From 24dfd0736c9fc01d096e5760c656032b5a07e962 Mon Sep 17 00:00:00 2001 From: Michel Thierry Date: Fri, 2 Oct 2015 14:16:53 +0100 Subject: [PATCH] drm/i915: prevent out of range pt in the PDE macros (take 3) We tried to fix this in commit fdc454c1484a ("drm/i915: Prevent out of range pt in gen6_for_each_pde"). But the static analyzer still complains that, just before we break due to "iter < I915_PDES", we do "pt = (pd)->page_table[iter]" with an iter value that is bigger than I915_PDES. Of course, this isn't really a problem since no one uses pt outside the macro. Still, every single new usage of the macro will create a new issue for us to mark as a false positive. Also, Paulo re-started the discussion a while ago [1], but didn't end up implemented. In order to "solve" this "problem", this patch takes the ideas from Chris and Dave, but that check would change the desired behavior of the code, because the object (for example pdp->page_directory[iter]) can be null during init/alloc, and C would take this as false, breaking the for loop immediately. This has been already verified with "static analysis tools". [1]http://lists.freedesktop.org/archives/intel-gfx/2015-June/068548.html v2: Make it a single statement, while preventing the common subexpression elimination (Chris) Cc: Paulo Zanoni Cc: Chris Wilson Cc: Dave Gordon Signed-off-by: Michel Thierry Reviewed-by: Chris Wilson Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/i915_gem_gtt.h | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h index 9fbb07d..a216397 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.h +++ b/drivers/gpu/drm/i915/i915_gem_gtt.h @@ -394,7 +394,8 @@ struct i915_hw_ppgtt { */ #define gen6_for_each_pde(pt, pd, start, length, temp, iter) \ for (iter = gen6_pde_index(start); \ - pt = (pd)->page_table[iter], length > 0 && iter < I915_PDES; \ + length > 0 && iter < I915_PDES ? \ + (pt = (pd)->page_table[iter]), 1 : 0; \ iter++, \ temp = ALIGN(start+1, 1 << GEN6_PDE_SHIFT) - start, \ temp = min_t(unsigned, temp, length), \ @@ -459,7 +460,8 @@ static inline uint32_t gen6_pde_index(uint32_t addr) */ #define gen8_for_each_pde(pt, pd, start, length, temp, iter) \ for (iter = gen8_pde_index(start); \ - pt = (pd)->page_table[iter], length > 0 && iter < I915_PDES; \ + length > 0 && iter < I915_PDES ? \ + (pt = (pd)->page_table[iter]), 1 : 0; \ iter++, \ temp = ALIGN(start+1, 1 << GEN8_PDE_SHIFT) - start, \ temp = min(temp, length), \ @@ -467,8 +469,8 @@ static inline uint32_t gen6_pde_index(uint32_t addr) #define gen8_for_each_pdpe(pd, pdp, start, length, temp, iter) \ for (iter = gen8_pdpe_index(start); \ - pd = (pdp)->page_directory[iter], \ - length > 0 && (iter < I915_PDPES_PER_PDP(dev)); \ + length > 0 && (iter < I915_PDPES_PER_PDP(dev)) ? \ + (pd = (pdp)->page_directory[iter]), 1 : 0; \ iter++, \ temp = ALIGN(start+1, 1 << GEN8_PDPE_SHIFT) - start, \ temp = min(temp, length), \ @@ -476,8 +478,8 @@ static inline uint32_t gen6_pde_index(uint32_t addr) #define gen8_for_each_pml4e(pdp, pml4, start, length, temp, iter) \ for (iter = gen8_pml4e_index(start); \ - pdp = (pml4)->pdps[iter], \ - length > 0 && iter < GEN8_PML4ES_PER_PML4; \ + length > 0 && iter < GEN8_PML4ES_PER_PML4 ? \ + (pdp = (pml4)->pdps[iter]), 1 : 0; \ iter++, \ temp = ALIGN(start+1, 1ULL << GEN8_PML4E_SHIFT) - start, \ temp = min(temp, length), \ -- 2.7.4