* [PATCH v2 0/2] objtool,drm/vmwgfx: Add unwind hints around RBP clobber @ 2023-06-05 16:12 Josh Poimboeuf 2023-06-05 16:12 ` [PATCH v2 1/2] objtool: Allow stack operations in UNWIND_HINT_UNDEFINED regions Josh Poimboeuf 2023-06-05 16:12 ` [PATCH v2 2/2] drm/vmwgfx: Add unwind hints around RBP clobber Josh Poimboeuf 0 siblings, 2 replies; 5+ messages in thread From: Josh Poimboeuf @ 2023-06-05 16:12 UTC (permalink / raw) To: x86 Cc: linux-kernel, Peter Zijlstra, Miroslav Benes, linux-graphics-maintainer, Zack Rusin v2: - Fix the (theoretical) ORC bug Josh Poimboeuf (2): objtool: Allow stack operations in UNWIND_HINT_UNDEFINED regions drm/vmwgfx: Add unwind hints around RBP clobber arch/x86/include/asm/unwind_hints.h | 9 +++++++++ drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h | 16 ++++++++++++---- tools/objtool/check.c | 12 ++++++++++++ tools/objtool/include/objtool/cfi.h | 1 + 4 files changed, 34 insertions(+), 4 deletions(-) -- 2.40.1 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v2 1/2] objtool: Allow stack operations in UNWIND_HINT_UNDEFINED regions 2023-06-05 16:12 [PATCH v2 0/2] objtool,drm/vmwgfx: Add unwind hints around RBP clobber Josh Poimboeuf @ 2023-06-05 16:12 ` Josh Poimboeuf 2023-06-09 7:47 ` [tip: objtool/core] " tip-bot2 for Josh Poimboeuf 2023-06-05 16:12 ` [PATCH v2 2/2] drm/vmwgfx: Add unwind hints around RBP clobber Josh Poimboeuf 1 sibling, 1 reply; 5+ messages in thread From: Josh Poimboeuf @ 2023-06-05 16:12 UTC (permalink / raw) To: x86 Cc: linux-kernel, Peter Zijlstra, Miroslav Benes, linux-graphics-maintainer, Zack Rusin If the code specified UNWIND_HINT_UNDEFINED, skip the "undefined stack state" warning due to a stack operation. Just ignore the stack op and continue to propagate the undefined state. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> --- tools/objtool/check.c | 12 ++++++++++++ tools/objtool/include/objtool/cfi.h | 1 + 2 files changed, 13 insertions(+) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 4b869de7e827..b11c25a715ac 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -33,6 +33,7 @@ static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache; static struct cfi_init_state initial_func_cfi; static struct cfi_state init_cfi; static struct cfi_state func_cfi; +static struct cfi_state force_undefined_cfi; struct instruction *find_insn(struct objtool_file *file, struct section *sec, unsigned long offset) @@ -2240,6 +2241,11 @@ static int read_unwind_hints(struct objtool_file *file) insn->hint = true; + if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) { + insn->cfi = &force_undefined_cfi; + continue; + } + if (hint->type == UNWIND_HINT_TYPE_SAVE) { insn->hint = false; insn->save = true; @@ -2793,6 +2799,10 @@ static int update_cfi_state(struct instruction *insn, struct cfi_reg *cfa = &cfi->cfa; struct cfi_reg *regs = cfi->regs; + /* ignore UNWIND_HINT_UNDEFINED regions */ + if (cfi->force_undefined) + return 0; + /* stack operations don't make sense with an undefined CFA */ if (cfa->base == CFI_UNDEFINED) { if (insn_func(insn)) { @@ -4607,6 +4617,8 @@ int check(struct objtool_file *file) init_cfi_state(&init_cfi); init_cfi_state(&func_cfi); set_func_state(&func_cfi); + init_cfi_state(&force_undefined_cfi); + force_undefined_cfi.force_undefined = true; if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3))) goto out; diff --git a/tools/objtool/include/objtool/cfi.h b/tools/objtool/include/objtool/cfi.h index b1258e79a1b7..c8a6bec4f6b9 100644 --- a/tools/objtool/include/objtool/cfi.h +++ b/tools/objtool/include/objtool/cfi.h @@ -36,6 +36,7 @@ struct cfi_state { bool drap; bool signal; bool end; + bool force_undefined; }; #endif /* _OBJTOOL_CFI_H */ -- 2.40.1 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* [tip: