 @@
#include <xen/init.h>
#include <asm/psci.h>
-extern const struct platform_desc _splatform[], _eplatform[];
+extern const struct platform_desc _splatform[] asm(".startof.(.arch.info)");
+extern const struct platform_desc _eplatform[];
/* Pointer to the current platform description */
static const struct platform_desc *platform;
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -31,7 +31,6 @@ SECTIONS
. = XEN_VIRT_START;
_start = .;
.text : /* XXX should be AT ( XEN_PHYS_START ) */ {
- _stext = .; /* Text section */
*(.text)
*(.text.cold)
*(.text.unlikely)
@@ -42,7 +41,6 @@ SECTIONS
. = ALIGN(PAGE_SIZE);
.rodata : {
- _srodata = .; /* Read-only data */
/* Bug frames table */
__start_bug_frames = .;
*(.bug_frames.0)
@@ -104,21 +102,18 @@ SECTIONS
. = ALIGN(8);
.arch.info : {
- _splatform = .;
*(.arch.info)
_eplatform = .;
} :text
. = ALIGN(8);
.dev.info : {
- _sdevice = .;
*(.dev.info)
_edevice = .;
} :text
. = ALIGN(8);
.adev.info : {
- _asdevice = .;
*(.adev.info)
_aedevice = .;
} :text
@@ -126,7 +121,6 @@ SECTIONS
. = ALIGN(PAGE_SIZE); /* Init code and data */
__init_begin = .;
.init.text : {
- _sinittext = .;
*(.init.text)
_einittext = .;
} :text
@@ -174,7 +168,6 @@ SECTIONS
__init_end = .;
.bss : { /* BSS */
- __bss_start = .;
*(.bss.stack_aligned)
. = ALIGN(PAGE_SIZE);
*(.bss.page_aligned)
@@ -186,7 +179,6 @@ SECTIONS
*(.bss.percpu.read_mostly)
. = ALIGN(SMP_CACHE_BYTES);
__per_cpu_data_end = .;
- __bss_end = .;
} :text
_end = . ;
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -124,9 +124,8 @@ __start:
mov %eax,sym_phys(multiboot_ptr)
/* Initialize BSS (no nasty surprises!) */
- mov $sym_phys(__bss_start),%edi
- mov $sym_phys(__bss_end),%ecx
- sub %edi,%ecx
+ mov $sym_phys(.startof.(.bss)),%edi
+ mov $.sizeof.(.bss),%ecx
xor %eax,%eax
shr $2,%ecx
rep stosl
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -39,13 +39,17 @@ extern const struct pe_base_relocs {
u32 rva;
u32 size;
u16 entries[];
-} __base_relocs_start[], __base_relocs_end[];
+} base_relocs_start[] asm(".startof.(.reloc)");
static void __init efi_arch_relocate_image(unsigned long delta)
{
- const struct pe_base_relocs *base_relocs;
+ const struct pe_base_relocs *base_relocs = base_relocs_start;
+ const struct pe_base_relocs *base_relocs_end = base_relocs;
- for ( base_relocs = __base_relocs_start; base_relocs < __base_relocs_end; )
+ /* Can't do without asm() due to -fPIC. */
+ asm ( "add $.sizeof.(.reloc),%0" : "+g" (base_relocs_end) );
+
+ while ( base_relocs < base_relocs_end )
{
unsigned int i = 0, n;
--- a/xen/arch/x86/efi/mkreloc.c
+++ b/xen/arch/x86/efi/mkreloc.c
@@ -314,9 +314,7 @@ int main(int argc, char *argv[])
}
puts("\t.section .reloc, \"a\", @progbits\n"
- "\t.balign 4\n"
- "\t.globl __base_relocs_start, __base_relocs_end\n"
- "__base_relocs_start:");
+ "\t.balign 4");
for ( i = 0; i < nsec; ++i )
{
@@ -368,8 +366,6 @@ int main(int argc, char *argv[])
diff_sections(NULL, NULL, NULL, 0, 0, 0, 0);
- puts("__base_relocs_end:");
-
close(in1);
close(in2);
--- a/xen/arch/x86/efi/relocs-dummy.S
+++ b/xen/arch/x86/efi/relocs-dummy.S
@@ -2,10 +2,8 @@
.section .reloc, "a", @progbits
.balign 4
-GLOBAL(__base_relocs_start)
.long 0
.long 8
-GLOBAL(__base_relocs_end)
.globl VIRT_START, ALT_START
.equ VIRT_START, XEN_VIRT_START
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -181,7 +181,7 @@ void __init discard_initial_images(void)
initial_images = NULL;
}
-extern char __init_begin[], __init_end[], __bss_start[], __bss_end[];
+extern char __init_begin[], __init_end[], __bss_end[];
static void __init init_idle_domain(void)
{
--- a/xen/arch/x86/tboot.c
+++ b/xen/arch/x86/tboot.c
@@ -48,7 +48,7 @@ static uint64_t __initdata sinit_base, _
#define TXTCR_HEAP_BASE 0x0300
#define TXTCR_HEAP_SIZE 0x0308
-extern char __init_begin[], __bss_start[], __bss_end[];
+extern char __init_begin[];
#define SHA1_SIZE 20
typedef uint8_t sha1_hash_t[SHA1_SIZE];
@@ -376,7 +376,12 @@ void tboot_shutdown(uint32_t shutdown_ty
