The following commit has been merged into the x86/percpu branch of tip:
Commit-ID: 17bce3b2ae2d52e8c5c12274ce4c3a631ce9e66b
Gitweb: https://git.kernel.org/tip/17bce3b2ae2d52e8c5c12274ce4c3a631ce9e66b
Author: Uros Bizjak <ubizjak@xxxxxxxxx>
AuthorDate: Sun, 05 Nov 2023 22:34:36 +01:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Thu, 30 Nov 2023 20:06:17 +01:00
x86/callthunks: Handle %rip-relative relocations in call thunk template
Contrary to alternatives, relocations are currently not supported in
call thunk templates. Re-use the existing infrastructure from
alternative.c to allow %rip-relative relocations when copying call
thunk template from its storage location.
The patch allows unification of ASM_INCREMENT_CALL_DEPTH, which already
uses PER_CPU_VAR macro, with INCREMENT_CALL_DEPTH, used in call thunk
template, which is currently limited to use absolute address.
Reuse existing relocation infrastructure from alternative.c.,
as suggested by Peter Zijlstra.
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20231105213731.1878100-3-ubizjak@xxxxxxxxx
---
arch/x86/include/asm/text-patching.h | 2 ++-
arch/x86/kernel/alternative.c | 3 +--
arch/x86/kernel/callthunks.c | 32 +++++++++++++++++++++------
3 files changed, 28 insertions(+), 9 deletions(-)
diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h
index 29832c3..ba8d900 100644
--- a/arch/x86/include/asm/text-patching.h
+++ b/arch/x86/include/asm/text-patching.h
@@ -18,6 +18,8 @@ static inline void apply_paravirt(struct paravirt_patch_site *start,
#define __parainstructions_end NULL
#endif
+void apply_relocation(u8 *buf, size_t len, u8 *dest, u8 *src, size_t src_len);
+
/*
* Currently, the max observed size in the kernel code is
* JUMP_LABEL_NOP_SIZE/RELATIVEJUMP_SIZE, which are 5.
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index a5ead6a..aa86415 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -325,8 +325,7 @@ bool need_reloc(unsigned long offset, u8 *src, size_t src_len)
return (target < src || target > src + src_len);
}
-static void __init_or_module noinline
-apply_relocation(u8 *buf, size_t len, u8 *dest, u8 *src, size_t src_len)
+void apply_relocation(u8 *buf, size_t len, u8 *dest, u8 *src, size_t src_len)
{
int prev, target = 0;
diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c
index c06bfc0..f56fa30 100644
--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -24,6 +24,8 @@
static int __initdata_or_module debug_callthunks;
+#define MAX_PATCH_LEN (255-1)
+
#define prdbg(fmt, args...) \
do { \
if (debug_callthunks) \
@@ -184,10 +186,15 @@ static const u8 nops[] = {
static void *patch_dest(void *dest, bool direct)
{
unsigned int tsize = SKL_TMPL_SIZE;
+ u8 insn_buff[MAX_PATCH_LEN];
u8 *pad = dest - tsize;
+ memcpy(insn_buff, skl_call_thunk_template, tsize);
+ apply_relocation(insn_buff, tsize, pad,
+ skl_call_thunk_template, tsize);
+
/* Already patched? */
- if (!bcmp(pad, skl_call_thunk_template, tsize))
+ if (!bcmp(pad, insn_buff, tsize))
return pad;
/* Ensure there are nops */
@@ -197,9 +204,9 @@ static void *patch_dest(void *dest, bool direct)
}
if (direct)
- memcpy(pad, skl_call_thunk_template, tsize);
+ memcpy(pad, insn_buff, tsize);
else
- text_poke_copy_locked(pad, skl_call_thunk_template, tsize, true);
+ text_poke_copy_locked(pad, insn_buff, tsize, true);
return pad;
}
@@ -297,20 +304,27 @@ void *callthunks_translate_call_dest(void *dest)
static bool is_callthunk(void *addr)
{
unsigned int tmpl_size = SKL_TMPL_SIZE;
- void *tmpl = skl_call_thunk_template;
+ u8 insn_buff[MAX_PATCH_LEN];
unsigned long dest;
+ u8 *pad;
dest = roundup((unsigned long)addr, CONFIG_FUNCTION_ALIGNMENT);
if (!thunks_initialized || skip_addr((void *)dest))
return false;
- return !bcmp((void *)(dest - tmpl_size), tmpl, tmpl_size);
+ *pad = dest - tmpl_size;
+
+ memcpy(insn_buff, skl_call_thunk_template, tmpl_size);
+ apply_relocation(insn_buff, tmpl_size, pad,
+ skl_call_thunk_template, tmpl_size);
+
+ return !bcmp(pad, insn_buff, tmpl_size);
}
int x86_call_depth_emit_accounting(u8 **pprog, void *func)
{
unsigned int tmpl_size = SKL_TMPL_SIZE;
- void *tmpl = skl_call_thunk_template;
+ u8 insn_buff[MAX_PATCH_LEN];
if (!thunks_initialized)
return 0;
@@ -319,7 +333,11 @@ int x86_call_depth_emit_accounting(u8 **pprog, void *func)
if (func && is_callthunk(func))
return 0;
- memcpy(*pprog, tmpl, tmpl_size);
+ memcpy(insn_buff, skl_call_thunk_template, tmpl_size);
+ apply_relocation(insn_buff, tmpl_size, *pprog,
+ skl_call_thunk_template, tmpl_size);
+
+ memcpy(*pprog, insn_buff, tmpl_size);
*pprog += tmpl_size;
return tmpl_size;
}
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