From be80788ef3e8c5af76344e7c19e32388651ad08c Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Tue, 11 Jul 2023 18:08:27 +0200 Subject: [PATCH 1/2] Revert "powerpc/bug: Provide better flexibility to WARN_ON/__WARN_FLAGS() with asm goto" This partly reverts commit 1e688dd2a3d6759d416616ff07afc4bb836c4213. That commit aimed at optimising the code around generation of WARN_ON/BUG_ON but this leads to a lot of dead code erroneously generated by GCC. That dead code becomes a problem when we start using objtool validation because objtool will abort validation with a warning as soon as it detects unreachable code. This is because unreachable code might be the indication that objtool doesn't properly decode object text. text data bss dec hex filename 9551585 3627834 224376 13403795 cc8693 vmlinux.before 9535281 3628358 224376 13388015 cc48ef vmlinux.after Once this change is reverted, in a standard configuration (pmac32 + function tracer) the text is reduced by 16k which is around 1.7% We already had problem with it when starting to use objtool on powerpc as a replacement for recordmcount, see commit 93e3f45a2631 ("powerpc: Fix __WARN_FLAGS() for use with Objtool") There is also a problem with at least GCC 12, on ppc64_defconfig + CONFIG_CC_OPTIMIZE_FOR_SIZE=y + CONFIG_DEBUG_SECTION_MISMATCH=y : LD .tmp_vmlinux.kallsyms1 powerpc64-linux-ld: net/ipv4/tcp_input.o:(__ex_table+0xc4): undefined reference to `.L2136' make[2]: *** [scripts/Makefile.vmlinux:36: vmlinux] Error 1 make[1]: *** [/home/chleroy/linux-powerpc/Makefile:1238: vmlinux] Error 2 Taking into account that other problems are encountered with that 'asm goto' in WARN_ON(), including build failures, keeping that change is not worth it allthough it is primarily a compiler bug. Revert it for now. mpe: Retain EMIT_WARN_ENTRY as a synonym for EMIT_BUG_ENTRY to reduce churn, as there are now nearly as many uses of EMIT_WARN_ENTRY as EMIT_BUG_ENTRY. Signed-off-by: Christophe Leroy Acked-by: Naveen N Rao Signed-off-by: Michael Ellerman Link: https://msgid.link/a7d6d0c20deaccfcbc74c3149e782538461fd6fe.1689091394.git.christophe.leroy@csgroup.eu --- arch/powerpc/include/asm/bug.h | 69 +++++++--------------------------- arch/powerpc/kernel/traps.c | 9 +---- 2 files changed, 15 insertions(+), 63 deletions(-) diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h index ef42adb44aa3f..00c6b0b4ede48 100644 --- a/arch/powerpc/include/asm/bug.h +++ b/arch/powerpc/include/asm/bug.h @@ -4,14 +4,13 @@ #ifdef __KERNEL__ #include -#include #ifdef CONFIG_BUG #ifdef __ASSEMBLY__ #include #ifdef CONFIG_DEBUG_BUGVERBOSE -.macro __EMIT_BUG_ENTRY addr,file,line,flags +.macro EMIT_BUG_ENTRY addr,file,line,flags .section __bug_table,"aw" 5001: .4byte \addr - . .4byte 5002f - . @@ -23,7 +22,7 @@ .previous .endm #else -.macro __EMIT_BUG_ENTRY addr,file,line,flags +.macro EMIT_BUG_ENTRY addr,file,line,flags .section __bug_table,"aw" 5001: .4byte \addr - . .short \flags @@ -32,18 +31,6 @@ .endm #endif /* verbose */ -.macro EMIT_WARN_ENTRY addr,file,line,flags - EX_TABLE(\addr,\addr+4) - __EMIT_BUG_ENTRY \addr,\file,\line,\flags -.endm - -.macro EMIT_BUG_ENTRY addr,file,line,flags - .if \flags & 1 /* BUGFLAG_WARNING */ - .err /* Use EMIT_WARN_ENTRY for warnings */ - .endif - __EMIT_BUG_ENTRY \addr,\file,\line,\flags -.endm - #else /* !__ASSEMBLY__ */ /* _EMIT_BUG_ENTRY expects args %0,%1,%2,%3 to be FILE, LINE, flags and sizeof(struct bug_entry), respectively */ @@ -73,16 +60,6 @@ "i" (sizeof(struct bug_entry)), \ ##__VA_ARGS__) -#define WARN_ENTRY(insn, flags, label, ...) \ - asm_volatile_goto( \ - "1: " insn "\n" \ - EX_TABLE(1b, %l[label]) \ - _EMIT_BUG_ENTRY \ - : : "i" (__FILE__), "i" (__LINE__), \ - "i" (flags), \ - "i" (sizeof(struct bug_entry)), \ - ##__VA_ARGS__ : : label) - /* * BUG_ON() and WARN_ON() do their best to cooperate with compile-time * optimisations. However depending on the complexity of the condition @@ -95,16 +72,7 @@ } while (0) #define HAVE_ARCH_BUG -#define __WARN_FLAGS(flags) do { \ - __label__ __label_warn_on; \ - \ - WARN_ENTRY("twi 31, 0, 0", BUGFLAG_WARNING | (flags), __label_warn_on); \ - barrier_before_unreachable(); \ - __builtin_unreachable(); \ - \ -__label_warn_on: \ - break; \ -} while (0) +#define __WARN_FLAGS(flags) BUG_ENTRY("twi 31, 0, 0", BUGFLAG_WARNING | (flags)) #ifdef CONFIG_PPC64 #define BUG_ON(x) do { \ @@ -117,25 +85,15 @@ __label_warn_on: \ } while (0) #define WARN_ON(x) ({ \ - bool __ret_warn_on = false; \ - do { \ - if (__builtin_constant_p((x))) { \ - if (!