objtool/core] objtool: Allow stack operations in UNWIND_HINT_UNDEFINED regions 2023-06-05 16:12 ` [PATCH v2 1/2] objtool: Allow stack operations in UNWIND_HINT_UNDEFINED regions Josh Poimboeuf @ 2023-06-09 7:47 ` tip-bot2 for Josh Poimboeuf 0 siblings, 0 replies; 5+ messages in thread From: tip-bot2 for Josh Poimboeuf @ 2023-06-09 7:47 UTC (permalink / raw) To: linux-tip-commits; +Cc: Josh Poimboeuf, x86, linux-kernel The following commit has been merged into the objtool/core branch of tip: Commit-ID: 1e4b619185e83e54aca617cf5070c64a88fe936b Gitweb: https://git.kernel.org/tip/1e4b619185e83e54aca617cf5070c64a88fe936b Author: Josh Poimboeuf <jpoimboe@kernel.org> AuthorDate: Mon, 05 Jun 2023 09:12:21 -07:00 Committer: Josh Poimboeuf <jpoimboe@kernel.org> CommitterDate: Wed, 07 Jun 2023 10:03:11 -07:00 objtool: Allow stack operations in UNWIND_HINT_UNDEFINED regions If the code specified UNWIND_HINT_UNDEFINED, skip the "undefined stack state" warning due to a stack operation. Just ignore the stack op and continue to propagate the undefined state. Link: https://lore.kernel.org/r/820c5b433f17c84e8761fb7465a8d319d706b1cf.1685981486.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> --- tools/objtool/check.c | 12 ++++++++++++ tools/objtool/include/objtool/cfi.h | 1 + 2 files changed, 13 insertions(+) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 4b869de..b11c25a 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -33,6 +33,7 @@ static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache; static struct cfi_init_state initial_func_cfi; static struct cfi_state init_cfi; static struct cfi_state func_cfi; +static struct cfi_state force_undefined_cfi; struct instruction *find_insn(struct objtool_file *file, struct section *sec, unsigned long offset) @@ -2240,6 +2241,11 @@ static int read_unwind_hints(struct objtool_file *file) insn->hint = true; + if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) { + insn->cfi = &force_undefined_cfi; + continue; + } + if (hint->type == UNWIND_HINT_TYPE_SAVE) { insn->hint = false; insn->save = true; @@ -2793,6 +2799,10 @@ static int update_cfi_state(struct instruction *insn, struct cfi_reg *cfa = &cfi->cfa; struct cfi_reg *regs = cfi->regs; + /* ignore UNWIND_HINT_UNDEFINED regions */ + if (cfi->force_undefined) + return 0; + /* stack operations don't make sense with an undefined CFA */ if (cfa->base == CFI_UNDEFINED) { if (insn_func(insn)) { @@ -4607,6 +4617,8 @@ int check(struct objtool_file *file) init_cfi_state(&init_cfi); init_cfi_state(&func_cfi); set_func_state(&func_cfi); + init_cfi_state(&force_undefined_cfi); + force_undefined_cfi.force_undefined = true; if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3))) goto out; diff --git a/tools/objtool/include/objtool/cfi.h b/tools/objtool/include/objtool/cfi.h index b1258e7..c8a6bec 100644 --- a/tools/objtool/include/objtool/cfi.h +++ b/tools/objtool/include/objtool/cfi.h @@ -36,6 +36,7 @@ struct cfi_state { bool drap; bool signal; bool end; + bool force_undefined; }; #endif /* _OBJTOOL_CFI_H */ ^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH v2 2/2] drm/vmwgfx: Add unwind hints around RBP clobber 2023-06-05 16:12 [PATCH v2 0/2] objtool,drm/vmwgfx: Add unwind hints around RBP clobber Josh Poimboeuf 2023-06-05 16:12 ` [PATCH v2 1/2] objtool: Allow stack operations in UNWIND_HINT_UNDEFINED regions Josh Poimboeuf @ 2023-06-05 16:12 ` Josh Poimboeuf 2023-06-09 7:47 ` [tip: objtool/core] " tip-bot2 for Josh Poimboeuf 1 sibling, 1 reply; 5+ messages in thread From: Josh Poimboeuf @ 2023-06-05 16:12 UTC (permalink / raw) To: x86 Cc: linux-kernel, Peter Zijlstra, Miroslav Benes, linux-graphics-maintainer, Zack Rusin, kernel test robot VMware high-bandwidth hypercalls take