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Message-ID: <20231105213731.1878100-3-ubizjak@gmail.com>
Date: Sun, 5 Nov 2023 22:34:36 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: x86@...nel.org, linux-kernel@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH -tip v2 2/3] 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.
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Uros Bizjak <ubizjak@...il.com>
---
v2: Reuse existing relocation infrastructure from alternative.c.
---
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 29832c338cdc..ba8d900f3ebe 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 73be3931e4f0..66140c54d4f6 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 e9ad518a5003..ef9c04707b3c 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) \
@@ -179,10 +181,15 @@ 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 */
@@ -192,9 +199,9 @@ 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;
}
@@ -291,20 +298,27 @@ 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;
@@ -313,7 +327,11 @@ 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;
}
--
2.41.0
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