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Check out which companies are making headlines before the bell:

Qualcomm — The chipmaker's stock dropped about 6 percent before the bell after the company slashed its fiscal third-quarter guidance. Qualcomm said Apple told the firm it's withholding royalty payments as part of an ongoing dispute between the two tech giants.

General Motors — The auto maker's quarterly results easily topped Wall Street's expectations, posting earnings per share of $1.70 on revenue of $41.2 billion. Analysts polled by Reuters expected GM to post earnings of $1.48 per share on sales of $40.752 billion. The automaker posted strong sales in its trucks and SUV segments.

Exxon Mobil — The energy giant posted mixed quarterly results, with earnings per share easily topping expectations while sales missed the mark. Exxon said its international upstream and downstream businesses netted $2.27 billion and $824 million, respectively. Its U.S. upstream and downstream segments posted a loss of $18 million and a net gain of $292 million, respectively.

Alphabet — Google's parent company smashed first-quarter earnings and sales estimates as mobile search and YouTube drove ad sales higher. The firm reported earnings per share of $7.73 on sales of $24.75 billion.

Amazon — Amazon posted better-than-expected quarterly results, with sales jumping 23 percent year over year. Revenue in Amazon Web Services, a key driver for the company, totaled $3.66 billion, matching analyst expectations.

Microsoft — Microsoft reported mixed fiscal third-quarter results, as earnings per share of 73 cents topped expectations while revenue of $23.56 billion missed. Sales in the firm's "more personal computing" segment totaled $8.84 billion, which missed expectations and represented a 7 percent year-over-year decline.

Starbucks — The coffee giant's shares fell more than 4 percent before the bell on the back of weaker-than-expected same-store sales for fiscal second quarter. Starbucks reported comparable store sales growth of 3 percent, below a StreetAccount estimate of 3.7 percent.

Western Digital — Western Digital's stock popped more than 6 percent in the premarket after reporting better-than-expected earnings. The firm's fiscal fourth-quarter guidance also topped Wall Street's expectations.

GoPro — The wearables maker reported a lower-than-expected quarterly loss, helped by strong sales of its flagship cameras and Karma drones. The stock briefly rose more than 7 percent after posting its results, before holding around the flatline.

Synchrony Financial — Synchrony's first-quarter earnings missed expectations by a wide margin, sending the stock reeling more than 7 percent. Synchrony posted earnings per share of 61 cents; analysts polled by Reuters expected the firm post a profit of 73 cents a share.

—Reuters contributed to this report.