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Message-ID: <173961699799.10177.2391674818298498916.tip-bot2@tip-bot2>
Date: Sat, 15 Feb 2025 10:56:37 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>,
Sami Tolvanen <samitolvanen@...gle.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/core] x86/alternative: Simplify callthunk patching
The following commit has been merged into the x86/core branch of tip:
Commit-ID: ab9fea59487d8b5149a323e2092b7c0f53994dd5
Gitweb: https://git.kernel.org/tip/ab9fea59487d8b5149a323e2092b7c0f53994dd5
Author: Peter Zijlstra <peterz@...radead.org>
AuthorDate: Fri, 07 Feb 2025 13:15:35 +01:00
Committer: Peter Zijlstra <peterz@...radead.org>
CommitterDate: Fri, 14 Feb 2025 10:32:06 +01:00
x86/alternative: Simplify callthunk patching
Now that paravirt call patching is implemented using alternatives, it
is possible to avoid having to patch the alternative sites by
including the altinstr_replacement calls in the call_sites list.
This means we're now stacking relative adjustments like so:
callthunks_patch_builtin_calls():
patches all function calls to target: func() -> func()-10
since the CALL accounting lives in the CALL_PADDING.
This explicitly includes .altinstr_replacement
alt_replace_call():
patches: x86_BUG() -> target()
this patching is done in a relative manner, and will preserve
the above adjustment, meaning that with calldepth patching it
will do: x86_BUG()-10 -> target()-10
apply_relocation():
does code relocation, and adjusts all RIP-relative instructions
to the new location, also in a relative manner.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Sami Tolvanen <samitolvanen@...gle.com>
Link: https://lore.kernel.org/r/20250207122546.617187089@infradead.org
---
arch/x86/include/asm/alternative.h | 1 -
arch/x86/kernel/alternative.c | 8 ++++----
arch/x86/kernel/callthunks.c | 13 -------------
arch/x86/kernel/module.c | 17 ++++++-----------
tools/objtool/arch/x86/decode.c | 1 +
tools/objtool/check.c | 12 ++----------
6 files changed, 13 insertions(+), 39 deletions(-)
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index a214166..853fbcf 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -100,7 +100,6 @@ struct module;
struct callthunk_sites {
s32 *call_start, *call_end;
- struct alt_instr *alt_start, *alt_end;
};
#ifdef CONFIG_CALL_THUNKS
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index e914a65..fda11df 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1705,14 +1705,14 @@ void __init alternative_instructions(void)
apply_retpolines(__retpoline_sites, __retpoline_sites_end);
apply_returns(__return_sites, __return_sites_end);
- apply_alternatives(__alt_instructions, __alt_instructions_end);
-
/*
- * Now all calls are established. Apply the call thunks if
- * required.
+ * Adjust all CALL instructions to point to func()-10, including
+ * those in .altinstr_replacement.
*/
callthunks_patch_builtin_calls();
+ apply_alternatives(__alt_instructions, __alt_instructions_end);
+
/*
* Seal all functions that do not have their address taken.
*/
diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c
index 8418a89..25ae542 100644
--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -240,21 +240,10 @@ patch_call_sites(s32 *start, s32 *end, const struct core_text *ct)
}
static __init_or_module void
-patch_alt_call_sites(struct alt_instr *start, struct alt_instr *end,
- const struct core_text *ct)
-{
- struct alt_instr *a;
-
- for (a = start; a < end; a++)
- patch_call((void *)&a->instr_offset + a->instr_offset, ct);
-}
-
-static __init_or_module void
callthunks_setup(struct callthunk_sites *cs, const struct core_text *ct)
{
prdbg("Patching call sites %s\n", ct->name);
patch_call_sites(cs->call_start, cs->call_end, ct);
- patch_alt_call_sites(cs->alt_start, cs->alt_end, ct);
prdbg("Patching call sites done%s\n", ct->name);
}
@@ -263,8 +252,6 @@ void __init callthunks_patch_builtin_calls(void)
struct callthunk_sites cs = {
.call_start = __call_sites,
.call_end = __call_sites_end,
- .alt_start = __alt_instructions,
- .alt_end = __alt_instructions_end
};
if (!cpu_feature_enabled(X86_FEATURE_CALL_DEPTH))
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index 837450b..cb9d295 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -275,12 +275,7 @@ int module_finalize(const Elf_Ehdr *hdr,
void *rseg = (void *)returns->sh_addr;
apply_returns(rseg, rseg + returns->sh_size);
}
- if (alt) {
- /* patch .altinstructions */
- void *aseg = (void *)alt->sh_addr;
- apply_alternatives(aseg, aseg + alt->sh_size);
- }
- if (calls || alt) {
+ if (calls) {
struct callthunk_sites cs = {};
if (calls) {
@@ -288,13 +283,13 @@ int module_finalize(const Elf_Ehdr *hdr,
cs.call_end = (void *)calls->sh_addr + calls->sh_size;
}
- if (alt) {
- cs.alt_start = (void *)alt->sh_addr;
- cs.alt_end = (void *)alt->sh_addr + alt->sh_size;
- }
-
callthunks_patch_module_calls(&cs, me);
}
+ if (alt) {
+ /* patch .altinstructions */
+ void *aseg = (void *)alt->sh_addr;
+ apply_alternatives(aseg, aseg + alt->sh_size);
+ }
if (ibt_endbr) {
void *iseg = (void *)ibt_endbr->sh_addr;
apply_seal_endbr(iseg, iseg + ibt_endbr->sh_size);
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index fe1362c..181aa60 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -850,5 +850,6 @@ bool arch_is_rethunk(struct symbol *sym)
bool arch_is_embedded_insn(struct symbol *sym)
{
return !strcmp(sym->name, "retbleed_return_thunk") ||
+ !strcmp(sym->name, "srso_alias_safe_ret") ||
!strcmp(sym->name, "srso_safe_ret");
}
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 753dbc4..26f2c1b 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1283,15 +1283,6 @@ static void annotate_call_site(struct objtool_file *file,
if (!sym)
sym = reloc->sym;
- /*
- * Alternative replacement code is just template code which is
- * sometimes copied to the original instruction. For now, don't
- * annotate it. (In the future we might consider annotating the
- * original instruction if/when it ever makes sense to do so.)
- */
- if (!strcmp(insn->sec->name, ".altinstr_replacement"))
- return;
-
if (sym->static_call_tramp) {
list_add_tail(&insn->call_node, &file->static_call_list);
return;
@@ -1349,7 +1340,8 @@ static void annotate_call_site(struct objtool_file *file,
return;
}
- if (insn->type == INSN_CALL && !insn->sec->init)
+ if (insn->type == INSN_CALL && !insn->sec->init &&
+ !insn->_call_dest->embedded_insn)
list_add_tail(&insn->call_node, &file->call_list);
if (!sibling && dead_end_function(file, sym))
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