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commit 3434518d05f9526400599f4a738c400322f65fcf
Author: Andrew Cooper <andrew.cooper3@citrix.com>
AuthorDate: Fri Mar 15 18:43:53 2024 +0000
Commit: Andrew Cooper <andrew.cooper3@citrix.com>
CommitDate: Thu Apr 11 13:23:08 2024 +0100

xen/virtual-region: Rework how bugframe linkage works

The start/stop1/etc linkage scheme predates struct virtual_region, and as
setup_virtual_regions() shows, it's awkward to express in the new scheme.

Change the linker to provide explicit start/stop symbols for each bugframe
type, and change virtual_region to have a stop pointer rather than a count.

This marginally simplifies both do_bug_frame()s and prepare_payload(), but it
massively simplifies setup_virtual_regions() by allowing the compiler to
initialise the .frame[] array at build time.

virtual_region.c is the only user of the linker symbols, and this is unlikely
to change given the purpose of struct virtual_region, so move their externs
out of bug.h

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Michal Orzel <michal.orzel@amd.com>
---
xen/arch/arm/traps.c | 5 ++---
xen/common/bug.c | 5 ++---
xen/common/livepatch.c | 7 +++----
xen/common/virtual_region.c | 45 ++++++++++++++++++----------------------
xen/include/xen/bug.h | 6 ------
xen/include/xen/virtual_region.h | 3 +--
xen/include/xen/xen.lds.h | 8 ++++++-
7 files changed, 35 insertions(+), 44 deletions(-)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 9cffe7f790..a8039087c8 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1226,10 +1226,9 @@ int do_bug_frame(const struct cpu_user_regs *regs, vaddr_t pc)
for ( id = 0; id < BUGFRAME_NR; id++ )
{
const struct bug_frame *b;
- unsigned int i;

- for ( i = 0, b = region->frame[id].bugs;
- i < region->frame[id].n_bugs; b++, i++ )
+ for ( b = region->frame[id].start;
+ b < region->frame[id].stop; b++ )
{
if ( ((vaddr_t)bug_loc(b)) == pc )
{
diff --git a/xen/common/bug.c b/xen/common/bug.c
index c43e7c4397..b7c5d8fd4d 100644
--- a/xen/common/bug.c
+++ b/xen/common/bug.c
@@ -25,10 +25,9 @@ int do_bug_frame(const struct cpu_user_regs *regs, unsigned long pc)
for ( id = 0; id < BUGFRAME_NR; id++ )
{
const struct bug_frame *b;
- size_t i;

- for ( i = 0, b = region->frame[id].bugs;
- i < region->frame[id].n_bugs; b++, i++ )
+ for ( b = region->frame[id].start;
+ b < region->frame[id].stop; b++ )
{
if ( bug_loc(b) == pc )
{
diff --git a/xen/common/livepatch.c b/xen/common/livepatch.c
index cabfb63911..351a3e0b9a 100644
--- a/xen/common/livepatch.c
+++ b/xen/common/livepatch.c
@@ -804,12 +804,11 @@ static int prepare_payload(struct payload *payload,
if ( !sec )
continue;

- if ( !section_ok(elf, sec, sizeof(*region->frame[i].bugs)) )
+ if ( !section_ok(elf, sec, sizeof(*region->frame[i].start)) )
return -EINVAL;

- region->frame[i].bugs = sec->load_addr;
- region->frame[i].n_bugs = sec->sec->sh_size /
- sizeof(*region->frame[i].bugs);
+ region->frame[i].start = sec->load_addr;
+ region->frame[i].stop = sec->load_addr + sec->sec->sh_size;
}

sec = livepatch_elf_sec_by_name(elf, ".altinstructions");
diff --git a/xen/common/virtual_region.c b/xen/common/virtual_region.c
index 142f21e181..7d8bdeb612 100644
--- a/xen/common/virtual_region.c
+++ b/xen/common/virtual_region.c
@@ -9,12 +9,25 @@
#include <xen/spinlock.h>
#include <xen/virtual_region.h>