__pa(&_stext);
/* bss */
g_tboot_shared->mac_regions[2].start = (uint64_t)__pa(&__bss_start);
- g_tboot_shared->mac_regions[2].size = __pa(&__bss_end) -
__pa(&__bss_start);
+#if 0 /* This doesn't work due to -fPIC. */
+ g_tboot_shared->mac_regions[2].size = _sizeof_bss;
+#else
+ asm ( "movl $.sizeof.(.bss),%0"
+ : "=m" (g_tboot_shared->mac_regions[2].size) );
+#endif
/*
* MAC domains and other Xen memory
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -58,7 +58,6 @@ SECTIONS
. = __XEN_VIRT_START + MB(1);
_start = .;
.text : {
- _stext = .; /* Text and read-only data */
*(.text)
*(.text.cold)
*(.text.unlikely)
@@ -77,7 +76,6 @@ SECTIONS
__2M_rodata_start = .; /* Start of 2M superpages, mapped RO. */
.rodata : {
- _srodata = .;
/* Bug frames table */
. = ALIGN(4);
__start_bug_frames = .;
@@ -149,7 +147,6 @@ SECTIONS
. = ALIGN(PAGE_SIZE); /* Init code and data */
__init_begin = .;
.init.text : {
- _sinittext = .;
*(.init.text)
/*
* Here are the replacement instructions. The linker sticks them
@@ -230,7 +227,6 @@ SECTIONS
} :text
.bss : { /* BSS */
- __bss_start = .;
*(.bss.stack_aligned)
*(.bss.page_aligned*)
*(.bss)
@@ -253,7 +249,6 @@ SECTIONS
__2M_rwdata_end = .;
#ifdef EFI
- . = ALIGN(4);
.reloc : {
*(.reloc)
} :text
@@ -323,5 +318,7 @@ ASSERT(IS_ALIGNED(__init_end, PAGE_SIZ
ASSERT(IS_ALIGNED(trampoline_start, 4), "trampoline_start misaligned")
ASSERT(IS_ALIGNED(trampoline_end, 4), "trampoline_end misaligned")
-ASSERT(IS_ALIGNED(__bss_start, 4), "__bss_start misaligned")
+/* This would be nice, but fails with older ld (observed on 2.20).
+ASSERT(IS_ALIGNED(.startof..bss, 4), ".bss misaligned")
+ */
ASSERT(IS_ALIGNED(__bss_end, 4), "__bss_end misaligned")
--- a/xen/include/xen/kernel.h
+++ b/xen/include/xen/kernel.h
@@ -71,24 +71,34 @@ extern char _start[], _end[], start[];
(__p >= _start) && (__p < _end); \
})
-extern char _stext[], _etext[];
+extern const char _stext[] asm(".startof.(.text)");
+extern const char _etext[];
#define is_kernel_text(p) ({ \
char *__p = (char *)(unsigned long)(p); \
(__p >= _stext) && (__p < _etext); \
})
-extern const char _srodata[], _erodata[];
+extern const char _sizeof_text[] asm(".sizeof.(.text)");
+#define _sizeof_text ((unsigned long)_sizeof_text)
+
+extern const char _srodata[] asm(".startof.(.rodata)");
+extern const char _erodata[];
#define is_kernel_rodata(p) ({ \
const char *__p = (const char *)(unsigned long)(p); \
(__p >= _srodata) && (__p < _erodata); \
})
-extern char _sinittext[], _einittext[];
+extern const char _sinittext[] asm(".startof.(.init.text)");
+extern const char _einittext[];
#define is_kernel_inittext(p) ({ \
char *__p = (char *)(unsigned long)(p); \
(__p >= _sinittext) && (__p < _einittext); \
})
+extern char __bss_start[] asm(".startof.(.bss)");
+extern const char _sizeof_bss[] asm(".sizeof.(.bss)");
+#define _sizeof_bss ((unsigned long)_sizeof_bss)
+
extern enum system_state {
SYS_STATE_early_boot,
SYS_STATE_boot,
--- a/xen/tools/symbols.c
+++ b/xen/tools/symbols.c
@@ -143,11 +143,12 @@ static int read_symbol(FILE *in, struct
sym++;
/* Ignore most absolute/undefined (?) symbols. */
- if (strcmp(sym, "_stext") == 0)
+ if (strcmp(sym, "_stext") == 0 || strcmp(sym, ".startof..text") == 0)
_stext = s->addr;
else if (strcmp(sym, "_etext") == 0)
_etext = s->addr;
- else if (strcmp(sym, "_sinittext") == 0)
+ else if (strcmp(sym, "_sinittext") == 0 ||
+ strcmp(sym, ".startof..init.text") == 0)
_sinittext = s->addr;
else if (strcmp(sym, "_einittext") == 0)
_einittext = s->addr;
@@ -168,6 +169,9 @@ static int read_symbol(FILE *in, struct
/* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
else if (str[0] == '$')
goto skip_tail;
+ /* Also strip .startof. symbols. */
+ if (strncmp(sym, ".startof.", 9) == 0)
+ goto skip_tail;
/* include the type field in the symbol name, so that it gets
* compressed together */
Attachment:
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