Messages in this thread Patch in this message | | | From | Uros Bizjak <> | Subject | [PATCH -tip v2 2/3] x86/callthunks: Handle %rip-relative relocations in call thunk template | Date | Sun, 5 Nov 2023 22:34:36 +0100 |
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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@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Uros Bizjak <ubizjak@gmail.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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