+extern const struct bug_frame
+ __start_bug_frames_0[], __stop_bug_frames_0[],
+ __start_bug_frames_1[], __stop_bug_frames_1[],
+ __start_bug_frames_2[], __stop_bug_frames_2[],
+ __start_bug_frames_3[], __stop_bug_frames_3[];
+
static struct virtual_region core = {
.list = LIST_HEAD_INIT(core.list),
.text_start = _stext,
.text_end = _etext,
.rodata_start = _srodata,
.rodata_end = _erodata,
+
+ .frame = {
+ { __start_bug_frames_0, __stop_bug_frames_0 },
+ { __start_bug_frames_1, __stop_bug_frames_1 },
+ { __start_bug_frames_2, __stop_bug_frames_2 },
+ { __start_bug_frames_3, __stop_bug_frames_3 },
+ },
};

/* Becomes irrelevant when __init sections are cleared. */
@@ -22,6 +35,13 @@ static struct virtual_region core_init __initdata = {
.list = LIST_HEAD_INIT(core_init.list),
.text_start = _sinittext,
.text_end = _einittext,
+
+ .frame = {
+ { __start_bug_frames_0, __stop_bug_frames_0 },
+ { __start_bug_frames_1, __stop_bug_frames_1 },
+ { __start_bug_frames_2, __stop_bug_frames_2 },
+ { __start_bug_frames_3, __stop_bug_frames_3 },
+ },
};

/*
@@ -133,31 +153,6 @@ void __init unregister_init_virtual_region(void)
void __init setup_virtual_regions(const struct exception_table_entry *start,
const struct exception_table_entry *end)
{
- size_t sz;
- unsigned int i;
- static const struct bug_frame *const __initconstrel bug_frames[] = {
- __start_bug_frames,
- __stop_bug_frames_0,
- __stop_bug_frames_1,
- __stop_bug_frames_2,
- __stop_bug_frames_3,
- NULL
- };
-
- for ( i = 1; bug_frames[i]; i++ )
- {
- const struct bug_frame *s;
-
- s = bug_frames[i - 1];
- sz = bug_frames[i] - s;
-
- core.frame[i - 1].n_bugs = sz;
- core.frame[i - 1].bugs = s;
-
- core_init.frame[i - 1].n_bugs = sz;
- core_init.frame[i - 1].bugs = s;
- }
-
core_init.ex = core.ex = start;
core_init.ex_end = core.ex_end = end;

diff --git a/xen/include/xen/bug.h b/xen/include/xen/bug.h
index 77fe1e1ba8..99814c4bef 100644
--- a/xen/include/xen/bug.h
+++ b/xen/include/xen/bug.h
@@ -155,12 +155,6 @@ int do_bug_frame(const struct cpu_user_regs *regs, unsigned long pc);

#endif /* CONFIG_GENERIC_BUG_FRAME */

-extern const struct bug_frame __start_bug_frames[],
- __stop_bug_frames_0[],
- __stop_bug_frames_1[],
- __stop_bug_frames_2[],
- __stop_bug_frames_3[];
-
#endif /* !__ASSEMBLY__ */

#endif /* __XEN_BUG_H__ */
diff --git a/xen/include/xen/virtual_region.h b/xen/include/xen/virtual_region.h
index dcdc95ba49..c8a90e3ef2 100644
--- a/xen/include/xen/virtual_region.h
+++ b/xen/include/xen/virtual_region.h
@@ -29,8 +29,7 @@ struct virtual_region
symbols_lookup_t *symbols_lookup;

struct {
- const struct bug_frame *bugs; /* The pointer to array of bug frames. */
- size_t n_bugs; /* The number of them. */
+ const struct bug_frame *start, *stop; /* Pointers to array of bug frames. */
} frame[BUGFRAME_NR];

const struct exception_table_entry *ex;
diff --git a/xen/include/xen/xen.lds.h b/xen/include/xen/xen.lds.h
index 7ab7aa5678..a17810bb28 100644
--- a/xen/include/xen/xen.lds.h
+++ b/xen/include/xen/xen.lds.h
@@ -115,13 +115,19 @@
/* List of constructs other than *_SECTIONS in alphabetical order. */

#define BUGFRAMES \
- __start_bug_frames = .; \
+ __start_bug_frames_0 = .; \
*(.bug_frames.0) \
__stop_bug_frames_0 = .; \
+ \
+ __start_bug_frames_1 = .; \
*(.bug_frames.1) \
__stop_bug_frames_1 = .; \
+ \
+ __start_bug_frames_2 = .; \
*(.bug_frames.2) \
__stop_bug_frames_2 = .; \
+ \
+ __start_bug_frames_3 = .; \
*(.bug_frames.3) \
__stop_bug_frames_3 = .;

--
generated by git-patchbot for /home/xen/git/xen.git#staging