the RBP register as input. This breaks basic frame pointer convention, as RBP should never be clobbered. So frame pointer unwinding is broken for the instructions surrounding the hypercalls. Fortunately this doesn't break live patching with CONFIG_FRAME_POINTER, as it only unwinds from blocking tasks, and stack traces from preempted tasks are already marked unreliable anyway. However, for live patching with ORC, this could actually be a theoretical problem if vmw_port_hb_{in,out}() were still compiled with a frame pointer due to having an aligned stack. In practice that hasn't seemed to be an issue since the objtool warnings have only been seen with CONFIG_FRAME_POINTER. Add unwind hint annotations to tell the ORC unwinder to mark stack traces as unreliable. Fixes the following warnings: vmlinux.o: warning: objtool: vmw_port_hb_in+0x1df: return with modified stack frame vmlinux.o: warning: objtool: vmw_port_hb_out+0x1dd: return with modified stack frame Fixes: 89da76fde68d ("drm/vmwgfx: Add VMWare host messaging capability") Reported-by: kernel test robot <lkp@intel.com> Link: https://lore.kernel.org/oe-kbuild-all/202305160135.97q0Elax-lkp@intel.com/ Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> --- arch/x86/include/asm/unwind_hints.h | 9 +++++++++ drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h | 16 ++++++++++++---- 2 files changed, 21 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/unwind_hints.h b/arch/x86/include/asm/unwind_hints.h index 01cb9692b160..85cc57cb6539 100644 --- a/arch/x86/include/asm/unwind_hints.h +++ b/arch/x86/include/asm/unwind_hints.h @@ -76,9 +76,18 @@ #else +#define UNWIND_HINT_UNDEFINED \ + UNWIND_HINT(UNWIND_HINT_TYPE_UNDEFINED, 0, 0, 0) + #define UNWIND_HINT_FUNC \ UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0) +#define UNWIND_HINT_SAVE \ + UNWIND_HINT(UNWIND_HINT_TYPE_SAVE, 0, 0, 0) + +#define UNWIND_HINT_RESTORE \ + UNWIND_HINT(UNWIND_HINT_TYPE_RESTORE, 0, 0, 0) + #endif /* __ASSEMBLY__ */ #endif /* _ASM_X86_UNWIND_HINTS_H */ diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h b/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h index 0b74ca2dfb7b..23899d743a90 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h @@ -105,10 +105,14 @@ flags, magic, bp, \ eax, ebx, ecx, edx, si, di) \ ({ \ - asm volatile ("push %%rbp;" \ + asm volatile ( \ + UNWIND_HINT_SAVE \ + "push %%rbp;" \ + UNWIND_HINT_UNDEFINED \ "mov %12, %%rbp;" \ VMWARE_HYPERCALL_HB_OUT \ - "pop %%rbp;" : \ + "pop %%rbp;" \ + UNWIND_HINT_RESTORE : \ "=a"(eax), \ "=b"(ebx), \ "=c"(ecx), \ @@ -130,10 +134,14 @@ flags, magic, bp, \ eax, ebx, ecx, edx, si, di) \ ({ \ - asm volatile ("push %%rbp;" \ + asm volatile ( \ + UNWIND_HINT_SAVE \ + "push %%rbp;" \ + UNWIND_HINT_UNDEFINED \ "mov %12, %%rbp;" \ VMWARE_HYPERCALL_HB_IN \ - "pop %%rbp" : \ + "pop %%rbp;" \ + UNWIND_HINT_RESTORE : \ "=a"(eax), \ "=b"(ebx), \ "=c"(ecx), \ -- 2.40.1 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* [tip: objtool/core] drm/vmwgfx: Add unwind hints around RBP clobber 2023-06-05 16:12 ` [PATCH v2 2/2] drm/vmwgfx: Add unwind hints around RBP clobber Josh Poimboeuf @ 2023-06-09 7:47 ` tip-bot2 for Josh Poimboeuf 0 siblings, 0 replies; 5+ messages in thread From: tip-bot2 for Josh Poimboeuf @ 2023-06-09 7:47 UTC (permalink / raw) To: linux-tip-commits; +Cc: kernel test robot, Josh Poimboeuf, x86, linux-kernel The following commit has been merged into the objtool/core branch of tip: Commit-ID: a9da8247627eefc73f909bf945031a5431a53993 Gitweb: https://git.kernel.org/tip/a9da8247627eefc73f909bf945031a5431a53993 Author: Josh Poimboeuf <jpoimboe@kernel.org> AuthorDate: Mon, 05 Jun 2023 09:12:22 -07:00 Committer: Josh Poimboeuf <jpoimboe@kernel.org> CommitterDate: Wed, 07 Jun 2023 