(x)) \ - break; \ + int __ret_warn_on = !!(x); \ + if (__builtin_constant_p(__ret_warn_on)) { \ + if (__ret_warn_on) \ __WARN(); \ - __ret_warn_on = true; \ - } else { \ - __label__ __label_warn_on; \ - \ - WARN_ENTRY(PPC_TLNEI " %4, 0", \ - BUGFLAG_WARNING | BUGFLAG_TAINT(TAINT_WARN), \ - __label_warn_on, \ - "r" ((__force long)(x))); \ - break; \ -__label_warn_on: \ - __ret_warn_on = true; \ - } \ - } while (0); \ + } else { \ + BUG_ENTRY(PPC_TLNEI " %4, 0", \ + BUGFLAG_WARNING | BUGFLAG_TAINT(TAINT_WARN), \ + "r" (__ret_warn_on)); \ + } \ unlikely(__ret_warn_on); \ }) @@ -148,14 +106,13 @@ __label_warn_on: \ #ifdef __ASSEMBLY__ .macro EMIT_BUG_ENTRY addr,file,line,flags .endm -.macro EMIT_WARN_ENTRY addr,file,line,flags -.endm #else /* !__ASSEMBLY__ */ #define _EMIT_BUG_ENTRY -#define _EMIT_WARN_ENTRY #endif #endif /* CONFIG_BUG */ +#define EMIT_WARN_ENTRY EMIT_BUG_ENTRY + #include #ifndef __ASSEMBLY__ diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index e59ec6d32d375..7ef147e2a20d7 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -1508,13 +1508,8 @@ static void do_program_check(struct pt_regs *regs) if (!(regs->msr & MSR_PR) && /* not user-mode */ report_bug(bugaddr, regs) == BUG_TRAP_TYPE_WARN) { - const struct exception_table_entry *entry; - - entry = search_exception_tables(bugaddr); - if (entry) { - regs_set_return_ip(regs, extable_fixup(entry) + regs->nip - bugaddr); - return; - } + regs_add_return_ip(regs, 4); + return; } if (cpu_has_feature(CPU_FTR_DEXCR_NPHIE) && user_mode(regs)) { From 36686e99e6e09c4043c34cf0c44f84f1e52f7ac9 Mon Sep 17 00:00:00 2001 From: Haren Myneni Date: Thu, 22 Jun 2023 00:42:46 -0700 Subject: [PATCH 2/2] powerpc/pseries/vas: Hold mmap_mutex after mmap lock during window close VAS mmap (coproc_mmap()) and its fault handler (vas_mmap_fault()) are called after holding mmap lock and acquire mmap_mutex to update VAS window status. The migration / DLPAR window close can hang while trying to acquire mmap lock if it is issued at the same time with the user space ioctl mmap or VAS fault handler execution. So this patch adds changes to acquire mmap lock before holding mmap_mutex. Fixes: 8ef7b9e1765a ("powerpc/pseries/vas: Close windows with DLPAR core removal") Signed-off-by: Haren Myneni Signed-off-by: Michael Ellerman Link: https://msgid.link/20230622074246.144729-1-haren@linux.ibm.com --- arch/powerpc/platforms/pseries/vas.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/platforms/pseries/vas.c b/arch/powerpc/platforms/pseries/vas.c index 9a44a98ba3420..3fbc2a6aa319d 100644 --- a/arch/powerpc/platforms/pseries/vas.c +++ b/arch/powerpc/platforms/pseries/vas.c @@ -744,6 +744,12 @@ static int reconfig_close_windows(struct vas_caps *vcap, int excess_creds, } task_ref = &win->vas_win.task_ref; + /* + * VAS mmap (coproc_mmap()) and its fault handler + * (vas_mmap_fault()) are called after holding mmap lock. + * So hold mmap mutex after mmap_lock to avoid deadlock. + */ + mmap_write_lock(task_ref->mm); mutex_lock(&task_ref->mmap_mutex); vma = task_ref->vma; /* @@ -752,7 +758,6 @@ static int reconfig_close_windows(struct vas_caps *vcap, int excess_creds, */ win->vas_win.status |= flag; - mmap_write_lock(task_ref->mm); /* * vma is set in the original mapping. But this mapping * is done with mmap() after the window is opened with ioctl. @@ -762,8 +767,8 @@ static int reconfig_close_windows(struct vas_caps *vcap, int excess_creds, if (vma) zap_vma_pages(vma); - mmap_write_unlock(task_ref->mm); mutex_unlock(&task_ref->mmap_mutex); + mmap_write_unlock(task_ref->mm); /* * Close VAS window in the hypervisor, but do not * free vas_window struct since it may be reused