10:03:12 -07:00 drm/vmwgfx: Add unwind hints around RBP clobber VMware high-bandwidth hypercalls take the RBP register as input. This breaks basic frame pointer convention, as RBP should never be clobbered. So frame pointer unwinding is broken for the instructions surrounding the hypercalls. Fortunately this doesn't break live patching with CONFIG_FRAME_POINTER, as it only unwinds from blocking tasks, and stack traces from preempted tasks are already marked unreliable anyway. However, for live patching with ORC, this could actually be a theoretical problem if vmw_port_hb_{in,out}() were still compiled with a frame pointer due to having an aligned stack. In practice that hasn't seemed to be an issue since the objtool warnings have only been seen with CONFIG_FRAME_POINTER. Add unwind hint annotations to tell the ORC unwinder to mark stack traces as unreliable. Fixes the following warnings: vmlinux.o: warning: objtool: vmw_port_hb_in+0x1df: return with modified stack frame vmlinux.o: warning: objtool: vmw_port_hb_out+0x1dd: return with modified stack frame Fixes: 89da76fde68d ("drm/vmwgfx: Add VMWare host messaging capability") Reported-by: kernel test robot <lkp@intel.com> Link: https://lore.kernel.org/oe-kbuild-all/202305160135.97q0Elax-lkp@intel.com/ Link: https://lore.kernel.org/r/4c795f2d87bc0391cf6543bcb224fa540b55ce4b.1685981486.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> --- arch/x86/include/asm/unwind_hints.h | 9 +++++++++ drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h | 16 ++++++++++++---- 2 files changed, 21 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/unwind_hints.h b/arch/x86/include/asm/unwind_hints.h index 01cb969..85cc57c 100644 --- a/arch/x86/include/asm/unwind_hints.h +++ b/arch/x86/include/asm/unwind_hints.h @@ -76,9 +76,18 @@ #else +#define UNWIND_HINT_UNDEFINED \ + UNWIND_HINT(UNWIND_HINT_TYPE_UNDEFINED, 0, 0, 0) + #define UNWIND_HINT_FUNC \ UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0) +#define UNWIND_HINT_SAVE \ + UNWIND_HINT(UNWIND_HINT_TYPE_SAVE, 0, 0, 0) + +#define UNWIND_HINT_RESTORE \ + UNWIND_HINT(UNWIND_HINT_TYPE_RESTORE, 0, 0, 0) + #endif /* __ASSEMBLY__ */ #endif /* _ASM_X86_UNWIND_HINTS_H */ diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h b/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h index 0b74ca2..23899d7 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h @@ -105,10 +105,14 @@ flags, magic, bp, \ eax, ebx, ecx, edx, si, di) \ ({ \ - asm volatile ("push %%rbp;" \ + asm volatile ( \ + UNWIND_HINT_SAVE \ + "push %%rbp;" \ + UNWIND_HINT_UNDEFINED \ "mov %12, %%rbp;" \ VMWARE_HYPERCALL_HB_OUT \ - "pop %%rbp;" : \ + "pop %%rbp;" \ + UNWIND_HINT_RESTORE : \ "=a"(eax), \ "=b"(ebx), \ "=c"(ecx), \ @@ -130,10 +134,14 @@ flags, magic, bp, \ eax, ebx, ecx, edx, si, di) \ ({ \ - asm volatile ("push %%rbp;" \ + asm volatile ( \ + UNWIND_HINT_SAVE \ + "push %%rbp;" \ + UNWIND_HINT_UNDEFINED \ "mov %12, %%rbp;" \ VMWARE_HYPERCALL_HB_IN \ - "pop %%rbp" : \ + "pop %%rbp;" \ + UNWIND_HINT_RESTORE : \ "=a"(eax), \ "=b"(ebx), \ "=c"(ecx), \ ^ permalink raw reply related [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-06-09 7:50 UTC | newest] Thread overview: 5+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2023-06-05 16:12 [PATCH v2 0/2] objtool,drm/vmwgfx: Add unwind hints around RBP clobber Josh Poimboeuf 2023-06-05 16:12 ` [PATCH v2 1/2] objtool: Allow stack operations in UNWIND_HINT_UNDEFINED regions Josh Poimboeuf 2023-06-09 7:47 ` [tip: objtool/core] " tip-bot2 for Josh Poimboeuf 2023-06-05 16:12 ` [PATCH v2 2/2] drm/vmwgfx: Add unwind hints around RBP clobber Josh Poimboeuf 2023-06-09 7:47 ` [tip: objtool/core] " tip-bot2 for Josh Poimboeuf
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